Add core metrics service (#58623)

* create base service and collectors

* wire the service into server, add mock

* add collector tests

* add main collector test

* export metric types from server

* add service and server tests

* updates generated doc

* improve doc

* nits and comments

* add disconnected requests test

docs/development/core/server/kibana-plugin-server.md

@@ -88,11 +88,16 @@ The plugin integrates with the core system via lifecycle events: `setup`<!-- -->
 |  [Logger](./kibana-plugin-server.logger.md) | Logger exposes all the necessary methods to log any type of information and this is the interface used by the logging consumers including plugins. |
 |  [LoggerFactory](./kibana-plugin-server.loggerfactory.md) | The single purpose of <code>LoggerFactory</code> interface is to define a way to retrieve a context-based logger instance. |
 |  [LogMeta](./kibana-plugin-server.logmeta.md) | Contextual metadata |
+|  [MetricsServiceSetup](./kibana-plugin-server.metricsservicesetup.md) | APIs to retrieves metrics gathered and exposed by the core platform. |
 |  [OnPostAuthToolkit](./kibana-plugin-server.onpostauthtoolkit.md) | A tool set defining an outcome of OnPostAuth interceptor for incoming request. |
 |  [OnPreAuthToolkit](./kibana-plugin-server.onpreauthtoolkit.md) | A tool set defining an outcome of OnPreAuth interceptor for incoming request. |
 |  [OnPreResponseExtensions](./kibana-plugin-server.onpreresponseextensions.md) | Additional data to extend a response. |
 |  [OnPreResponseInfo](./kibana-plugin-server.onpreresponseinfo.md) | Response status code. |
 |  [OnPreResponseToolkit](./kibana-plugin-server.onpreresponsetoolkit.md) | A tool set defining an outcome of OnPreAuth interceptor for incoming request. |
+|  [OpsMetrics](./kibana-plugin-server.opsmetrics.md) | Regroups metrics gathered by all the collectors. This contains metrics about the os/runtime, the kibana process and the http server. |
+|  [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md) | OS related metrics |
+|  [OpsProcessMetrics](./kibana-plugin-server.opsprocessmetrics.md) | Process related metrics |
+|  [OpsServerMetrics](./kibana-plugin-server.opsservermetrics.md) | server related metrics |
 |  [PackageInfo](./kibana-plugin-server.packageinfo.md) |  |
 |  [Plugin](./kibana-plugin-server.plugin.md) | The interface that should be returned by a <code>PluginInitializer</code>. |
 |  [PluginConfigDescriptor](./kibana-plugin-server.pluginconfigdescriptor.md) | Describes a plugin configuration properties. |

docs/development/core/server/kibana-plugin-server.metricsservicesetup.getopsmetrics_.md

@@ -0,0 +1,24 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [MetricsServiceSetup](./kibana-plugin-server.metricsservicesetup.md) &gt; [getOpsMetrics$](./kibana-plugin-server.metricsservicesetup.getopsmetrics_.md)
+
+## MetricsServiceSetup.getOpsMetrics$ property
+
+Retrieve an observable emitting the [OpsMetrics](./kibana-plugin-server.opsmetrics.md) gathered. The observable will emit an initial value during core's `start` phase, and a new value every fixed interval of time, based on the `opts.interval` configuration property.
+
+<b>Signature:</b>
+
+```typescript
+getOpsMetrics$: () => Observable<OpsMetrics>;
+```
+
+## Example
+
+
+```ts
+core.metrics.getOpsMetrics$().subscribe(metrics => {
+  // do something with the metrics
+})
+
+```
+

docs/development/core/server/kibana-plugin-server.metricsservicesetup.md

@@ -0,0 +1,20 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [MetricsServiceSetup](./kibana-plugin-server.metricsservicesetup.md)
+
+## MetricsServiceSetup interface
+
+APIs to retrieves metrics gathered and exposed by the core platform.
+
+<b>Signature:</b>
+
+```typescript
+export interface MetricsServiceSetup 
+```
+
+## Properties
+
+|  Property | Type | Description |
+|  --- | --- | --- |
+|  [getOpsMetrics$](./kibana-plugin-server.metricsservicesetup.getopsmetrics_.md) | <code>() =&gt; Observable&lt;OpsMetrics&gt;</code> | Retrieve an observable emitting the [OpsMetrics](./kibana-plugin-server.opsmetrics.md) gathered. The observable will emit an initial value during core's <code>start</code> phase, and a new value every fixed interval of time, based on the <code>opts.interval</code> configuration property. |
+

