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Archive for October, 2020

Could not send replication command “TIMELINE_HISTORY”: ERROR: could not open file pg_wal/00xxxx.history

Posted by FatDBA on October 20, 2020

Hi All,

Ever encountered a situation where the backup history (TIMELINE_HISTORY) file was deleted by mistake or maybe someone removed it purposely, it was quite old and you try to restore a new backup. I remember many issues related with replication, backup tools (BARMAN & BART) that you might face if that file is removed from PG_WAL directory. Would like to discuss a problem that we encountered while taking BART backup on EDB version 10.

These ‘timeline files’ are quite important, as using the timeline history files, the pg_basebackup can follow the latest timeline present in the primary, just as it can follow new timelines appearing in an archive WAL directory. So, in short, it shows which timeline it branched off from and when. These history files are necessary to allow the system to pick the right WAL segment files when recovering from an archive that contains multiple timelines. So, its important to have this file there in WAL directory.


[enterprisedb@fatdba ~]$ bart -c /usr/edb-bart-1.1/etc/bart.cfg BACKUP -s edbserver --backup-name MAINFULLBKP_10-13-20
INFO:  DebugTarget - getVar(checkDiskSpace.bytesAvailable)
INFO:  creating full backup using pg_basebackup for server 'edbserver'
INFO:  creating backup for server 'edbserver'
INFO:  backup identifier: '1602788909136'
ERROR: backup failed for server 'edbserver' 

pg_basebackup: could not send replication command "TIMELINE_HISTORY": ERROR:  could not open file "pg_wal/00000002.history": No such file or directory 

1633701/1633701 kB (100%), 2/2 tablespaces
pg_basebackup: child process exited with error 1
pg_basebackup: removing data directory "/edbbackup/edbserver/1602788909136"
 

The file is not there under said directory.


[enterprisedb@fatdba ~]$ cd /edb/as10/as10/data/pg_wal/
[enterprisedb@fatdba pg_wal]$ ls
0000000200000005000000EA  0000000200000005000000EB.00000060.backup  0000000200000005000000ED  archive_status
0000000200000005000000EB  0000000200000005000000EC                  0000000200000005000000EE
 

In case of file missing/moved, you can always create a brand new empty file and that will be used by the respective utility and will be populated with metadata soon after. So, in order to quickly restore this issue, let’s create one.

 [enterprisedb@fatdba pg_wal]$ touch 00000002.history
[enterprisedb@fatdba pg_wal]$
[enterprisedb@fatdba pg_wal]$ ls *hist*
00000002.history 

Let’s try to take the backup once again.


[enterprisedb@fatdba pg_wal]$ bart -c /usr/edb-bart-1.1/etc/bart.cfg BACKUP -s edbserver --backup-name MAINFULLBKP_10-13-20
INFO:  DebugTarget - getVar(checkDiskSpace.bytesAvailable)
INFO:  creating full backup using pg_basebackup for server 'edbserver'
INFO:  creating backup for server 'edbserver'
INFO:  backup identifier: '1602789425665'
INFO:  backup completed successfully
INFO:
BART VERSION: 2.5.5
BACKUP DETAILS:
BACKUP STATUS: active
BACKUP IDENTIFIER: 1602789425665
BACKUP NAME: MAINFULLBKP_10-13-20
BACKUP PARENT: none
BACKUP LOCATION: /edbbackup/edbserver/1602789425665
BACKUP SIZE: 1.57 GB
BACKUP FORMAT: tar
BACKUP TIMEZONE: Europe/Berlin
XLOG METHOD: stream
BACKUP CHECKSUM(s): 0
TABLESPACE(s): 1
 Oid     Name      Location
 42250   UNKNOWN   /edb/as10/as10/data_test/pg_tblspc

START WAL LOCATION: 0000000200000005000000ED
BACKUP METHOD: streamed
BACKUP FROM: master
START TIME: 2020-10-15 21:17:05 CEST
STOP TIME: 2020-10-15 21:17:38 CEST
TOTAL DURATION: 33 sec(s)


