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Merge pull request #2993 from xiang90/md

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doc: add doc for metrics feature
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Xiang Li 2015-06-16 14:22:16 -07:00
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Documentation/glossary.md
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@ -22,6 +22,10 @@ The node in each member follows raft consensus protocol to replicate logs. Clust
Peer is another member of the same cluster.
### Proposal
A proposal is a request (for example a write request, a configuration change request) that needs to go through raft protocol.
### Client
Client is a caller of the cluster's HTTP API.

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Documentation/metrics.md Normal file
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## Metrics
**NOTE: The metrics feature is considered as an experimental. We might add/change/remove metrics without warning in the future releases.**
etcd uses [Prometheus](http://prometheus.io/) for metrics reporting in the server. The metrics can be used for real-time monitoring and debugging.
The simplest way to see the available metrics is to cURL the metrics endpoint `/metrics` of etcd. The format is described [here](http://prometheus.io/docs/instrumenting/exposition_formats/).
You can also follow the doc [here](http://prometheus.io/docs/introduction/getting_started/) to start a Promethus server and monitor etcd metrics.
The naming of metrics follows the suggested [best practice of Promethus](http://prometheus.io/docs/practices/naming/). A metric name has an `etcd` prefix as its namespace and a subsystem prefix (for example `wal` and `etcdserver`).
etcd now exposes the following metrics:
### etcdserver
| Name | Description | Type |
|-----------------------------------------|--------------------------------------------------|---------|
| file_descriptors_used_total | The total number of file descriptors used | Gauge |
| proposal_durations_milliseconds | The latency distributions of committing proposal | Summary |
| pending_proposal_total | The total number of pending proposals | Gauge |
| proposal_failed_total | The total number of failed proposals | Counter |
High file descriptors (`file_descriptors_used_total`) usage (near the file descriptors limitation of the process) indicates a potential out of file descriptors issue. That might cause etcd fails to create new WAL files and panics.
[Proposal](glossary.md#proposal) durations (`proposal_durations_milliseconds`) give you an summary about the proposal commit latency. Latency can be introduced into this process by network and disk IO.
Pending proposal (`pending_proposal_total`) gives you an idea about how many proposal are in the queue and waiting for commit. An increasing pending number indicates a high client load or an unstable cluster.
Failed proposals (`proposal_failed_total`) are normally related to two issues: temporary failures related to a leader election or longer duration downtime caused by a loss of quorum in the cluster.
### wal
| Name | Description | Type |
|------------------------------------|--------------------------------------------------|---------|
| fsync_durations_microseconds | The latency distributions of fsync called by wal | Summary |
| last_index_saved | The index of the last entry saved by wal | Gauge |
Abnormally high fsync duration (`fsync_durations_microseconds`) indicates disk issues and might cause the cluster to be unstable.
### snapshot
| Name | Description | Type |
|--------------------------------------------|------------------------------------------------------------|---------|
| snapshot_save_total_durations_microseconds | The total latency distributions of save called by snapshot | Summary |
Abnormally high snapshot duration (`snapshot_save_total_durations_microseconds`) indicates disk issues and might cause the cluster to be unstable.