ray/src/plasma/plasma_manager.c

/* PLASMA MANAGER: Local to a node, connects to other managers to send and
 * receive objects from them
 *
 * The storage manager listens on its main listening port, and if a request for
 * transfering an object to another object store comes in, it ships the data
 * using a new connection to the target object manager. */

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <stdbool.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <strings.h>
#include <poll.h>
#include <assert.h>
#include <netinet/in.h>
#include <netdb.h>

#include "uthash.h"
#include "utlist.h"
#include "utarray.h"
#include "utstring.h"
#include "common.h"
#include "io.h"
#include "net.h"
#include "event_loop.h"
#include "plasma.h"
#include "plasma_protocol.h"
#include "plasma_client.h"
#include "plasma_manager.h"
#include "state/db.h"
#include "state/object_table.h"

/**
 * Process either the fetch or the status request.
 *
 * @param client_conn Client connection.
 * @param object_id ID of the object for which we process this request.
 * @return Void.
 */
void process_status_request(client_connection *client_conn,
                            object_id object_id);

/**
 * Request the transfer from a remote node or get the status of
 * a given object. This is called for an object that is stored at
 * a remote Plasma Store.
 *
 * @param object_id ID of the object to transfer or to get its status.
 * @param manager_cont Number of remote nodes object_id is stored at.
 * @param manager_vector Array containing the Plasma Managers
 *                       running at the nodes where object_id is stored.
 * @param context Client connection.
 * @return Status of object_id as defined in plasma.h
 */
int request_status(object_id object_id,
                   int manager_count,
                   const char *manager_vector[],
                   void *context);

/**
 * Send requested object_id back to the Plasma Manager identified
 * by (addr, port) which requested it. This is done via a
 * data Request message.
 *
 * @param loop
 * @param object_id The ID of the object being transferred to (addr, port).
 * @param addr The address of the Plasma Manager object_id is sent to.
 * @param port The port number of the Plasma Manager object_id is sent to.
 * @param conn The client connection object.
 */
void process_transfer_request(event_loop *loop,
                              object_id object_id,
                              const char *addr,
                              int port,
                              client_connection *conn);

/**
 * Receive object_id requested by this Plamsa Manager from the remote Plasma
 * Manager identified by client_sock. The object_id is sent via the data request
 * message.
 *
 * @param loop The event data structure.
 * @param client_sock The sender's socket.
 * @param object_id ID of the object being received.
 * @param data_size Size of the data of object_id.
 * @param metadata_size Size of the metadata of object_id.
 * @param conn The connection object.
 */
void process_data_request(event_loop *loop,
                          int client_sock,
                          object_id object_id,
                          int64_t data_size,
                          int64_t metadata_size,
                          client_connection *conn);

/** Entry of the hashtable of objects that are available locally. */
typedef struct {
  /** Object id of this object. */
  object_id object_id;
  /** Handle for the uthash table. */
  UT_hash_handle hh;
} available_object;

typedef struct {
  /** The ID of the object we are fetching or waiting for. */
  object_id object_id;
  /** The plasma manager state. */
  plasma_manager_state *manager_state;
  /** The ID for the timer that will time out the current request to the state
   *  database or another plasma manager. */
  int64_t timer;
  /** Pointer to the array containing the manager locations of this object. This
   *  struct owns and must free each entry. */
  char **manager_vector;
  /** The number of manager locations in the array manager_vector. */
  int manager_count;
  /** The next manager we should try to contact. This is set to an index in
   *  manager_vector in the retry handler, in case the current attempt fails to
   *  contact a manager. */
  int next_manager;
  /** Handle for the uthash table in the manager state that keeps track of
   *  outstanding fetch requests. */
  UT_hash_handle hh;
} fetch_request;

/**
 * There are fundamentally two data structures used for handling wait requests.
 * There is the "wait_request" struct and the "object_wait_requests" struct. A
 * wait_request keeps track of all of the object IDs that a wait_request is
 * waiting for. An object_wait_requests struct keeps track of all of the
 * wait_request structs that are waiting for a particular object iD. The
 * plasma_manager_state contains a hash table mapping object IDs to their
 * coresponding object_wait_requests structs.
 *
 * These data structures are updated by several methods:
 *   - add_wait_request_for_object adds a wait_request to the
 *     object_wait_requests struct corresponding to a particular object ID. This
 *     is called when a client calls plasma_wait.
 *   - remove_wait_request_for_object removes a wait_request from an
 *     object_wait_requests struct. When a wait request returns, this method is
 *     called for all of the object IDs involved in that wait_request.
 *   - update_object_wait_requests removes an object_wait_requests struct and
 *     does some processing for each wait_request involved in that
 *     object_wait_requests struct.
 */
typedef struct {
  /** The client connection that called wait. */
  client_connection *client_conn;
  /** The ID of the timer that will time out and cause this wait to return to
   *  the client if it hasn't already returned. */
  int64_t timer;
  /** The number of objects in this wait request. */
  int64_t num_object_requests;
  /** The object requests for this wait request. Each object request has a
   *  status field which is either PLASMA_QUERY_LOCAL or PLASMA_QUERY_ANYWHERE.
   */
  object_request *object_requests;
  /** The minimum number of objects to wait for in this request. */
  int64_t num_objects_to_wait_for;
  /** The number of object requests in this wait request that are already
   *  satisfied. */
  int64_t num_satisfied;
} wait_request;

/** This is used to define the utarray of wait requests in the
 *  object_wait_requests struct. */
UT_icd wait_request_icd = {sizeof(wait_request *), NULL, NULL, NULL};

typedef struct {
  /** The ID of the object. This is used as a key in a hash table. */
  object_id object_id;
  /** An array of the wait requests involving this object ID. */
  UT_array *wait_requests;
  /** Handle for the uthash table in the manager state that keeps track of the
   *  wait requests involving this object ID. */
  UT_hash_handle hh;
} object_wait_requests;

struct plasma_manager_state {
  /** Event loop. */
  event_loop *loop;
  /** Connection to the local plasma store for reading or writing data. */
  plasma_connection *plasma_conn;
  /** Hash table of all contexts for active connections to
   *  other plasma managers. These are used for writing data to
   *  other plasma stores. */
  client_connection *manager_connections;
  db_handle *db;
  /** Our address. */
  const char *addr;
  /** Our port. */
  int port;
  /** Hash table of outstanding fetch requests. The key is the object ID. The
   *  value is the data needed to perform the fetch. */
  fetch_request *fetch_requests;
  /** A hash table mapping object IDs to a vector of the wait requests that
   *  are waiting for the object to arrive locally. */
  object_wait_requests *object_wait_requests_local;
  /** A hash table mapping object IDs to a vector of the wait requests that
   *  are waiting for the object to be available somewhere in the system. */
  object_wait_requests *object_wait_requests_remote;
  /** Initialize an empty hash map for the cache of local available object. */
  available_object *local_available_objects;
  /** Buffer that holds memory for serializing plasma protocol messages. */
  protocol_builder *builder;
};

plasma_manager_state *g_manager_state = NULL;

