[Postgres-xl-developers] Postgres XL and Npgsql: Coordinator Exception

Koichi Suzuki koichi.dbms at gmail.com
Wed Apr 8 19:43:48 PDT 2015


It is XL's specification that no direct updating operation is allowed
to maintain data integrity within the cluster.   In other words,
datanode is a backend element and is normally invisible from
applications.

Could you let me know the background that you are updating datanode directly?

Regards;
---
Koichi Suzuki


2015-04-09 8:25 GMT+09:00 Jaaromy Zierse <jzierse at ghostery.com>:
> I am getting the following error when using Npgsql to execute any statement
> against any of my Postgres XL coordinators:
>
> ERROR: XX000: Could not begin transaction on data node.
>
> Connecting via pgAdmin III and executing a query against the coordinators
> successfully executes and distributes the data.
>
> Strangely, if I connect directly to the Datanodes using Npgsql, then the
> statements execute successfully.
>
> Here is an example of the Npgsql code:
>
> using (var connection = new NpgsqlConnection(connectionString))
> {
> 	connection.Open();
>
> 	using (var command = connection.CreateCommand())
> 	{
> 		command.CommandText = @"SET TRANSACTION READ WRITE;
> 														INSERT INTO test_table(
> 														id, name)
> 														VALUES (1, 'Rando');";
>
> 		command.ExecuteNonQuery();
> 	}
> }
>
>
> Below is a description of our cluster configuration:
>
> Server: DEV-PGGTM
> Postgres XL Components: GTM and GTM Proxy
>
> Server: DEV-PG1
> Postgres XL Components: Coordinator 1 (Coord1) and Datanode1 (Datanode1)
>
> Server: DEV-PG2
> Postgres XL Components: Coordinator 2 (Coord2) and Datanode2 (Datanode2)
>
> Server: DEV-PG1
> Postgres XL Components: Coordinator 1 (Coord3) and Datanode3 (Datanode3)
>
> All coordinators run on port 5432 and all datanodes run on port 15432.
>
> The GTM is using port 6666 and the GTM Proxy is using port 6668.
>
>
> Thank you.
>
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