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ApacheHttp2Transport connection did not return to the pool when it is failed

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#1,134 1 comment 0 reactions 1 assignee View on GitHub

@jonathanedey is already working on this.

Since Oct 1, 2025.

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Description

Firebase Admin Java SDK v9.6.0

FirebaseOptions.Builder builder = FirebaseOptions.builder()
...
.setHttpTransport(new ApacheHttp2Transport(httpClient));

ApiFuture<BatchResponse> futures = firebaseMessaging.sendEachAsync(messages, dryRun);
BatchResponse response;
try {
      response = futures.get(TIME_OUT_MS, TimeUnit.MILLISECONDS);
 } catch (TimeoutException e) {
   ...
}

final PoolStats total = poolingAsyncClientConnectionManager.getTotalStats();
return String.format("Available=%d, leased=%d, pending=%d, max=%d",
                total.getAvailable(),
                total.getLeased(),
                total.getPending(),
                total.getMax());

Observation:
Under very busy network, FCM backend may return Unknown error while making a remote service call: Write Timeout or other errors.

Log writing (successful or failed response) become slow and slower. Afterward, all pending requests were timed out at response = futures.get(TIME_OUT_MS, TimeUnit.MILLISECONDS);

When the program just started:
Available=95, leased=5, pending=0, max=200

After some times:
Available=0, leased=0, pending=0, max=200

Update:

When using Google APIs Transports:
There is disconnect implementation in google-http-java-client

However, when using ApacheHttp2Transport:
There is no such implementation in ApacheHttp2Response
when it is disconnected, no matter the response is successfully or failed.

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