/* The context for fetch and wait requests. These are per client, per object. */
struct client_object_request {
  /** The ID of the object we are fetching or waiting for. */
  object_id object_id;
  /** The client connection context, shared between other
   *  client_object_requests for the same client. */
  client_connection *client_conn;
  /** The ID for the timer that will time out the current request to the state
   *  database or another plasma manager. */
  int64_t timer;
  /** How many retries we have left for the request. Decremented on every
   *  timeout. */
  int num_retries;
  /** Handle for a linked list. */
  client_object_request *next;
  /** Pointer to the array containing the manager locations of
   *  this object. */
  char **manager_vector;
  /** The number of manager locations in the array manager_vector. */
  int manager_count;
  /** The next manager we should try to contact. This is set to an index in
   * manager_vector in the retry handler, in case the current attempt fails to
   * contact a manager. */
  int next_manager;
  /** Handle for the uthash table in the client connection
   *  context that keeps track of active object connection
   *  contexts. */
  UT_hash_handle active_hh;
  /** Handle for the uthash table in the manager state that
   *  keeps track of outstanding fetch requests. */
  UT_hash_handle fetch_hh;
};

/* Context for a client connection to another plasma manager. */
struct client_connection {
  /** Current state for this plasma manager. This is shared
   *  between all client connections to the plasma manager. */
  plasma_manager_state *manager_state;
  /** Current position in the buffer. */
  int64_t cursor;
  /** Buffer that this connection is reading from. If this is a connection to
   *  write data to another plasma store, then it is a linked
   *  list of buffers to write. */
  /* TODO(swang): Split into two queues, data transfers and data requests. */
  plasma_request_buffer *transfer_queue;
  /** Buffer used to receive transfers (data fetches) we want to ignore */
  plasma_request_buffer *ignore_buffer;
  /** File descriptor for the socket connected to the other
   *  plasma manager. */
  int fd;
  /** Timer id for timing out wait (or fetch). */
  int64_t timer_id;
  /** The objects that we are waiting for and their callback
   *  contexts, for either a fetch or a wait operation. */
  client_object_request *active_objects;
  /** The number of objects that we have left to return for
   *  this fetch or wait operation. */
  int num_return_objects;
  /** Fields specific to connections to plasma managers.  Key that uniquely
   * identifies the plasma manager that we're connected to. We will use the
   * string <address>:<port> as an identifier. */
  char *ip_addr_port;
  /** Handle for the uthash table. */
  UT_hash_handle manager_hh;
};

object_wait_requests **object_wait_requests_table_ptr_from_type(
    plasma_manager_state *manager_state,
    int type) {
  /* We use different types of hash tables for different requests. */
  if (type == PLASMA_QUERY_LOCAL) {
    return &manager_state->object_wait_requests_local;
  } else if (type == PLASMA_QUERY_ANYWHERE) {
    return &manager_state->object_wait_requests_remote;
  } else {
    LOG_FATAL("This code should be unreachable.");
  }
}

void add_wait_request_for_object(plasma_manager_state *manager_state,
                                 object_id object_id,
                                 int type,
                                 wait_request *wait_req) {
  object_wait_requests **object_wait_requests_table_ptr =
      object_wait_requests_table_ptr_from_type(manager_state, type);
  object_wait_requests *object_wait_reqs;
  HASH_FIND(hh, *object_wait_requests_table_ptr, &object_id, sizeof(object_id),
            object_wait_reqs);
  /* If there are currently no wait requests involving this object ID, create a
   * new object_wait_requests struct for this object ID and add it to the hash
   * table. */
  if (object_wait_reqs == NULL) {
    object_wait_reqs = malloc(sizeof(object_wait_requests));
    object_wait_reqs->object_id = object_id;
    utarray_new(object_wait_reqs->wait_requests, &wait_request_icd);
    HASH_ADD(hh, *object_wait_requests_table_ptr, object_id,
             sizeof(object_wait_reqs->object_id), object_wait_reqs);
  }
  /* Add this wait request to the vector of wait requests involving this object
   * ID. */
  utarray_push_back(object_wait_reqs->wait_requests, &wait_req);
}

void remove_wait_request_for_object(plasma_manager_state *manager_state,
                                    object_id object_id,
                                    int type,
                                    wait_request *wait_req) {
  object_wait_requests **object_wait_requests_table_ptr =
      object_wait_requests_table_ptr_from_type(manager_state, type);
  object_wait_requests *object_wait_reqs;
  HASH_FIND(hh, *object_wait_requests_table_ptr, &object_id, sizeof(object_id),
            object_wait_reqs);
  /* If there is a vector of wait requests for this object ID, and if this
   * vector contains the wait request, then remove the wait request from the
   * vector. */
  if (object_wait_reqs != NULL) {
    for (int i = 0; i < utarray_len(object_wait_reqs->wait_requests); ++i) {
      wait_request **wait_req_ptr =
          (wait_request **) utarray_eltptr(object_wait_reqs->wait_requests, i);
      if (*wait_req_ptr == wait_req) {
        /* Remove the wait request from the array. */
        utarray_erase(object_wait_reqs->wait_requests, i, 1);
        break;
      }
    }
    /* In principle, if there are no more wait requests involving this object
     * ID, then we could remove the object_wait_reqs struct. However, the
     * object_wait_reqs struct gets removed in update_object_wait_requests. */
  }
}

void remove_wait_request(plasma_manager_state *manager_state,
                         wait_request *wait_req) {
  if (wait_req->timer != -1) {
    CHECK(event_loop_remove_timer(manager_state->loop, wait_req->timer) ==
          AE_OK);
  }
  free(wait_req->object_requests);
  free(wait_req);
}

void return_from_wait(plasma_manager_state *manager_state,
                      wait_request *wait_req) {
  /* Send the reply to the client. */
  warn_if_sigpipe(plasma_send_WaitReply(
                      wait_req->client_conn->fd, manager_state->builder,
                      wait_req->object_requests, wait_req->num_object_requests),
                  wait_req->client_conn->fd);
  /* Remove the wait request from each of the relevant object_wait_requests hash
   * tables if it is present there. */
  for (int i = 0; i < wait_req->num_object_requests; ++i) {
    remove_wait_request_for_object(manager_state,
                                   wait_req->object_requests[i].object_id,
                                   wait_req->object_requests[i].type, wait_req);
  }
  /* Remove the wait request. */
  remove_wait_request(manager_state, wait_req);
}

