Rollback monitoring client

E-Maj delivers an external client to run as a command that monitors the progress of rollback operations in execution.

Prerequisite

Two equivalent tools are actually provided, one coded in php and the other in perl. Both need that some software components be installed on the server that executes the command (which is not necessarily the same as the one that hosts the PostgreSQL instance) :

  • for the php client, the php software and its PostgreSQL interface,

  • for the perl client, the perl software with the DBI and DBD::Pg modules.

In order to get detailed information about the in-progress rollback operations, it is necessary to set the dblink_user_password parameter and give right to execute the dblink_connect_u function. More details…

Syntax

Both php and perl commands share the same syntax:

emajRollbackMonitor.php [OPTIONS]...

and:

emajRollbackMonitor.pl [OPTIONS]...

The general options are:

  • -i <time interval between 2 displays> (in seconds, default = 5s)

  • -n <number of displays> (default = 1)

  • -a <maximum time interval for rollback operations to display> (in hours, default = 24h)

  • -l <maximum number of completed rollback operations to display> (default = 3)

  • –help only displays a command help

  • –version only displays the software version

The connection options are:

  • -d <database to connect to>

  • -h <host to connect to>

  • -p <ip-port to connect to>

  • -U <connection role to use>

  • -W <password associated to the role>

To replace some or all these parameters, the usual PGDATABASE, PGPORT, PGHOST and/or PGUSER environment variables can be used.

The supplied connection role must either be a superuser or have emaj_adm or emaj_viewer rights.

For security reasons, it is not recommended to use the -W option to supply a password. Rather, it is advisable to use the .pgpass file (see PostgreSQL documentation).

Examples

The command:

emajRollbackMonitor.php -i 3 -n 10

displays 10 times and every 3 seconds, the list of in progress rollback operations and the list of the at most 3 latest rollback operations completed in the latest 24 hours.

The command:

emajRollbackMonitor.pl -a 12 -l 10

displays only once the list of in progress rollback operations and the list of at most 10 operations completed in the latest 12 hours.

Example of display:

 E-Maj (version 4.2.0) - Monitoring rollbacks activity
---------------------------------------------------------------
21/03/2023 - 08:31:23
** rollback 34 started at 2023-03-21 08:31:16.777887+01 for groups {myGroup1,myGroup2}
   status: COMMITTED ; ended at 2023-03-21 08:31:16.9553+01
** rollback 35 started at 2023-03-21 08:31:17.180421+01 for groups {myGroup1}
   status: COMMITTED ; ended at 2023-03-21 08:31:17.480194+01
-> rollback 36 started at 2023-03-21 08:29:26.003502+01 for groups {group20101}
   status: EXECUTING ; completion 85 %; 00:00:20 remaining
-> rollback 37 started at 2023-03-21 08:29:16.123386+01 for groups {group20102}
   status: LOCKING ; completion 0 %; 00:22:20 remaining
-> rollback 38 started at 2023-03-21 08:30:16.130833+01 for groups {group20103}
   status: PLANNING ; completion 0 %