Lightest way of checking if postgresql is running at the other end of an ssh tunnel?

On Wed, May 11, 2016 at 11:17:54AM +0200, Niels Kristian Schjødt wrote:

We have an ssh connection running from one server to our
postgresql database on another server. Some times we
experience that the ssh tunnel does not work anymore and
needs to be restarted, even though we use the autossh
package. I would like to write a script that “pings”
postgresql on the specified port, to check if the connection
goes through. I have tried with netcat, but it does not
really check if postgresql is in the other end of the tunnel,
it only check if there is as service (the tunnel) listing on
the port on the local machine. Is there another way of
pinging the port, to see if postgresql is alive at the other
end? If possible, I would like to NOT actually establishing a
connection to postgresql like if i used psql -c “select 1;”,
to avoid connection overhead.

This

http://www.postgresql.org/docs/devel/static/libpq-connect.html

talks about ping functionality. Maybe you can use a tiny
custom piece of code ?

Karsten
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On 05/11/2016 11:41 AM, Karsten Hilbert wrote:

On Wed, May 11, 2016 at 11:17:54AM +0200, Niels Kristian Schjødt wrote:

We have an ssh connection running from one server to our
postgresql database on another server. Some times we
experience that the ssh tunnel does not work anymore and
needs to be restarted, even though we use the autossh
package. I would like to write a script that “pings”
postgresql on the specified port, to check if the connection
goes through. I have tried with netcat, but it does not
really check if postgresql is in the other end of the tunnel,
it only check if there is as service (the tunnel) listing on
the port on the local machine. Is there another way of
pinging the port, to see if postgresql is alive at the other
end? If possible, I would like to NOT actually establishing a
connection to postgresql like if i used psql -c “select 1;”,
to avoid connection overhead.

This

http://www.postgresql.org/docs/devel/static/libpq-connect.html

talks about ping functionality. Maybe you can use a tiny
custom piece of code ?

That tiny custom piece of code would be this:

http://www.postgresql.org/docs/current/static/app-pg-isready.html

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Vik Fearing +33 6 46 75 15 36
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

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On Wed, May 11, 2016 at 02:28:47PM +0200, Vik Fearing wrote:

We have an ssh connection running from one server to our
postgresql database on another server. Some times we
experience that the ssh tunnel does not work anymore and
needs to be restarted, even though we use the autossh
package. I would like to write a script that “pings”
postgresql on the specified port, to check if the connection
goes through. I have tried with netcat, but it does not
really check if postgresql is in the other end of the tunnel,
it only check if there is as service (the tunnel) listing on
the port on the local machine. Is there another way of
pinging the port, to see if postgresql is alive at the other
end? If possible, I would like to NOT actually establishing a
connection to postgresql like if i used psql -c “select 1;”,
to avoid connection overhead.

This

http://www.postgresql.org/docs/devel/static/libpq-connect.html

talks about ping functionality. Maybe you can use a tiny
custom piece of code ?

That tiny custom piece of code would be this:

http://www.postgresql.org/docs/current/static/app-pg-isready.html

That's what I had in mind :-)

Thanks,
Karsten
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