[jira] [Commented] (HAWQ-1521) Idle QE Processes Can't Quit After An Interval

["Hubert Zhang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HAWQ-1521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16148589#comment-16148589 ] 

Hubert Zhang commented on HAWQ-1521:
------------------------------------

HAWQ remove allocateGang to record gang information in the following variables.
static List *allocatedReaderGangsN = NIL;
static List *availableReaderGangsN = NIL;
static List *allocatedReaderGangs1 = NIL;
static List *availableReaderGangs1 = NIL;
static Gang *primaryWriterGang = NULL;
As a result, calling gangsExist will always return false.
But the cached gang information, to be more specific the cached QE information could be found in other places at QD side. 
The following struct ExecutorCache(the two pools) contains the all the cached QE by a session. We could use this data structure to quit idle QE when session is idled for a long time.
typedef struct ExecutorCache {
	bool				init;
	MemoryContext		ctx;
	struct PoolMgrState	*pool;
	struct PoolMgrState *entrydb_pool; // pool for entry db connection
	int		cached_num;
	int		allocated_num;
	int		takeover_num;
} ExecutorCache;

static ExecutorCache	executor_cache;

> Idle QE Processes Can't Quit After An Interval
> ----------------------------------------------
>
>                 Key: HAWQ-1521
>                 URL: https://issues.apache.org/jira/browse/HAWQ-1521
>             Project: Apache HAWQ
>          Issue Type: Bug
>            Reporter: Lin Wen
>            Assignee: Radar Lei
>
> After a query is finished, there are some idle QE processes on segments. These QE processes are expected to quit after a time interval, this interval is controlled by a GUC gp_vmem_idle_resource_timeout, the default value is 18 seconds.
> However, this does't act as expected. Idle QE processes on segments always exist there, unless the QD process quit. 
> The reason is in postgres.c, the codes to enable this timer can't get executed. function gangsExist() always return false, since gang related structures are all NULL.
> 	if (IdleSessionGangTimeout > 0 && gangsExist())
> 		if (!enable_sig_alarm( IdleSessionGangTimeout /* ms */, false))
> 			elog(FATAL, "could not set timer for client wait timeout");



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