Postgresql – How to properly monitor the number of PostgreSQL database connections

monitoringperformancepostgresql

I tried to use a Nagios script for monitoring the number of database connections on a Postgres database and I reached this problem: these are counted as currently open-connections and measured every 5 minutes.

SELECT sum(numbackends) FROM pg_stat_database;

Still, this seems to miss a huge number of short-lived connections, so the statistics are far from the reality.

I tried to run the script manually and I observed big changes even between two connections made few seconds away one from another.

How could I get this information in a reliable way? like max(connectios) happened during a time interval.

Best Answer

Its better to use Workload monitoring tools like pgbadger for checking database connections and overall load. It will help you understand which users are connecting for how much time and what queries are being fired by them. For information on installing and configuring pgbadger, refer this page.

If you just want to check the number of active connections, you can use select count(*) from pg_stat_activity where state='active'

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Mysql – How to get the maxium number of concurrent connections to MySQL over a specific time interval

The only thing I can think of is finding some what (maybe through a cron job) to record the 'Threads_connected' values every minute, and then calculate the max of these values.

I'm not sure if you can do exactly what you are asking for without resetting the 'Max_used_connections' before your monitoring period.

Sql-server – How to monitor the call count per stored procedure per timespan

You can get this (and more) from Dynamic Management Views (DMVs). To get statistics for a particular stored procedure, try the following query.

SELECT
    OBJECT_NAME(qt.objectid)
  , qs.execution_count AS [Execution Count]
  , qs.execution_count / DATEDIFF(Second, qs.creation_time, GETDATE()) AS [Calls/Second]
  , qs.total_worker_time / qs.execution_count AS [AvgWorkerTime]
  , qs.total_worker_time AS [TotalWorkerTime]
  , qs.total_elapsed_time / qs.execution_count AS [AvgElapsedTime]
  , qs.max_logical_reads
  , qs.max_logical_writes
  , qs.total_physical_reads
  , DATEDIFF(Minute, qs.creation_time, GETDATE()) AS [Age in Cache]
FROM
    sys.dm_exec_query_stats AS qs
CROSS APPLY 
    sys.dm_exec_sql_text(qs.[sql_handle]) AS qt
WHERE
    qt.[dbid] = DB_ID()
AND qt.objectid = OBJECT_ID('StoredProcedureName')
OPTION (RECOMPILE);

To look at the most frequently executed procedures:

SELECT
    OBJECT_NAME(qt.objectid)
  , qs.execution_count AS [Execution Count]
  , qs.execution_count / DATEDIFF(Second, qs.creation_time, GETDATE()) AS [Calls/Second]
  , qs.total_worker_time / qs.execution_count AS [AvgWorkerTime]
  , qs.total_worker_time AS [TotalWorkerTime]
  , qs.total_elapsed_time / qs.execution_count AS [AvgElapsedTime]
  , qs.max_logical_reads
  , qs.max_logical_writes
  , qs.total_physical_reads
  , DATEDIFF(Minute, qs.creation_time, GETDATE()) AS [Age in Cache]
FROM
    sys.dm_exec_query_stats AS qs
CROSS APPLY 
    sys.dm_exec_sql_text(qs.[sql_handle]) AS qt
WHERE
    qt.[dbid] = DB_ID()
ORDER BY
    qs.execution_count DESC
OPTION (RECOMPILE);

The values reported are cumulative since the last restart. If you want to measure over a fixed period, use the command below to reset wait stats.

DBCC SQLPERF("sys.dm_os_wait_stats",CLEAR);

If you wanted to measure fixed timespans across the day, you could feed the query output to a table via an agent job and either a) calculate the values between two runs or b) issue the wait stats reset as the last step in the agent job.

Alternatively, capture a profiler trace and run it through Clear Trace.

Best Answer

Related Solutions

Mysql – How to get the maxium number of concurrent connections to MySQL over a specific time interval

Sql-server – How to monitor the call count per stored procedure per timespan

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