Update metrics docs.

doc/administration/monitoring/prometheus/gitlab_metrics.md

@@ -24,19 +24,22 @@ Currently the embedded Prometheus server is not automatically configured to coll
 In this experimental phase, only a few metrics are available:
 
 | Metric                            | Type      | Description |
-| ------ | ---- | ----------- |
+| --------------------------------- | --------- | ----------- |
 | db_ping_timeout                   | Gauge     | Whether or not the last database ping timed out |
 | db_ping_success                   | Gauge     | Whether or not the last database ping succeeded |
 | db_ping_latency_seconds           | Gauge     | Round trip time of the database ping |
+| filesystem_access_latency_seconds | Gauge     | Latency in accessing a specific filesystem |
+| filesystem_accessible             | Gauge     | Whether or not a specific filesystem is accessible |
+| filesystem_write_latency_seconds  | Gauge     | Write latency of a specific filesystem |
+| filesystem_writable               | Gauge     | Whether or not the filesystem is writable |
+| filesystem_read_latency_seconds   | Gauge     | Read latency of a specific filesystem |
+| filesystem_readable               | Gauge     | Whether or not the filesystem is readable |
+| http_requests_total               | Counter   | Rack request count |
+| http_request_duration_seconds     | Histogram | HTTP response time from rack middleware |
+| rack_uncaught_errors_total        | Counter   | Rack connections handling uncaught errors count |
 | redis_ping_timeout                | Gauge     | Whether or not the last redis ping timed out |
 | redis_ping_success                | Gauge     | Whether or not the last redis ping succeeded |
 | redis_ping_latency_seconds        | Gauge     | Round trip time of the redis ping |
-| filesystem_access_latency_seconds | gauge | Latency in accessing a specific filesystem |
-| filesystem_accessible | gauge | Whether or not a specific filesystem is accessible |
-| filesystem_write_latency_seconds | gauge | Write latency of a specific filesystem |
-| filesystem_writable | gauge | Whether or not the filesystem is writable |
-| filesystem_read_latency_seconds | gauge | Read latency of a specific filesystem |
-| filesystem_readable | gauge | Whether or not the filesystem is readable |
 | user_sessions_logins              | Counter   | Counter of how many users have logged in |
 
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