Introducing Warm Agents, a TeamCity Plugin

Summary

The Warm Agents plugin for TeamCity reduces build queue time by maintaining a target number of idle, pre-started cloud agents, addressing the delay when builds wait for a starting agent. When idle agents drop below the target, TeamCity automatically provisions a new instance from the cloud image, ensuring builds start immediately; instances start in batches with short delays. The plugin works with any cloud provider TeamCity supports, requires TeamCity 2024.12.3 or later, and respects the cloud image’s hard limit on total running agents. Administrators configure warm agents via REST API calls, setting a target count per cloud image, and can schedule target changes using build triggers to scale down overnight and restore in the morning. The plugin trades cost for latency, as each idle agent consumes a build license and cloud instance cost, and exposes utilization and saturation metrics in Prometheus format.

Takeaways

1. 1

   The Warm Agents plugin reduces build queue time by keeping a target number of idle agents pre-started, so builds start immediately without waiting for instance spin-up.

2. 2

   Each idle warm agent consumes a build agent license and incurs cloud instance cost, trading cost for latency; administrators must budget for this.

3. 3

   The plugin exposes utilization and saturation metrics per cloud image in Prometheus format, and supports scheduling target changes via build triggers to scale down overnight.

FAQ