void update_object_wait_requests(plasma_manager_state *manager_state,
                                 object_id obj_id,
                                 int type,
                                 int status) {
  object_wait_requests **object_wait_requests_table_ptr =
      object_wait_requests_table_ptr_from_type(manager_state, type);
  /* Update the in-progress wait requests in the specified table. */
  object_wait_requests *object_wait_reqs;
  HASH_FIND(hh, *object_wait_requests_table_ptr, &obj_id, sizeof(obj_id),
            object_wait_reqs);
  if (object_wait_reqs != NULL) {
    /* We compute the number of requests first because the length of the utarray
     * will change as we iterate over it (because each call to return_from_wait
     * will remove one element). */
    int num_requests = utarray_len(object_wait_reqs->wait_requests);
    /* The argument index is the index of the current element of the utarray
     * that we are processing. It may differ from the counter i when elements
     * are removed from the array. */
    int index = 0;
    for (int i = 0; i < num_requests; ++i) {
      wait_request **wait_req_ptr = (wait_request **) utarray_eltptr(
          object_wait_reqs->wait_requests, index);
      wait_request *wait_req = *wait_req_ptr;
      wait_req->num_satisfied += 1;
      /* Mark the object as present in the wait request. */
      int j = 0;
      for (; j < wait_req->num_object_requests; ++j) {
        if (object_ids_equal(wait_req->object_requests[j].object_id, obj_id)) {
          /* Check that this object is currently nonexistent. */
          CHECK(wait_req->object_requests[j].status ==
                ObjectStatus_Nonexistent);
          wait_req->object_requests[j].status = status;
          break;
        }
      }
      /* Make sure that we actually marked an object as available.*/
      CHECK(j != wait_req->num_object_requests);
      /* If this wait request is done, reply to the client. */
      if (wait_req->num_satisfied == wait_req->num_objects_to_wait_for) {
        return_from_wait(manager_state, wait_req);
      } else {
        /* The call to return_from_wait will remove the current element in the
         * array, so we only increment the counter in the else branch. */
        index += 1;
      }
    }
    DCHECK(index == utarray_len(object_wait_reqs->wait_requests));
    /* Remove the array of wait requests for this object, since no one should be
     * waiting for this object anymore. */
    HASH_DELETE(hh, *object_wait_requests_table_ptr, object_wait_reqs);
    utarray_free(object_wait_reqs->wait_requests);
    free(object_wait_reqs);
  }
}

fetch_request *create_fetch_request(plasma_manager_state *manager_state,
                                    object_id object_id) {
  fetch_request *fetch_req = malloc(sizeof(fetch_request));
  fetch_req->manager_state = manager_state;
  fetch_req->object_id = object_id;
  fetch_req->timer = -1;
  fetch_req->manager_count = 0;
  fetch_req->manager_vector = NULL;
  return fetch_req;
}

void remove_fetch_request(plasma_manager_state *manager_state,
                          fetch_request *fetch_req) {
  /* Remove the fetch request from the table of fetch requests. */
  HASH_DELETE(hh, manager_state->fetch_requests, fetch_req);
  /* Remove the timer associated with this fetch request. */
  if (fetch_req->timer != -1) {
    CHECK(event_loop_remove_timer(manager_state->loop, fetch_req->timer) ==
          AE_OK);
  }
  /* Free the fetch request and everything in it. */
  for (int i = 0; i < fetch_req->manager_count; ++i) {
    free(fetch_req->manager_vector[i]);
  }
  if (fetch_req->manager_vector != NULL) {
    free(fetch_req->manager_vector);
  }
  free(fetch_req);
}

plasma_manager_state *init_plasma_manager_state(const char *store_socket_name,
                                                const char *manager_socket_name,
                                                const char *manager_addr,
                                                int manager_port,
                                                const char *db_addr,
                                                int db_port) {
  plasma_manager_state *state = malloc(sizeof(plasma_manager_state));
  state->loop = event_loop_create();
  state->plasma_conn =
      plasma_connect(store_socket_name, NULL, PLASMA_DEFAULT_RELEASE_DELAY);
  state->manager_connections = NULL;
  state->fetch_requests = NULL;
  state->object_wait_requests_local = NULL;
  state->object_wait_requests_remote = NULL;
  if (db_addr) {
    /* Get the manager port as a string. */
    UT_string *manager_address_str;
    utstring_new(manager_address_str);
    utstring_printf(manager_address_str, "%s:%d", manager_addr, manager_port);

    int num_args = 6;
    const char **db_connect_args = malloc(sizeof(char *) * num_args);
    db_connect_args[0] = "store_socket_name";
    db_connect_args[1] = store_socket_name;
    db_connect_args[2] = "manager_socket_name";
    db_connect_args[3] = manager_socket_name;
    db_connect_args[4] = "address";
    db_connect_args[5] = utstring_body(manager_address_str);
    state->db = db_connect(db_addr, db_port, "plasma_manager", manager_addr,
                           num_args, db_connect_args);
    utstring_free(manager_address_str);
    free(db_connect_args);
    db_attach(state->db, state->loop, false);
  } else {
    state->db = NULL;
    LOG_DEBUG("No db connection specified");
  }
  state->addr = manager_addr;
  state->port = manager_port;
  /* Initialize an empty hash map for the cache of local available objects. */
  state->local_available_objects = NULL;
  /* Subscribe to notifications about sealed objects. */
  int plasma_fd = plasma_subscribe(state->plasma_conn);
  /* Add the callback that processes the notification to the event loop. */
  event_loop_add_file(state->loop, plasma_fd, EVENT_LOOP_READ,
                      process_object_notification, state);
  state->builder = make_protocol_builder();
  return state;
}

void destroy_plasma_manager_state(plasma_manager_state *state) {
  client_connection *manager_conn, *tmp;
  HASH_ITER(manager_hh, state->manager_connections, manager_conn, tmp) {
    HASH_DELETE(manager_hh, state->manager_connections, manager_conn);
    plasma_request_buffer *head = manager_conn->transfer_queue;
    while (head) {
      LL_DELETE(manager_conn->transfer_queue, head);
      free(head);
      head = manager_conn->transfer_queue;
    }
    close(manager_conn->fd);
    free(manager_conn->ip_addr_port);
    free(manager_conn);
  }

  if (state->fetch_requests != NULL) {
    fetch_request *fetch_req, *tmp;
    HASH_ITER(hh, state->fetch_requests, fetch_req, tmp) {
      remove_fetch_request(fetch_req->manager_state, fetch_req);
    }
  }

  plasma_disconnect(state->plasma_conn);
  event_loop_destroy(state->loop);
  free_protocol_builder(state->builder);
  free(state);
}

event_loop *get_event_loop(plasma_manager_state *state) {
  return state->loop;
}

/* Handle a command request that came in through a socket (transfering data,
 * or accepting incoming data). */
void process_message(event_loop *loop,
                     int client_sock,
                     void *context,
                     int events);

void write_object_chunk(client_connection *conn, plasma_request_buffer *buf) {
  LOG_DEBUG("Writing data to fd %d", conn->fd);
  ssize_t r, s;
  /* Try to write one BUFSIZE at a time. */
  s = buf->data_size + buf->metadata_size - conn->cursor;
  if (s > BUFSIZE)
    s = BUFSIZE;
  r = write(conn->fd, buf->data + conn->cursor, s);

  if (r != s) {
    if (r > 0) {
      LOG_ERROR("partial write on fd %d", conn->fd);
    } else {
      /* TODO(swang): This should not be a fatal error, since connections can
       * close at any time. */
      LOG_FATAL("write error");
    }
  } else {
    conn->cursor += r;
  }
  if (r == 0) {
    /* If we've finished writing this buffer, reset the cursor to zero. */
    LOG_DEBUG("writing on channel %d finished", conn->fd);
    conn->cursor = 0;
    /* We are done sending the object, so release it. The corresponding call to
     * plasma_get occurred in process_transfer_request. */
    plasma_release(conn->manager_state->plasma_conn, buf->object_id);
  }
}

void send_queued_request(event_loop *loop,
                         int data_sock,
                         void *context,
                         int events) {
  client_connection *conn = (client_connection *) context;
  plasma_manager_state *state = conn->manager_state;

  if (conn->transfer_queue == NULL) {
    /* If there are no objects to transfer, temporarily remove this connection
     * from the event loop. It will be reawoken when we receive another
     * data request. */
    event_loop_remove_file(loop, conn->fd);
    return;
  }

  plasma_request_buffer *buf = conn->transfer_queue;
  switch (buf->type) {
  case MessageType_PlasmaDataRequest:
    warn_if_sigpipe(
        plasma_send_DataRequest(conn->fd, state->builder, buf->object_id,
                                state->addr, state->port),
        conn->fd);
    break;
  case MessageType_PlasmaDataReply:
    LOG_DEBUG("Transferring object to manager");
    if (conn->cursor == 0) {
      /* If the cursor is zero, we haven't sent any requests for this object
       * yet, so send the initial data request. */
      warn_if_sigpipe(
          plasma_send_DataReply(conn->fd, state->builder, buf->object_id,
                                buf->data_size, buf->metadata_size),
          conn->fd);
    }
    write_object_chunk(conn, buf);
    break;
  default:
    LOG_FATAL("Buffered request has unknown type.");
  }

