Idle PostgreSQL connections from Grafana if autorefresh ON

olegz · July 30, 2018, 8:44pm

Using Grafana Cloud Free. Have set up a dashboard and a data source is PostgreSQl hosted on elephantsql.com. Service limits a user to have 5 ocnnections at the same time, but grafana keeps creating connections without closing it if autorefresh ON or if I refresh very fast:

And after some time I get next error message:

svenklemm · July 31, 2018, 8:03am

The number of connections is set to 10 for sql datasources in grafana. But this number is not configurable:

github.com

grafana/grafana/blob/master/pkg/tsdb/sql_engine.go#L97


			queryEndpoint.engine = engine
			return &queryEndpoint, nil
		}
	}


	engine, err := NewXormEngine(config.DriverName, config.ConnectionString)
	if err != nil {
		return nil, err
	}


	engine.SetMaxOpenConns(10)
	engine.SetMaxIdleConns(10)


	engineCache.versions[config.Datasource.Id] = config.Datasource.Version
	engineCache.cache[config.Datasource.Id] = engine
	queryEndpoint.engine = engine


	return &queryEndpoint, nil
}


const rowLimit = 1000000

olegz · July 31, 2018, 1:19pm

Thank you @svenklemm for the answer! What is the purpose to keep a connection open and at the same time open another one?

svenklemm · July 31, 2018, 3:57pm

To query data for different panels in parallel. Or if a panel has multiple queries do those in parallel aswell.

mefraimsson · July 31, 2018, 4:56pm

v5.2.2 fixes a bug which could cause postgres/mysql/mssql datasources to leak connections, see https://github.com/grafana/grafana/issues/12636.

Marcus