You are viewing a plain text version of this content. The canonical link for it is here.
Posted to dev@hc.apache.org by "ASF subversion and git services (Jira)" <ji...@apache.org> on 2026/06/15 17:06:00 UTC
[jira] [Commented] (HTTPCORE-774) Race condition causing java.lang.ArithmeticException: Update causes flow control window to exceed 2147483647
[ https://issues.apache.org/jira/browse/HTTPCORE-774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18089202#comment-18089202 ]
ASF subversion and git services commented on HTTPCORE-774:
----------------------------------------------------------
Commit af61c1ea5a852caeece257e7fa8295365db765fa in httpcomponents-core's branch refs/heads/5.4.x from Oleg Kalnichevski
[ https://gitbox.apache.org/repos/asf?p=httpcomponents-core.git;h=af61c1ea5 ]
HTTPCORE-774: fixed a race condition caused by concurrent update of the connection input window to the max value.
(cherry picked from commit d31d0000084d1ffdd37a9596b53e2aa7779451bc)
> Race condition causing java.lang.ArithmeticException: Update causes flow control window to exceed 2147483647
> ------------------------------------------------------------------------------------------------------------
>
> Key: HTTPCORE-774
> URL: https://issues.apache.org/jira/browse/HTTPCORE-774
> Project: HttpComponents HttpCore
> Issue Type: Bug
> Affects Versions: 5.3.1
> Reporter: Mark Slater
> Priority: Critical
> Fix For: 5.3.2, 5.4-alpha1
>
> Attachments: apache-client-flow-control.log, apache-client.log
>
> Time Spent: 2h 20m
> Remaining Estimate: 0h
>
> I’m getting {{java.lang.ArithmeticException: Update causes flow control window to exceed 2147483647}} intermittently when making HTTP/2 requests using HTTP Client 5.3.1 as the engine for the [Ktor HTTP Client 3.0.3|https://github.com/ktorio/ktor/tree/3.0.3]. It occurs in about 10% of requests to some addresses from my desktop.
> I’ve found what seems to be a race condition that appears to be the root cause of the problem in {{[org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer|https://github.com/apache/httpcomponents-core/blob/rel/v5.2.4/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/AbstractH2StreamMultiplexer.java]}} (version 5.2.4 is used by this version of HTTP Client).
> This is the stack trace I get:
> {code:java}
> Caused by: java.lang.ArithmeticException: Update causes flow control window to exceed 2147483647
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer.updateWindow(AbstractH2StreamMultiplexer.java:215)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer.updateInputWindow(AbstractH2StreamMultiplexer.java:225)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer.incrementInputCapacity(AbstractH2StreamMultiplexer.java:385)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer.access$1200(AbstractH2StreamMultiplexer.java:94)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer$H2StreamChannelImpl.update(AbstractH2StreamMultiplexer.java:1448)
> at io.ktor.client.engine.apache5.ApacheResponseConsumer.updateCapacity(ApacheResponseConsumer.kt:131)
> at io.ktor.client.engine.apache5.BasicResponseConsumer.updateCapacity(ApacheResponseConsumer.kt:54)
> at org.apache.hc.client5.http.impl.async.HttpAsyncMainClientExec$1.updateCapacity(HttpAsyncMainClientExec.java:233)
> at org.apache.hc.core5.http2.impl.nio.ClientH2StreamHandler.updateInputCapacity(ClientH2StreamHandler.java:226)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer$H2Stream.produceInputCapacityUpdate(AbstractH2StreamMultiplexer.java:1662)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer.consumeDataFrame(AbstractH2StreamMultiplexer.java:1030)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer.consumeFrame(AbstractH2StreamMultiplexer.java:735)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2StreamMultiplexer.onInput(AbstractH2StreamMultiplexer.java:446)
> at org.apache.hc.core5.http2.impl.nio.AbstractH2IOEventHandler.inputReady(AbstractH2IOEventHandler.java:65)
> at org.apache.hc.core5.http2.impl.nio.ClientH2IOEventHandler.inputReady(ClientH2IOEventHandler.java:39)
> at org.apache.hc.core5.reactor.ssl.SSLIOSession.decryptData(SSLIOSession.java:609)
> at org.apache.hc.core5.reactor.ssl.SSLIOSession.access$200(SSLIOSession.java:74)
> at org.apache.hc.core5.reactor.ssl.SSLIOSession$1.inputReady(SSLIOSession.java:202)
> at org.apache.hc.core5.reactor.InternalDataChannel.onIOEvent(InternalDataChannel.java:142)
> at org.apache.hc.core5.reactor.InternalChannel.handleIOEvent(InternalChannel.java:51)
> ... 5 more
> {code}
> The problem is in the {{[updateWindow|https://github.com/apache/httpcomponents-core/blob/rel/v5.2.4/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/AbstractH2StreamMultiplexer.java#L202]}} method, which attempts to adjust the flow control window by a delta computed previously. The method caters for the window size changing concurrently with the computation and validation of the new size by aborting and retrying conflicted calls. However, it doesn’t cater for the consequences of out-of-order deltas.
> On connect, the size of {{connInputWindow}} is increased by the {{[maximizeConnWindow|https://github.com/apache/httpcomponents-core/blob/rel/v5.2.4/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/AbstractH2StreamMultiplexer.java#L1049]}} method to {{{}Integer.MAX_VALUE{}}}, the largest permitted size. As data is consumed and received, the {{[updateWindow|https://github.com/apache/httpcomponents-core/blob/rel/v5.2.4/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/AbstractH2StreamMultiplexer.java#L202]}} method is called with positive and negative deltas to reflect the changes in available capacity. However, the order in which these updates are applied is not guaranteed. If a negative delta due to the receipt of data is applied after the positive delta due to some of that data being consumed, the window size will be increased beyond {{Integer.MAX_VALUE,}} and {{ArithmeticException}} will be thrown.
> It would be possible to mitigate this somewhat (perhaps entirely) if {{[maximizeConnWindow|https://github.com/apache/httpcomponents-core/blob/rel/v5.2.4/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/AbstractH2StreamMultiplexer.java#L1049]}} could be configured to use a maximum size somewhat less than {{{}Integer.MAX_VALUE{}}}, but I’m not familiar enough with HTTP/2 to know if this would have wider consequences.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@hc.apache.org
For additional commands, e-mail: dev-help@hc.apache.org