atelet: close ateom conns evicted from the dialer cache - #1010
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Da Huang (git286) wants to merge 1 commit into
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atelet: close ateom conns evicted from the dialer cache#1010Da Huang (git286) wants to merge 1 commit into
Da Huang (git286) wants to merge 1 commit into
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AteomDialer caches one grpc.ClientConn per worker pod UID in a 256-entry LRU, but the cache had no eviction function: a conn pushed out to make room was forgotten, never closed. grpc does not reclaim an un-Closed conn -- measured against a dead socket, each one holds 4 goroutines, and the channel idle timeout later parks only one of them, so ~3 goroutines and their buffers leak per eviction for the life of the process. Today evictions need >256 distinct worker pods dialed since atelet started, so the leak is a slow drip reset by restarts. The stats poller proposed in agent-substrate#961 would sweep every ateoms/ directory (including the stale ones nothing garbage-collects) through this cache every minute, turning the drip into hundreds of leaked conns per tick on long-lived nodes. Close evicted conns via the cache's eviction hook. The trade is that an RPC still in flight on a conn that aged to the LRU tail now fails visibly instead of completing on a leaked conn; that needs the same >256-pod churn, and the failure is retryable. Fixes agent-substrate#1009.
Da Huang (git286)
requested review from
Benjamin Elder (BenTheElder) and
Julian Gutierrez Oschmann (juli4n)
August 17, 2026 19:33
| func newAteomDialer(size int) *AteomDialer { | ||
| return &AteomDialer{ | ||
| conns: lru.NewWithEvictionFunc(size, func(_ lru.Key, value interface{}) { | ||
| value.(*grpc.ClientConn).Close() |
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A made the same comment in #480 : If we blindly close on eviction, can this close a connection which is already in use?
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Get moves an entry to the front. Every RPC starts with DialAteomPod → Get, so a conn with an RPC in flight was most-recently-used the moment the RPC began. For it to reach the eviction end of the queue mid-RPC, atelet would have to dial 256 other distinct pod UIDs in the window between that RPC starting and finishing, which is extremely unlikely, right?
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IIRC ate-apiserver has the same issue as it also caches connections (to atelet). |
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AteomDialer caches one grpc.ClientConn per worker pod UID in a 256-entry LRU, but the cache had no eviction function: a conn pushed out to make room was forgotten, never closed. grpc does not reclaim an un-Closed conn -- measured against a dead socket, each one holds 4 goroutines, and the channel idle timeout later parks only one of them, so ~3 goroutines and their buffers leak per eviction for the life of the process.
Today evictions need >256 distinct worker pods dialed since atelet started, so the leak is a slow drip reset by restarts. Close evicted conns via the cache's eviction hook. The trade is that an RPC still in flight on a conn that aged to the LRU tail now fails visibly instead of completing on a leaked conn; that needs the same >256-pod churn, and the failure is retryable.
Fixes #1009.