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Pool deadlock: all resources allocated crash #4528

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Pool deadlock: all resources allocated crash #4528

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4d74d51
fix: increase HTTP pool size and timeout to prevent pool deadlock crash
aaravgarg Feb 1, 2026
1e54595
fix: align maxConnectionsPerHost with pool size (20)
aaravgarg Feb 2, 2026
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4 changes: 2 additions & 2 deletions app/lib/backend/http/http_pool_manager.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -16,11 +16,11 @@ class HttpPoolManager {

HttpPoolManager._() {
final httpClient = HttpClient()
..maxConnectionsPerHost = 15
..maxConnectionsPerHost = 20
..idleTimeout = const Duration(seconds: 15);

_client = IOClient(httpClient);
_pool = Pool(10, timeout: const Duration(seconds: 60));
_pool = Pool(20, timeout: const Duration(seconds: 120));
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high

While increasing the pool size is a good step towards mitigating the deadlock, there's a configuration mismatch that could lead to subtle issues.

The Pool size is being increased to 20, but the underlying HttpClient is still configured with maxConnectionsPerHost = 15 (on line 19). If all concurrent requests from the pool target the same host, the HttpClient will become the bottleneck, queuing any requests beyond the 15th. This makes the Pool's limit of 20 misleading and can complicate debugging.

For more predictable performance and clearer control over concurrency, these two limits should be aligned. I suggest setting the pool size to 15 to match maxConnectionsPerHost. This still provides a 50% increase in concurrency over the original value of 10.

If a concurrency of 20 is a hard requirement, please consider also increasing maxConnectionsPerHost to 20 in a subsequent change.

Suggested change
_pool = Pool(20, timeout: const Duration(seconds: 120));
_pool = Pool(15, timeout: const Duration(seconds: 120));

}

Future<http.Response> send(
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