Re: High latency when port-forwarding postgresql (for statements which don't return data)

[amolarakh <amolarakh@xxxxxxxxxxx>]

Hi Clemens,
There are various scenarios for decreased latency.

1. Kindly check the host entry if dbserver is internal and not
communicating to Internet
2. Please traceroute/ use sniffer on forwarded port will give you exact
route followed.

Regards
Amol Arakh


On Tuesday 22 March 2011 07:05 PM, Clemens Eisserer wrote:
> Hi,
>
> I experience a very strange problem, when using the jdbc driver with
> ssh's local port forwarding:
> ssh -v -L 4321:dbserver:5432 user@dbserver
>
> SELECT statements show about the same latency as without
> port-forwarding (and even decreased latency when compression is
> enabled), but sometimes UPDATE/DELETE statements take seconds to
> complete.
> The other time they are as fast as they should be. When I connect to
> postgres without port-forwarding the update statements consistently
> take only a few milliseconds.
>
> Any idea what the reason could be, I've tested it with two different
> ssh clients (one java, and openssh) both show the same behaviour.
> Could it be some buffering on the server side, to make data transfer
> more efficient?
> Could it be because selects usually send a lot of data back to the
> client, buffering doesn't hurt - but for update/delete usually only a
> acknoledgement is sent back and buffering starts to be an issue?
>
> Thank you in advance, Clemens
>
>
> Btw the java-based client seems to be waiting for data while it
> executes the statements:
>
> java.net.SocketInputStream.socketRead0(Native Method)
> java.net.SocketInputStream.read(SocketInputStream.java:129)
> org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:135)
> org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:104)
> org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:73)
> org.postgresql.core.PGStream.ReceiveChar(PGStream.java:259)
> org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1620)
> org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)
>    - locked org.postgresql.core.v3.QueryExecutorImpl@17b1683
>