overleaf/libraries/metrics/README.md
Christopher Hoskin 5855ba7b49 Merge pull request #15241 from overleaf/em-gcp-opentelemetry
Replace the GCP trace agent with OpenTelemetry

GitOrigin-RevId: 591410029349e4ef5a39a5b79868e57c7bd089b6
2023-10-19 08:02:52 +00:00

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# 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:
```
// Metrics must be initialized before importing anything else
require('@overleaf/metrics/initialize')
const express = require('express')
const metrics = require('@overleaf/metrics')
const app = express()
metrics.injectMetricsRoute(app)
```
Request logging can be enabled:
```
const logger = require('@overleaf/logger')
...
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.
- `GCP_OPENTELEMETRY` - enables OpenTelemetry tracing for GCP
- `JAEGER_OPENTELEMETRY` - enables OpenTelemetry tracing for Jaeger (in the dev environment)
- `METRICS_APP_NAME` - the app label for metrics and spans
- `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