Persistent workers: a configurable pool with an idle sweeper, the action environment, namespaces, measured usage, and a wait at the cap

[amankrx]

What and why

The persistent worker pool had no configuration, no idle reaping, and served an action without its environment, outside the worker's namespaces and with no usage reported. persistent_workers on the worker config now sizes it: max_workers_per_key (default 4), idle_timeout_s (default 300, a sweeper retires a process idle past it), max_requests_per_worker (default 200), shutdown_grace_ms and acquire_timeout_s. The pool key carries the executable, its arguments, the environment and the protocol; the process starts with the worker's additional_environment (the sources that are the same for every action) and the action's own variables on top, as a one-shot action does, a process is spawned in the same namespaces as a one-shot action, its measured usage goes into the result, and an action at the cap waits acquire_timeout_s (default 30) for a returned process before it runs one-shot; that wait is raced against the scheduler's kill and bounded by the action's own timeout, which the dispatch then gets the remainder of. The key's Debug prints environment names, never values, since it is logged and quoted in errors; the CPU reported for a pooled action is the process's spend from the moment sampling began, and its peak memory is documented as a whole-process figure.

How was this verified?

Pool tests: the key tells environments apart and ignores their order, the sweeper retires a worker idle past the timeout, and an acquire at the cap waits for a returned worker. The running actions manager tests build the configuration with the new settings, the persistent workers page and the config reference are updated, and the snippet lint passes.

Risk

PersistentWorkersConfig::default() has the pool on, as the serde default and the docs say. Defaults match what the pool did before, except that the sweeper now retires a process idle for five minutes and an action at the cap waits up to thirty seconds before falling back. A pooled process stays outside soft memory enforcement, as the enforcement docs say.

AI assistance

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Project	Deployment	Actions	Updated
nativelink	Ready	Preview	Sep 30, 2026 3:02am UTC
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