Staying alive...
An all too common web site failure is running out of space in log
partition. It can happen due to a failure to rotate and offload log
files, unexpected spike in traffic and similar conditions.
A normal reaction to such out-of-space condition is for web server to
abort serving requests (exit) and hope that some kind of monitoring
system catches such down condition, someone notices the alert, logs in
and rectifies the problem. All the while the users are receiving error
message. Clearly less than desirable situation.
If it is more important to you to continue serving user requests than
it is to make sure each user request is logged, you can instruct
aiCache to ignore write failures via
stay_up_on_write_error global
setting.
Log rotation for aiCache
AiCache server provides several options for automated or on-demand log rotation
Size-based access log file rotation
aiCache
provides automated, on-the-fly, size-based access log file rotation.
This feature is typically used to cut down size of the access log files
to some reasonable value, as it might be easier to deal with 10 files
of 100MB each, as opposed to a single file of 1GB. To enable, simply
set in the cfg file:
max_log_file_size 100000000
Be careful with those zeroes – the size is specified in bytes !
When max_log_file_size is set, aiCache rotates present log file upon it
reaching the maximum size. The renamed access file has a timestamp
added to the name of the file. The size-based rotation is a
zero-downtime operation and happens automagically.
On-demand log file rotation via USR1 signal.
To
execute on-the-fly, on-demand log file rotation, send SIGUSR1 to
aiCache’s process ID at time of your choosing - manually or using a
script driven by Linux cron facility. For example:
pkill -USR1 aicache
Simply add this command to be scheduled by Linux cron facility at time that is convenient for you.
aiCache’s
log file rotation – size-based or on demand, is a zero-overhead and
zero-downtime operation, so feel free to do it on schedule that is
convenient for you, there’s no performance impact. Please note that
aiCache rotates log files after the rotation is requested, upon
receiving first log-enabled request.
On-demand log file rotation via CLI command
You can also tell aiCache to rotate the log files from the CLI, using rotatelog command. After logging into CLI
>rl
Log
file rotation is not cluster-wide, it is only the aiCache instance that
the command is directed at, that executes the rotation.
