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Nodetool fails with SocketTimeoutException ‘Read timed out’¶
This troubleshooting article describes what to do when Nodetool fails with a ‘Read timed out’ error.
Problem¶
When running any Nodetool command, users may see the following error:
Failed to connect to '127.0.0.1:7199' - SocketTimeoutException: 'Read timed out'
Analysis¶
Nodetool is a Java based application which requires memory. Scylla by default consumes 93% of the node’s RAM (for MemTables + Cache) and leaves 7% for other applications, such as nodetool.
If cases where this is not enough memory (e.g. small instances with ~64GB RAM or lower), Nodetool may not be able to run due to insufficient memory. In this case an out of memory (OOM) error may appear and scylla-jmx will not run.
Example¶
The error you will see is similar to:
OpenJDK 64-Bit Server VM warning: INFO: os::commit_memory(0x00000005c0000000,
671088640, 0) failed; error='Cannot allocate memory' (err no=12)
In order to check if the issue is scylla-jmx, use the following command (systemd-based Linux distribution) to check the status of the service:
sudo systemctl status scylla-jmx
If the service is running you will see something similar to:
sudo service scylla-jmx status
● scylla-jmx.service - Scylla JMX
Loaded: loaded (/lib/systemd/system/scylla-jmx.service; disabled; vendor preset: enabled)
Active: active (running) since Wed 2018-07-18 20:59:08 UTC; 3s ago
Main PID: 256050 (scylla-jmx)
Tasks: 27
Memory: 119.5M
CPU: 1.959s
CGroup: /system.slice/scylla-jmx.service
└─256050 /usr/lib/scylla/jmx/symlinks/scylla-jmx -Xmx384m -XX:+UseSerialGC -Dcom.sun.management.jmxremote.auth
If it isn’t, you will see an error similar to:
sudo systemctl status scylla-jmx
● scylla-jmx.service - Scylla JMX
Loaded: loaded (/usr/lib/systemd/system/scylla-jmx.service; disabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Thu 2018-05-10 10:34:15 EDT; 3min 47s ago
Process: 1417 ExecStart=/usr/lib/scylla/jmx/scylla-jmx $SCYLLA_JMX_PORT $SCYLLA_API_PORT $SCYLLA_API_ADDR $SCYLLA_JMX_ADDR
$SCYLLA_JMX_FILE $SCYLLA_JMX_LOCAL $SCYLLA_JMX_REMOTE $SCYLLA_JMX_DEBUG (code=exited, status=127)
Main PID: 1417 (code=exited, status=127)
or
sudo service scylla-jmx status
● scylla-jmx.service
Loaded: not-found (Reason: No such file or directory)
Active: failed (Result: exit-code) since Wed 2018-07-18 20:38:58 UTC; 12min ago
Main PID: 141256 (code=exited, status=143)
You will need to restart the service or change the RAM allocation as per the Solution below.
Solution¶
There are two ways to fix this problem, one is faster but may not permanently fix the issue and the other solution is more robust.
The immediate solution
service scylla-jmx restart
Note
This is not a permanent fix as the problem might manifest again at a later time.
The more robust solution
Take the size of your node’s RAM, calculate 7% of that size, increase it by another 40%, and use this new size as your RAM requirement.
For example: on a GCP n1-highmem-8 instance (52GB RAM)
7% would be ~3.6GB.
Increasing it by ~40% means you need to increase your RAM ~5GB.
Open one of the following files (as per your OS platform):
Ubuntu:
/etc/default/scylla-server.Red Hat/ CentOS:
/etc/sysconfig/scylla-server
In the file you are editing, add to the
SCYLLA_ARGSstatement--reserve-memory 5G(the amount you calculated above). Save and exit.Restart Scylla server
sudo systemctl restart scylla-server
Note
If the initial calculation and reserve memory is not enough and problem persists and/or reappears, repeat the procedure from step 2 and increase the RAM in 1GB increments.