greenplumn event_version 源码
greenplumn event_version 代码
文件路径：/src/backend/utils/mmgr/event_version.c
/*-------------------------------------------------------------------------
*
* event_version.c
* Implementation of the event version provider. This module does not provide
* any API. Instead it just sets up shared memory variables so that other
* modules can track and update event versions as necessary. Event versions
* are used to provide a temporal ordering of runaway events and cleanup events,
* as well as the idle and the activation events of different processes.
*
* Copyright (c) 2014-Present VMware, Inc. or its affiliates.
*
*
* IDENTIFICATION
* src/backend/utils/mmgr/event_version.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "cdb/cdbvars.h"
#include "miscadmin.h"
#include "storage/shmem.h"
#include "utils/vmem_tracker.h"
/* External dependencies within the runaway cleanup framework */
extern bool vmemTrackerInited;
#define SHMEM_EVENT_VERSION_PROVIDER "The shared counter for event version provider"
#define SHMEM_RUNAWAY_EVENT_VERSION "Most recent runaway detection version"
/*
* A shared memory counter that provides a set of monotonically
* increasing values. The counter is only incremented by the runaway
* detector, at the time of a new runaway event. In fact, at the time
* of runaway event, the detector would increment it by 2, using the
* skipped value as the version of the runaway event. This ensures
* that the runaway version doesn't overlap with any other version
* as used by other processes on the segment as activation and
* deactivation version.
*
* The current version would be used by processes during activation
* or deactivation to identify when it becmes idle/active.
*/
volatile EventVersion *CurrentVersion = NULL;
/* The event version of the latest runaway event */
volatile EventVersion *latestRunawayVersion = 0;
void EventVersion_ShmemInit(void);
/*
* Initializes the event version provider's shared memory states.
*/
void
EventVersion_ShmemInit()
{
Assert(!vmemTrackerInited);
bool alreadyInShmem = false;
CurrentVersion = (EventVersion *)
ShmemInitStruct(SHMEM_EVENT_VERSION_PROVIDER,
sizeof(EventVersion),
&alreadyInShmem);
Assert(alreadyInShmem || !IsUnderPostmaster);
latestRunawayVersion = (EventVersion *)
ShmemInitStruct(SHMEM_RUNAWAY_EVENT_VERSION,
sizeof(EventVersion),
&alreadyInShmem);
Assert(alreadyInShmem || !IsUnderPostmaster);
Assert(NULL != CurrentVersion);
Assert(NULL != latestRunawayVersion);
if(!IsUnderPostmaster)
{
*latestRunawayVersion = 0;
/*
* As no runaway event has happened yet, we must make sure that
* the CurrentVersion is larger than latestRunawayVersion
*/
*CurrentVersion = *latestRunawayVersion + 1;
}
}
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