[Serve] Rewrite Ray.Serve From Scratch (#5562)

* Commit and format files

* address stylistic concerns

* Replcae "Usage" by "Example" in doc

* Rename srv to serve

* Add serve to CI process; Fix 3.5 compat

* Improve determine_tests_to_run.py

* Quick cosmetic for determien_tests

* Address comments

* Address comments

* Address comment

* Fix typos and grammar

Co-Authored-By: Edward Oakes <ed.nmi.oakes@gmail.com>

* Update python/ray/experimental/serve/global_state.py

Co-Authored-By: Edward Oakes <ed.nmi.oakes@gmail.com>

* Use __init__ for Query and WorkIntent class

* Remove dataclasses dependency

* Rename oid to object_id for clarity

* Rename produce->enqueue_request, consume->dequeue_request

* Address last round of comment

.travis.yml

@@ -175,6 +175,7 @@ script:
   # ray tests
   # Python3.5+ only. Otherwise we will get `SyntaxError` regardless of how we set the tester.
   - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then python -c 'import sys;exit(sys.version_info>=(3,5))' || python -m pytest -v --durations=5 --timeout=300 python/ray/experimental/test/async_test.py; fi
+  - if [ $RAY_CI_SERVE_AFFECTED == "1" ]; then python -c 'import sys;exit(sys.version_info>=(3,5))' || python -m pytest -v --durations=5 --timeout=300 python/ray/experimental/serve/tests; fi
   - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then python -m pytest -v --durations=10 --timeout=300 python/ray/tests --ignore=python/ray/tests/perf_integration_tests; fi
 
 deploy:

ci/travis/determine_tests_to_run.py

@@ -5,6 +5,9 @@ from __future__ import print_function
 
 import os
 import subprocess
+import sys
+from functools import partial
+from pprint import pformat
 
 
 def list_changed_files(commit_range):
@@ -30,6 +33,7 @@ if __name__ == "__main__":
 
     RAY_CI_TUNE_AFFECTED = 0
     RAY_CI_RLLIB_AFFECTED = 0
+    RAY_CI_SERVE_AFFECTED = 0
     RAY_CI_JAVA_AFFECTED = 0
     RAY_CI_PYTHON_AFFECTED = 0
     RAY_CI_LINUX_WHEELS_AFFECTED = 0
@@ -40,6 +44,8 @@ if __name__ == "__main__":
         files = list_changed_files(os.environ["TRAVIS_COMMIT_RANGE"].replace(
             "...", ".."))
 
+        print(pformat(files), file=sys.stderr)
+
         skip_prefix_list = [
             "doc/", "examples/", "dev/", "docker/", "kubernetes/", "site/"
         ]
@@ -54,9 +60,14 @@ if __name__ == "__main__":
                 RAY_CI_RLLIB_AFFECTED = 1
                 RAY_CI_LINUX_WHEELS_AFFECTED = 1
                 RAY_CI_MACOS_WHEELS_AFFECTED = 1
+            elif changed_file.startswith("python/ray/experimental/serve"):
+                RAY_CI_SERVE_AFFECTED = 1
+                RAY_CI_LINUX_WHEELS_AFFECTED = 1
+                RAY_CI_MACOS_WHEELS_AFFECTED = 1
             elif changed_file.startswith("python/"):
                 RAY_CI_TUNE_AFFECTED = 1
                 RAY_CI_RLLIB_AFFECTED = 1
+                RAY_CI_SERVE_AFFECTED = 1
                 RAY_CI_PYTHON_AFFECTED = 1
                 RAY_CI_LINUX_WHEELS_AFFECTED = 1
                 RAY_CI_MACOS_WHEELS_AFFECTED = 1
@@ -70,6 +81,7 @@ if __name__ == "__main__":
             elif changed_file.startswith("src/"):
                 RAY_CI_TUNE_AFFECTED = 1
                 RAY_CI_RLLIB_AFFECTED = 1
+                RAY_CI_SERVE_AFFECTED = 1
                 RAY_CI_JAVA_AFFECTED = 1
                 RAY_CI_PYTHON_AFFECTED = 1
                 RAY_CI_LINUX_WHEELS_AFFECTED = 1
@@ -77,6 +89,7 @@ if __name__ == "__main__":
             else:
                 RAY_CI_TUNE_AFFECTED = 1
                 RAY_CI_RLLIB_AFFECTED = 1
+                RAY_CI_SERVE_AFFECTED = 1
                 RAY_CI_JAVA_AFFECTED = 1
                 RAY_CI_PYTHON_AFFECTED = 1
                 RAY_CI_LINUX_WHEELS_AFFECTED = 1
@@ -84,16 +97,22 @@ if __name__ == "__main__":
     else:
         RAY_CI_TUNE_AFFECTED = 1
         RAY_CI_RLLIB_AFFECTED = 1
+        RAY_CI_SERVE_AFFECTED = 1
         RAY_CI_JAVA_AFFECTED = 1
         RAY_CI_PYTHON_AFFECTED = 1
         RAY_CI_LINUX_WHEELS_AFFECTED = 1
         RAY_CI_MACOS_WHEELS_AFFECTED = 1
 
-    print("export RAY_CI_TUNE_AFFECTED={}".format(RAY_CI_TUNE_AFFECTED))
-    print("export RAY_CI_RLLIB_AFFECTED={}".format(RAY_CI_RLLIB_AFFECTED))
-    print("export RAY_CI_JAVA_AFFECTED={}".format(RAY_CI_JAVA_AFFECTED))
-    print("export RAY_CI_PYTHON_AFFECTED={}".format(RAY_CI_PYTHON_AFFECTED))
-    print("export RAY_CI_LINUX_WHEELS_AFFECTED={}"
+    # Log the modified environment variables visible in console.
+    for output_stream in [sys.stdout, sys.stderr]:
+        _print = partial(print, file=output_stream)
+        _print("export RAY_CI_TUNE_AFFECTED={}".format(RAY_CI_TUNE_AFFECTED))
+        _print("export RAY_CI_RLLIB_AFFECTED={}".format(RAY_CI_RLLIB_AFFECTED))
+        _print("export RAY_CI_SERVE_AFFECTED={}".format(RAY_CI_SERVE_AFFECTED))
+        _print("export RAY_CI_JAVA_AFFECTED={}".format(RAY_CI_JAVA_AFFECTED))
+        _print(
+            "export RAY_CI_PYTHON_AFFECTED={}".format(RAY_CI_PYTHON_AFFECTED))
+        _print("export RAY_CI_LINUX_WHEELS_AFFECTED={}"
                .format(RAY_CI_LINUX_WHEELS_AFFECTED))
-    print("export RAY_CI_MACOS_WHEELS_AFFECTED={}"
+        _print("export RAY_CI_MACOS_WHEELS_AFFECTED={}"
                .format(RAY_CI_MACOS_WHEELS_AFFECTED))

