This is an unopinionated middleware that provides http_request_duration_milliseconds
metric for Express apps.
It's mainly derived from morgan and uses prom-client under the hood. I made this middleware while learning how to instrument Express apps with Prometheus metrics.
var promClient = require('prom-client');
var expressPrometheus = require('express-prometheus-request-metrics');
app.configure(function () {
// ...
app.use(expressPrometheus(promClient));
});
app.get('/hello', function (req, res) {
res.send('Hello World!')
});
// This is a special endpoint you need to set up
// to let Prometheus scrape the metrics:
app.get('/metrics', function(req, res) {
res.end(promClient.register.metrics());
});Run your app and query for metrics:
curl http://localhost:3000/metrics
You will get a text response. The http_request_duration_milliseconds metric is preceded by
some default metrics collected
by prom-client.
# HELP process_start_time_seconds Start time of the process since unix epoch in seconds.
# TYPE process_start_time_seconds gauge
process_start_time_seconds 1489022945
# HELP process_open_fds Number of open file descriptors.
# TYPE process_open_fds gauge
process_open_fds 14
# ...
# HELP http_request_duration_milliseconds Request duration in milliseconds.
# TYPE http_request_duration_milliseconds summary
http_request_duration_milliseconds{quantile="0.01",code="200",handler="/hello",method="get"} 114.4
http_request_duration_milliseconds{quantile="0.05",code="200",handler="/hello",method="get"} 143.4
http_request_duration_milliseconds{quantile="0.5",code="200",handler="/hello",method="get"} 174.75
http_request_duration_milliseconds{quantile="0.9",code="200",handler="/hello",method="get"} 267.90
http_request_duration_milliseconds{quantile="0.95",code="200",handler="/hello",method="get"} 298.79
http_request_duration_milliseconds{quantile="0.99",code="200",handler="/hello",method="get"} 728.60
http_request_duration_milliseconds{quantile="0.999",code="200",handler="/hello",method="get"} 763
http_request_duration_milliseconds_sum{method="get",handler="/hello",code="200"} 11444
http_request_duration_milliseconds_count{method="get",handler="/hello",code="200"} 58
npm install --save github:burnash/express-prometheus-request-metrics
Other more feature-rich and refined libraries are: