overleaf/metrics-module
=======================

Wrappers the [prom-client](https://github.com/siimon/prom-client) npm module to provide [Prometheus](https://prometheus.io/) metrics at `/metrics`.

Use:
```
const metrics = require('@overleaf/metrics')
metrics.initialize('myapp')

const express = require('express')
const app = express()
metrics.injectMetricsRoute(app)
```
Request logging can be enabled:
```
const logger = require('logger-sharelatex')
...
app.use(metrics.http.monitor(logger))
```

The metrics module can be configured through the following environment variables:

* `DEBUG_METRICS` - enables display of debugging messages to the console.
* `ENABLE_TRACE_AGENT` - enables @google-cloud/trace-agent on Google Cloud
* `ENABLE_DEBUG_AGENT` - enables @google-cloud/debug-agent on Google Cloud
* `ENABLE_PROFILE_AGENT` - enables @google-cloud/profiler on Google Cloud
* `METRICS_COMPRESSION_LEVEL` - sets the [compression level](https://www.npmjs.com/package/compression#level) for `/metrics`
* `STACKDRIVER_LOGGING` - toggles the request logging format
* `UV_THREADPOOL_SIZE` - sets the libuv [thread pool](http://docs.libuv.org/en/v1.x/threadpool.html) size