Currently I am using postgresql9.5 for my read replica. Also if possible please elaborate how I can implement master - master configuration for servers to be read-writable and 2 way synchronization
A PostgreSQL read replica(same or different region) is a physical copy, and PostgreSQL doesn't allow for a read replica to be made writable although you can promote a PostgreSQL read replica into a standalone DB instance.
This is a good read about best practices regarding RDS PostgreSQL read replicas replication
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I have an Azure-managed PostgreSQL database.
I want to create a logical replica of it at GCP, (Google-managed, if possible).
At Azure, I've set the Azure replication support to Logical. However, this just seems to allow me to create replicas inside Azure. What I want is to create a replica in GCP.
If this was not Azure-managed, but self-managed, I would be able to create a tunnel from Azure to GCP and then do the WAL copy replication.
One might wonder: why? Because I don't want to be locked with one vendor.
If that cross-cloud replication is not possible, what's the easiest way to pull the entire database off (possibly not just the data with pgdump, but all its internals too).
While this question is Azure -> GCP, it seems other alternatives like GCP -> AWS or other vendors are also not supported. Or what am I missing?
Cross-Cloud Replication from Azure Source PostgreSQL to GCP destination CloudSQL through Conventional Native Logical Replication is possible and I've tested that it's working. I'm sure that it would work for self managed database too.
I have a Aurora postgresql cluster in AWS and have one DB instance in this cluster. The postgresql DB is only used for write not for read. I use it as a backup database. I know Aurora has read scaling policy and I can create multiple DB instances in this cluster to improve read performance. But it doesn't benefit my case (write only). My question is that is there any benefits for me to spin up multiple db instances in the cluster. Aurura postgresql is a single master mode which means only one instance can take write. If I deploy multiple instances/replicas, they are basically useless. Do I understand it correctly?
Yes, you are correct. In your case there is no reason to launch additional instances in the cluster.
In the future, you may be able to use Aurora multi-master to give you more performance for writes. This is only available for MySQL 5.6 at the moment. See https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-multi-master.html
I have created a replicated Postgresql database (Master - Slave). I did this with an already existing Ansible Playbook (Role) , which I don't fully understand yet. The cluster currently consists of only 2 databases on different VMs.
So I want to test this replication now.
Unfortunately I have little experience with Postgresql.
How can I control whether they connect stable?
If the slave really takes over the task if the master should fail?
Many thanks for any information, tips & tricks.
Postgresql v. 9.6
Official PostgreSQL does not yet support automatic failover (Although there are multiple third-party projects which support this feature). Therefore if the deployment you have mentioned is only official PostgreSQL, after master failure, none of replicas take over the write task. But they can answer read queries if they are configured as hot_standby.
If you want to check the state of replication, in master you can check out pg_stat_replication in master.
Also these official docs would help you understand Postgres streaming replication & failover better:
https://www.postgresql.org/docs/9.6/warm-standby.html#STREAMING-REPLICATION
https://www.postgresql.org/docs/9.6/warm-standby-failover.html
Is there some kind of native Postgres tool they use, or is it a custom one? Are the replicas always in sync or do they drift apart from time to time?
With Multi-AZ RDS replication is synchronous. And since AWS like to be in full control of their software, it’s most likely a customised replication (but I couldn’t tell you for sure).
Can we replicate data from one RDS server to another? Or can we set master slave relationship between two RDS servers?
Should we replicate data from non RDS instance to RDS instance?
RDS can replicate from external mysql and also be a master of an external slave. It depends on your usecase if you "should" do it.
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/MySQL.Procedural.Importing.External.Repl.html
While i guess you could setup replication between two RDS instances yourself I don't see why you should since starting a RDS read replica is just a few clicks in AWS console or an api call.
It can be possible to replicate data from RDS to RDS. It is also possible to replicate data from RDS to some other MySQL server.
Steps:
You can go creating your ec2 server and install MySQL.
Change configuration to replicate data.
That will require additional work to manage ec2 instance in case if your data is increasing and crossing the server limits
Then you have to do all the manual work again to replicate data as we can't increase storage in ec2 server.
RDS provides an easy mechanism to create Read replica via a few clicks. (Note: replica is quite a costlier option.)
But going with that you will save manual work one person salary who will be managing the database and doing these setups regularly.
If you are using postgresql database on RDS then you can use bucardo for asynchronous replication. You need to create a EC2 or use can use local system also but it will not be fast enough.
Use the following tutorial if you want to use bucardo.
https://www.installvirtual.com/how-to-install-bucardo-for-postgres-replication/
I think you can using snapshot to clone another rds database