Functionality

The MsgLogger class originally had two handlers:

• A console handler that formats and sends the messages to the console
• A file handler that formats and saves the messages to a log file

The additional syslog handler formats and sends the messages via the well established Syslog protocol.

It can be configured, enabled or disabled and the current LogLevel can be set exactly as with the other MsgLogger handlers.

Syslog in a nutshell

The syslog protocol is a veteran of the UNIX ecosystem, now-days implemented in the various Linux distributions by packages like syslog, rsyslog, systemd and others.

It always involves a UDP listener (port 514) that listens to messages on the local machine (127.0.0.1) and uses configuration files for further formatting and redirecting them to files, other processes or other machines.

Messages are labeled with a facility and a severity level

Implementation

The current implementation within the AstroPack:

• Maps the MsgLogger priorities (Fatal, Error, Debug, Warning, etc.) into the respective pre-defined syslog severity-levels (LOG_CRIT, LOG_ERR, LOG_DEBUG, LOG_WARNING, etc.).
• Composes a syslog message according to the standard definition that includes:
  • The facility is always 16 (LOG_LOCAL0). This allows for easy location of our messages in log-files afterwards
  • The mapped severity-level
  • Timestamp
  • Originating hostname
  • Originating program name and process id
  • The original message
• Uses a udpport socket to send the syslog message to 127.0.0.1:514

Syslog in the LAST ecosystem

Management

The subsystem is handled by the logs section of last-tool, as in.

root@last02e:/home/ocs# last-tool -n check logs

[SECT] Logs
[ OK ] config: "/etc/rsyslog.conf" contains 1 "\*\.\* @last0" lines.
[ OK ] config: "imudp" is enabled
[ OK ] directory: "/var/log/ocs" exists.
[ OK ] directory: "/var/log/ocs" owner is ocs.ocs
[ OK ] directory: "/var/log/ocs" access is 775

Where are the logs?

• Each of the last01[ew] to last12[ew] machines are configured to forward the messages to last0
• last0 is configured to:
  • Store the messages labeled with the LOG_LOCAL0 functionality into /var/log/remote/<originating-hostname>
  • Rotate the log files (see below)

ocs@last0:/var/log/remote$ cd
ocs@last0:~$ ls /var/log/remote
10.23.0.18  10.23.0.2  10.23.1.254  last01e  last02e  last03e  last04e	last05e  last06e  last08e  last10e  last12w    wis100mx-smadar-lab.weizmann.ac.il
10.23.0.19  10.23.0.6  10.23.3.9    last01w  last02w  last03w  last04w	last05w  last06w  last08w  last10w  localhost

ocs@last0:~$ ls /var/log/remote/last01e
auth.log      authpriv.log.1  daemon.log    kern.log.1		 last-messages.log.2.gz  last-messages.log.5.gz  syslog.log    user.log.1
auth.log.1    cron.log	      daemon.log.1  last-messages.log	 last-messages.log.3.gz  last-messages.log.6.gz  syslog.log.1
authpriv.log  cron.log.1      kern.log	    last-messages.log.1  last-messages.log.4.gz  last-messages.log.7.gz  user.log

The logrotate subsystem is configured on last0 by the /etc/logrotate.d/last-logs file:

ocs@last0:~$ cat /etc/logrotate.d/last-logs 
/var/log/remote/*/*.log
{
  rotate 7
  daily
  missingok
  notifempty
  delaycompress
  compress
  postrotate
    /usr/lib/rsyslog/rsyslog-rotate
  endscript
}