  /* We are done sending this request. */
  if (conn->cursor == 0) {
    LL_DELETE(conn->transfer_queue, buf);
    free(buf);
  }
}

int read_object_chunk(client_connection *conn, plasma_request_buffer *buf) {
  LOG_DEBUG("Reading data from fd %d to %p", conn->fd,
            buf->data + conn->cursor);
  ssize_t r, s;
  CHECK(buf != NULL);
  /* Try to read one BUFSIZE at a time. */
  s = buf->data_size + buf->metadata_size - conn->cursor;
  if (s > BUFSIZE) {
    s = BUFSIZE;
  }
  r = read(conn->fd, buf->data + conn->cursor, s);

  if (r == -1) {
    LOG_ERROR("read error");
  } else if (r == 0) {
    LOG_DEBUG("end of file");
  } else {
    conn->cursor += r;
  }
  /* If the cursor is equal to the full object size, reset the cursor and we're
   * done. */
  if (conn->cursor == buf->data_size + buf->metadata_size) {
    conn->cursor = 0;
    return 1;
  } else {
    return 0;
  }
}

void process_data_chunk(event_loop *loop,
                        int data_sock,
                        void *context,
                        int events) {
  /* Read the object chunk. */
  client_connection *conn = (client_connection *) context;
  plasma_request_buffer *buf = conn->transfer_queue;
  int done = read_object_chunk(conn, buf);
  if (!done) {
    return;
  }

  /* Seal the object and release it. The release corresponds to the call to
   * plasma_create that occurred in process_data_request. */
  LOG_DEBUG("reading on channel %d finished", data_sock);
  /* The following seal also triggers notification of clients for fetch or
   * wait requests, see process_object_notification. */
  plasma_seal(conn->manager_state->plasma_conn, buf->object_id);
  plasma_release(conn->manager_state->plasma_conn, buf->object_id);
  /* Remove the request buffer used for reading this object's data. */
  LL_DELETE(conn->transfer_queue, buf);
  free(buf);
  /* Switch to listening for requests from this socket, instead of reading
   * object data. */
  event_loop_remove_file(loop, data_sock);
  event_loop_add_file(loop, data_sock, EVENT_LOOP_READ, process_message, conn);
}

void ignore_data_chunk(event_loop *loop,
                       int data_sock,
                       void *context,
                       int events) {
  /* Read the object chunk. */
  client_connection *conn = (client_connection *) context;
  plasma_request_buffer *buf = conn->ignore_buffer;

  /* Just read the transferred data into ignore_buf and then drop (free) it. */
  int done = read_object_chunk(conn, buf);
  if (!done) {
    return;
  }

  free(buf->data);
  free(buf);
  /* Switch to listening for requests from this socket, instead of reading
   * object data. */
  event_loop_remove_file(loop, data_sock);
  event_loop_add_file(loop, data_sock, EVENT_LOOP_READ, process_message, conn);
}

client_connection *get_manager_connection(plasma_manager_state *state,
                                          const char *ip_addr,
                                          int port) {
  /* TODO(swang): Should probably check whether ip_addr and port belong to us.
   */
  UT_string *ip_addr_port;
  utstring_new(ip_addr_port);
  utstring_printf(ip_addr_port, "%s:%d", ip_addr, port);
  client_connection *manager_conn;
  HASH_FIND(manager_hh, state->manager_connections, utstring_body(ip_addr_port),
            utstring_len(ip_addr_port), manager_conn);
  if (!manager_conn) {
    /* If we don't already have a connection to this manager, start one. */
    int fd = plasma_manager_connect(ip_addr, port);
    /* TODO(swang): Handle the case when connection to this manager was
     * unsuccessful. */
    CHECK(fd >= 0);
    manager_conn = malloc(sizeof(client_connection));
    manager_conn->fd = fd;
    manager_conn->manager_state = state;
    manager_conn->transfer_queue = NULL;
    manager_conn->cursor = 0;
    manager_conn->ip_addr_port = strdup(utstring_body(ip_addr_port));
    HASH_ADD_KEYPTR(manager_hh,
                    manager_conn->manager_state->manager_connections,
                    manager_conn->ip_addr_port,
                    strlen(manager_conn->ip_addr_port), manager_conn);
  }
  utstring_free(ip_addr_port);
  return manager_conn;
}

void process_transfer_request(event_loop *loop,
                              object_id obj_id,
                              const char *addr,
                              int port,
                              client_connection *conn) {
  uint8_t *data;
  int64_t data_size;
  uint8_t *metadata;
  int64_t metadata_size;
  /* TODO(swang): A non-blocking plasma_get, or else we could block here
   * forever if we don't end up sealing this object. */
  /* The corresponding call to plasma_release will happen in
   * write_object_chunk. */
  /* TODO(rkn): The manager currently will block here if the object is not
   * present in the store. This is completely unacceptable. The manager should
   * do a non-blocking get call on the store, and if the object isn't there then
   * perhaps the manager should initiate the transfer when it receives a
   * notification from the store that the object is present. */
  object_buffer obj_buffer;
  int counter = 0;
  do {
    /* We pass in 0 to indicate that the command should return immediately. */
    object_id obj_id_array[1] = {obj_id};
    plasma_get(conn->manager_state->plasma_conn, obj_id_array, 1, 0,
               &obj_buffer);
    if (counter > 0) {
      LOG_WARN("Blocking in the plasma manager.");
    }
    counter += 1;
  } while (obj_buffer.data_size == -1);
  DCHECK(obj_buffer.metadata == obj_buffer.data + obj_buffer.data_size);
  plasma_request_buffer *buf = malloc(sizeof(plasma_request_buffer));
  buf->type = MessageType_PlasmaDataReply;
  buf->object_id = obj_id;
  /* We treat buf->data as a pointer to the concatenated data and metadata, so
   * we don't actually use buf->metadata. */
  buf->data = obj_buffer.data;
  buf->data_size = obj_buffer.data_size;
  buf->metadata_size = obj_buffer.metadata_size;

  client_connection *manager_conn =
      get_manager_connection(conn->manager_state, addr, port);

  if (manager_conn->transfer_queue == NULL) {
    /* If we already have a connection to this manager and its inactive,
     * (re)register it with the event loop again. */
    event_loop_add_file(loop, manager_conn->fd, EVENT_LOOP_WRITE,
                        send_queued_request, manager_conn);
  }
  /* Add this transfer request to this connection's transfer queue if there
   * isn't already a request with the same object ID. */
  plasma_request_buffer *pending;
  LL_FOREACH(manager_conn->transfer_queue, pending) {
    if (object_ids_equal(pending->object_id, buf->object_id)) {
      return;
    }
  }
  LL_APPEND(manager_conn->transfer_queue, buf);
}