ci/travis/install-dependencies.sh

@@ -34,7 +34,8 @@ elif [[ "$PYTHON" == "3.5" ]] && [[ "$platform" == "linux" ]]; then
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
   pip install -q scipy tensorflow cython==0.29.0 gym opencv-python-headless pyyaml pandas==0.24.2 requests \
-    feather-format lxml openpyxl xlrd py-spy setproctitle pytest-timeout flaky networkx tabulate psutil aiohttp
+    feather-format lxml openpyxl xlrd py-spy setproctitle pytest-timeout flaky networkx tabulate psutil aiohttp \
+    uvicorn dataclasses pygments werkzeug
 elif [[ "$PYTHON" == "2.7" ]] && [[ "$platform" == "macosx" ]]; then
   # Install miniconda.
   wget https://repo.continuum.io/miniconda/Miniconda2-4.5.4-MacOSX-x86_64.sh -O miniconda.sh -nv
@@ -48,7 +49,8 @@ elif [[ "$PYTHON" == "3.5" ]] && [[ "$platform" == "macosx" ]]; then
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
   pip install -q cython==0.29.0 tensorflow gym opencv-python-headless pyyaml pandas==0.24.2 requests \
-    feather-format lxml openpyxl xlrd py-spy setproctitle pytest-timeout flaky networkx tabulate psutil aiohttp
+    feather-format lxml openpyxl xlrd py-spy setproctitle pytest-timeout flaky networkx tabulate psutil aiohttp \
+    uvicorn dataclasses pygments werkzeug
 elif [[ "$LINT" == "1" ]]; then
   sudo apt-get update
   sudo apt-get install -y build-essential curl unzip

python/ray/experimental/serve/__init__.py

@@ -0,0 +1,12 @@
+import sys
+if sys.version_info < (3, 0):
+    raise ImportError("serve is Python 3 only.")
+
+from ray.experimental.serve.api import (init, create_backend, create_endpoint,
+                                        link, split, rollback, get_handle,
+                                        global_state)  # noqa: E402
+
+__all__ = [
+    "init", "create_backend", "create_endpoint", "link", "split", "rollback",
+    "get_handle", "global_state"
+]

python/ray/experimental/serve/api.py

@@ -0,0 +1,187 @@
+import inspect
+
+import numpy as np
+
+import ray
+from ray.experimental.serve.task_runner import RayServeMixin, TaskRunnerActor
+from ray.experimental.serve.utils import pformat_color_json, logger
+from ray.experimental.serve.global_state import GlobalState
+
+global_state = GlobalState()
+
+
+def init(blocking=False, object_store_memory=int(1e8)):
+    """Initialize a serve cluster.
+
+    Calling `ray.init` before `serve.init` is optional. When there is not a ray
+    cluster initialized, serve will call `ray.init` with `object_store_memory`
+    requirement.
+
+    Args:
+        blocking (bool): If true, the function will wait for the HTTP server to
+            be healthy before returns.
+        object_store_memory (int): Allocated shared memory size in bytes. The
+            default is 100MiB. The default is kept low for latency stability
+            reason.
+    """
+    if not ray.is_initialized():
+        ray.init(object_store_memory=object_store_memory)
+
+    # NOTE(simon): Currently the initialization order is fixed.
+    # HTTP server depends on the API server.
+    global_state.init_api_server()
+    global_state.init_router()
+    global_state.init_http_server()
+
+    if blocking:
+        global_state.wait_until_http_ready()
+
+
+def create_endpoint(endpoint_name, route_expression, blocking=True):
+    """Create a service endpoint given route_expression.
+
+    Args:
+        endpoint_name (str): A name to associate to the endpoint. It will be
+            used as key to set traffic policy.
+        route_expression (str): A string begin with "/". HTTP server will use
+            the string to match the path.
+        blocking (bool): If true, the function will wait for service to be
+            registered before returning
+    """
+    future = global_state.kv_store_actor_handle.register_service.remote(
+        route_expression, endpoint_name)
+    if blocking:
+        ray.get(future)
+    global_state.registered_endpoints.add(endpoint_name)
+
+
+def create_backend(func_or_class, backend_tag, *actor_init_args):
+    """Create a backend using func_or_class and assign backend_tag.
+
+    Args:
+        func_or_class (callable, class): a function or a class implements
+            __call__ protocol.
+        backend_tag (str): a unique tag assign to this backend. It will be used
+            to associate services in traffic policy.
+        *actor_init_args (optional): the argument to pass to the class
+            initialization method.
+    """
+    if inspect.isfunction(func_or_class):
+        runner = TaskRunnerActor.remote(func_or_class)
+    elif inspect.isclass(func_or_class):
+        # Python inheritance order is right-to-left. We put RayServeMixin
+        # on the left to make sure its methods are not overriden.
+        @ray.remote
+        class CustomActor(RayServeMixin, func_or_class):
+            pass
+
+        runner = CustomActor.remote(*actor_init_args)
+    else:
+        raise TypeError(
+            "Backend must be a function or class, it is {}.".format(
+                type(func_or_class)))
+
+    global_state.backend_actor_handles.append(runner)
+
+    runner._ray_serve_setup.remote(backend_tag,
+                                   global_state.router_actor_handle)
+    runner._ray_serve_main_loop.remote(runner)
+
+    global_state.registered_backends.add(backend_tag)
+
+
+def link(endpoint_name, backend_tag):
+    """Associate a service endpoint with backend tag.
+
+    Example:
+
+    >>> serve.link("service-name", "backend:v1")
+
+    Note:
+    This is equivalent to
+
+    >>> serve.split("service-name", {"backend:v1": 1.0})
+    """
+    assert endpoint_name in global_state.registered_endpoints
+
+    global_state.router_actor_handle.link.remote(endpoint_name, backend_tag)
+    global_state.policy_action_history[endpoint_name].append({backend_tag: 1})
+
+
+def split(endpoint_name, traffic_policy_dictionary):
+    """Associate a service endpoint with traffic policy.
+
+    Example:
+
+    >>> serve.split("service-name", {
+        "backend:v1": 0.5,
+        "backend:v2": 0.5
+    })
+
+    Args:
+        endpoint_name (str): A registered service endpoint.
+        traffic_policy_dictionary (dict): a dictionary maps backend names
+            to their traffic weights. The weights must sum to 1.
+    """
+
+    # Perform dictionary checks
+    assert endpoint_name in global_state.registered_endpoints
+
+    assert isinstance(traffic_policy_dictionary,
+                      dict), "Traffic policy must be dictionary"
+    prob = 0
+    for backend, weight in traffic_policy_dictionary.items():
+        prob += weight
+        assert (backend in global_state.registered_backends
+                ), "backend {} is not registered".format(backend)
+    assert np.isclose(
+        prob, 1,
+        atol=0.02), "weights must sum to 1, currently it sums to {}".format(
+            prob)
+
+    global_state.router_actor_handle.set_traffic.remote(
+        endpoint_name, traffic_policy_dictionary)
+    global_state.policy_action_history[endpoint_name].append(
+        traffic_policy_dictionary)
+
+
+def rollback(endpoint_name):
+    """Rollback a traffic policy decision.
+
+    Args:
+        endpoint_name (str): A registered service endpoint.
+    """
+    assert endpoint_name in global_state.registered_endpoints
+    action_queues = global_state.policy_action_history[endpoint_name]
+    cur_policy, prev_policy = action_queues[-1], action_queues[-2]
+
+    logger.warning("""
+Current traffic policy is:
+{cur_policy}
+
+Will rollback to:
+{prev_policy}
+""".format(
+        cur_policy=pformat_color_json(cur_policy),
+        prev_policy=pformat_color_json(prev_policy)))
+
+    action_queues.pop()
+    global_state.router_actor_handle.set_traffic.remote(
+        endpoint_name, prev_policy)
+
+
+def get_handle(endpoint_name):
+    """Retrieve RayServeHandle for service endpoint to invoke it from Python.
+
+    Args:
+        endpoint_name (str): A registered service endpoint.
+
+    Returns:
+        RayServeHandle
+    """
+    assert endpoint_name in global_state.registered_endpoints
+
+    # Delay import due to it's dependency on global_state
+    from ray.experimental.serve.handle import RayServeHandle
+
+    return RayServeHandle(global_state.router_actor_handle, endpoint_name)

