Update DIAGNOSTICS.md
Philip O'Toole
2 years ago
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# Monitoring rqlite
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## Status API
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A status API exists, which returns extensive diagnostic and statistical information, as well as basic information about the underlying Raft subsystem. Assuming the rqlite node is started with default settings, node status is available via a HTTP `GET` request. To see the raw data, you can issue a `curl` command like so:
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```bash
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curl localhost:4001/status?pretty
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```
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The use of the URL param `pretty` is optional, and results in pretty-printed JSON responses.
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You can also request the same status information via the CLI:
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```
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$ ./rqlite
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Welcome to the rqlite CLI. Enter ".help" for usage hints.
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127.0.0.1:4001> .status
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build:
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build_time: unknown
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commit: unknown
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version: 5
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branch: unknown
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http:
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addr: 127.0.0.1:4001
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auth: disabled
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redirect:
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node:
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start_time: 2019-12-23T22:34:46.215507011-05:00
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uptime: 16.963009139s
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runtime:
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num_goroutine: 9
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version: go1.13
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```
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## Nodes API
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The _nodes_ API returns basic information for nodes in the cluster, as seen by the node receiving the _nodes_ request. The receiving node will also check whether it can actually connect to all other nodes in the cluster. This is an effective way to determine the cluster leader, and the leader's HTTP API address. It can also be used to check if the cluster is **basically** running -- if the other nodes are reachable, it probably is.
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By default, the node only checks if _voting_ nodes are contactable.
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```bash
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curl localhost:4001/nodes?pretty
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curl localhost:4001/nodes?nonvoters&pretty # Also check non-voting nodes.
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curl localhost:4001/nodes?timeout=5s # Give up if all nodes don't respond within 5 seconds. Default is 30 seconds.
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```
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You can also request the same nodes information via the CLI:
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```
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$ ./rqlite
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Welcome to the rqlite CLI. Enter ".help" for usage hints.
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127.0.0.1:4001> .nodes
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1:
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api_addr: http://localhost:4001
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addr: 127.0.0.1:4002
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reachable: true
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leader: true
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2:
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api_addr: http://localhost:4003
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addr: 127.0.0.1:4004
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reachable: true
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leader: false
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3:
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api_addr: http://localhost:4005
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addr: 127.0.0.1:4006
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reachable: true
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leader: false
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```
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## Readiness checks
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rqlite nodes serve a "ready" status at `/readyz`. The endpoint will return `HTTP 200 OK` if the node is ready to respond to database requests and cluster management operations. An example access is shown below.
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```bash
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$ curl localhost:4001/readyz
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[+]node ok
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[+]leader ok
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```
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Note that a subsequent request to the cluster may still fail even if `/readyz` returns `HTTP 200 OK`. This is because there is a window of time (determined by the Raft-related timings configured at start-up) when a node may still be able to contact the Leader, but the Leader has not yet detected that the cluster cannot reach consensus due to failed Followers. This window of time is quite small (less than 1 second) by default, however.
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If you wish to check if the node is running, and responding to HTTP requests, regardless of Leader status, add `noleader` to the URL. This form may be more useful for automated deployments, which simply need to know if the node is responsive.
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```bash
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$ curl localhost:4001/readyz?noleader
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[+]node ok
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```
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## expvar support
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rqlite also exports [expvar](https://pkg.go.dev/expvar) information, which are mostly counters of various rqlite activity. The standard expvar information, as well as some custom information, is exposed. This data can be retrieved like so (assuming the node is started in its default configuration):
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```bash
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curl localhost:4001/debug/vars
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```
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You can optionally set the query parmameter `key` if you wish to retrieve just a subsection of the expvar output e.g. the URL `localhost:4001/debug/vars?key=http` will return just HTTP information.
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You can also request the same expvar information via the CLI:
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```
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$ rqlite
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127.0.0.1:4001> .expvar
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cmdline: [./rqlited data]
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db:
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execute_transactions: 0
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execution_errors: 1
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executions: 1
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queries: 0
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query_transactions: 0
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http:
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backups: 0
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executions: 0
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queries: 0
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memstats:
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Mallocs: 8950
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HeapSys: 2.588672e+06
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StackInuse: 557056
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LastGC: 0...
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```
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## pprof support
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[pprof](https://golang.org/pkg/net/http/pprof/) information is available by default and can be accessed as follows:
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```bash
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curl localhost:4001/debug/pprof/cmdline
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curl localhost:4001/debug/pprof/profile
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curl localhost:4001/debug/pprof/symbol
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```
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Check out the [monitoring guide](https://rqlite.io/docs/guides/monitoring-rqlite/).
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