http-metrics-middleware
v2.1.6
Published
Express middleware for adding common prometheus metrics
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http-metrics-middleware
Express middleware with useful prometheus metrics.
This wraps prom-client, and adds some default metrics.
Note: As of v1.2.0, this module requires Node.js v10 or above.
Contributing
Contributions are welcome and encouraged! Please follow the instructions in CONTRIBUTING.md.
Usage
Simplest usage is:
const MetricsMiddleware = require('http-metrics-middleware')
const express = require('express')
var metrics = new MetricsMiddleware()
app.use(metrics.initRoutes())
With koa
using koa-connect
:
const MetricsMiddleware = require('http-metrics-middleware')
const c2k = require('koa-connect')
var metrics = new MetricsMiddleware()
app.use(c2k(metrics.initRoutes()))
Options
The middleware can be configured by providing an options
object to the
constructor.
| option | default | info |
|--------|---------|------|
| metricsPath
| /metrics
| the metrics exposed path |
| timeBuckets
| [ 0.01, 0.1, 0.5, 1, 5 ]
| the buckets to assign to duration histogram (in seconds) |
| quantileBuckets
| [ 0.1, 0.5, 0.95, 0.99 ]
| the quantiles to assign to duration summary (0.0 - 1.0) |
| quantileMaxAge
| 600
| configures sliding time window for summary (in seconds) |
| quantileAgeBuckets
| 5
| configures number of sliding time window buckets for summary |
| includeError
| false
| whether or not to include presence of an unhandled error as a label |
| includePath
| true
| whether or not to include normalized URL path as a metric label - see about includePath
below |
| normalizePath
| | a function(req)
- generates path values from the express req
object |
| paramIgnores
| []
| array of path parameters not to replace. Use with caution as this may cause high label cardinality. |
| formatStatusCode
| (res) => res.status_code \|\| res.statusCode
| a function(res)
- generates path values from the express res
object |
| enableDurationHistogram
| true
| whether to enable the request duration histogram |
| enableDurationSummary
| true
| whether to enable the request duration summary |
| durationHistogramName
| http_request_duration_seconds
| the name of the duration histogram metric - must be unique |
| durationSummaryName
| http_request_duration_quantile_seconds
| the name of duration summary metric - must be unique |
about includePath
While it can be useful to know which endpoints are being exercised, including
the path
label can cause an explosion in tracked metrics from your service
when the malicious or poorly-configured clients send strange URLs.
For this reason, it is recommended that you set includePath
to false
, unless
your route parameters are restricted to include only desired values.
Paths are never included on requests which were not handled by a route
with an explicit path (i.e. app.use
where the first argument is a callback).
For example:
// here, the path label will be tracked if `includePath` is enabled
// BUT don't do this - restrict the param with a regex like the next example
app.get('/api/v1/:resource/*', (req, res) => {
res.send('foo')
})
// this is better, as the resource param only matches a certain pattern
app.get('/api/v1/:resource([a-z]+)/*', (req, res) => {
res.send('foo')
})
// here, the path label will never be tracked
app.use((req, res) => {
res.send('foo')
})
Defining custom metrics
The underlying prom-client
module is available for specifying your own custom metrics:
const promClient = require('http-metrics-middleware').promClient
var myHistogram = new promClient.Histogram({
name: 'foo_duration_seconds',
help: 'track the duration of foo',
labelNames: [ 'bar', 'baz' ],
buckets: [1, 2, 3, 4, 5]
})
Metrics
In additional to the default metrics provided by prom-client, this module adds:
http_request_duration_seconds
- (optional, enabled by default) http latency histogram labeled withstatus_code
,method
,path
, anderror
(disabled by default - enable withincludeError
option)- use the
enableDurationHistogram
boolean property to control whether or not this is enabled - use the
durationHistogramName
property to give this metric a different name (required if you want both the histogram and summary)
- use the
http_request_duration_seconds
- (optional, disabled by default) http latency summary labeled withstatus_code
,method
,path
, anderror
(disabled by default - enable withincludeError
option)- use the
enableDurationSummary
boolean property to control whether or not this is enabled - use the
durationSummaryName
property to give this metric a different name (required if you want both the histogram and summary)
- use the
*_build_info
- build information about the service (initialized withinitBuildInfo
function)const MetricsMiddleware = require('http-metrics-middleware') var metrics = new MetricsMiddleware() var ns = 'myservice' var version = '1.2.3' var revision = 'abcd1234' var buildTime = '2017-07-07T07:07:07.007Z' metrics.initBuildInfo(ns, version, revision, buildTime)
Sample output
http_request_duration_seconds_bucket{le="0.05",status_code="200",path="/",method="GET"} 5
http_request_duration_seconds_bucket{le="0.1",status_code="200",path="/",method="GET"} 7
http_request_duration_seconds_bucket{le="0.5",status_code="200",path="/",method="GET"} 10
http_request_duration_seconds_bucket{le="1",status_code="200",path="/",method="GET"} 13
http_request_duration_seconds_bucket{le="+Inf",status_code="200",path="/",method="GET"} 15
http_request_duration_seconds_count{status_code="200",path="/",method="GET"} 15
http_request_duration_seconds_sum{status_code="200",path="/",method="GET"} 18.534