QA: Waiting query for WalSenderMain

Products

• VMware Tanzu Greenplum

Issue/Introduction

During querying of the catalog on Greenplum 7, the following query can be seen running all the time.

Is this new to Greenplum 7.

 

pid	datname	state	wait_event_type	username	wait_event
1770639		active	Activity	gpadmin	WalSenderMain

Cause

The walsender process is used for Greenplum Database Write-Ahead Logging (WAL) replication when coordinator or segment mirroring is enabled. This process can be additionally tracked using gp_stat_replication view.

Greenplum 7 additionally provides new columns in pg_stat_activity for tracking query waiting events.

These columns include "wait_event_type" and "wait_event" which you are showing to indicate the values of "Activity" and "WalSenderMain" respectively.

Please refer to this document for more description of this state tracking.

Resolution

It is suggested to query pg_stat_replication with the pid for observing details and tracking progress.