Express middleware with popular prometheus metrics in one bundle. It's also compatible with koa v1 and v2 (see below).
Internally it uses prom-client. See: https://github.com/siimon/prom-client (^9.0.0)
Included metrics:
up
: normally is just 1http_request_duration_seconds
: http latency histogram labeled withstatus_code
,method
andpath
npm install express-prom-bundle
const promBundle = require("express-prom-bundle");
const app = require("express")();
const metricsMiddleware = promBundle({includeMethod: true});
app.use(metricsMiddleware);
app.use(/* your middleware */);
app.listen(3000);
- call your endpoints
- see your metrics here: http://localhost:3000/metrics
ALERT!
The order in which the routes are registered is important, since only the routes registered after the express-prom-bundle will be measured
You can use this to your advantage to bypass some of the routes. See the example below.
Which labels to include in http_request_duration_seconds
metric:
- includeStatusCode: HTTP status code (200, 400, 404 etc.), default: true
- includeMethod: HTTP method (GET, PUT, ...), default: false
- includePath: URL path (see importent details below), default: false
- customLabels: an object containing extra labels, e.g.
{project_name: 'hello_world'}
. Most useful together with transformLabels callback, otherwise it's better to use native Prometheus relabeling.
Extra transformation callbacks:
- normalizePath:
function(req)
generates path values from expressreq
(see details below) - formatStatusCode:
function(res)
producing final status code from expressres
object, e.g. you can combine200
,201
and204
to just2xx
. - transformLabels:
function(labels, req, res)
transforms the labels object, e.g. setting dynamic values to customLabels
Other options:
- buckets: buckets used for
http_request_duration_seconds
histogram - autoregister: if
/metrics
endpoint should be registered. (Default: true)
Deprecated:
- whitelist, blacklist: array of strings or regexp specifying which metrics to include/exclude (there are only 2 metrics)
- excludeRoutes: array of strings or regexp specifying which routes should be skipped for
http_request_duration_seconds
metric. It usesreq.originalUrl
as subject when checking. You want to use express or meddleware features instead of this option. - httpDurationMetricName: name of the request duration histogram metric. (Default:
http_request_duration_seconds
)
Let's say you want to have latency statistics by URL path,
e.g. separate metrics for /my-app/user/
, /products/by-category
etc.
Just taking req.path
as a label value won't work as IDs are often part of the URL,
like /user/12352/profile
. So what we actually need is a path template.
The module tries to figure out what parts of the path are values or IDs,
and what is an actual path. The example mentioned before would be
normalized to /user/#val/profile
and that will become the value for the label.
You can override this magical behavior and define your own function by providing an optional callback using normalizePath option. You can also replace the default normalizePath function globally.
app.use(promBundle(/* options? */));
// let's reuse the existing one and just add some
// functionality on top
const originalNormalize = promBunle.normalizePath;
promBunle.normalizePath = (req, opts) => {
const path = originalNormalize(req, opts);
// count all docs (no matter which file) as a single path
return path.match(/^\/docs/) ? '/docs/*' : path;
};
For more details:
- url-value-parser - magic behind automatic path normalization
- normalizePath.js - source code for path processing
setup std. metrics but exclude up
-metric:
const express = require("express");
const app = express();
const promBundle = require("express-prom-bundle");
// calls to this route will not appear in metrics
// because it's applied before promBundle
app.get("/status", (req, res) => res.send("i am healthy"));
// register metrics collection for all routes
// ... except those starting with /foo
app.use("/((?!foo))*", promBundle({includePath: true}));
// this call will NOT appear in metrics,
// because express will skip the metrics middleware
app.get("/foo", (req, res) => res.send("bar"));
// calls to this route will appear in metrics
app.get("/hello", (req, res) => res.send("ok"));
app.listen(3000);
See an advanced example on github
const promBundle = require("express-prom-bundle");
const Koa = require("koa");
const c2k = require("koa-connect");
const metricsMiddleware = promBundle({/* options */ });
const app = new Koa();
app.use(c2k(metricsMiddleware));
app.use(/* your middleware */);
app.listen(3000);
Here is meddleware config sample, which can be used in a standard kraken.js application:
{
"middleware": {
"expressPromBundle": {
"route": "/((?!status|favicon.ico|robots.txt))*",
"priority": 0,
"module": {
"name": "express-prom-bundle",
"arguments": [
{
"includeMethod": true,
"buckets": [0.1, 1, 5]
}
]
}
}
}
}
-
3.2.0
- added options customLabels, transformLabels
- upgrade prom-client to 10.1.0
-
3.1.0
- upgrade prom-client to 10.0.0
-
3.0.0
- upgrade dependencies, most notably prom-client to 9.0.0
- switch to koa v2 in koa unittest
- only node v6 or higher is supported (stop supporting node v4 and v5)
- switch to npm5 and use package-lock.json
- options added: includeStatusCode, formatStatusCode
-
2.1.0
- deprecate excludeRoutes, use req.originalUrl instead of req.path
-
2.0.0
- the reason for the version lift were:
- compliance to official naming recommendation: https://prometheus.io/docs/practices/naming/
- stopping promotion of an anti-pattern - see https://groups.google.com/d/msg/prometheus-developers/XjlOnDCK9qc/ovKzV3AIBwAJ
- dealing with prom-client being a singleton with a built-in registry
- main histogram metric renamed from
http_request_seconds
tohttp_request_duration_seconds
- options removed: prefix, keepDefaultMetrics
- factory removed (as the only reason of it was adding the prefix)
- upgrade prom-client to 6.3.0
- code style changed to the one closer to express
- the reason for the version lift were:
-
1.2.1
- upgrade prom-client to 6.1.2
- add options: includeMethod, includePath, keepDefaultMetrics
MIT