[jira] [Created] (NIFI-14977) NiFi 2.4 Fails to Start Due to Bitbucket Flow Registry Client – “Too Many Concurrent Streams” Errors

["Pete Vlad (Jira)" <ji...@apache.org>]

Pete Vlad created NIFI-14977:
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             Summary: 	NiFi 2.4 Fails to Start Due to Bitbucket Flow Registry Client – “Too Many Concurrent Streams” Errors
                 Key: NIFI-14977
                 URL: https://issues.apache.org/jira/browse/NIFI-14977
             Project: Apache NiFi
          Issue Type: Bug
          Components: Flow Versioning, NiFi API
    Affects Versions: 2.4.0
         Environment: Kubernetes, NiFiKop helm chart
            Reporter: Pete Vlad


We are running *Apache NiFi 2.4* (NifiKop Helm chart) in a clustered environment.
When NiFi attempts to start up and synchronize with {*}Bitbucket Cloud Registry Client{*}, the application fails to fully initialize.
 * We have:

 ** *72 process groups* under version control (Bitbucket Cloud registry).

 ** nifi.web.jetty.threads=30 (max web threads).

 ** nifi-atlassian-nar-2.5.0-SNAPSHOT.nar
We are observing inconsistent startup behavior:

 ** In some cases, NiFi {*}starts successfully{*}, but the logs contain repeated errors:
*java.io.IOException: too many concurrent streams* (from the JDK HTTP/2 client used by the Bitbucket registry integration).
Even though these errors appear, the cluster eventually loads, and the UI becomes available.

 ** In other cases, NiFi {*}fails to start entirely{*}. It gets stuck ( The UI is visible for a few minutes but then it appear like an empty canvas where you cannot change or create anything)  at the following log entry and does not progress further:

2025-09-04 13:57:41,246 INFO [Framework Task Thread-27] o.a.n.a.b.BitbucketFlowRegistryClient BitbucketFlowRegistryClient[id=XXXXXX] Initializing repository client

When this occurs, the Controller Settings → Registry Clients page cannot load, and NiFi remains blocked.



If we disable the Bitbucket registry (by modifying the registry client URL so it cannot connect), NiFi starts consistently without issue.



We need guidance on:
 # Whether this is a {*}known issue in NiFi 2.4’s Bitbucket Flow Registry Client{*}.

 # Whether there is a *configuration option* to force HTTP/1.1 or limit HTTP/2 concurrency for registry communications. (Not sure if this is the case)

 # Whether there is a *supported workaround* to prevent registry client initialization from blocking NiFi startup when many versioned process groups are present.