docs/development/core/server/kibana-plugin-server.opsmetrics.concurrent_connections.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsMetrics](./kibana-plugin-server.opsmetrics.md) &gt; [concurrent\_connections](./kibana-plugin-server.opsmetrics.concurrent_connections.md)
+
+## OpsMetrics.concurrent\_connections property
+
+number of current concurrent connections to the server
+
+<b>Signature:</b>
+
+```typescript
+concurrent_connections: OpsServerMetrics['concurrent_connections'];
+```

docs/development/core/server/kibana-plugin-server.opsmetrics.md

@@ -0,0 +1,24 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsMetrics](./kibana-plugin-server.opsmetrics.md)
+
+## OpsMetrics interface
+
+Regroups metrics gathered by all the collectors. This contains metrics about the os/runtime, the kibana process and the http server.
+
+<b>Signature:</b>
+
+```typescript
+export interface OpsMetrics 
+```
+
+## Properties
+
+|  Property | Type | Description |
+|  --- | --- | --- |
+|  [concurrent\_connections](./kibana-plugin-server.opsmetrics.concurrent_connections.md) | <code>OpsServerMetrics['concurrent_connections']</code> | number of current concurrent connections to the server |
+|  [os](./kibana-plugin-server.opsmetrics.os.md) | <code>OpsOsMetrics</code> | OS related metrics |
+|  [process](./kibana-plugin-server.opsmetrics.process.md) | <code>OpsProcessMetrics</code> | Process related metrics |
+|  [requests](./kibana-plugin-server.opsmetrics.requests.md) | <code>OpsServerMetrics['requests']</code> | server requests stats |
+|  [response\_times](./kibana-plugin-server.opsmetrics.response_times.md) | <code>OpsServerMetrics['response_times']</code> | server response time stats |
+

docs/development/core/server/kibana-plugin-server.opsmetrics.os.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsMetrics](./kibana-plugin-server.opsmetrics.md) &gt; [os](./kibana-plugin-server.opsmetrics.os.md)
+
+## OpsMetrics.os property
+
+OS related metrics
+
+<b>Signature:</b>
+
+```typescript
+os: OpsOsMetrics;
+```

docs/development/core/server/kibana-plugin-server.opsmetrics.process.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsMetrics](./kibana-plugin-server.opsmetrics.md) &gt; [process](./kibana-plugin-server.opsmetrics.process.md)
+
+## OpsMetrics.process property
+
+Process related metrics
+
+<b>Signature:</b>
+
+```typescript
+process: OpsProcessMetrics;
+```

docs/development/core/server/kibana-plugin-server.opsmetrics.requests.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsMetrics](./kibana-plugin-server.opsmetrics.md) &gt; [requests](./kibana-plugin-server.opsmetrics.requests.md)
+
+## OpsMetrics.requests property
+
+server requests stats
+
+<b>Signature:</b>
+
+```typescript
+requests: OpsServerMetrics['requests'];
+```

docs/development/core/server/kibana-plugin-server.opsmetrics.response_times.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsMetrics](./kibana-plugin-server.opsmetrics.md) &gt; [response\_times](./kibana-plugin-server.opsmetrics.response_times.md)
+
+## OpsMetrics.response\_times property
+
+server response time stats
+
+<b>Signature:</b>
+
+```typescript
+response_times: OpsServerMetrics['response_times'];
+```

docs/development/core/server/kibana-plugin-server.opsosmetrics.distro.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md) &gt; [distro](./kibana-plugin-server.opsosmetrics.distro.md)
+
+## OpsOsMetrics.distro property
+
+The os distrib. Only present for linux platforms
+
+<b>Signature:</b>
+
+```typescript
+distro?: string;
+```

