Barman 2.11: barman-cloud-restore and barman-cloud-wal-restore

Thanks to the new utilities barman-cloud-restore and barman-cloud-wal-restore introduced in Barman 2.11, it is now possible to execute the recovery of a PostgreSQL instance using a full backup previously executed using barman-cloud-wal-archive and barman-cloud-backup commands. Let’s discover together how to implement this in the following article.

It is worth noting that in Barman 2.11, all cloud utilities for Barman are now in a separate package called barman-cli-cloud.

Requirements

1. barman-cli-cloud package
2. A PostgreSQL instance
3. An AWS S3 bucket
4. A second virtual machine where to execute the restore

In this article, we will test barman-cli-cloud functionalities in a virtual machine with Debian Buster and PostgreSQL 12. In order to properly follow the instructions contained within this article, we also assume you have:

• configured Postgres to archive WAL files to an existing S3 bucket using barman-cloud-wal-archive
• executed a backup and ship it to the same S3 bucket through barman-cloud-backup

You may easily achieve this by following the instructions contained in these previous blog articles:

• Barman Cloud – Part 1: WAL Archive
• Barman Cloud – Part 2: Cloud Backup

Set-up the recovery server

As a result, we have an S3 bucket on AWS named barman-s3-test which already contains the WAL files and backup archived via barman-cloud-wal-archive and barman-cloud-backup tools, now we need to properly configure a server that will be the host for the recovery of the PostgreSQL instance.

1. Install PostgreSQL 12 from the official PGDG repository

2. Install the 2ndQuadrant Public repository

3. Install the barman-cli-cloud package:

[email protected]:~# apt update
[email protected]:~# apt install barman-cli-cloud

4. Install awscli package:

[email protected]:~# apt install awscli

5. Configure AWS credentials with the awscli tool as the postgres user:

[email protected]:~$ aws configure --profile barman-cloud
AWS Access Key ID [None]: AKI*****************
AWS Secret Access Key [None]: ****************************************
Default region name [None]: eu-west-1
Default output format [None]: json

Execute the restore procedure

Now that the recovery server is correctly configured, we are ready to start the restore procedure.

Barman 2.11 introduces the barman-cloud-backup-list command that allows you to retrieve information about the backups made with barman-cloud-backup:

[email protected]:~$ barman-cloud-backup-list \
  --profile barman-cloud \
  s3://barman-s3-test pg12
Backup ID           End Time                 Begin Wal
20200713T120856     2020-07-13 12:09:05      00000001000000000000000C

We are now ready to execute the restore using the barman-cloud-restore command:

[email protected]:~$ barman-cloud-restore \
  --profile barman-cloud \
  s3://barman-s3-test \
  pg12 20200713T120856 \
  /var/lib/postgresql/12/main/

Once the restore terminates successfully we can check the PGDATA directory contents:

[email protected]:~$ ls /var/lib/postgresql/12/main/
PG_VERSION    global        pg_hba.conf    pg_multixact  pg_serial     pg_stat_tmp  pg_twophase  postgresql.auto.conf
backup_label  pg_commit_ts  pg_ident.conf  pg_notify     pg_snapshots  pg_subtrans  pg_wal       postgresql.conf
base          pg_dynshmem   pg_logical     pg_replslot   pg_stat       pg_tblspc    pg_xact

Now, in order to be sure that the restore process worked properly, we need to start the recovered PostgreSQL instance and verify that everything works as expected. This process requires some additional steps.

First, since we are on a Debian system, we need to copy the files containing the PostgreSQL configuration under the /etc/postgresql/12/main/ directory:

[email protected]:~$ cp /var/lib/postgresql/12/main/postgresql.conf /etc/postgresql/12/main/

[email protected]:~$ cp /var/lib/postgresql/12/main/pg_hba.conf /etc/postgresql/12/main/

[email protected]:~$ cp /var/lib/postgresql/12/main/pg_ident.conf /etc/postgresql/12/main/

Second, create the recovery.signal file:

[email protected]:~$ touch /var/lib/postgresql/12/main/recovery.signal

Then, disable the archive_command to prevent the recovered instance from writing in the same bucket as the original instance:

[email protected]:~$ echo \"archive_command = 'cd .'\" >> /etc/postgresql/12/main/postgresql.conf

After that, you need to configure PostgreSQL to retrieve the WAL files of the latest available timeline from the S3 bucket by using the barman-cloud-wal-restore in the restore_command:

[email protected]:~$ echo \"restore_command = 'barman-cloud-wal-restore --profile barman-cloud s3://barman-s3-test pg12 %f %p'\" >> /etc/postgresql/12/main/postgresql.conf
[email protected]:~$ echo \"recovery_target_timeline = 'latest'\" >> /etc/postgresql/12/main/postgresql.conf

IMPORTANT: Before proceeding please ensure that the PostgreSQL instance is not running, and that the destination directory (the default PostgreSQL datadir) is empty.

Finally, we are ready to start the new recovered instance:

ro[email protected]:~# systemctl restart [email protected]

Great! As we can see from the PostgreSQL log, WAL files are recovered from the S3 bucket and the instance was correctly started:

[email protected]:~$ less /var/log/postgresql/postgresql-12-main.log
...
2020-07-13 12:43:25.093 UTC [9458] LOG:  starting PostgreSQL 12.3 (Debian 12.3-1.pgdg100+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 8.3.0-6) 8.3.0, 64-bit
2020-07-13 12:43:25.093 UTC [9458] LOG:  listening on IPv4 address "127.0.0.1", port 5432
2020-07-13 12:43:25.095 UTC [9458] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2020-07-13 12:43:25.111 UTC [9459] LOG:  database system was interrupted; last known up at 2020-07-13 12:08:56 UTC
2020-07-13 12:43:25.508 UTC [9459] LOG:  starting archive recovery
2020-07-13 12:43:26.010 UTC [9459] LOG:  restored log file "00000001000000000000000C" from archive
2020-07-13 12:43:26.052 UTC [9459] LOG:  redo starts at 0/C000028
2020-07-13 12:43:26.054 UTC [9459] LOG:  consistent recovery state reached at 0/C000138
2020-07-13 12:43:26.054 UTC [9458] LOG:  database system is ready to accept read only connections
2020-07-13 12:43:26.469 UTC [9459] LOG:  restored log file "00000001000000000000000D" from archive
2020-07-13 12:43:26.823 UTC [9459] LOG:  redo done at 0/D0001B0
2020-07-13 12:43:27.242 UTC [9459] LOG:  restored log file "00000001000000000000000D" from archive
2020-07-13 12:43:27.592 UTC [9459] LOG:  selected new timeline ID: 2
2020-07-13 12:43:27.644 UTC [9459] LOG:  archive recovery complete
2020-07-13 12:43:27.979 UTC [9458] LOG:  database system is ready to accept connections

Conclusion

As usual with any new release of Barman, we recommend that everyone updates their systems to the latest version. A complete list of changes and bug fixes is available here.

Please note that if you are using already barman-cloud-wal-archive or barman-cloud-backup installed via RPM/Apt package and you are upgrading your system, you must install the barman-cli-cloud package. This is due to the fact that, with the Barman 2.11 release, all cloud related tools are part of the barman-cli-cloud package as explained at the beginning of the article.

The next versions of Barman might improve the usability and automation capabilities of the recover command, for example by preparing a recovery.conf or recovery.signal file like the actual Barman does.