python/ray/experimental/serve/constants.py

@@ -0,0 +1,2 @@
+#: The interval which http server refreshes its routing table
+HTTP_ROUTER_CHECKER_INTERVAL_S = 2

python/ray/experimental/serve/examples/echo.py

@@ -0,0 +1,28 @@
+"""
+Example service that prints out http context.
+"""
+
+import time
+
+import requests
+
+from ray.experimental import serve
+from ray.experimental.serve.utils import pformat_color_json
+
+
+def echo(context):
+    return context
+
+
+serve.init(blocking=True)
+
+serve.create_endpoint("my_endpoint", "/echo", blocking=True)
+serve.create_backend(echo, "echo:v1")
+serve.link("my_endpoint", "echo:v1")
+
+while True:
+    resp = requests.get("http://127.0.0.1:8000/echo").json()
+    print(pformat_color_json(resp))
+
+    print("...Sleeping for 2 seconds...")
+    time.sleep(2)

python/ray/experimental/serve/examples/echo_actor.py

@@ -0,0 +1,41 @@
+"""
+Example actor that adds message to the end of query_string.
+"""
+
+import time
+
+import requests
+from werkzeug import urls
+
+from ray.experimental import serve
+from ray.experimental.serve.utils import pformat_color_json
+
+
+class EchoActor:
+    def __init__(self, message):
+        self.message = message
+
+    def __call__(self, context):
+        query_string_dict = urls.url_decode(context["query_string"])
+        message = ""
+        message += query_string_dict.get("message", "")
+        message += " "
+        message += self.message
+        return message
+
+
+serve.init(blocking=True)
+
+serve.create_endpoint("my_endpoint", "/echo", blocking=True)
+serve.create_backend(EchoActor, "echo:v1", "world")
+serve.link("my_endpoint", "echo:v1")
+
+while True:
+    resp = requests.get("http://127.0.0.1:8000/echo?message=hello").json()
+    print(pformat_color_json(resp))
+
+    resp = requests.get("http://127.0.0.1:8000/echo").json()
+    print(pformat_color_json(resp))
+
+    print("...Sleeping for 2 seconds...")
+    time.sleep(2)

python/ray/experimental/serve/examples/echo_error.py

@@ -0,0 +1,44 @@
+"""
+Example of error handling mechanism in ray serve.
+
+We are going to define a buggy function that raise some exception:
+>>> def echo(_):
+        raise Exception("oh no")
+
+The expected behavior is:
+- HTTP server should respond with "internal error" in the response JSON
+- ray.get(handle.remote(33)) should raise RayTaskError with traceback.
+
+This shows that error is hidden from HTTP side but always visible when calling
+from Python.
+"""
+
+import time
+
+import requests
+
+import ray
+from ray.experimental import serve
+from ray.experimental.serve.utils import pformat_color_json
+
+
+def echo(_):
+    raise Exception("Something went wrong...")
+
+
+serve.init(blocking=True)
+
+serve.create_endpoint("my_endpoint", "/echo", blocking=True)
+serve.create_backend(echo, "echo:v1")
+serve.link("my_endpoint", "echo:v1")
+
+for _ in range(2):
+    resp = requests.get("http://127.0.0.1:8000/echo").json()
+    print(pformat_color_json(resp))
+
+    print("...Sleeping for 2 seconds...")
+    time.sleep(2)
+
+handle = serve.get_handle("my_endpoint")
+
+ray.get(handle.remote(33))

python/ray/experimental/serve/examples/echo_rollback.py

@@ -0,0 +1,50 @@
+"""
+Example rollback action in ray serve. We first deploy only v1, then set a
+ 50/50 deployment between v1 and v2, and finally roll back to only v1.
+"""
+import time
+
+import requests
+
+from ray.experimental import serve
+from ray.experimental.serve.utils import pformat_color_json
+
+
+def echo_v1(_):
+    return "v1"
+
+
+def echo_v2(_):
+    return "v2"
+
+
+serve.init(blocking=True)
+
+serve.create_endpoint("my_endpoint", "/echo", blocking=True)
+serve.create_backend(echo_v1, "echo:v1")
+serve.link("my_endpoint", "echo:v1")
+
+for _ in range(3):
+    resp = requests.get("http://127.0.0.1:8000/echo").json()
+    print(pformat_color_json(resp))
+
+    print("...Sleeping for 2 seconds...")
+    time.sleep(2)
+
+serve.create_backend(echo_v2, "echo:v2")
+serve.split("my_endpoint", {"echo:v1": 0.5, "echo:v2": 0.5})
+
+for _ in range(6):
+    resp = requests.get("http://127.0.0.1:8000/echo").json()
+    print(pformat_color_json(resp))
+
+    print("...Sleeping for 2 seconds...")
+    time.sleep(2)
+
+serve.rollback("my_endpoint")
+for _ in range(6):
+    resp = requests.get("http://127.0.0.1:8000/echo").json()
+    print(pformat_color_json(resp))
+
+    print("...Sleeping for 2 seconds...")
+    time.sleep(2)