docs/development/core/server/kibana-plugin-server.opsosmetrics.distrorelease.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md) &gt; [distroRelease](./kibana-plugin-server.opsosmetrics.distrorelease.md)
+
+## OpsOsMetrics.distroRelease property
+
+The os distrib release, prefixed by the os distrib. Only present for linux platforms
+
+<b>Signature:</b>
+
+```typescript
+distroRelease?: string;
+```

docs/development/core/server/kibana-plugin-server.opsosmetrics.load.md

@@ -0,0 +1,17 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md) &gt; [load](./kibana-plugin-server.opsosmetrics.load.md)
+
+## OpsOsMetrics.load property
+
+cpu load metrics
+
+<b>Signature:</b>
+
+```typescript
+load: {
+        '1m': number;
+        '5m': number;
+        '15m': number;
+    };
+```

docs/development/core/server/kibana-plugin-server.opsosmetrics.md

@@ -0,0 +1,26 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md)
+
+## OpsOsMetrics interface
+
+OS related metrics
+
+<b>Signature:</b>
+
+```typescript
+export interface OpsOsMetrics 
+```
+
+## Properties
+
+|  Property | Type | Description |
+|  --- | --- | --- |
+|  [distro](./kibana-plugin-server.opsosmetrics.distro.md) | <code>string</code> | The os distrib. Only present for linux platforms |
+|  [distroRelease](./kibana-plugin-server.opsosmetrics.distrorelease.md) | <code>string</code> | The os distrib release, prefixed by the os distrib. Only present for linux platforms |
+|  [load](./kibana-plugin-server.opsosmetrics.load.md) | <code>{</code><br/><code>        '1m': number;</code><br/><code>        '5m': number;</code><br/><code>        '15m': number;</code><br/><code>    }</code> | cpu load metrics |
+|  [memory](./kibana-plugin-server.opsosmetrics.memory.md) | <code>{</code><br/><code>        total_in_bytes: number;</code><br/><code>        free_in_bytes: number;</code><br/><code>        used_in_bytes: number;</code><br/><code>    }</code> | system memory usage metrics |
+|  [platform](./kibana-plugin-server.opsosmetrics.platform.md) | <code>NodeJS.Platform</code> | The os platform |
+|  [platformRelease](./kibana-plugin-server.opsosmetrics.platformrelease.md) | <code>string</code> | The os platform release, prefixed by the platform name |
+|  [uptime\_in\_millis](./kibana-plugin-server.opsosmetrics.uptime_in_millis.md) | <code>number</code> | the OS uptime |
+

docs/development/core/server/kibana-plugin-server.opsosmetrics.memory.md

@@ -0,0 +1,17 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md) &gt; [memory](./kibana-plugin-server.opsosmetrics.memory.md)
+
+## OpsOsMetrics.memory property
+
+system memory usage metrics
+
+<b>Signature:</b>
+
+```typescript
+memory: {
+        total_in_bytes: number;
+        free_in_bytes: number;
+        used_in_bytes: number;
+    };
+```

docs/development/core/server/kibana-plugin-server.opsosmetrics.platform.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md) &gt; [platform](./kibana-plugin-server.opsosmetrics.platform.md)
+
+## OpsOsMetrics.platform property
+
+The os platform
+
+<b>Signature:</b>
+
+```typescript
+platform: NodeJS.Platform;
+```

docs/development/core/server/kibana-plugin-server.opsosmetrics.platformrelease.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md) &gt; [platformRelease](./kibana-plugin-server.opsosmetrics.platformrelease.md)
+
+## OpsOsMetrics.platformRelease property
+
+The os platform release, prefixed by the platform name
+
+<b>Signature:</b>
+
+```typescript
+platformRelease: string;
+```

docs/development/core/server/kibana-plugin-server.opsosmetrics.uptime_in_millis.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsOsMetrics](./kibana-plugin-server.opsosmetrics.md) &gt; [uptime\_in\_millis](./kibana-plugin-server.opsosmetrics.uptime_in_millis.md)
+
+## OpsOsMetrics.uptime\_in\_millis property
+
+the OS uptime
+
+<b>Signature:</b>
+
+```typescript
+uptime_in_millis: number;
+```

