初步学习pg_control文件之六

接前文：初步学习pg_control文件之五 ，DB_IN_ARCHIVE_RECOVERY何时出现？

看代码：如果recovery.conf文件存在，则返回 InArchiveRecovery = true。

/*
 * See if there is a recovery command file (recovery.conf), and if so
 * read in parameters for archive recovery and XLOG streaming.
 * The file is parsed using the main configuration parser.
 */
static void
readRecoveryCommandFile(void)
{
    …
    fd = AllocateFile(RECOVERY_COMMAND_FILE, "r");
    if (fd == NULL)
    {
        if (errno == ENOENT)
            return;                /* not there, so no archive recovery */
        ereport(FATAL,
                (errcode_for_file_access(),
                 errmsg("could not open recovery command file \"%s\": %m",
                        RECOVERY_COMMAND_FILE)));
    }
    …                                    

    /* Enable fetching from archive recovery area */
    InArchiveRecovery = true;                                    

    …
}                                        

然后，如果pg_control文件的state不是 DB_SHUTDOWNED状态，则可以认为需要recovery，

此时，如果 InArchiveRecovery 为true，则开始设置DB_IN_ARCHIVE_RECOVERY 状态。

/*
 * This must be called ONCE during postmaster or standalone-backend startup
 */
void
StartupXLOG(void)
{
    …                                    

    /*
     * Check for recovery control file, and if so set up state for offline
     * recovery
     */
    readRecoveryCommandFile();                                    

    …                                    

    /*
     * Check whether we need to force recovery from WAL.  If it appears to
     * have been a clean shutdown and we did not have a recovery.conf file,
     * then assume no recovery needed.
     */
    if (XLByteLT(checkPoint.redo, RecPtr))
    {
        if (wasShutdown)
            ereport(PANIC,
                    (errmsg("invalid redo record in shutdown checkpoint")));
        InRecovery = true;
    }
    else if (ControlFile->state != DB_SHUTDOWNED)
        InRecovery = true;
    else if (InArchiveRecovery)
    {
        /* force recovery due to presence of recovery.conf */
        InRecovery = true;
    }                                    

    /* REDO */
    if (InRecovery)
    {
        int            rmid;                    

        /* use volatile pointer to prevent code rearrangement */
        volatile XLogCtlData *xlogctl = XLogCtl;                                

        /*
         * Update pg_control to show that we are recovering and to show the
         * selected checkpoint as the place we are starting from. We also mark
         * pg_control with any minimum recovery stop point obtained from a
         * backup history file.
         */
        if (InArchiveRecovery)
            ControlFile->state = DB_IN_ARCHIVE_RECOVERY;
        else
        {
            ereport(LOG,
                    (errmsg("database system was not properly shut down; "
                            automatic recovery in progress)));
            ControlFile->state = DB_IN_CRASH_RECOVERY;
        }                                

        …
        UpdateControlFile();
        …
    }
    …                                    

}