POC: Support v2 of the APM Server intake API (#5)

BREAKING CHANGE: The client no longer supports v1 of the intake API and
the client API have changed as well.

.codecov.yml

@@ -0,0 +1,2 @@
+# Disable comments on Pull Requests
+comment: false

.gitignore

@@ -1 +1,2 @@
+.nyc_output
 node_modules

.npmignore

@@ -0,0 +1,4 @@
+.codecov.yml
+.travis.yml
+.nyc_output
+test

.travis.yml

@@ -1,9 +1,6 @@
 language: node_js
 node_js:
 - '10'
-- '9'
 - '8'
-- '7'
 - '6'
-- '5'
-- '4'
+after_success: npm run coverage

README.md

@@ -2,6 +2,7 @@
 
 [![npm](https://img.shields.io/npm/v/elastic-apm-http-client.svg)](https://www.npmjs.com/package/elastic-apm-http-client)
 [![Build status](https://travis-ci.org/elastic/apm-nodejs-http-client.svg?branch=master)](https://travis-ci.org/elastic/apm-nodejs-http-client)
+[![codecov](https://img.shields.io/codecov/c/github/elastic/apm-nodejs-http-client.svg)](https://codecov.io/gh/elastic/apm-nodejs-http-client)
 [![Standard - JavaScript Style Guide](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat)](https://github.com/feross/standard)
 
 A low-level HTTP client for communicating with the Elastic APM intake
@@ -23,73 +24,155 @@ npm install elastic-apm-http-client --save
 ## Example Usage
 
 ```js
-var client = require('elastic-apm-http-client')({
-  userAgent: '...'
+const Client = require('elastic-apm-http-client')
+
+const client = new Client({
+  userAgent: 'My Custom Elastic APM Agent',
+  meta: function () {
+    return {
+      // meta data object sent as the first ndjson object in all HTTP
+      // requests to the APM Server
+    }
+  }
 })
 
-client.request('errors', body, function (err, res, body) {
-  if (err) throw err
-  console.log(body)
-})
+const span = {
+  name: 'SELECT FROM users',
+  duration: 42,
+  start: 0,
+  type: 'db.mysql.query'
+}
+
+client.sendSpan(span)
 ```
 
 ## API
 
-The module exposes an initialize function which takes a single options
-hash as the 1st argument:
+### `new Client(options)`
 
-- `userAgent` - The HTTP user agent that your module should identify it
-  self with
-- `secretToken` - (optional) The Elastic APM intake API secret token
-- `serverUrl` - (optional) The APM Server URL (default:
-  `http://localhost:8200`)
-- `rejectUnauthorized` - (optional) Set to `false` if the client
-  shouldn't verify the APM Server TLS certificates (default: `true`)
-- `serverTimeout` - (optional) Set request timeout in milliseconds
+Construct a new `client` object. Data given to the client will be
+converted to ndjson, compressed using gzip, and streamed to the APM
+Server.
 
-The init function will return a low level HTTP client primed for
-communicating with the Elastic APM intake API.
+Arguments:
 
-### `client.request(endpoint[, headers], body, callback)`
+- `options` - An object containing config options (see below)
 
-#### endpoint
+HTTP client configuration:
 
-The Elastic APM intake API currently support the following endpoints:
+- `userAgent` - (required) The HTTP user agent that your module should
+  identify it self as
+- `meta` - (required) A function which will be called every time the a
+  new HTTP request is being made to the APM Server. It's expected that
+  you return a metadata object. This object will be sent as the first
+  ndjson object to the API
+- `secretToken` - The Elastic APM intake API secret token
+- `serverUrl` - The APM Server URL (default: `http://localhost:8200`)
+- `headers` - An object containing extra HTTP headers that should be
+  used when making HTTP requests to he APM Server
+- `rejectUnauthorized` - Set to `false` if the client shouldn't verify
+  the APM Server TLS certificates (default: `true`)
+- `serverTimeout` - HTTP request timeout in milliseconds. If no data is
+  sent or received on the socket for this amount of time, the request
+  will be aborted. It's not recommended to set a `serverTimeout` lower
+  than the `time` config option. That might result in healthy requests
+  being aborted prematurely (default: `15000` ms)
+- `keepAlive` - If set the `false` the client will not reuse sockets
+  between requests (default: `true`)
+- `keepAliveMsecs` - When using the `keepAlive` option, specifies the
+  initial delay for TCP Keep-Alive packets. Ignored when the `keepAlive`
+  option is `false` or `undefined` (default: `1000` ms)
+- `maxSockets` - Maximum number of sockets to allow per host (default:
+  `Infinity`)
+- `maxFreeSockets` - Maximum number of sockets to leave open in a free
+  state. Only relevant if `keepAlive` is set to `true` (default: `256`)
 
