I am new to PostgreSQL, I am trying to replicate single database like only one database need to replicate from Master to Slave Server.
I think you can find more information here: https://www.postgresql.org/docs/10/static/logical-replication.html
I am not sure without a sample code (from your side) what is your code/error/etc.
Related
I'd like to preface this by saying I'm not a DBA, so sorry for any gaps in technical knowledge.
I am working within a microservices architecture, where we have about a dozen or applications, each supported by its Postgres database instance (which is in RDS, if that helps). Each of the microservices' databases contains a few tables. It's safe to assume that there's no naming conflicts across any of the schemas/tables, and that there's no sharding of any data across the databases.
One of the issues we keep running into is wanting to analyze/join data across the databases. Right now, we're relying on a 3rd Party tool that caches our data and makes it possible to query across multiple database sources (via the shared cache).
Is it possible to create read-replicas of the schemas/tables from all of our production databases and have them available to query in a single database?
Are there any other ways to configure Postgres or RDS to make joining across our databases possible?
Is it possible to create read-replicas of the schemas/tables from all of our production databases and have them available to query in a single database?
Yes, that's possible and it's actually quite easy.
Setup one Postgres server that acts as the master.
For each remote server, create a foreign server then you then use to create a foreign table that makes the data accessible from the master server.
If you have multiple tables in multiple server that should be viewed as a single table in the master, you can setup inheritance to make all those tables appear like one. If you can define a "sharding" key that identifies a distinct attribute between those server, you can even make Postgres request the data only from the specific server.
All foreign tables can be joined as if they were local tables. Depending on the kind of query, some (or a lot) of the filter and join criteria can even be pushed down to the remote server to distribute the work.
As the Postgres Foreign Data Wrapper is writeable, you can even update the remote tables from the master server.
If the remote access and joins is too slow, you can create materialized views based on the remote tables to create a local copy of the data. This however means that it's not a real time copy and you have to manage the regular refresh of the tables.
Other (more complicated) options are the BDR project or pglogical. It seems that logical replication will be built into the next Postgres version (to be released a the end of this year).
Or you could use a distributed, shared-nothing system like Postgres-XL (which probably is the most complicated system to setup and maintain)
I run a couple of PostgreSQL databases (9.3), one of which does not need archiving the other of which I'd rather run in WAL archive mode by can get away with not.
I now have a need for a data which is archived.
As far as I can tell the setting is on an instance basis, so I wouldn't be able to just choose which databases to archive and which not, which would indicate that I will need to create a new PostgreSQL instance.
Am I missing something?
Also, FWIW, will I be able to create database links between databases on the two instances?
Thanks, --sw
You cannot to choose database for archiving - only all (or none) in PostgreSQL instance can be archived. There are not any pother possibility now.
You can send query to other PostgreSQL instance via dblink extension or with Foreign Data Wrappers API. FDW API should be preferred, although dblink has some usage still.
I have created custom script in Express that actually migrates SQL Server database to MongoDB.
But I am facing problems in live syncing between the two databases.
Currently I have added a column updated_by in both the databases.
Then I fetch the latest updated_by row from MongoDb and SQL Server database.
Then I check the date difference and based on it I update my MongoDB database.
There are lots of db tables and I am finding it difficult to identify that, which table is being updated.
Is there any log in SQL Server 2008 R2 that states which table is updated and at what time?
I need a mechanism like, any data update in the db table should immediately sync that rows into my MongoDB.
Any more suggestions on live data syncing is also welcome.
Thanks in advance. :)
When i have such requirement to Sync between Relational DB say (MYSQL) and Non-Relational DB (Mongodb).
I had followed following steps which may help others in future. and the concept is generally called as Change Data Capture
Capture changes (For MYSQL iam using triggers.)
Transform changes to a suitable changes
ie RDBMS to Non RDBMS
Update changes
Remember to sync the structural changes of database and corresponding implementaions.
Following links may help
https://www.flydata.com/blog/what-change-data-capture-cdc-is-and-why-its-important/
I have 5 users which uses 5 different servers(using openerp), each one uses the same database copy. Whenever the user enters data to his database, then it should sync to the 6th server's database an then sync the data in the 6th database to all other 4 users databases. So any data entry in any database should sync to the other databases running in different servers. Is that possible? how can I achieve it?
Edit:
I found Bucardo, but it need primary key for every table. But in openerp, there are many2many relation tables which doesn't have a primary key.
This is called master-master or multi-master replication:
http://en.wikipedia.org/wiki/Multi-master_replication#PostgreSQL
http://wiki.postgresql.org/wiki/Replication,_Clustering,_and_Connection_Pooling
You can also check out SymmetricDS or Daffodil which let you sync over HTTP.
A pure PostgreSQL installation supports currently only single master replication.
However you may achieve multi-master replication by installing additional tools http://wiki.postgresql.org/wiki/Clustering.
You should also check out Pg documentation on this topic Chapter 25. High Availability, Load Balancing, and Replication
What would be the best way to replicate individual DB tables from a Master postgresql server to a slave machine? It can be done with cron+rsync, or with whatever postgresql might have build in, or some sort of OSS tool, but so far the postgres docs don't seem to cover how to do table replication. I'm not able to do a full DB replication because some tables have license->IP stuff connected to it, and I can't replicate those on the slave machine. I don't need instant replication, hourly would be acceptable as well.
If I need to just rsync, can someone help identify what files within the /var/lib/pgsql directory would need to be synced, or how I would know what tables they are.
Starting with Postgres 10, logical replication is built into Postgres! This is often a better solution than external solutions. The Postgres docs are great and easy to follow. It's very easy. See the quick setup docs, which in essense boils down to running this:
-- On publisher DB
CREATE PUBLICATION mypub FOR TABLE users, departments;
-- On subscriber DB
CREATE SUBSCRIPTION mysub CONNECTION 'dbname=foo host=bar user=repuser' PUBLICATION mypub;
You might want to try Bucardo, which is an open source software to synchronize rows between tables even if they are in a remote location. It's a very simple software, and it is capable of creating one-way synchronization relationships as well.
Check out http://bucardo.org/wiki/Bucardo
You cannot get anything useful by copying individual tables files in the data directory. If you want to replicate selected tables, there are a number of good options.
http://wiki.postgresql.org/wiki/Replication,_Clustering,_and_Connection_Pooling