Parsing JSON-structured Docker logs with the OpenTelemetry Collector

We deploy our Rails apps with Kamal , which runs them as Docker containers. Alongside the Prometheus metrics collection we set up earlier, we run the OpenTelemetry Collector on each host to ship logs to Loki . Our Rails apps emit one JSON object per request to stdout: controller, status code, duration and the full Rails log output, all in a single line. Docker’s json-file logging driver then wraps each of those lines in another layer of JSON. Here’s how we use the collector’s filelog receiver...