docs: add section on logging under features

docs/_config.yml

@@ -17,6 +17,7 @@ sidebar_categories:
     - features/resolvers
     - features/mocking
     - features/errors
+    - features/logging
     - features/scalars-enums
     - features/unions-interfaces
     - features/directives

docs/source/features/logging.md

@@ -0,0 +1,51 @@
+---
+title: Logging
+description: Ensuring Actions can be Recreated
+---
+
+Apollo Server provides two ways to log a server: by input,response, and errors or periodically throughout a request's lifecycle. Treating the GraphQL execution as a black box by logging the inputs and outputs of the system allows developers to diagnose issues quickly without being mired by lower level logs. Once a problem has been found at a high level, the lower level logs enable accurate tracing of how a request was handled.
+
+## High Level Logging
+
+To log the inputs, response, and request, Apollo Server provides three methods: `formatParams`, `formatError`, and `formatResponse`. This example uses `console.log` to record the information, servers can use other more sophisticated tools.
+
+```js
+const server = new ApolloServer({
+  typeDefs,
+  resolvers,
+  formatParams: params => {
+    console.log(params);
+    return params;
+  },
+  formatError: error => {
+    console.log(error);
+    return error;
+  },
+  formatResponse: response => {
+    console.log(response);
+    return response;
+  },
+});
+
+server.listen().then(({ url }) => {
+  console.log(`🚀  Server ready at ${url}`);
+});
+```
+
+## Granular Logs
+
+Apollo Server provides a `logFunction` option that receives the start and completion information for each major phase of GraphQL execution: parse, validate, and execute. Additionally, `logFunction` receives the information that initiates the request and response data. This example uses `console.log`:
+
+```js
+const server = new ApolloServer({
+  typeDefs,
+  resolvers,
+  logFunction: information => {
+    console.log(information)
+  },
+});
+
+server.listen().then(({ url }) => {
+  console.log(`🚀  Server ready at ${url}`);
+});
+```