/**
 * Receive object_id requested by this Plamsa Manager from the remote Plasma
 * Manager identified by client_sock. The object_id is sent via the data requst
 * message.
 *
 * @param loop The event data structure.
 * @param client_sock The sender's socket.
 * @param object_id ID of the object being received.
 * @param data_size Size of the data of object_id.
 * @param metadata_size Size of the metadata of object_id.
 * @param conn The connection object.
 * @return Void.
 */
void process_data_request(event_loop *loop,
                          int client_sock,
                          object_id object_id,
                          int64_t data_size,
                          int64_t metadata_size,
                          client_connection *conn) {
  plasma_request_buffer *buf = malloc(sizeof(plasma_request_buffer));
  buf->object_id = object_id;
  buf->data_size = data_size;
  buf->metadata_size = metadata_size;

  /* The corresponding call to plasma_release should happen in
   * process_data_chunk. */
  int error_code = plasma_create(conn->manager_state->plasma_conn, object_id,
                                 data_size, NULL, metadata_size, &(buf->data));
  /* If success_create == true, a new object has been created.
   * If success_create == false the object creation has failed, possibly
   * due to an object with the same ID already existing in the Plasma Store. */
  if (error_code == PlasmaError_OK) {
    /* Add buffer where the fetched data is to be stored to
     * conn->transfer_queue. */
    LL_APPEND(conn->transfer_queue, buf);
  }
  CHECK(conn->cursor == 0);

  /* Switch to reading the data from this socket, instead of listening for
   * other requests. */
  event_loop_remove_file(loop, client_sock);
  if (error_code == PlasmaError_OK) {
    event_loop_add_file(loop, client_sock, EVENT_LOOP_READ, process_data_chunk,
                        conn);
  } else {
    /* Since plasma_create() has failed, we ignore the data transfer. We will
     * receive this transfer in g_ignore_buf and then drop it. Allocate memory
     * for data and metadata, if needed. All memory associated with
     * buf/g_ignore_buf will be freed in ignore_data_chunkc(). */
    conn->ignore_buffer = buf;
    buf->data = (uint8_t *) malloc(buf->data_size + buf->metadata_size);
    event_loop_add_file(loop, client_sock, EVENT_LOOP_READ, ignore_data_chunk,
                        conn);
  }
}

void request_transfer_from(plasma_manager_state *manager_state,
                           object_id object_id) {
  fetch_request *fetch_req;
  HASH_FIND(hh, manager_state->fetch_requests, &object_id, sizeof(object_id),
            fetch_req);
  /* TODO(rkn): This probably can be NULL so we should remove this check, and
   * instead return in the case where there is no fetch request. */
  CHECK(fetch_req != NULL);

  CHECK(fetch_req->manager_count > 0);
  CHECK(fetch_req->next_manager >= 0 &&
        fetch_req->next_manager < fetch_req->manager_count);
  char addr[16];
  int port;
  parse_ip_addr_port(fetch_req->manager_vector[fetch_req->next_manager], addr,
                     &port);

  client_connection *manager_conn =
      get_manager_connection(manager_state, addr, port);

  /* Check that this manager isn't trying to request an object from itself.
   * TODO(rkn): Later this should not be fatal. */
  uint8_t temp_addr[4];
  sscanf(addr, "%hhu.%hhu.%hhu.%hhu", &temp_addr[0], &temp_addr[1],
         &temp_addr[2], &temp_addr[3]);
  if (memcmp(temp_addr, manager_state->addr, 4) == 0 &&
      port == manager_state->port) {
    LOG_FATAL("This manager is attempting to request a transfer from itself.");
  }

  plasma_request_buffer *transfer_request =
      malloc(sizeof(plasma_request_buffer));
  transfer_request->type = MessageType_PlasmaDataRequest;
  transfer_request->object_id = fetch_req->object_id;

  if (manager_conn->transfer_queue == NULL) {
    /* If we already have a connection to this manager and its inactive,
     * (re)register it with the event loop. */
    event_loop_add_file(manager_state->loop, manager_conn->fd, EVENT_LOOP_WRITE,
                        send_queued_request, manager_conn);
  }
  /* Add this transfer request to this connection's transfer queue. */
  LL_APPEND(manager_conn->transfer_queue, transfer_request);
  /* On the next attempt, try the next manager in manager_vector. */
  fetch_req->next_manager += 1;
  fetch_req->next_manager %= fetch_req->manager_count;
}

int manager_timeout_handler(event_loop *loop, timer_id id, void *context) {
  fetch_request *fetch_req = context;
  plasma_manager_state *manager_state = fetch_req->manager_state;
  request_transfer_from(manager_state, fetch_req->object_id);
  return MANAGER_TIMEOUT;
}

bool is_object_local(plasma_manager_state *state, object_id object_id) {
  available_object *entry;
  HASH_FIND(hh, state->local_available_objects, &object_id, sizeof(object_id),
            entry);
  return entry != NULL;
}

void request_transfer(object_id object_id,
                      int manager_count,
                      const char *manager_vector[],
                      void *context) {
  plasma_manager_state *manager_state = (plasma_manager_state *) context;
  /* This callback is called from object_table_subscribe, which guarantees that
   * the manager vector contains at least one element. */
  CHECK(manager_count >= 1);
  fetch_request *fetch_req;
  HASH_FIND(hh, manager_state->fetch_requests, &object_id, sizeof(object_id),
            fetch_req);

  if (is_object_local(manager_state, object_id)) {
    /* If the object is already here, then the fetch request should have been
     * removed. */
    CHECK(fetch_req == NULL);
    return;
  }

  /* If the object is not present, then the fetch request should still be here.
   * TODO(rkn): We actually have to remove this check to handle the rare
   * scenario where the object is transferred here and then evicted before this
   * callback gets called. */
  CHECK(fetch_req != NULL);

  /* This method may be run multiple times, so if we are updating the manager
   * vector, we need to free the previous manager vector. */
  if (fetch_req->manager_count != 0) {
    for (int i = 0; i < fetch_req->manager_count; ++i) {
      free(fetch_req->manager_vector[i]);
    }
    free(fetch_req->manager_vector);
  }
  /* Update the manager vector. */
  fetch_req->manager_count = manager_count;
  fetch_req->manager_vector = malloc(manager_count * sizeof(char *));
  fetch_req->next_manager = 0;
  memset(fetch_req->manager_vector, 0, manager_count * sizeof(char *));
  for (int i = 0; i < manager_count; ++i) {
    int len = strlen(manager_vector[i]);
    fetch_req->manager_vector[i] = malloc(len + 1);
    strncpy(fetch_req->manager_vector[i], manager_vector[i], len);
    fetch_req->manager_vector[i][len] = '\0';
  }
  /* Wait for the object data for the default number of retries, which timeout
   * after a default interval. */
  request_transfer_from(manager_state, object_id);
  /* It is possible for this method to be called multiple times, but we only
   * need to create a timer once. */
  if (fetch_req->timer == -1) {
    fetch_req->timer =
        event_loop_add_timer(manager_state->loop, MANAGER_TIMEOUT,
                             manager_timeout_handler, fetch_req);
  }
}