docs/development/core/server/kibana-plugin-server.opsprocessmetrics.event_loop_delay.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsProcessMetrics](./kibana-plugin-server.opsprocessmetrics.md) &gt; [event\_loop\_delay](./kibana-plugin-server.opsprocessmetrics.event_loop_delay.md)
+
+## OpsProcessMetrics.event\_loop\_delay property
+
+node event loop delay
+
+<b>Signature:</b>
+
+```typescript
+event_loop_delay: number;
+```

docs/development/core/server/kibana-plugin-server.opsprocessmetrics.md

@@ -0,0 +1,23 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsProcessMetrics](./kibana-plugin-server.opsprocessmetrics.md)
+
+## OpsProcessMetrics interface
+
+Process related metrics
+
+<b>Signature:</b>
+
+```typescript
+export interface OpsProcessMetrics 
+```
+
+## Properties
+
+|  Property | Type | Description |
+|  --- | --- | --- |
+|  [event\_loop\_delay](./kibana-plugin-server.opsprocessmetrics.event_loop_delay.md) | <code>number</code> | node event loop delay |
+|  [memory](./kibana-plugin-server.opsprocessmetrics.memory.md) | <code>{</code><br/><code>        heap: {</code><br/><code>            total_in_bytes: number;</code><br/><code>            used_in_bytes: number;</code><br/><code>            size_limit: number;</code><br/><code>        };</code><br/><code>        resident_set_size_in_bytes: number;</code><br/><code>    }</code> | process memory usage |
+|  [pid](./kibana-plugin-server.opsprocessmetrics.pid.md) | <code>number</code> | pid of the kibana process |
+|  [uptime\_in\_millis](./kibana-plugin-server.opsprocessmetrics.uptime_in_millis.md) | <code>number</code> | uptime of the kibana process |
+

docs/development/core/server/kibana-plugin-server.opsprocessmetrics.memory.md

@@ -0,0 +1,20 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsProcessMetrics](./kibana-plugin-server.opsprocessmetrics.md) &gt; [memory](./kibana-plugin-server.opsprocessmetrics.memory.md)
+
+## OpsProcessMetrics.memory property
+
+process memory usage
+
+<b>Signature:</b>
+
+```typescript
+memory: {
+        heap: {
+            total_in_bytes: number;
+            used_in_bytes: number;
+            size_limit: number;
+        };
+        resident_set_size_in_bytes: number;
+    };
+```

docs/development/core/server/kibana-plugin-server.opsprocessmetrics.pid.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsProcessMetrics](./kibana-plugin-server.opsprocessmetrics.md) &gt; [pid](./kibana-plugin-server.opsprocessmetrics.pid.md)
+
+## OpsProcessMetrics.pid property
+
+pid of the kibana process
+
+<b>Signature:</b>
+
+```typescript
+pid: number;
+```

docs/development/core/server/kibana-plugin-server.opsprocessmetrics.uptime_in_millis.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsProcessMetrics](./kibana-plugin-server.opsprocessmetrics.md) &gt; [uptime\_in\_millis](./kibana-plugin-server.opsprocessmetrics.uptime_in_millis.md)
+
+## OpsProcessMetrics.uptime\_in\_millis property
+
+uptime of the kibana process
+
+<b>Signature:</b>
+
+```typescript
+uptime_in_millis: number;
+```

docs/development/core/server/kibana-plugin-server.opsservermetrics.concurrent_connections.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-server](./kibana-plugin-server.md) &gt; [OpsServerMetrics](./kibana-plugin-server.opsservermetrics.md) &gt; [concurrent\_connections](./kibana-plugin-server.opsservermetrics.concurrent_connections.md)
+
+## OpsServerMetrics.concurrent\_connections property
+
+number of current concurrent connections to the server
+
+<b>Signature:</b>
+
+```typescript
+concurrent_connections: number;
+```