python/ray/experimental/serve/examples/echo_split.py

@@ -0,0 +1,41 @@
+"""
+Example of traffic splitting. We will first use echo:v1. Then v1 and v2
+will split the incoming traffic evenly.
+"""
+import time
+
+import requests
+
+from ray.experimental import serve
+from ray.experimental.serve.utils import pformat_color_json
+
+
+def echo_v1(_):
+    return "v1"
+
+
+def echo_v2(_):
+    return "v2"
+
+
+serve.init(blocking=True)
+
+serve.create_endpoint("my_endpoint", "/echo", blocking=True)
+serve.create_backend(echo_v1, "echo:v1")
+serve.link("my_endpoint", "echo:v1")
+
+for _ in range(3):
+    resp = requests.get("http://127.0.0.1:8000/echo").json()
+    print(pformat_color_json(resp))
+
+    print("...Sleeping for 2 seconds...")
+    time.sleep(2)
+
+serve.create_backend(echo_v2, "echo:v2")
+serve.split("my_endpoint", {"echo:v1": 0.5, "echo:v2": 0.5})
+while True:
+    resp = requests.get("http://127.0.0.1:8000/echo").json()
+    print(pformat_color_json(resp))
+
+    print("...Sleeping for 2 seconds...")
+    time.sleep(2)

python/ray/experimental/serve/global_state.py

@@ -0,0 +1,84 @@
+import time
+from collections import defaultdict, deque
+
+import ray
+from ray.experimental.serve.kv_store_service import KVStoreProxyActor
+from ray.experimental.serve.queues import CentralizedQueuesActor
+from ray.experimental.serve.utils import logger
+from ray.experimental.serve.server import HTTPActor
+
+# TODO(simon): Global state currently is designed to resides in the driver
+#     process. In the next iteration, we will move all mutable states into
+#     two actors: (1) namespaced key-value store backed by persistent store
+#     (2) actor supervisors holding all actor handles and is responsible
+#     for new actor instantiation and dead actor termination.
+
+LOG_PREFIX = "[Global State] "
+
+
+class GlobalState:
+    """Encapsulate all global state in the serving system.
+
+    Warning:
+        Currently the state resides inside driver process. The state will be
+        moved into a key value stored service AND a supervisor service.
+    """
+
+    def __init__(self):
+        #: holds all actor handles.
+        self.backend_actor_handles = []
+
+        #: actor handle to KV store actor
+        self.kv_store_actor_handle = None
+        #: actor handle to HTTP server
+        self.http_actor_handle = None
+        #: actor handle the router actor
+        self.router_actor_handle = None
+
+        #: Set[str] list of backend names, used for deduplication
+        self.registered_backends = set()
+        #: Set[str] list of service endpoint names, used for deduplication
+        self.registered_endpoints = set()
+
+        #: Mapping of endpoints -> a stack of traffic policy
+        self.policy_action_history = defaultdict(deque)
+
+        #: HTTP address. Currently it's hard coded to localhost with port 8000
+        #  In future iteration, HTTP server will be started on every node and
+        #  use random/available port in a pre-defined port range. TODO(simon)
+        self.http_address = ""
+
+    def init_api_server(self):
+        logger.info(LOG_PREFIX + "Initalizing routing table")
+        self.kv_store_actor_handle = KVStoreProxyActor.remote()
+        logger.info((LOG_PREFIX + "Health checking routing table {}").format(
+            ray.get(self.kv_store_actor_handle.get_request_count.remote())), )
+
+    def init_http_server(self):
+        logger.info(LOG_PREFIX + "Initializing HTTP server")
+        self.http_actor_handle = HTTPActor.remote(self.kv_store_actor_handle,
+                                                  self.router_actor_handle)
+        self.http_actor_handle.run.remote(host="0.0.0.0", port=8000)
+        self.http_address = "http://localhost:8000"
+
+    def init_router(self):
+        logger.info(LOG_PREFIX + "Initializing queuing system")
+        self.router_actor_handle = CentralizedQueuesActor.remote()
+        self.router_actor_handle.register_self_handle.remote(
+            self.router_actor_handle)
+
+    def wait_until_http_ready(self, num_retries=5, backoff_time_s=1):
+        routing_table_request_count = 0
+        retries = num_retries
+
+        while not routing_table_request_count:
+            routing_table_request_count = (ray.get(
+                self.kv_store_actor_handle.get_request_count.remote()))
+            logger.debug((LOG_PREFIX + "Checking if HTTP server is ready."
+                          "{} retries left.").format(retries))
+            time.sleep(backoff_time_s)
+            retries -= 1
+            if retries == 0:
+                raise Exception(
+                    "HTTP server not ready after {} retries.".format(
+                        num_retries))

python/ray/experimental/serve/handle.py

@@ -0,0 +1,64 @@
+import ray
+from ray.experimental import serve
+
+
+class RayServeHandle:
+    """A handle to a service endpoint.
+
+    Invoking this endpoint with .remote is equivalent to pinging
+    an HTTP endpoint.
+
+    Example:
+       >>> handle = serve.get_handle("my_endpoint")
+       >>> handle
+       RayServeHandle(
+            Endpoint="my_endpoint",
+            URL="...",
+            Traffic=...
+       )
+       >>> handle.remote(my_request_content)
+       ObjectID(...)
+       >>> ray.get(handle.remote(...))
+       # result
+       >>> ray.get(handle.remote(let_it_crash_request))
+       # raises RayTaskError Exception
+    """
+
+    def __init__(self, router_handle, endpoint_name):
+        self.router_handle = router_handle
+        self.endpoint_name = endpoint_name
+
+    def remote(self, *args):
+        # TODO(simon): Support kwargs once #5606 is merged.
+        result_object_id_bytes = ray.get(
+            self.router_handle.enqueue_request.remote(self.endpoint_name,
+                                                      *args))
+        return ray.ObjectID(result_object_id_bytes)
+
+    def get_traffic_policy(self):
+        # TODO(simon): This method is implemented via checking global state
+        # because we are sure handle and global_state are in the same process.
+        # However, once global_state is deprecated, this method need to be
+        # updated accordingly.
+        history = serve.global_state.policy_action_history[self.endpoint_name]
+        if len(history):
+            return history[-1]
+        else:
+            return None
+
+    def get_http_endpoint(self):
+        return serve.global_state.http_address
+
+    def __repr__(self):
+        return """
+RayServeHandle(
+    Endpoint="{endpoint_name}",
+    URL="{http_endpoint}/{endpoint_name},
+    Traffic={traffic_policy}
+)
+""".format(endpoint_name=self.endpoint_name,
+           http_endpoint=self.get_http_endpoint(),
+           traffic_policy=self.get_traffic_policy())
+
+    # TODO(simon): a convenience function that dumps equivalent requests
+    # code for a given call.