/* This method is only called from the tests. */
void call_request_transfer(object_id object_id,
                           int manager_count,
                           const char *manager_vector[],
                           void *context) {
  plasma_manager_state *manager_state = (plasma_manager_state *) context;
  fetch_request *fetch_req;
  /* Check that there isn't already a fetch request for this object. */
  HASH_FIND(hh, manager_state->fetch_requests, &object_id, sizeof(object_id),
            fetch_req);
  CHECK(fetch_req == NULL);
  /* Create a fetch request. */
  fetch_req = create_fetch_request(manager_state, object_id);
  HASH_ADD(hh, manager_state->fetch_requests, object_id,
           sizeof(fetch_req->object_id), fetch_req);
  request_transfer(object_id, manager_count, manager_vector, context);
}

void fatal_table_callback(object_id id, void *user_context, void *user_data) {
  CHECK(0);
}

void object_present_callback(object_id object_id,
                             int manager_count,
                             const char *manager_vector[],
                             void *context) {
  plasma_manager_state *manager_state = (plasma_manager_state *) context;
  /* This callback is called from object_table_subscribe, which guarantees that
   * the manager vector contains at least one element. */
  CHECK(manager_count >= 1);

  /* Update the in-progress remote wait requests. */
  update_object_wait_requests(manager_state, object_id, PLASMA_QUERY_ANYWHERE,
                              ObjectStatus_Remote);
}

/* This callback is used by both fetch and wait. Therefore, it may have to
 * handle outstanding fetch and wait requests. */
void object_table_subscribe_callback(object_id object_id,
                                     int64_t data_size,
                                     int manager_count,
                                     const char *manager_vector[],
                                     void *context) {
  plasma_manager_state *manager_state = (plasma_manager_state *) context;
  /* Run the callback for fetch requests if there is a fetch request. */
  fetch_request *fetch_req;
  HASH_FIND(hh, manager_state->fetch_requests, &object_id, sizeof(object_id),
            fetch_req);
  if (fetch_req != NULL) {
    request_transfer(object_id, manager_count, manager_vector, context);
  }
  /* Run the callback for wait requests. */
  object_present_callback(object_id, manager_count, manager_vector, context);
}

void process_fetch_requests(client_connection *client_conn,
                            int num_object_ids,
                            object_id object_ids[]) {
  plasma_manager_state *manager_state = client_conn->manager_state;

  int num_object_ids_to_request = 0;
  /* This is allocating more space than necessary, but we do not know the exact
   * number of object IDs to request notifications for yet. */
  object_id *object_ids_to_request = malloc(num_object_ids * sizeof(object_id));

  for (int i = 0; i < num_object_ids; ++i) {
    object_id obj_id = object_ids[i];

    /* Check if this object is already present locally. If so, do nothing. */
    if (is_object_local(manager_state, obj_id)) {
      continue;
    }

    /* Check if this object is already being fetched. If so, do nothing. */
    fetch_request *entry;
    HASH_FIND(hh, manager_state->fetch_requests, &obj_id, sizeof(obj_id),
              entry);
    if (entry != NULL) {
      continue;
    }

    /* Add an entry to the fetch requests data structure to indidate that the
     * object is being fetched. */
    entry = create_fetch_request(manager_state, obj_id);
    HASH_ADD(hh, manager_state->fetch_requests, object_id,
             sizeof(entry->object_id), entry);
    /* Add this object ID to the list of object IDs to request notifications for
     * from the object table. */
    object_ids_to_request[num_object_ids_to_request] = obj_id;
    num_object_ids_to_request += 1;
  }
  if (num_object_ids_to_request > 0) {
    /* Request notifications from the object table when these object IDs become
     * available. The notifications will call the callback that was passed to
     * object_table_subscribe_to_notifications, which will initiate a transfer
     * of the object to this plasma manager. */
    retry_info retry;
    memset(&retry, 0, sizeof(retry));
    retry.num_retries = 0;
    retry.timeout = MANAGER_TIMEOUT;
    retry.fail_callback = fatal_table_callback;
    object_table_request_notifications(manager_state->db,
                                       num_object_ids_to_request,
                                       object_ids_to_request, &retry);
  }
  free(object_ids_to_request);
}

int wait_timeout_handler(event_loop *loop, timer_id id, void *context) {
  wait_request *wait_req = context;
  return_from_wait(wait_req->client_conn->manager_state, wait_req);
  return EVENT_LOOP_TIMER_DONE;
}

void process_wait_request(client_connection *client_conn,
                          int num_object_requests,
                          object_request object_requests[],
                          uint64_t timeout_ms,
                          int num_ready_objects) {
  CHECK(client_conn != NULL);
  plasma_manager_state *manager_state = client_conn->manager_state;

  /* Create a wait request for this object. */
  wait_request *wait_req = malloc(sizeof(wait_request));
  memset(wait_req, 0, sizeof(wait_request));
  wait_req->client_conn = client_conn;
  wait_req->timer = -1;
  wait_req->num_object_requests = num_object_requests;
  wait_req->object_requests =
      malloc(num_object_requests * sizeof(object_request));
  for (int i = 0; i < num_object_requests; ++i) {
    wait_req->object_requests[i].object_id = object_requests[i].object_id;
    wait_req->object_requests[i].type = object_requests[i].type;
    wait_req->object_requests[i].status = ObjectStatus_Nonexistent;
  }
  wait_req->num_objects_to_wait_for = num_ready_objects;
  wait_req->num_satisfied = 0;

  int num_object_ids_to_request = 0;
  /* This is allocating more space than necessary, but we do not know the exact
   * number of object IDs to request notifications for yet. */
  object_id *object_ids_to_request =
      malloc(num_object_requests * sizeof(object_id));

  for (int i = 0; i < num_object_requests; ++i) {
    object_id obj_id = object_requests[i].object_id;

    /* Check if this object is already present locally. If so, mark the object
     * as present. */
    if (is_object_local(manager_state, obj_id)) {
      wait_req->object_requests[i].status = ObjectStatus_Local;
      wait_req->num_satisfied += 1;
      continue;
    }

    /* Add the wait request to the relevant data structures. */
    add_wait_request_for_object(manager_state, obj_id,
                                wait_req->object_requests[i].type, wait_req);

    if (wait_req->object_requests[i].type == PLASMA_QUERY_LOCAL) {
      /* TODO(rkn): If desired, we could issue a fetch command here to retrieve
       * the object. */
    } else if (wait_req->object_requests[i].type == PLASMA_QUERY_ANYWHERE) {
      /* Add this object ID to the list of object IDs to request notifications
       * for from the object table. */
      object_ids_to_request[num_object_ids_to_request] = obj_id;
      num_object_ids_to_request += 1;
    } else {
      /* This code should be unreachable. */
      CHECK(0);
    }
  }

