how many coordinator server can be put in cluster

[Sang Gyu Kim]

Hello I am trying to test Citus with PostgreSQL. I wonder how many coordinator server can be built on a set of cluster. and how to shard table by regional code like code 1 put it in worker node 1 in East and code 2 put in worker node 2 in West like instead of hashing it.

If anyone has any idea about this, please give some idea.

Thanks,

[Eric Lee Green]

1) Only one coordinator server is allowed with the current released Open
Source product. This coordinator server can however have a streaming
replica for failover purposes.

2) The hashing algorithm is built into the Citus source code and is not
configurable. If you need to do specific placement based upon geography,
you may wish to use the built-in partitioning mechanism in PostgreSQL 12
instead, which allows you to explicitly specify the partition key
partitioning algorithm (meaning you could use your number as the
partiton key) and, combined with foreign tables, would allow you to
place the partitions upon different servers. This is rather difficult to
configure and manage but if you are always planning to have a fixed
number of partitions and a fixed number of servers, it should be
manageable for your purposes.

Another option you should look at is CockroachDB, which purportedly can
do geographical distribution. Do note that it does not implement the
full PostgreSQL query language and functionality, does not perform well
with many traditional data processing workloads, and its level of
maturity might not be sufficient for some applications. I'd have no
problem building an analytical data warehouse on CockroachDB right now,
but I wouldn't use it to handle the financial data for a bank. But that
is my opinion as someone who has been in this business for 35 years,
your opinion may differ.

[Sang Gyu Kim]

Hello Eric,  

I really appreciate you for your response. I will check it with postgres 12 and also cockroachdb.  

Thanks again,

Sang

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[Sang Gyu Kim]

Hello Eric,

I have one more question. so Can users can connect db through only coordination server to see db objects, right?

Thanks,

Sang

[Murat Tuncer]

Yes that’s correct.  User’s don’t even need to know about workers in regular usage.

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[Sang Gyu Kim]

Great, thanks again.

Sang

[Denise]

BAERISD