[enterprisedb@fatdba pg_wal]$  bart -c /usr/edb-bart-1.1/etc/bart.cfg SHOW-BACKUPS
 SERVER NAME   BACKUP ID       BACKUP NAME            BACKUP PARENT   BACKUP TIME                BACKUP SIZE   WAL(s) SIZE   WAL FILES   STATUS

 edbserver     1602789425665   MAINFULLBKP_10-13-20   none            2020-10-15 21:17:38 CEST   1.57 GB       16.00 MB      1           active
 

And it worked.


Hope It Helped!
Prashant Dixit

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pg_dump: aborting because of server version mismatch — pg_restore: [archiver] unsupported version (1.13) in file header

Posted by FatDBA on October 16, 2020

Hi Guys,

First of all, this isn’t a problem but something that you should always set in case if your have multiple PostgreSQL versions or flavors running on the same host, else you might encounter some really strange errors. Few of the examples – You have PostgreSQL Community and EDB running or you have two different installations (versions) on the same server.

This can cause some basic command to fail, like in below example the pg_dump utility throwed an error about “server version mismatch” and it was all because this a POC box where we have more than three different PostgreSQL installations (Community PostgreSQL and EDB) and all of different versions. Two of them are for the EDB with same user ‘enterprisedb’ and one for community version. So either you set your bash_profile smartly, else you try something what I will be discussing next.

Okay, so this was the exact error what I have got when I tried to call pg_dump.


-bash-4.1$ pg_dump -p 6001 -U postgres -t classes > /tmp/classestable_psql_commdb_dump.dmp
pg_dump: server version: 11.9; pg_dump version: 8.4.20
pg_dump: aborting because of server version mismatch
 

There could be multiple issues or errors that you might encounter, one more that could arise due to multiple installations on same host.
Below, pg_restore failed with ‘unsupported version’ error.


-bash-4.1$ pg_restore -d postgresqlnew -h 10.0.0.144 -U postgres /tmp/commpsql_fulldbbkp.dmp
pg_restore: [archiver] unsupported version (1.13) in file header
 

This seems strange initially because the version of the utlity and postgresql is exactly the same.


-bash-4.1$ pg_restore --version
pg_restore (PostgreSQL) 8.4.20
-bash-4.1$ psql --version
psql (PostgreSQL) 8.4.20
 

Okay, let’s find how many pg_dump utilities exists in this database and their location.


-bash-4.1$ find / -name pg_dump -type f 2>/dev/null
/opt/edb/as10_BACKP_10042020SATIND/bin/pg_dump
/edb/as10/as10/bin/pg_dump
/usr/bin/pg_dump
/usr/pgsql-11/bin/pg_dump
/usr/edb/as10/bin/pg_dump
/usr/edb/as11/bin/pg_dump
 

So, we have 3 different pg_dump utlities here, all from different locations, and I know which version I would like to call. So, I can create a symbolic link to get rid of this error or to avoid writing the full/absolute path.


-bash-4.1$ sudo ln -s /usr/pgsql-11/bin/pg_dump /usr/bin/pg_dump --force
[sudo] password for postgres:
 

Great, It’s done. You can do the same for pg_restore too. Now lets try to call the same command all over again, to take a backup of single table with name ‘classes’.


-bash-4.1$ pg_dump -p 6001 -U postgres -t classes > /tmp/classestable_psql_commdb_dump.dmp

-bash-4.1$ ls -ll /tmp/classes*
-rw-r--r--. 1 postgres postgres 915 Oct 15 11:41 /tmp/classestable_psql_commdb_dump.dmp
-bash-4.1$
 

And it worked as expected.