  /* If enough of the wait requests have already been satisfied, return to the
   * client. */
  if (wait_req->num_satisfied >= wait_req->num_objects_to_wait_for) {
    return_from_wait(manager_state, wait_req);
  } else {
    if (num_object_ids_to_request > 0) {
      /* Request notifications from the object table when these object IDs
       * become available. The notifications will call the callback that was
       * passed to object_table_subscribe_to_notifications, which will update
       * the wait request. */
      retry_info retry;
      memset(&retry, 0, sizeof(retry));
      retry.num_retries = 0;
      retry.timeout = MANAGER_TIMEOUT;
      retry.fail_callback = fatal_table_callback;
      object_table_request_notifications(manager_state->db,
                                         num_object_ids_to_request,
                                         object_ids_to_request, &retry);
    }

    /* Set a timer that will cause the wait request to return to the client. */
    wait_req->timer = event_loop_add_timer(manager_state->loop, timeout_ms,
                                           wait_timeout_handler, wait_req);
  }
  free(object_ids_to_request);
}

/**
 * Check whether a non-local object is stored on any remot enote or not.
 *
 * @param object_id ID of the object whose status we require.
 * @param manager_cont Number of remote nodes object_id is stored at. If
 *        manager_count > 0, then object_id exists on a remote node an its
 *        status is ObjectStatus_Remote. Otherwise, if manager_count == 0, the
 *        object doesn't exist in the system and its status is
 *        ObjectStatus_Nonexistent.
 * @param manager_vector Array containing the Plasma Managers running at the
 *        nodes where object_id is stored. Not used; it will be eventually
 *        deallocated.
 * @param context Client connection.
 * @return Void.
 */
void request_status_done(object_id object_id,
                         int manager_count,
                         const char *manager_vector[],
                         void *context) {
  client_connection *client_conn = (client_connection *) context;
  int status =
      request_status(object_id, manager_count, manager_vector, context);
  warn_if_sigpipe(plasma_send_StatusReply(client_conn->fd,
                                          client_conn->manager_state->builder,
                                          &object_id, &status, 1),
                  client_conn->fd);
}

int request_status(object_id object_id,
                   int manager_count,
                   const char *manager_vector[],
                   void *context) {
  client_connection *client_conn = (client_connection *) context;

  /* Return success immediately if we already have this object. */
  if (is_object_local(client_conn->manager_state, object_id)) {
    return ObjectStatus_Local;
  }

  /* Since object is not stored at the local locally, manager_count > 0 means
   * that the object is stored at another remote object. Otherwise, if
   * manager_count == 0, the object is not stored anywhere. */
  return (manager_count > 0 ? ObjectStatus_Remote : ObjectStatus_Nonexistent);
}

void object_table_lookup_fail_callback(object_id object_id,
                                       void *user_context,
                                       void *user_data) {
  /* Fail for now. Later, we may want to send a ObjectStatus_Nonexistent to the
   * client. */
  CHECK(0);
}

void process_status_request(client_connection *client_conn,
                            object_id object_id) {
  /* Return success immediately if we already have this object. */
  if (is_object_local(client_conn->manager_state, object_id)) {
    int status = ObjectStatus_Local;
    warn_if_sigpipe(plasma_send_StatusReply(client_conn->fd,
                                            client_conn->manager_state->builder,
                                            &object_id, &status, 1),
                    client_conn->fd);
    return;
  }

  if (client_conn->manager_state->db == NULL) {
    int status = ObjectStatus_Nonexistent;
    warn_if_sigpipe(plasma_send_StatusReply(client_conn->fd,
                                            client_conn->manager_state->builder,
                                            &object_id, &status, 1),
                    client_conn->fd);
    return;
  }

  /* The object is not local, so check whether it is stored remotely. */
  retry_info retry = {
      .num_retries = NUM_RETRIES,
      .timeout = MANAGER_TIMEOUT,
      .fail_callback = object_table_lookup_fail_callback,
  };

  object_table_lookup(client_conn->manager_state->db, object_id, &retry,
                      request_status_done, client_conn);
}

void process_delete_object_notification(plasma_manager_state *state,
                                        object_info object_info) {
  object_id obj_id = object_info.obj_id;
  available_object *entry;
  HASH_FIND(hh, state->local_available_objects, &obj_id, sizeof(obj_id), entry);
  if (entry != NULL) {
    HASH_DELETE(hh, state->local_available_objects, entry);
    free(entry);
  }

  /* Remove this object from the (redis) object table. */
  if (state->db) {
    retry_info retry = {
        .num_retries = NUM_RETRIES,
        .timeout = MANAGER_TIMEOUT,
        .fail_callback = NULL,
    };
    object_table_remove(state->db, obj_id, NULL, &retry, NULL, NULL);
  }

  /* NOTE: There could be pending wait requests for this object that will now
   * return when the object is not actually available. For simplicity, we allow
   * this scenario rather than try to keep the wait request statuses exactly
   * up-to-date. */
}

void process_add_object_notification(plasma_manager_state *state,
                                     object_info object_info) {
  object_id obj_id = object_info.obj_id;
  available_object *entry =
      (available_object *) malloc(sizeof(available_object));
  entry->object_id = obj_id;
  HASH_ADD(hh, state->local_available_objects, object_id, sizeof(object_id),
           entry);

  /* Add this object to the (redis) object table. */
  if (state->db) {
    /* TODO(swang): Log the error if we fail to add the object, and possibly
     * retry later? */
    retry_info retry = {
        .num_retries = NUM_RETRIES,
        .timeout = MANAGER_TIMEOUT,
        .fail_callback = NULL,
    };
    object_table_add(state->db, obj_id,
                     object_info.data_size + object_info.metadata_size,
                     object_info.digest, &retry, NULL, NULL);
  }

  /* If we were trying to fetch this object, finish up the fetch request. */
  fetch_request *fetch_req;
  HASH_FIND(hh, state->fetch_requests, &obj_id, sizeof(obj_id), fetch_req);
  if (fetch_req != NULL) {
    remove_fetch_request(state, fetch_req);
    /* TODO(rkn): We also really should unsubscribe from the object table. */
  }

  /* Update the in-progress local and remote wait requests. */
  update_object_wait_requests(state, obj_id, PLASMA_QUERY_LOCAL,
                              ObjectStatus_Local);
  update_object_wait_requests(state, obj_id, PLASMA_QUERY_ANYWHERE,
                              ObjectStatus_Local);
}

void process_object_notification(event_loop *loop,
                                 int client_sock,
                                 void *context,
                                 int events) {
  plasma_manager_state *state = context;
  object_info object_info;
  /* Read the notification from Plasma. */
  int error =
      read_bytes(client_sock, (uint8_t *) &object_info, sizeof(object_info));
  if (error < 0) {
    /* The store has closed the socket. */
    LOG_DEBUG(
        "The plasma store has closed the object notification socket, or some "
        "other error has occurred.");
    event_loop_remove_file(loop, client_sock);
    close(client_sock);
    return;
  }
  /* Add object to locally available object. */
  if (object_info.is_deletion) {
    process_delete_object_notification(state, object_info);
  } else {
    process_add_object_notification(state, object_info);
  }
}

void process_message(event_loop *loop,
                     int client_sock,
                     void *context,
                     int events) {
  client_connection *conn = (client_connection *) context;

  int64_t length;
  int64_t type;
  uint8_t *data;
  read_message(client_sock, &type, &length, &data);

