Question 1

How to integrate Einhorn with a Go HTTP server?

Accepted Answer

Use the go-einhorn library to handle socket file descriptors from environment variables, or implement manual ACK by sending JSON messages to the command socket as described in the README. Ensure your server binds to the passed descriptors instead of creating new sockets.

Question 2

Einhorn vs Gunicorn for Python apps?

Accepted Answer

Einhorn is language-agnostic and focuses on socket sharing for seamless upgrades, while Gunicorn is Python-specific with built-in HTTP worker management. Choose Einhorn for multi-protocol servers or mixed-language environments, and Gunicorn for pure Python web apps with more HTTP features.

Question 3

Can Einhorn handle database connection pooling across workers?

Accepted Answer

No, Einhorn only manages sockets and processes; each worker must handle its own database connections and pooling. You'll need to implement graceful shutdown logic to avoid connection leaks during upgrades, as Einhorn sends SIGUSR2 but doesn't manage app state.

Question 4

How to monitor Einhorn worker health in production?

Accepted Answer

Einhorn provides basic ACKs but no built-in metrics; use external tools to check process status via PID files or custom health endpoints. The command socket allows manual queries, but for dashboards, you'll need to integrate with systems like Prometheus or logging services.

Question 5

What happens if Einhorn master process crashes?

Accepted Answer

Workers may continue running but lose management; use the -k option with the fiddle gem on Linux to gracefully kill children on exit, but this is limited and not cross-platform, so additional supervision like systemd is recommended for high availability.

Question 6

How to dynamically add or remove workers with Einhorn?

Accepted Answer

Use the command socket via einhornsh to reconfigure worker counts on the fly, but it requires manual intervention. For auto-scaling, you'll need external scripts to trigger commands based on load, as Einhorn doesn't support automatic scaling out of the box.

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