Cassandra usually output all its logs in a system.log file. It uses log4j old 1.2 version for cassandra 2.0, and since 2.1, logback, which of course use different syntax :)

Logs can be enhanced with some configuration. These explanations works with Cassandra 2.0.x and Cassandra 2.1.x, I haven’t tested others versions yet.

I wanted to split logs in different files, depending on their “sources” (repair, compaction, tombstones etc), to ease debugging, while keeping the system.log as usual.

For example, to declare 2 new files to handle, say Repair and Tombstones logs :

Cassandra 2.0 :

You need to declare each new log files in log4j-server.properties file.

[ ...] ## Repair log4j.appender.Repair = org.apache.log4j.RollingFileAppender log4j.appender.Repair.maxFileSize = 20MB log4j.appender.Repair.maxBackupIndex = 50 log4j.appender.Repair.layout = org.apache.log4j.PatternLayout log4j.appender.Repair.layout.ConversionPattern = %5p [ %t] %d { ISO8601 } %F ( line %L ) %m%n ## Edit the next line to point to your logs directory log4j.appender.Repair.File = /var/log/cassandra/repair.log ## Tombstones log4j.appender.Tombstones = org.apache.log4j.RollingFileAppender log4j.appender.Tombstones.maxFileSize = 20MB log4j.appender.Tombstones.maxBackupIndex = 50 log4j.appender.Tombstones.layout = org.apache.log4j.PatternLayout log4j.appender.Tombstones.layout.ConversionPattern = %5p [ %t] %d { ISO8601 } %F ( line %L ) %m%n ### Edit the next line to point to your logs directory log4j.appender.Tombstones.File = /home/log/cassandra/tombstones.log

Cassandra 2.1 :

It is in the logback.xml file.

<appender name= "Repair" class= "ch.qos.logback.core.rolling.RollingFileAppender" > <file> ${cassandra.logdir}/repair.log </file> <rollingPolicy class= "ch.qos.logback.core.rolling.FixedWindowRollingPolicy" > <fileNamePattern> ${cassandra.logdir}/system.log.%i.zip </fileNamePattern> <minIndex> 1 </minIndex> <maxIndex> 20 </maxIndex> </rollingPolicy> <triggeringPolicy class= "ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy" > <maxFileSize> 20MB </maxFileSize> </triggeringPolicy> <encoder> <pattern> %-5level [%thread] %date{ISO8601} %F:%L - %msg%n </pattern> <!-- old-style log format <pattern>%5level [%thread] %date{ISO8601} %F (line %L) %msg%n</pattern> --> </encoder> </appender> <appender name= "Tombstones" class= "ch.qos.logback.core.rolling.RollingFileAppender" > <file> ${cassandra.logdir}/tombstones.log </file> <rollingPolicy class= "ch.qos.logback.core.rolling.FixedWindowRollingPolicy" > <fileNamePattern> ${cassandra.logdir}/tombstones.log.%i.zip </fileNamePattern> <minIndex> 1 </minIndex> <maxIndex> 20 </maxIndex> </rollingPolicy> <triggeringPolicy class= "ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy" > <maxFileSize> 20MB </maxFileSize> </triggeringPolicy> <encoder> <pattern> %-5level [%thread] %date{ISO8601} %F:%L - %msg%n </pattern> <!-- old-style log format <pattern>%5level [%thread] %date{ISO8601} %F (line %L) %msg%n</pattern> --> </encoder> </appender>

Now that theses new files are declared, we need to fill them with logs. To do that, simply redirect some Java class to the good file. To redirect the class org.apache.cassandra.db.filter.SliceQueryFilter, loglevel WARN to the Tombstone file, simply add :

Cassandra 2.0 :

log4j.logger.org.apache.cassandra.db.filter.SliceQueryFilter = WARN,Tombstones

Cassandra 2.1 :

<logger name= "org.apache.cassandra.db.filter.SliceQueryFilter" level= "WARN" > <appender-ref ref= "Tombstones" /> </logger>

It’s a on-the-fly configuration, so no need to restart Cassandra !

Now you will have dedicated files for each kind of logs.

A list of interesting Cassandra classes :

org.apache.cassandra.service.StorageService, WARN : Repair org.apache.cassandra.net.OutboundTcpConnection, DEBUG : Repair ( haha, theses fucking stuck repair ) org.apache.cassandra.repair, INFO : Repair org.apache.cassandra.db.HintedHandOffManager, DEBUG : Repair org.apache.cassandra.streaming.StreamResultFuture, DEBUG : Repair org.apache.cassandra.cql3.statements.BatchStatement, WARN : Statements org.apache.cassandra.db.filter.SliceQueryFilter, WARN : Tombstones

You can find from which java class a log message come from by adding “%c” in log4j/logback “ConversionPattern” :

org.apache.cassandra.db.ColumnFamilyStore INFO [ BatchlogTasks:1] 2015-09-18 16:43:48,261 ColumnFamilyStore.java:939 - Enqueuing flush of batchlog: 226172 ( 0% ) on-heap, 0 ( 0% ) off-heap org.apache.cassandra.db.Memtable INFO [ MemtableFlushWriter:4213] 2015-09-18 16:43:48,262 Memtable.java:347 - Writing Memtable-batchlog@1145616338 ( 195.566KiB serialized bytes, 205 ops, 0%/0% of on/off-heap limit ) org.apache.cassandra.db.Memtable INFO [ MemtableFlushWriter:4213] 2015-09-18 16:43:48,264 Memtable.java:393 - Completed flushing /home/cassandra/data/system/batchlog/system-batchlog-tmp-ka-4267-Data.db ; nothing needed to be retained. Commitlog position was ReplayPosition ( segmentId = 1442331704273, position = 17281204 )

You can disable “additivity” (i.e avoid adding messages in system.log for example) in log4j for a specific class by adding :

log4j.additivity.org.apache.cassandra.db.filter.SliceQueryFilter = false

For logback, you can add additivity=”false” to <logger .../> elements.

To migrate from log4j logs to logback.xml, you can look at http://logback.qos.ch/translator/

Sources :

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