Hope It Helped!
Prashant Dixit

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EDB PostgreSQL BART Error: tablespace_path is not set

Posted by FatDBA on October 16, 2020

Today would like to discuss about the issue that we faced while doing a BART restore operation of one of the EDB 11 PostgreSQL instance. This was a new system under realization phase (before delivery to customer). So, during one of the test we saw the restore got failed with a message which says something about the value ‘tablespace_path’. I know I have a tablespace in this system, but I initially though that BART will take care of it by its own, but its was not the case.

Below was the error what I have encountered during the test.


[enterprisedb@fatdba archived_wals]$ bart -c /usr/edb-bart-1.1/etc/bart.cfg RESTORE -s edbserver -i 1602187005158 -p /edb/as10/as10/data/
INFO:  restoring backup '1602187005158' of server 'edbserver'
ERROR: "tablespace_path" is not set
[enterprisedb@fatdba archived_wals]$
 

Okay, let’s first check tablespace details, we use the metacommand of ‘db’ to get that info about tablespaces. Okay, so we have it’s location, size details.
Let’s go inside the said directoy and see what all is there.
Note: Last two are the default tablespaces so need to worry about them.


enterprisedb=# \db+
                                              List of tablespaces
    Name    |    Owner     |           Location           | Access privileges | Options |  Size   | Description
------------+--------------+------------------------------+-------------------+---------+---------+-------------
 newtblspc  | dixit        | /home/enterprisedb/newtblspc |                   |         | 52 kB   |
 pg_default | enterprisedb |                              |                   |         | 1362 MB |
 pg_global  | enterprisedb |                              |                   |         | 774 kB  |
(3 rows)

[enterprisedb@fatdba pg_tblspc]$ pwd
/edb/as10/as10/data_test/pg_tblspc
[enterprisedb@fatdba pg_tblspc]$ ls -ltrh
total 4.0K
lrwxrwxrwx. 1 enterprisedb enterprisedb   28 May  5 17:58 42250 -> /home/enterprisedb/newtblspc
drwx------. 3 enterprisedb enterprisedb 4.0K Oct  8 21:56 PG_10_201707211
 

Okay, so we have a soft-link created for the tablespace under PG_TBLSPC directory under DATA dir with OID 42250.
Now when we have all the information, time to add requisite parameter in bart.cfg file to consider tablespaces, just like below.
Format: OID_1=tablespace_path_1;OID_2=tablespace_path_2 …
example: tablespace_path = 42250=/edb/as10/as10/data_test/pg_tblspc
Note: tablespace_path parameter must exist or to be empty at the time you perform the BART RESTORE operation.

Now let’s modify our bart confguration file, will look something like below with the ‘tablespace_path’ option set.


[EDBSERVER]
host = 10.0.0.144
port = 5444
user = enterprisedb
backup_name = mktg_%year-%month-%dayT%hour:%minute
cluster_owner = enterprisedb
description = "EDB PROD server"
archive_command='scp %p enterprisedb@10.0.0.144:/edbbackup/edbserver/archived_wals/%f'
tablespace_path = 42250=/edb/as10/as10/data_test/pg_tblspc
allow_incremental_backups=enabled
 

All set for the restore now, let’s try that.


[enterprisedb@fatdba pg_tblspc]$ bart -c /usr/edb-bart-1.1/etc/bart.cfg RESTORE -s edbserver -i 1602187005158 -p /edb/as10/as10/data/
INFO:  restoring backup '1602187005158' of server 'edbserver'
WARNING: tablespace restore path is not empty (/edb/as10/as10/data_test/pg_tblspc), restoring anyway
INFO:  base backup restored
INFO:  writing recovery.conf file
INFO:  WAL file(s) will be streamed from the BART host
INFO:  archiving is disabled
INFO:  permissions set on $PGDATA
INFO:  restore completed successfully
[enterprisedb@fatdba pg_tblspc]$
[enterprisedb@fatdba pg_tblspc]$
 

This is fixed.

Hope That Helped!
Prashant Dixit

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