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From jun...@apache.org
Subject svn commit: r1357671 - /incubator/kafka/site/faq.html
Date Thu, 05 Jul 2012 15:12:43 GMT
Author: junrao
Date: Thu Jul  5 15:12:43 2012
New Revision: 1357671

URL: http://svn.apache.org/viewvc?rev=1357671&view=rev
Log:
add FAQ for stopped consumer

Modified:
    incubator/kafka/site/faq.html

Modified: incubator/kafka/site/faq.html
URL: http://svn.apache.org/viewvc/incubator/kafka/site/faq.html?rev=1357671&r1=1357670&r2=1357671&view=diff
==============================================================================
--- incubator/kafka/site/faq.html (original)
+++ incubator/kafka/site/faq.html Thu Jul  5 15:12:43 2012
@@ -8,6 +8,21 @@ This typically means that the "fetch siz
 <li> <h3> On EC2, why can't my high-level consumers connect to the brokers? </h3>
 When a broker starts up, it registers its host ip in ZK. The high-level consumer later uses
the registered host ip to establish the socket connection to the broker. By default, the registered
ip is given by InetAddress.getLocalHost.getHostAddress. Typically, this should return the
real ip of the host. However, in EC2, the returned ip is an internal one and can't be connected
to from outside. The solution is to explicitly set the host ip to be registered in ZK by setting
the "hostname" property in server.properties.
 
+<li> <h3> My consumer seems to have stopped, why? </h3>
+First, try to figure out if the consumer has really stopped or is just slow, using our tool
<code>ConsumerOffsetChecker</code>.
+<pre>
+bin/kafka-run-class.sh kafka.tools.ConsumerOffsetChecker --group consumer-group1 --zkconnect
zkhost:zkport --topic topic1
+consumer-group1,topic1,0-0 (Group,Topic,BrokerId-PartitionId)
+            Owner = consumer-group1-consumer1
+  Consumer offset = 70121994703
+                  = 70,121,994,703 (65.31G)
+         Log size = 70122018287
+                  = 70,122,018,287 (65.31G)
+     Consumer lag = 23584
+                  = 23,584 (0.00G)
+</pre>
+If consumer offset is not moving after some time, then consumer is likely to have stopped.
If consumer offset is moving, but consumer lag (difference between the end of the log and
the consumer offset) is increasing, the consumer is slower than the producer. If the consumer
is slow, the typical solution is to increase the degree of parallelism in the consumer. This
may require increasing the number of partitions of a topic. If a consumer has stopped, one
of the typical causes is that the application code that consumes messages somehow died and
therefore killed the consumer thread. We recommend using a try/catch clause to log all <code>Throwable</code>
in the consumer logic.
+
 </ol>
 
-<!--#include virtual="includes/footer.html" -->
\ No newline at end of file
+<!--#include virtual="includes/footer.html" -->



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