python/ray/experimental/serve/kv_store_service.py

@@ -0,0 +1,173 @@
+import json
+from abc import ABC
+
+import ray
+import ray.experimental.internal_kv as ray_kv
+from ray.experimental.serve.utils import logger
+
+
+class NamespacedKVStore(ABC):
+    """Abstract base class for a namespaced key-value store.
+
+    The idea is that multiple key-value stores can be created while sharing
+    the same storage system. The keys of each instance are namespaced to avoid
+    object_id key collision.
+
+    Example:
+
+    >>> store_ns1 = NamespacedKVStore(namespace="ns1")
+    >>> store_ns2 = NamespacedKVStore(namespace="ns2")
+    # Two stores can share the same connection like Redis or SQL Table
+    >>> store_ns1.put("same-key", 1)
+    >>> store_ns1.get("same-key")
+    1
+    >>> store_ns2.put("same-key", 2)
+    >>> store_ns2.get("same-key", 2)
+    2
+    """
+
+    def __init__(self, namespace):
+        raise NotImplementedError()
+
+    def get(self, key):
+        """Retrieve the value for the given key.
+
+        Args:
+            key (str)
+        """
+        raise NotImplementedError()
+
+    def put(self, key, value):
+        """Serialize the value and store it under the given key.
+
+        Args:
+            key (str)
+            value (object): any serializable object. The serialization method
+                is determined by the subclass implementation.
+        """
+        raise NotImplementedError()
+
+    def as_dict(self):
+        """Return the entire namespace as a dictionary.
+
+        Returns:
+            data (dict): key value pairs in current namespace
+        """
+        raise NotImplementedError()
+
+
+class InMemoryKVStore(NamespacedKVStore):
+    """A reference implementation used for testing."""
+
+    def __init__(self, namespace):
+        self.data = dict()
+
+        # Namespace is ignored, because each namespace is backed by
+        # an in-memory Python dictionary.
+        self.namespace = namespace
+
+    def get(self, key):
+        return self.data[key]
+
+    def put(self, key, value):
+        self.data[key] = value
+
+    def as_dict(self):
+        return self.data.copy()
+
+
+class RayInternalKVStore(NamespacedKVStore):
+    """A NamespacedKVStore implementation using ray's `internal_kv`."""
+
+    def __init__(self, namespace):
+        assert ray_kv._internal_kv_initialized()
+        self.index_key = "RAY_SERVE_INDEX"
+        self.namespace = namespace
+        self._put(self.index_key, [])
+
+    def _format_key(self, key):
+        return "{ns}-{key}".format(ns=self.namespace, key=key)
+
+    def _remove_format_key(self, formatted_key):
+        return formatted_key.replace(self.namespace + "-", "", 1)
+
+    def _serialize(self, obj):
+        return json.dumps(obj)
+
+    def _deserialize(self, buffer):
+        return json.loads(buffer)
+
+    def _put(self, key, value):
+        ray_kv._internal_kv_put(
+            self._format_key(self._serialize(key)),
+            self._serialize(value),
+            overwrite=True,
+        )
+
+    def _get(self, key):
+        return self._deserialize(
+            ray_kv._internal_kv_get(self._format_key(self._serialize(key))))
+
+    def get(self, key):
+        return self._get(key)
+
+    def put(self, key, value):
+        assert isinstance(key, str), "Key must be a string."
+
+        self._put(key, value)
+
+        all_keys = set(self._get(self.index_key))
+        all_keys.add(key)
+        self._put(self.index_key, list(all_keys))
+
+    def as_dict(self):
+        data = {}
+        all_keys = self._get(self.index_key)
+        for key in all_keys:
+            data[self._remove_format_key(key)] = self._get(key)
+        return data
+
+
+class KVStoreProxy:
+    def __init__(self, kv_class=InMemoryKVStore):
+        self.routing_table = kv_class(namespace="routes")
+        self.request_count = 0
+
+    def register_service(self, route: str, service: str):
+        """Create an entry in the routing table
+
+        Args:
+            route: http path name. Must begin with '/'.
+            service: service name. This is the name http actor will push
+                the request to.
+        """
+        logger.debug("[KV] Registering route {} to service {}.".format(
+            route, service))
+        self.routing_table.put(route, service)
+
+    def list_service(self):
+        """Returns the routing table."""
+        self.request_count += 1
+        table = self.routing_table.as_dict()
+        return table
+
+    def get_request_count(self):
+        """Return the number of requests that fetched the routing table.
+
+        This method is used for two purpose:
+
+        1. Make sure HTTP server has started and healthy. Incremented request
+           count means HTTP server is actively fetching routing table.
+
+        2. Make sure HTTP server does not have stale routing table. This number
+           should be incremented every HTTP_ROUTER_CHECKER_INTERVAL_S seconds.
+           Supervisor should check this number as indirect indicator of http
+           server's health.
+        """
+        return self.request_count
+
+
+@ray.remote
+class KVStoreProxyActor(KVStoreProxy):
+    def __init__(self, kv_class=RayInternalKVStore):
+        super().__init__(kv_class=kv_class)

