Rollback Monitoring Client

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

Prerequisites

The provided tool is coded in Perl. It requires that the Perl software with the DBI and DBD::Pg modules be installed on the server that executes the command (which is not necessarily the same as the one hosting the PostgreSQL instance).

To obtain detailed information about in-progress rollback operations, it is necessary to set the dblink_user_password E-Maj parameter.

If the extension has been installed by a non-SUPERUSER role, the role must have been granted the right to execute the dblink_connect_u(text,text) function.

Syntax

The syntax is:

emajRollbackMonitor.pl [OPTIONS]...

General Options

-i <time interval between displays>: Time interval between displays (in seconds, default = 5s).
-n <number of displays>: Number of displays (default = 1, 0 for infinite loop).
-a <maximum time interval for rollback operations to display>: Maximum time interval for rollback operations to display (in hours, default = 24h).
-l <maximum number of completed rollback operations to display>: Maximum number of completed rollback operations to display (default = 3).
--help: Displays only the command help.
--version: Displays only the software version.

Connection Options

-d <database to connect to>: Database to connect to.
-h <host to connect to>: Host to connect to.
-p <IP port to connect to>: IP port to connect to.
-U <connection role to use>: Connection role to use.
-W <password associated with the role>: Password associated with the role.

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

The supplied connection role must be allowed to view E-Maj data.

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

Examples

The command:

emajRollbackMonitor.pl -i 3 -n 10

displays 10 times, every 3 seconds, the list of in-progress rollback operations and the list of at most 3 latest rollback operations completed in the last 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 last 12 hours.

Display Example

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 %