h3. *Logs when NiFi Starts Successfully (but with Errors)*

Example log with *“too many concurrent streams”* during startup:
at org.apache.nifi.web.client.StandardWebClientService$StandardHttpRequestBodySpec.getResponse(StandardWebClientService.java:366)
	at org.apache.nifi.web.client.StandardWebClientService$StandardHttpRequestBodySpec.retrieve(StandardWebClientService.java:349)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at org.apache.nifi.controller.service.StandardControllerServiceInvocationHandler.invoke(StandardControllerServiceInvocationHandler.java:251)
	at org.apache.nifi.controller.service.StandardControllerServiceInvocationHandler$ProxiedReturnObjectInvocationHandler.invoke(StandardControllerServiceInvocationHandler.java:237)
	at jdk.proxy26/jdk.proxy26.$Proxy234.retrieve(Unknown Source)
	at org.apache.nifi.atlassian.bitbucket.BitbucketRepositoryClient.getPagedResponseValues(BitbucketRepositoryClient.java:373)
	at org.apache.nifi.atlassian.bitbucket.BitbucketRepositoryClient.getListCommits(BitbucketRepositoryClient.java:362)
	at org.apache.nifi.atlassian.bitbucket.BitbucketRepositoryClient.getLatestCommit(BitbucketRepositoryClient.java:403)
	at org.apache.nifi.atlassian.bitbucket.BitbucketRepositoryClient.getContentFromBranch(BitbucketRepositoryClient.java:244)
	at org.apache.nifi.registry.flow.git.AbstractGitFlowRegistryClient.getSnapshot(AbstractGitFlowRegistryClient.java:491)
	at org.apache.nifi.registry.flow.git.AbstractGitFlowRegistryClient.getFlow(AbstractGitFlowRegistryClient.java:279)
	at org.apache.nifi.registry.flow.StandardFlowRegistryClientNode.lambda$getFlow$6(StandardFlowRegistryClientNode.java:231)
	at org.apache.nifi.registry.flow.StandardFlowRegistryClientNode.execute(StandardFlowRegistryClientNode.java:314)
	at org.apache.nifi.registry.flow.StandardFlowRegistryClientNode.getFlow(StandardFlowRegistryClientNode.java:231)
	at org.apache.nifi.groups.StandardProcessGroup.synchronizeWithFlowRegistry(StandardProcessGroup.java:3769)
	at org.apache.nifi.groups.StandardProcessGroup.lambda$setVersionControlInformation$27(StandardProcessGroup.java:3575)
	at org.apache.nifi.controller.scheduling.StandardProcessScheduler.lambda$wrapTask$1(StandardProcessScheduler.java:177)
	at java.base/java.lang.VirtualThread.run(VirtualThread.java:329)
Caused by: java.io.IOException: too many concurrent streams
	at java.net.http/jdk.internal.net.http.HttpClientImpl.send(HttpClientImpl.java:967)
	at java.net.http/jdk.internal.net.http.HttpClientFacade.send(HttpClientFacade.java:133)
	at org.apache.nifi.web.client.StandardWebClientService$StandardHttpRequestBodySpec.getResponse(StandardWebClientService.java:364)
	... 19 common frames omitted
Caused by: java.io.IOException: too many concurrent streams
	at java.net.http/jdk.internal.net.http.Http2Connection.reserveStream0(Http2Connection.java:616)
	at java.net.http/jdk.internal.net.http.Http2Connection.reserveStream(Http2Connection.java:583)
	at java.net.http/jdk.internal.net.http.Http2ClientImpl.getConnectionFor(Http2ClientImpl.java:109)
	at java.net.http/jdk.internal.net.http.ExchangeImpl.get(ExchangeImpl.java:94)
	at java.net.http/jdk.internal.net.http.Exchange.establishExchange(Exchange.java:391)
	at java.net.http/jdk.internal.net.http.Exchange.responseAsyncImpl0(Exchange.java:584)
	at java.net.http/jdk.internal.net.http.Exchange.responseAsyncImpl(Exchange.java:428)
	at java.net.http/jdk.internal.net.http.Exchange.responseAsync(Exchange.java:420)
	at java.net.http/jdk.internal.net.http.MultiExchange.responseAsyncImpl(MultiExchange.java:414)
	at java.net.http/jdk.internal.net.http.MultiExchange.lambda$responseAsync0$2(MultiExchange.java:347)
	at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1150)
	at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510)
	at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1773)
	at java.net.http/jdk.internal.net.http.HttpClientImpl$DelegatingExecutor.execute(HttpClientImpl.java:177)
	at java.base/java.util.concurrent.CompletableFuture.completeAsync(CompletableFuture.java:2719)
	at java.net.http/jdk.internal.net.http.MultiExchange.responseAsync(MultiExchange.java:300)
	at java.net.http/jdk.internal.net.http.HttpClientImpl.sendAsync(HttpClientImpl.java:1050)
	at java.net.http/jdk.internal.net.http.HttpClientImpl.send(HttpClientImpl.java:931)
	... 21 common frames omitted​ What worked was creating a {{StandardWebClientProvider}} for each Bitbucket registry. However, I’m now running into the same issue again: when too many calls are made too quickly to the NiFi API, I hit the *“too many concurrent streams”* error. This causes the UI to become unusable and displays the following error:



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