Merge pull request #143 from rust-lang/docs-document-fastly-exporter

docs: document fastly-exporter

service-catalog/fastly/README.md

@@ -3,9 +3,21 @@
 [Fastly] is a [Content Delivery Network] (CDN) that caches content and makes it
 available closer to the user.
 
+## Fastly Exporter
+
+[terraform/fastly-exporter] deploys the fastly-exporter, which makes the [Fastly Real-time analytics](https://www.fastly.com/documentation/reference/api/metrics-stats/realtime/) data available to Prometheus.
+
+### Versions
+
+These are the versions we need to keep up-to-date:
+
+- Docker version of `ghcr.io/fastly/fastly-exporter`
+- Terraform providers
+
 ## How-to Guides
 
 - [How to test cache invalidations](./how-to-test-cache-invalidations.md)
 
 [content delivery network]: https://en.wikipedia.org/wiki/Content_delivery_network
 [fastly]: https://www.fastly.com/
+[terraform/fastly-exporter]: https://github.com/rust-lang/simpleinfra/tree/master/terraform/fastly-exporter