Database Reference
In-Depth Information
Cassandra log
Last, but not least, Cassandra log is a good tool for monitoring what is going on inside Cas-
sandra. However, monitoring the log file is an extremely non-scalable option. Therefore, if
you are starting with fewer than five Cassandra machines, you may consider occasionally
looking into their log files. The most common use of the Cassandra log is to perform the
postmortem for a failure when you do not have any other monitoring and reporting mech-
anism in place.
The location of the log4j log can be found from Cassandra's
conf/log4j-serv-
er.properties
file:
# This has been altered during installation
log4j.appender.R.File=/mnt/cassandra-logs/system.log
As long as you view this file filled with lines, starting with
INFO
, you may think the sys-
tem has been behaving alright. Lines with
WARN
may or may not be interesting.
For example, it is ok to have some
WARN
messages in the system, as follows:
INFO [MemoryMeter:1] 2013-05-24 12:31:39,099 Memtable.java
(line 213) CFS(Keyspace='Keyspace1',
ColumnFamily='Standard1') liveRatio is 1.0 (just-counted was
1.0).calculation took 3ms for 325 columns
WARN [MemoryMeter:1] 2013-05-24 12:31:39,135 Memtable.java
(line 197) setting live ratio to minimum of 1.0 instead of
0.8662032831217121
However, some warnings, as shown in the following lines, may be a definite sign of danger
and should be fixed to avoid a catastrophe (it may not be a big deal if you have RF and CL
set properly):
# May be a future crash due to lack of disk space
WARN [CompactionExecutor:45] 2013-05-24 17:34:03,709
CompactionTask.java (line 82) insufficient space to compact
all requested files SSTableReader(path='/mnt/cassandra- data/
data/Keyspace1/Standard1/Keyspace1-Standard1-hf-34-
Data.db'), SSTableReader(path='/mnt/cassandra- data/data/
Keyspace1/Standard1/Keyspace1-Standard1-hf-35- Data.db'),
