fix(orchestration): exponential backoff in DagScheduler when concurrency limit hit#1620
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fix(orchestration): exponential backoff in DagScheduler when concurrency limit hit#1620
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…ncy limit hit When all SubAgentManager slots are occupied, DagScheduler::wait_event() was sleeping the fixed deferral_backoff (250ms) and retrying immediately, producing a tight spin that flooded logs with ERROR messages every 250ms. Replace the fixed sleep with exponential backoff: each consecutive ConcurrencyLimit failure doubles the delay (250ms → 500ms → 1s → 2s → 4s), capped at 5 seconds. The counter resets to zero on the first successful spawn. Adds three regression tests covering backoff growth, counter reset, and counter increment. Closes #1618.
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Summary
DagScheduler::wait_event()was sleeping a fixed 250ms and retrying whenSubAgentManagerwas saturated, causing a tight spin loop that flooded logs withERROR spawn_for_task failed: concurrency limit reachedevery 250msconsecutive_spawn_failures: u32field toDagScheduler; helpercurrent_deferral_backoff()computes the scaled durationTest plan
test_current_deferral_backoff_exponential_growth— verifies doubling per failure, cap at 5stest_record_spawn_resets_consecutive_failures— verifies counter reset on successtest_record_spawn_failure_increments_consecutive_failures— verifies counter increment perConcurrencyLimitfailuretest_wait_event_sleeps_deferral_backoff_when_running_empty— existing regression test still passesCloses #1618.