Is there any way to Switchover the role of Master & Slave FREQUENTLY and synchronize Slave with Master and vice-verse?
Let see my network of machine goes off for 5 minutes on Master, then my Slave became the Master, but when my old Master network problem solved, then instead of building old Master with 'rsync' command, is there any possible way to synchronize old Master with only those changes made within 5 minutes?
Hoping for expert reply.
i have been working on postgresql replication right now
you have not give proper description about your problem
1) how you down the master killing postgres process or stop the master
there is no solution when master down using killing postgres except rsync because when master kill down master may have committed locally so there is inconsistency in data of master and slave due to master go ahead and slave left behind so next when old master try to came up as slave it will try to redo log at last checkpoint but it will not find that wal file from new master (old slave).
Related
After completed streaming replication in my master server the archive folder size is increasing continuously in my master server. it is taking whole system space, how can i fix this issue in master server not in the slave server.
I am in the process of writing a bash script to upgrade Postgres servers in our org from 9.6 to 10.4, under Ubuntu trusty. I've got the master upgrade done, but we have instances in dev, staging and production with and without standby servers. I know how to upgrade a standby server, but I am struggling with a generic way to determine if a master has standby's, and if so, their hostnames. Anybody done this already and can share some light on this?
On the master, you can see the listening standby servers in pg_stat_replication:
select client_addr, client_hostname from pg_stat_replication
On the standby, you can see the master in pg_stat_wal_receiver:
select conninfo from pg_stat_wal_receiver
This may be a very basic question, but I'm struggling with it. I'm attempting to set up logical decoding between 2 separate servers.
On the Master, I've gotten it setup so that the changes that I make to a table (INSERT, UPDATE, DELETE) are sent to my logical replication slot, and I can see the changes using the pg_logical_slot_get/peek_changes functions - all on my Master server.
On the Slave, I'm attempting to run the pg_revclogical command (using command prompt), however, I can't seem to get it to receive the changes made on the Master. I've realized that no where have I told the 2 to communicate to each other. I tried to define the host as the Master to tell the replication process that I have to pull the changes from the Master to the Slave.
I've made all of the required changes to the postgresql.conf (wal_level=logical; max_replication_slots=3; max_wal_senders=3) and pg_hba.conf (whatever it told me to do to fix errors) files on both Master and Slave. The pg_recvlogical command and the resulting error message are below. Could someone please help me get my Master and Slave communicating?
pg_recvlogical --start --slot=wendy_test --plugin=test_decoding --dbname=testdb --file=C:\Logical_Decoding_Test.log --username=dbaadmin --host=127.##.##.### --port=5432
When I execute this command on the Slave, I don't receive any error messages, but it doesn't return to a command prompt either? While it's doing its thing, I can check the database and see that the wendy_test slot is active, so it appears to be doing something. However, when I INSERT a row into the table on my Master, nothing happens on my Slave (even after 5 minutes).
I can add all of the code that I have used to create the replication slots, populate the queue, etc. I was trying to limit the amount of reading and figured those to be more basic. Also, my end game is to transition this to have our AWS RDS system as our Slave, so any recommendations for that is appreciated as well. THank you for your time.
I am very new to postgres and being new I got stuck at a point and need some help, please pardon if you find it silly.
I am doing a pgpool HA and at postgres level i have streaming replication between 3 nodes of postgresql-9.5 - 1 master and 2 slaves
I was trying to configure auto failover but when i switched back to my original master, and restarted the postgres service, I am getting the following error:
slave 1-highest timeline 1 of the primary is behind recovery timeline 11
slave 2-highest timeline 1 of the primary is behind recovery timeline 10
slave 3-highest timeline 1 of the primary is behind recovery timeline 3
I tried deleting pg_xlog files in slaves and copying all the files from master pg_xlog into the slaves and then did a rsync.
i also did a pg_rewind but it says:
target server needs to use either data checksums or wal_log_hints = on
(I have wal_log_hints = on set in postgresql.conf already)
I've tried doing a pg_basebackup but since the data base server in slaves are still starting up its not able to connect to the server
Is there any way to bring the master and the slave at a same timeline?
In my case, it happened because ( experimentally ), I updated the standby database tables and again when I simulate the master-standby streaming replication I got the same errors.
So once again I cleaned the whole standby database directory and migrate the master database using cmd like
"pg_basebackup -P -R -X stream -c fast -h 10.10.40.105 -U postgres -D standby/"
I think something is wrong in your pgpool configuration. What tool you have been using for manement of replication and master-slave control? Is it post master or repmgr?
I was trying to configure pgpool with 3 data nodes using a tutorial from http://jensd.be/591/linux/setup-a-redundant-postgresql-database-with-repmgr-and-pgpool and have done it correctly.
Also you can lean auto failover here.
(These question is obviously duplicate of this one, so I'll repeat the answer also.)
I'm not sure what you exactly mean by "when i switched back to my original master", but it looks that you are doing the wrongest possible thing in PostgreSQL streaming replication - introducing the second master.
The most important thing you should know about PostgreSQL replication is that once the failover is performed, you cannot simply "switch back to original master" - there's now a new master in cluster, and existence of two masters will make damage.
After a slave is promoted to master, the only way for you to re-join the old master is to:
Destroy it (delete the data directory);
Join it as a slave.
If you want it to be master again you'll continue with the following:
Let it run for awhile as a slave so that it can sync the data;
Kill temporary master and failover to old master;
Rejoin temporary master again as a slave.
You cannot simply switch master servers! Master can be created ONLY by failover (promoting a slave)
You should also know that whenever you are performing failover (whenever the master is changed), all slaves (except for the one that is promoted) need to be reconfigured to target the new master.
I suggest you reading this tutorial - it'll help.
I have a server that I want to use for testing new app verson (say staging server), but at same time I want to use it as replication slave for MongoDB. So, there is two roles:
always replicate an database to this server (only one database, original, with real data)
after deployment, make a copy of original db, to a new one (*-staging db), and test my deployment against this database
I see from docs how to replicate only specified database from one server to another, seems that it's working fine. But the problem that when i've tried to make a copy of existing database, on slave server, it fails with error not master. I don't want to make this database copy on master server, because it means that all staging tests will be executed against master server, that doesn't work for me.
Does it mean that I can't have MongoDB master for one database, and slave for another?
Slaves by default are read only but you can achieve what you are trying to do by making it master and slave at the same time by passing both --master and --slave when starting your server:
mongod --slave --source master:1234 --master