-- `errors`
-- `transactions`
+Streaming configuration:
 
-The default full URL's for those are:
+- `size` - The maxiumum compressed body size (in bytes) of each HTTP
+  request to the APM Server. An overshoot of up to the size of the
+  internal zlib buffer should be expected as the buffer is flushed after
+  this limit is reached. The default zlib buffer size is 16 kb (default:
+  `1048576` bytes / 1 MB)
+- `time` - The maxiumum number of milliseconds a streaming HTTP request
+  to the APM Server can be ongoing before it's ended (default: `10000`
+  ms)
 
-```
-http://localhost:8200/<endpoint>
-```
+### Event: `close`
+
+The `close` event is emitted when the client and any of its underlying
+resources have been closed. The event indicates that no more events will
+be emitted, and no more data can be sent by the client.
+
+### Event: `error`
+
+Emitted if an error occurs. The listener callback is passed a single
+Error argument when called.
+
+The client is not closed when the `error` event is emitted.
+
+### Event: `finish`
+
+The `finish` event is emitted after the `client.end()` method has been
+called, and all data has been flushed to the underlying system.
+
+### `client.sendSpan(span[, callback])`
+
+Send a span to the APM Server.
+
+Arguments:
+
+- `span` - A span object that can be serialized to JSON
+- `callback` - Callback is called when the `span` have been flushed to
+  the underlying system
+
+### `client.sendTransaction(transaction[, callback])`
+
+Send a transaction to the APM Server.
+
+Arguments:
+
+- `transaction` - A transaction object that can be serialized to JSON
+- `callback` - Callback is called when the `transaction` have been
+  flushed to the underlying system
+
+### `client.sendError(error[, callback])`
+
+Send a error to the APM Server.
+
+Arguments:
+
+- `error` - A error object that can be serialized to JSON
+- `callback` - Callback is called when the `error` have been flushed to
+  the underlying system
+
+### `client.flush([callback])`
+
+Flush the internal buffer and end the current HTTP request to the APM
+Server. If no HTTP request is in process nothing happens.
 
-When specifying the `endpoint` argument in the `client.request()`
-method, you just have to specify that last part of the URL, e.g.
-"releases".
+Arguments:
 
-#### headers
+- `callback` - Callback is called when the internal buffer have been
+  flushed and the HTTP request ended. If no HTTP request is in progress
+  the callback is called in the next tick.
 
-An optional object that you can use to supply custom headers that should
-be sent to the Elastic APM intake API.
+### `client.end([callback])`
 
-#### body
+Calling the `client.end()` method signals that no more data will be sent
+to the `client`. If the internal buffer contains any data, this is
+flushed before ending.
 
-The body should be in the form of a JavaScript object literal. The
-elastic-apm-http-client will take care of encoding it correctly.
+Arguments:
 
-#### callback
+- `callback` - If provided, the optional `callback` function is attached
+  as a listener for the 'finish' event
 
-The callback function is called with 3 arguments:
+### `client.destroy()`
 
-1. An error when applicable (usually from the
-   [http.ClientRequest](https://nodejs.org/api/http.html#http_class_http_clientrequest)
-   object)
-1. An
-   [http.IncomingMessage](https://nodejs.org/api/http.html#http_http_incomingmessage)
-   object
-1. The response body (as a String)
+Destroy the `client`. After this call, the client has ended and
+subsequent calls to `sendSpan()`, `sendTransaction()`, `sendError()`,
+`flush()`, or `end()` will result in an error.
 
 ## License