9.1 KiB
Metrics
NOTE: The metrics feature is considered experimental. We may add/change/remove metrics without warning in future releases.
etcd uses Prometheus for metrics reporting in the server. The metrics can be used for real-time monitoring and debugging. etcd only stores these data in memory. If a member restarts, metrics will reset.
The simplest way to see the available metrics is to cURL the metrics endpoint /metrics of etcd. The format is described here.
Follow the [Prometheus getting started doc][prometheus-getting-started] to spin up a Prometheus server to collect etcd metrics.
The naming of metrics follows the suggested [best practice of Prometheus][prometheus-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_seconds | The latency distributions of committing proposal | Histogram |
| 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 durations (proposal_durations_seconds) provides a histogram 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_seconds | The latency distributions of fsync called by wal | Histogram |
| last_index_saved | The index of the last entry saved by wal | Gauge |
Abnormally high fsync duration (fsync_durations_seconds) indicates disk issues and might cause the cluster to be unstable.
http requests
These metrics describe the serving of requests (non-watch events) served by etcd members in non-proxy mode: total incoming requests, request failures and processing latency (inc. raft rounds for storage). They are useful for tracking user-generated traffic hitting the etcd cluster .
All these metrics are prefixed with etcd_http_
| Name | Description | Type |
|---|---|---|
| received_total | Total number of events after parsing and auth. | Counter(method) |
| failed_total | Total number of failed events. | Counter(method,error) |
| successful_duration_second | Bucketed handling times of the requests, including raft rounds for writes. | Histogram(method) |
Example Prometheus queries that may be useful from these metrics (across all etcd members):
-
sum(rate(etcd_http_failed_total{job="etcd"}[1m]) by (method) / sum(rate(etcd_http_events_received_total{job="etcd"})[1m]) by (method)Shows the fraction of events that failed by HTTP method across all members, across a time window of
1m. -
sum(rate(etcd_http_received_total{job="etcd",method="GET})[1m]) by (method)sum(rate(etcd_http_received_total{job="etcd",method~="GET})[1m]) by (method)Shows the rate of successful readonly/write queries across all servers, across a time window of
1m. -
histogram_quantile(0.9, sum(increase(etcd_http_successful_processing_seconds{job="etcd",method="GET"}[5m]) ) by (le))histogram_quantile(0.9, sum(increase(etcd_http_successful_processing_seconds{job="etcd",method!="GET"}[5m]) ) by (le))Show the 0.90-tile latency (in seconds) of read/write (respectively) event handling across all members, with a window of
5m.
snapshot
| Name | Description | Type |
|---|---|---|
| snapshot_save_total_durations_seconds | The total latency distributions of save called by snapshot | Histogram |
Abnormally high snapshot duration (snapshot_save_total_durations_seconds) indicates disk issues and might cause the cluster to be unstable.
rafthttp
| Name | Description | Type | Labels |
|---|---|---|---|
| message_sent_latency_seconds | The latency distributions of messages sent | HistogramVec | sendingType, msgType, remoteID |
| message_sent_failed_total | The total number of failed messages sent | Summary | sendingType, msgType, remoteID |
Abnormally high message duration (message_sent_latency_seconds) indicates network issues and might cause the cluster to be unstable.
An increase in message failures (message_sent_failed_total) indicates more severe network issues and might cause the cluster to be unstable.
Label sendingType is the connection type to send messages. message, msgapp and msgappv2 use HTTP streaming, while pipeline does HTTP request for each message.
Label msgType is the type of raft message. MsgApp is log replication message; MsgSnap is snapshot install message; MsgProp is proposal forward message; the others are used to maintain raft internal status. If you have a large snapshot, you would expect a long msgSnap sending latency. For other types of messages, you would expect low latency, which is comparable to your ping latency if you have enough network bandwidth.
Label remoteID is the member ID of the message destination.
proxy
etcd members operating in proxy mode do not do store operations. They forward all requests to cluster instances.
Tracking the rate of requests coming from a proxy allows one to pin down which machine is performing most reads/writes.
All these metrics are prefixed with etcd_proxy_
| Name | Description | Type |
|---|---|---|
| requests_total | Total number of requests by this proxy instance. . | Counter(method) |
| handled_total | Total number of fully handled requests, with responses from etcd members. | Counter(method) |
| dropped_total | Total number of dropped requests due to forwarding errors to etcd members. | Counter(method,error) |
| handling_duration_seconds | Bucketed handling times by HTTP method, including round trip to member instances. | Histogram(method) |
Example Prometheus queries that may be useful from these metrics (across all etcd servers):
-
sum(rate(etcd_proxy_handled_total{job="etcd"}[1m])) by (method)Rate of requests (by HTTP method) handled by all proxies, across a window of
1m. -
histogram_quantile(0.9, sum(increase(etcd_proxy_events_handling_time_seconds_bucket{job="etcd",method="GET"}[5m])) by (le))histogram_quantile(0.9, sum(increase(etcd_proxy_events_handling_time_seconds_bucket{job="etcd",method!="GET"}[5m])) by (le))Show the 0.90-tile latency (in seconds) of handling of user requests across all proxy machines, with a window of
5m. -
sum(rate(etcd_proxy_dropped_total{job="etcd"}[1m])) by (proxying_error)Number of failed request on the proxy. This should be 0, spikes here indicate connectivity issues to etcd cluster.
prometheus-getting-started [prometheus-naming]: http://prometheus.io/docs/practices/naming/