python/ray/experimental/serve/queues.py

@@ -0,0 +1,155 @@
+from collections import defaultdict, deque
+
+import numpy as np
+
+import ray
+from ray.experimental.serve.utils import get_custom_object_id, logger
+
+
+class Query:
+    def __init__(self, request_body, result_object_id=None):
+        self.request_body = request_body
+        if result_object_id is None:
+            self.result_object_id = get_custom_object_id()
+        else:
+            self.result_object_id = result_object_id
+
+
+class WorkIntent:
+    def __init__(self, work_object_id=None):
+        if work_object_id is None:
+            self.work_object_id = get_custom_object_id()
+        else:
+            self.work_object_id = work_object_id
+
+
+class CentralizedQueues:
+    """A router that routes request to available workers.
+
+    Router aceepts each request from the `enqueue_request` method and enqueues
+    it. It also accepts worker request to work (called work_intention in code)
+    from workers via the `dequeue_request` method. The traffic policy is used
+    to match requests with their corresponding workers.
+
+    Behavior:
+        >>> # psuedo-code
+        >>> queue = CentralizedQueues()
+        >>> queue.enqueue_request('service-name', data)
+        # nothing happens, request is queued.
+        # returns result ObjectID, which will contains the final result
+        >>> queue.dequeue_request('backend-1')
+        # nothing happens, work intention is queued.
+        # return work ObjectID, which will contains the future request payload
+        >>> queue.link('service-name', 'backend-1')
+        # here the enqueue_requester is matched with worker, request
+        # data is put into work ObjectID, and the worker processes the request
+        # and store the result into result ObjectID
+
+    Traffic policy splits the traffic among different workers
+    probabilistically:
+
+    1. When all backends are ready to receive traffic, we will randomly
+       choose a backend based on the weights assigned by the traffic policy
+       dictionary.
+
+    2. When more than 1 but not all backends are ready, we will normalize the
+       weights of the ready backends to 1 and choose a backend via sampling.
+
+    3. When there is only 1 backend ready, we will only use that backend.
+    """
+
+    def __init__(self):
+        # service_name -> request queue
+        self.queues = defaultdict(deque)
+
+        # service_name -> traffic_policy
+        self.traffic = defaultdict(dict)
+
+        # backend_name -> worker queue
+        self.workers = defaultdict(deque)
+
+    def enqueue_request(self, service, request_data):
+        query = Query(request_data)
+        self.queues[service].append(query)
+        self.flush()
+        return query.result_object_id.binary()
+
+    def dequeue_request(self, backend):
+        intention = WorkIntent()
+        self.workers[backend].append(intention)
+        self.flush()
+        return intention.work_object_id.binary()
+
+    def link(self, service, backend):
+        logger.debug("Link %s with %s", service, backend)
+        self.traffic[service][backend] = 1.0
+        self.flush()
+
+    def set_traffic(self, service, traffic_dict):
+        logger.debug("Setting traffic for service %s to %s", service,
+                     traffic_dict)
+        self.traffic[service] = traffic_dict
+        self.flush()
+
+    def flush(self):
+        """In the default case, flush calls ._flush.
+
+        When this class is a Ray actor, .flush can be scheduled as a remote
+        method invocation.
+        """
+        self._flush()
+
+    def _get_available_backends(self, service):
+        backends_in_policy = set(self.traffic[service].keys())
+        available_workers = set((backend
+                                 for backend, queues in self.workers.items()
+                                 if len(queues) > 0))
+        return list(backends_in_policy.intersection(available_workers))
+
+    def _flush(self):
+        for service, queue in self.queues.items():
+            ready_backends = self._get_available_backends(service)
+
+            while len(queue) and len(ready_backends):
+                # Fast path, only one backend available.
+                if len(ready_backends) == 1:
+                    backend = ready_backends[0]
+                    request, work = (queue.popleft(),
+                                     self.workers[backend].popleft())
+                    ray.worker.global_worker.put_object(
+                        work.work_object_id, request)
+
+                # We have more than one backend available.
+                # We will roll a dice among the multiple backends.
+                else:
+                    backend_weights = np.array([
+                        self.traffic[service][backend_name]
+                        for backend_name in ready_backends
+                    ])
+                    # Normalize the weights to 1.
+                    backend_weights /= backend_weights.sum()
+                    chosen_backend = np.random.choice(
+                        ready_backends, p=backend_weights).squeeze()
+
+                    request, work = (
+                        queue.popleft(),
+                        self.workers[chosen_backend].popleft(),
+                    )
+                    ray.worker.global_worker.put_object(
+                        work.work_object_id, request)
+
+                ready_backends = self._get_available_backends(service)
+
+
+@ray.remote
+class CentralizedQueuesActor(CentralizedQueues):
+    self_handle = None
+
+    def register_self_handle(self, handle_to_this_actor):
+        self.self_handle = handle_to_this_actor
+
+    def flush(self):
+        if self.self_handle:
+            self.self_handle._flush.remote()
+        else:
+            self._flush()

python/ray/experimental/serve/server.py

@@ -0,0 +1,125 @@
+import asyncio
+import json
+
+import uvicorn
+
+import ray
+from ray.experimental.async_api import _async_init, as_future
+from ray.experimental.serve.utils import BytesEncoder
+from ray.experimental.serve.constants import HTTP_ROUTER_CHECKER_INTERVAL_S
+
+
+class JSONResponse:
+    """ASGI compliant response class.
+
+    It is expected to be called in async context and pass along
+    `scope, receive, send` as in ASGI spec.
+
+    >>> await JSONResponse({"k": "v"})(scope, receive, send)
+    """
+
+    def __init__(self, content=None, status_code=200):
+        """Construct a JSON HTTP Response.
+
+        Args:
+            content (optional): Any JSON serializable object.
+            status_code (int, optional): Default status code is 200.
+        """
+        self.body = self.render(content)
+        self.status_code = status_code
+        self.raw_headers = [[b"content-type", b"application/json"]]
+
+    def render(self, content):
+        if content is None:
+            return b""
+        if isinstance(content, bytes):
+            return content
+        return json.dumps(content, cls=BytesEncoder, indent=2).encode()
+
+    async def __call__(self, scope, receive, send):
+        await send({
+            "type": "http.response.start",
+            "status": self.status_code,
+            "headers": self.raw_headers,
+        })
+        await send({"type": "http.response.body", "body": self.body})
+
+
+class HTTPProxy:
+    """
+    This class should be instantiated and ran by ASGI server.
+
+    >>> import uvicorn
+    >>> uvicorn.run(HTTPProxy(kv_store_actor_handle, router_handle))
+    # blocks forever
+    """
+
+    def __init__(self, kv_store_actor_handle, router_handle):
+        """
+        Args:
+            kv_store_actor_handle (ray.actor.ActorHandle): handle to routing
+               table actor. It will be used to populate routing table. It
+               should implement `handle.list_service()`
+            router_handle (ray.actor.ActorHandle): actor handle to push request
+               to. It should implement
+               `handle.enqueue_request.remote(endpoint, body)`
+        """
+        assert ray.is_initialized()
+
+        self.admin_actor = kv_store_actor_handle
+        self.router = router_handle
+        self.route_table = dict()
+
+    async def route_checker(self, interval):
+        while True:
+            try:
+                self.route_table = await as_future(
+                    self.admin_actor.list_service.remote())
+            except ray.exceptions.RayletError:  # Gracefully handle termination
+                return
+
+            await asyncio.sleep(interval)
+
+    async def __call__(self, scope, receive, send):
+        # NOTE: This implements ASGI protocol specified in
+        #       https://asgi.readthedocs.io/en/latest/specs/index.html
+
+        if scope["type"] == "lifespan":
+            await _async_init()
+            asyncio.ensure_future(
+                self.route_checker(interval=HTTP_ROUTER_CHECKER_INTERVAL_S))
+            return
+
+        current_path = scope["path"]
+        if current_path == "/":
+            await JSONResponse(self.route_table)(scope, receive, send)
+        elif current_path in self.route_table:
+            endpoint_name = self.route_table[current_path]
+            result_object_id_bytes = await as_future(
+                self.router.enqueue_request.remote(endpoint_name, scope))
+            result = await as_future(ray.ObjectID(result_object_id_bytes))
+
+            if isinstance(result, ray.exceptions.RayTaskError):
+                await JSONResponse({
+                    "error": "internal error, please use python API to debug"
+                })(scope, receive, send)
+            else:
+                await JSONResponse({"result": result})(scope, receive, send)
+        else:
+            error_message = ("Path {} not found. "
+                             "Please ping http://.../ for routing table"
+                             ).format(current_path)
+
+            await JSONResponse(
+                {
+                    "error": error_message
+                }, status_code=404)(scope, receive, send)
+
+
+@ray.remote
+class HTTPActor:
+    def __init__(self, kv_store_actor_handle, router_handle):
+        self.app = HTTPProxy(kv_store_actor_handle, router_handle)
+
+    def run(self, host="0.0.0.0", port=8000):
+        uvicorn.run(self.app, host=host, port=port, lifespan="on")

