![]() ![]() The filename will be trimmed for removing the extension.ĬleanupPriorWALFiles(void): This function opens the directory and iterates over all the files in that directory.ĮxclusiveCleanupFileName is used as a reference for comparison. TrimExtension(char *filename, char *extension): This function will be called for every file in the directory for the removal of extension. It checks whether the directory location provided in the command line (value ofĪrchiveLocation ) is a directory. Initialize(void): As the name indicates, this function will be called only once as part of the initialization of the program. Xlog center code#So this writeup is about the walkthrough of the code and its normal functionality.Ī couple of important variables which this program uses are: Since it is a standalone program, users with minimal C knowledge can easily customize the program. It is designed for user customization, including extensive comments. Luckily this is a very small, standalone, single file, (no need of postgresql server), easy to read source code with less than 400 lines. pg_archivecleanup code walkthrough for the novice user partial file which gets generated as part of standby promotion as a reference WAL. We may also think about adding more capabilities to pg_archivecleanup for addressing custom requirements. ![]() If we want to implement WAL retention policies with its own logic, we may end up executing pg_archivecleanup from multiple wrapper scripts. This backup history file can be directly specified pg_archivelogcleanup as follows:Īll these different criteria create a set of requirements which can be addressed by custom scripts or are already addressed by different backup solutions for PostgreSQL. Xlog center archive#But luckily PostgreSQL helps us by generating a backup history file in the archive location with aĪny WALs older than this is not required for backup. Any file older than the backup retention period is a candidate for deletion.Ĭriteria No. Xlog center how to#Now think about how to implement all these criteria for WAL retention in archive location.Ĭriteria No.1 is simple to implement. Pg_archivecleanup doesn’t have all the intelligence built-in, but it can be utilized inside custom scripts as an intelligent way to achieve the goals of WAL retention. This is similar to Checkpoint on the Primary side.Ĭriteria 4: All the WALs from the last checkpoint is required by Primary for any crash recovery. A restart point is a point from where standby can restart the recovery operation. If the backup tool/script is not taking care of WALs, the responsibility falls on us as a DBA.Ĭriteria 3: All WALs from the restart point of Standby is required by the Standby database. Many times, backup tools make a copy of WAL and include it as part of Backup. In such a case, the DBA needs to get an old backup and associated WAL files.Ĭriteria 2: All WALs from the start position of a backup until the end of the backup is required to consistently restore any backup. Restore the database to another location and recover the table as of latest time possible. In order to do a clean up of WALs, we need to keep in mind the WAL retention requirements and criteria, as losing essential WALs can be disastrous.Ĭriteria 1: All WALs from the time of the oldest backup, which still falls in the backup retention policy and Point-in-time requirement, need to be preserved.įor example, a user may ask for restore like: A table X was accidentally deleted as part of last change rolled out on Sunday night 12. In the following demonstration, I am listing all WALs which are still in the default wal location (pg_wal) inside my data directory and older than a specific WAL: ![]() This feature is useful to list all WALs older than a specific WAL. This program can operate in dryrun mode (-n option) or delete mode (-d option). It can also be used in Standby side for cleaning up WAL files which are no longer required for Standby.Can be used as a standalone program to clean up old WAL files from any file system location.It is extremely simple and useful, and it can work in 2 scenarios: pg_archivecleanup is probably the least talked about utility among standard PostgreSQL binaries. But there is a simple program named pg_archivecleanup which comes along with PostgreSQL binaries which might be useful in both maintaining the WAL retention as well as handling an emergency situation. Necessary WALs are no longer preservedĮxternal backup projects for PostgreSQL are good in addressing retention policies. WALs filling up pg_wal/pg_xlog directory due to failing archiveģ. Several TBs of WALs piled up in archive destinationĢ. But very often we come across DBAs getting into surprise situations such as:ġ. WAL retention is a very important topic for PostgreSQL database management. ![]()
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