[#159] Add new pool metric pgagroal_query_count and Query rate panel

[An-DJ]

Issue

#159

Task

• Add pgagroal_query_count which characterizes the number of queries.
• Add new panel Query rate in Grafana dashboard,

[jesperpedersen]

This would count all client requests as a query - it would be better to just count the actual SQL queries.

See https://www.postgresql.org/docs/devel/protocol-message-formats.html for the message protocol - you will need support for the simple query and the prepared query format. You can use https://github.com/jesperpedersen/pgprtdbg for protocol debugging.

You can likely reuse code from pipeline_transaction.c to track message boundaries, but we need guard against this extra overhead - maybe a statistics configuration variable with a default of on.

Only pipeline_session.c and pipeline_transaction.c needs to support this -- pipeline_perf.c won't support extended statistics.

[An-DJ]

This would count all client requests as a query - it would be better to just count the actual SQL queries.

See https://www.postgresql.org/docs/devel/protocol-message-formats.html for the message protocol - you will need support for the simple query and the prepared query format. You can use https://github.com/jesperpedersen/pgprtdbg for protocol debugging.

You can likely reuse code from pipeline_transaction.c to track message boundaries, but we need guard against this extra overhead - maybe a statistics configuration variable with a default of on.

Only pipeline_session.c and pipeline_transaction.c needs to support this -- pipeline_perf.c won't support extended statistics.

Thanks for your guidance. I am implementing the filtering of SQL queries by protocol key info. I will push newer code soon.

[An-DJ]

@jesperpedersen I have check the message kind in Simple Query and Extended Query(prepare-statement).

• For the SimpleQuery, a query can be created by a Q message.
• For the PrepareQuery, a prepare query can be created by a P message which is used to parse the unsettled sql. Then a execute query can be created by a E message which is used to execute the settled sql.

So the query_count should be increased by 'Q' 'P' and 'E'. The newer commit includes that implementation.

[jesperpedersen]

White space

[jesperpedersen]

P is Parse which we shouldn't count as a query, as B (Bind) won't need it after 5 statements.

Lets start with Q and E in this category.

[jesperpedersen]

Same here.

[jesperpedersen]

You are missing the reset part for the new metric

[An-DJ]

You are missing the reset part for the new metric

Done. I found that a 'P' message(parse) can be sent by prepare statement, and 'B','E'... messages can be sent by execute statement. Maybe the parsing phase should not be considered as query. I have removed it just now.

[jesperpedersen]

Thanks for your contribution !