  switch (type) {
  case MessageType_PlasmaDataRequest: {
    LOG_DEBUG("Processing data request");
    object_id object_id;
    char *address;
    int port;
    plasma_read_DataRequest(data, &object_id, &address, &port);
    process_transfer_request(loop, object_id, address, port, conn);
    free(address);
  } break;
  case MessageType_PlasmaDataReply: {
    LOG_DEBUG("Processing data reply");
    object_id object_id;
    int64_t object_size;
    int64_t metadata_size;
    plasma_read_DataReply(data, &object_id, &object_size, &metadata_size);
    process_data_request(loop, client_sock, object_id, object_size,
                         metadata_size, conn);
  } break;
  case MessageType_PlasmaFetchRequest: {
    LOG_DEBUG("Processing fetch remote");
    int64_t num_objects = plasma_read_FetchRequest_num_objects(data);
    object_id object_ids_to_fetch[num_objects];
    plasma_read_FetchRequest(data, object_ids_to_fetch, num_objects);
    process_fetch_requests(conn, num_objects, &object_ids_to_fetch[0]);
  } break;
  case MessageType_PlasmaWaitRequest: {
    LOG_DEBUG("Processing wait");
    int num_object_ids = plasma_read_WaitRequest_num_object_ids(data);
    int64_t timeout_ms;
    int num_ready_objects;
    object_request object_requests[num_object_ids];
    plasma_read_WaitRequest(data, &object_requests[0], num_object_ids,
                            &timeout_ms, &num_ready_objects);
    process_wait_request(conn, num_object_ids, &object_requests[0], timeout_ms,
                         num_ready_objects);
  } break;
  case MessageType_PlasmaStatusRequest: {
    LOG_DEBUG("Processing status");
    object_id object_id;
    int64_t num_objects = plasma_read_StatusRequest_num_objects(data);
    CHECK(num_objects == 1);
    plasma_read_StatusRequest(data, &object_id, 1);
    process_status_request(conn, object_id);
  } break;
  case DISCONNECT_CLIENT: {
    LOG_INFO("Disconnecting client on fd %d", client_sock);
    /* TODO(swang): Check if this connection was to a plasma manager. If so,
     * delete it. */
    event_loop_remove_file(loop, client_sock);
    close(client_sock);
    free(conn);
  } break;
  default:
    LOG_FATAL("invalid request %" PRId64, type);
  }
  free(data);
}

/* TODO(pcm): Split this into two methods: new_worker_connection
 * and new_manager_connection and also split client_connection
 * into two structs, one for workers and one for other plasma managers. */
client_connection *new_client_connection(event_loop *loop,
                                         int listener_sock,
                                         void *context,
                                         int events) {
  int new_socket = accept_client(listener_sock);
  /* Create a new data connection context per client. */
  client_connection *conn = malloc(sizeof(client_connection));
  conn->manager_state = (plasma_manager_state *) context;
  conn->cursor = 0;
  conn->transfer_queue = NULL;
  conn->fd = new_socket;
  conn->active_objects = NULL;
  conn->num_return_objects = 0;
  event_loop_add_file(loop, new_socket, EVENT_LOOP_READ, process_message, conn);
  LOG_DEBUG("New client connection with fd %d", new_socket);
  return conn;
}

void handle_new_client(event_loop *loop,
                       int listener_sock,
                       void *context,
                       int events) {
  (void) new_client_connection(loop, listener_sock, context, events);
}

int get_client_sock(client_connection *conn) {
  return conn->fd;
}

void start_server(const char *store_socket_name,
                  const char *manager_socket_name,
                  const char *master_addr,
                  int port,
                  const char *db_addr,
                  int db_port) {
  /* Ignore SIGPIPE signals. If we don't do this, then when we attempt to write
   * to a client that has already died, the manager could die. */
  signal(SIGPIPE, SIG_IGN);
  /* Bind the sockets before we try to connect to the plasma store.
   * In case the bind does not succeed, we want to be able to exit
   * without breaking the pipe to the store. */
  int remote_sock = bind_inet_sock(port, false);
  if (remote_sock < 0) {
    exit(EXIT_COULD_NOT_BIND_PORT);
  }

  int local_sock = bind_ipc_sock(manager_socket_name, false);
  CHECKM(local_sock >= 0, "Unable to bind local manager socket");

  g_manager_state =
      init_plasma_manager_state(store_socket_name, manager_socket_name,
                                master_addr, port, db_addr, db_port);
  CHECK(g_manager_state);

  CHECK(listen(remote_sock, 5) != -1);
  CHECK(listen(local_sock, 5) != -1);

  LOG_DEBUG("Started server connected to store %s, listening on port %d",
            store_socket_name, port);
  event_loop_add_file(g_manager_state->loop, local_sock, EVENT_LOOP_READ,
                      handle_new_client, g_manager_state);
  event_loop_add_file(g_manager_state->loop, remote_sock, EVENT_LOOP_READ,
                      handle_new_client, g_manager_state);
  /* Set up a client-specific channel to receive notifications from the object
   * table. */
  object_table_subscribe_to_notifications(g_manager_state->db, false,
                                          object_table_subscribe_callback,
                                          g_manager_state, NULL, NULL, NULL);
  /* Run the event loop. */
  event_loop_run(g_manager_state->loop);
}

/* Report "success" to valgrind. */
void signal_handler(int signal) {
  if (signal == SIGTERM) {
    if (g_manager_state) {
      db_disconnect(g_manager_state->db);
    }
    exit(0);
  }
}

/* Only declare the main function if we are not in testing mode, since the test
 * suite has its own declaration of main. */
#ifndef PLASMA_TEST
int main(int argc, char *argv[]) {
  signal(SIGTERM, signal_handler);
  /* Socket name of the plasma store this manager is connected to. */
  char *store_socket_name = NULL;
  /* Socket name this manager will bind to. */
  char *manager_socket_name = NULL;
  /* IP address of this node. */
  char *master_addr = NULL;
  /* Port number the manager should use. */
  int port = -1;
  /* IP address and port of state database. */
  char *db_host = NULL;
  int c;
  while ((c = getopt(argc, argv, "s:m:h:p:r:")) != -1) {
    switch (c) {
    case 's':
      store_socket_name = optarg;
      break;
    case 'm':
      manager_socket_name = optarg;
      break;
    case 'h':
      master_addr = optarg;
      break;
    case 'p':
      port = atoi(optarg);
      break;
    case 'r':
      db_host = optarg;
      break;
    default:
      LOG_FATAL("unknown option %c", c);
    }
  }
  if (!store_socket_name) {
    LOG_FATAL(
        "please specify socket for connecting to the plasma store with -s "
        "switch");
  }
  if (!manager_socket_name) {
    LOG_FATAL(
        "please specify socket name of the manager's local socket with -m "
        "switch");
  }
  if (!master_addr) {
    LOG_FATAL(
        "please specify ip address of the current host in the format "
        "123.456.789.10 with -h switch");
  }
  if (port == -1) {
    LOG_FATAL(
        "please specify port the plasma manager shall listen to in the"
        "format 12345 with -p switch");
  }
  char db_addr[16];
  int db_port;
  if (db_host) {
    parse_ip_addr_port(db_host, db_addr, &db_port);
    start_server(store_socket_name, manager_socket_name, master_addr, port,
                 db_addr, db_port);
  } else {
    start_server(store_socket_name, manager_socket_name, master_addr, port,
                 NULL, 0);
  }
}
#endif