python/ray/experimental/serve/task_runner.py

@@ -0,0 +1,96 @@
+import traceback
+
+import ray
+
+
+class TaskRunner:
+    """A simple class that runs a function.
+
+    The purpose of this class is to model what the most basic actor could be.
+    That is, a ray serve actor should implement the TaskRunner interface.
+    """
+
+    def __init__(self, func_to_run):
+        self.func = func_to_run
+
+    def __call__(self, *args):
+        return self.func(*args)
+
+
+def wrap_to_ray_error(callable_obj, *args):
+    """Utility method that catch and seal exceptions in execution"""
+    try:
+        return callable_obj(*args)
+    except Exception:
+        traceback_str = ray.utils.format_error_message(traceback.format_exc())
+        return ray.exceptions.RayTaskError(str(callable_obj), traceback_str)
+
+
+class RayServeMixin:
+    """This mixin class adds the functionality to fetch from router queues.
+
+    Warning:
+        It assumes the main execution method is `__call__` of the user defined
+        class. This means that serve will call `your_instance.__call__` when
+        each request comes in. This behavior will be fixed in the future to
+        allow assigning artibrary methods.
+
+    Example:
+        >>> # Use ray.remote decorator and RayServeMixin
+        >>> # to make MyClass servable.
+        >>> @ray.remote
+            class RayServeActor(RayServeMixin, MyClass):
+                pass
+    """
+    _ray_serve_self_handle = None
+    _ray_serve_router_handle = None
+    _ray_serve_setup_completed = False
+    _ray_serve_dequeue_requestr_name = None
+
+    def _ray_serve_setup(self, my_name, _ray_serve_router_handle):
+        self._ray_serve_dequeue_requestr_name = my_name
+        self._ray_serve_router_handle = _ray_serve_router_handle
+        self._ray_serve_setup_completed = True
+
+    def _ray_serve_main_loop(self, my_handle):
+        assert self._ray_serve_setup_completed
+        self._ray_serve_self_handle = my_handle
+
+        work_token = ray.get(
+            self._ray_serve_router_handle.dequeue_request.remote(
+                self._ray_serve_dequeue_requestr_name))
+        work_item = ray.get(ray.ObjectID(work_token))
+
+        # TODO(simon):
+        # __call__ should be able to take multiple *args and **kwargs.
+        result = wrap_to_ray_error(self.__call__, work_item.request_body)
+        result_object_id = work_item.result_object_id
+        ray.worker.global_worker.put_object(result_object_id, result)
+
+        # The worker finished one unit of work.
+        # It will now tail recursively schedule the main_loop again.
+
+        # TODO(simon): remove tail recursion, ask router to callback instead
+        self._ray_serve_self_handle._ray_serve_main_loop.remote(my_handle)
+
+
+class TaskRunnerBackend(TaskRunner, RayServeMixin):
+    """A simple function serving backend
+
+    Note that this is not yet an actor. To make it an actor:
+
+    >>> @ray.remote
+        class TaskRunnerActor(TaskRunnerBackend):
+            pass
+
+    Note:
+    This class is not used in the actual ray serve system. It exists
+    for documentation purpose.
+    """
+
+    pass
+
+
+@ray.remote
+class TaskRunnerActor(TaskRunnerBackend):
+    pass

python/ray/experimental/serve/tests/conftest.py

@@ -0,0 +1,21 @@
+import pytest
+
+import ray
+from ray.experimental import serve
+
+
+@pytest.fixture(scope="session")
+def serve_instance():
+    serve.init()
+    serve.global_state.wait_until_http_ready()
+    yield
+
+
+@pytest.fixture(scope="session")
+def ray_instance():
+    ray_already_initialized = ray.is_initialized()
+    if not ray_already_initialized:
+        ray.init(object_store_memory=int(1e8))
+    yield
+    if not ray_already_initialized:
+        ray.shutdown()

python/ray/experimental/serve/tests/test_api.py

@@ -0,0 +1,33 @@
+import time
+
+import requests
+from flaky import flaky
+
+import ray
+from ray.experimental import serve
+
+
+def delay_rerun(*_):
+    time.sleep(1)
+    return True
+
+
+# flaky test because the routing table might not be populated
+@flaky(rerun_filter=delay_rerun)
+def test_e2e(serve_instance):
+    serve.create_endpoint("endpoint", "/api")
+    result = ray.get(
+        serve.global_state.kv_store_actor_handle.list_service.remote())
+    assert result == {"/api": "endpoint"}
+
+    assert requests.get("http://127.0.0.1:8000/").json() == result
+
+    def echo(i):
+        return i
+
+    serve.create_backend(echo, "echo:v1")
+    serve.link("endpoint", "echo:v1")
+
+    resp = requests.get("http://127.0.0.1:8000/api").json()["result"]
+    assert resp["path"] == "/api"
+    assert resp["method"] == "GET"

python/ray/experimental/serve/tests/test_queue.py

@@ -0,0 +1,72 @@
+import ray
+from ray.experimental.serve.queues import CentralizedQueues
+
+
+def test_single_prod_cons_queue(serve_instance):
+    q = CentralizedQueues()
+    q.link("svc", "backend")
+
+    result_object_id = q.enqueue_request("svc", 1)
+    work_object_id = q.dequeue_request("backend")
+    got_work = ray.get(ray.ObjectID(work_object_id))
+    assert got_work.request_body == 1
+
+    ray.worker.global_worker.put_object(got_work.result_object_id, 2)
+    assert ray.get(ray.ObjectID(result_object_id)) == 2
+
+
+def test_alter_backend(serve_instance):
+    q = CentralizedQueues()
+
+    result_object_id = q.enqueue_request("svc", 1)
+    work_object_id = q.dequeue_request("backend-1")
+    q.set_traffic("svc", {"backend-1": 1})
+    got_work = ray.get(ray.ObjectID(work_object_id))
+    assert got_work.request_body == 1
+    ray.worker.global_worker.put_object(got_work.result_object_id, 2)
+    assert ray.get(ray.ObjectID(result_object_id)) == 2
+
+    result_object_id = q.enqueue_request("svc", 1)
+    work_object_id = q.dequeue_request("backend-2")
+    q.set_traffic("svc", {"backend-2": 1})
+    got_work = ray.get(ray.ObjectID(work_object_id))
+    assert got_work.request_body == 1
+    ray.worker.global_worker.put_object(got_work.result_object_id, 2)
+    assert ray.get(ray.ObjectID(result_object_id)) == 2
+
+
+def test_split_traffic(serve_instance):
+    q = CentralizedQueues()
+
+    q.enqueue_request("svc", 1)
+    q.enqueue_request("svc", 1)
+    q.set_traffic("svc", {})
+    work_object_id_1 = q.dequeue_request("backend-1")
+    work_object_id_2 = q.dequeue_request("backend-2")
+    q.set_traffic("svc", {"backend-1": 0.5, "backend-2": 0.5})
+
+    got_work = ray.get(
+        [ray.ObjectID(work_object_id_1),
+         ray.ObjectID(work_object_id_2)])
+    assert [g.request_body for g in got_work] == [1, 1]
+
+
+def test_probabilities(serve_instance):
+    q = CentralizedQueues()
+
+    [q.enqueue_request("svc", 1) for i in range(100)]
+
+    work_object_id_1_s = [
+        ray.ObjectID(q.dequeue_request("backend-1")) for i in range(100)
+    ]
+    work_object_id_2_s = [
+        ray.ObjectID(q.dequeue_request("backend-2")) for i in range(100)
+    ]
+
+    q.set_traffic("svc", {"backend-1": 0.1, "backend-2": 0.9})
+
+    backend_1_ready_object_ids, _ = ray.wait(
+        work_object_id_1_s, num_returns=100, timeout=0.0)
+    backend_2_ready_object_ids, _ = ray.wait(
+        work_object_id_2_s, num_returns=100, timeout=0.0)
+    assert len(backend_1_ready_object_ids) < len(backend_2_ready_object_ids)

