Triage and Fix with Confidence: heroku run and OTel on Heroku Fir

Summary

Heroku Fir addresses production troubleshooting when a release causes failures, such as a background worker breaking after a database schema change, without requiring access to a live formation dyno. Its interactive heroku run command launches a dedicated one-off dyno with the application code and environment variables, relaying terminal input and output for tasks such as rake db:migrate; using it requires a public SSH key and a deployed application. The platform’s native OpenTelemetry (OTel) signals add router request-duration summaries and percentiles, represent heroku.router.connect and heroku.router.service as floats, and attach heroku.app.name to application signals. Together with service.name filtering for first-party services, these capabilities support identifying affected applications, applying isolated fixes, and verifying latency and errors through an observability platform.

Takeaways

1. 1

   heroku run provides an interactive session on a dedicated one-off dyno, separate from formation dynos; Fir requires a public SSH key and a deployed application.

2. 2

   Heroku router telemetry includes request-duration summary statistics and percentiles, including http.server.request.duration.p0-999 for the 99th percentile.

3. 3

   The heroku.app.name attribute is added to application logs, metrics, and traces, while service.name enables filtering signals from services such as Heroku Postgres and Heroku Kafka.