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https://issues.apache.org/jira/browse/KAFKA-6415?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16310133#comment-16310133
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ASF GitHub Bot commented on KAFKA-6415:
---------------------------------------
rajinisivaram closed pull request #4375: KAFKA-6415: Use WARN log level for
Metadata in system test
URL: https://github.com/apache/kafka/pull/4375
This is a PR merged from a forked repository.
As GitHub hides the original diff on merge, it is displayed below for
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diff --git
a/tools/src/main/java/org/apache/kafka/tools/VerifiableLog4jAppender.java
b/tools/src/main/java/org/apache/kafka/tools/VerifiableLog4jAppender.java
index 4dd7bee9791..9533f6e58aa 100644
--- a/tools/src/main/java/org/apache/kafka/tools/VerifiableLog4jAppender.java
+++ b/tools/src/main/java/org/apache/kafka/tools/VerifiableLog4jAppender.java
@@ -204,6 +204,9 @@ public static VerifiableLog4jAppender
createFromArgs(String[] args) {
props.setProperty("log4j.appender.KAFKA.kerb5ConfPath",
res.getString("kerb5ConfPath"));
}
props.setProperty("log4j.logger.kafka.log4j", "INFO, KAFKA");
+ // Changing log level from INFO to WARN as a temporary workaround
for KAFKA-6415. This is to
+ // avoid deadlock in system tests when producer network thread
appends to log while updating metadata.
+
props.setProperty("log4j.logger.org.apache.kafka.clients.Metadata", "WARN,
KAFKA");
if (configFile != null) {
try {
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> KafkaLog4jAppender deadlocks when logging from producer network thread
> ----------------------------------------------------------------------
>
> Key: KAFKA-6415
> URL: https://issues.apache.org/jira/browse/KAFKA-6415
> Project: Kafka
> Issue Type: Bug
> Components: log
> Reporter: Rajini Sivaram
> Assignee: Rajini Sivaram
> Fix For: 1.1.0
>
>
> When a log entry is appended to a Kafka topic using KafkaLog4jAppender, the
> producer.send operation may block waiting for metadata. This can result in
> deadlocks in a couple of scenarios if a log entry from the producer network
> thread is also at a log level that results in the entry being appended to a
> Kafka topic.
> 1. Producer's network thread will attempt to send data to a Kafka topic and
> this is unsafe since producer.send may block waiting for metadata, causing a
> deadlock since the thread will not process the metadata request/response.
> 2. KafkaLog4jAppender#append is invoked while holding the lock of the logger.
> So the thread waiting for metadata in the initial send will be holding the
> logger lock. If the producer network thread has.a log entry that needs to be
> appended, it will attempt to acquire the logger lock and deadlock.
> This was probably the case right from the beginning when KafkaLog4jAppender
> was introduced, but did not cause any issues so far since there were only
> debug log entries in that path which were not logged to a Kafka topic by any
> of the tests. A recent info level log entry introduced by the commit
> https://github.com/apache/kafka/commit/a3aea3cf4dbedb293f2d7859e0298bebc8e2185f
> is causing system test failures in log4j_appender_test.py due to the
> deadlock.
> The asynchronous append case can be fixed by moving all send operations to a
> separate thread. But KafkaLog4jAppender also has a syncSend option which
> blocks append while holding the logger lock until the send completes. Not
> sure how this can be fixed if we want to support log appends from the
> producer network thread.
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