python/ray/experimental/serve/tests/test_routing.py

@@ -0,0 +1,27 @@
+from ray.experimental.serve.kv_store_service import (InMemoryKVStore,
+                                                     RayInternalKVStore)
+
+
+def test_default_in_memory_kv():
+    kv = InMemoryKVStore("")
+    kv.put("1", 2)
+    assert kv.get("1") == 2
+    kv.put("1", 3)
+    assert kv.get("1") == 3
+    assert kv.as_dict() == {"1": 3}
+
+
+def test_ray_interal_kv(ray_instance):
+    kv = RayInternalKVStore("")
+    kv.put("1", 2)
+    assert kv.get("1") == 2
+    kv.put("1", 3)
+    assert kv.get("1") == 3
+    assert kv.as_dict() == {"1": 3}
+
+    kv = RayInternalKVStore("othernamespace")
+    kv.put("1", 2)
+    assert kv.get("1") == 2
+    kv.put("1", 3)
+    assert kv.get("1") == 3
+    assert kv.as_dict() == {"1": 3}

python/ray/experimental/serve/tests/test_task_runner.py

@@ -0,0 +1,80 @@
+import ray
+from ray.experimental.serve.queues import CentralizedQueuesActor
+from ray.experimental.serve.task_runner import (
+    RayServeMixin,
+    TaskRunner,
+    TaskRunnerActor,
+    wrap_to_ray_error,
+)
+
+
+def test_runner_basic():
+    def echo(i):
+        return i
+
+    r = TaskRunner(echo)
+    assert r(1) == 1
+
+
+def test_runner_wraps_error():
+    def echo(i):
+        return i
+
+    assert wrap_to_ray_error(echo, 2) == 2
+
+    def error(_):
+        return 1 / 0
+
+    assert isinstance(wrap_to_ray_error(error, 1), ray.exceptions.RayTaskError)
+
+
+def test_runner_actor(serve_instance):
+    q = CentralizedQueuesActor.remote()
+
+    def echo(i):
+        return i
+
+    CONSUMER_NAME = "runner"
+    PRODUCER_NAME = "prod"
+
+    runner = TaskRunnerActor.remote(echo)
+
+    runner._ray_serve_setup.remote(CONSUMER_NAME, q)
+    runner._ray_serve_main_loop.remote(runner)
+
+    q.link.remote(PRODUCER_NAME, CONSUMER_NAME)
+
+    for query in [333, 444, 555]:
+        result_token = ray.ObjectID(
+            ray.get(q.enqueue_request.remote(PRODUCER_NAME, query)))
+        assert ray.get(result_token) == query
+
+
+def test_ray_serve_mixin(serve_instance):
+    q = CentralizedQueuesActor.remote()
+
+    CONSUMER_NAME = "runner-cls"
+    PRODUCER_NAME = "prod-cls"
+
+    class MyAdder:
+        def __init__(self, inc):
+            self.increment = inc
+
+        def __call__(self, context):
+            return context + self.increment
+
+    @ray.remote
+    class CustomActor(MyAdder, RayServeMixin):
+        pass
+
+    runner = CustomActor.remote(3)
+
+    runner._ray_serve_setup.remote(CONSUMER_NAME, q)
+    runner._ray_serve_main_loop.remote(runner)
+
+    q.link.remote(PRODUCER_NAME, CONSUMER_NAME)
+
+    for query in [333, 444, 555]:
+        result_token = ray.ObjectID(
+            ray.get(q.enqueue_request.remote(PRODUCER_NAME, query)))
+        assert ray.get(result_token) == query + 3

python/ray/experimental/serve/tests/test_util.py

@@ -0,0 +1,9 @@
+import json
+
+from ray.experimental.serve.utils import BytesEncoder
+
+
+def test_bytes_encoder():
+    data_before = {"inp": {"nest": b"bytes"}}
+    data_after = {"inp": {"nest": "bytes"}}
+    assert json.loads(json.dumps(data_before, cls=BytesEncoder)) == data_after

python/ray/experimental/serve/utils.py

@@ -0,0 +1,51 @@
+import json
+import logging
+
+from pygments import formatters, highlight, lexers
+
+import ray
+
+
+def _get_logger():
+    logger = logging.getLogger("ray.serve")
+    # TODO(simon): Make logging level configurable.
+    logger.setLevel(logging.INFO)
+    return logger
+
+
+logger = _get_logger()
+
+
+class BytesEncoder(json.JSONEncoder):
+    """Allow bytes to be part of the JSON document.
+
+    BytesEncoder will walk the JSON tree and decode bytes with utf-8 codec.
+
+    Example:
+    >>> json.dumps({b'a': b'c'}, cls=BytesEncoder)
+    '{"a":"c"}'
+    """
+
+    def default(self, o):  # pylint: disable=E0202
+        if isinstance(o, bytes):
+            return o.decode("utf-8")
+        return super().default(o)
+
+
+def get_custom_object_id():
+    """Use ray worker API to get computed ObjectID"""
+    worker = ray.worker.global_worker
+    object_id = ray._raylet.compute_put_id(worker.current_task_id,
+                                           worker.task_context.put_index)
+    worker.task_context.put_index += 1
+    return object_id
+
+
+def pformat_color_json(d):
+    """Use pygments to pretty format and colroize dictionary"""
+    formatted_json = json.dumps(d, sort_keys=True, indent=4)
+
+    colorful_json = highlight(formatted_json, lexers.JsonLexer(),
+                              formatters.TerminalFormatter())
+
+    return colorful_json

python/setup.py

@@ -68,6 +68,7 @@ extras = {
     ],
     "debug": ["psutil", "setproctitle", "py-spy"],
     "dashboard": ["psutil", "aiohttp"],
+    "serve": ["uvicorn", "pygments", "werkzeug"],
 }