]> granicus.if.org Git - postgresql/commitdiff
Add /contrib/pg_standby:
authorBruce Momjian <bruce@momjian.us>
Thu, 8 Feb 2007 15:16:19 +0000 (15:16 +0000)
committerBruce Momjian <bruce@momjian.us>
Thu, 8 Feb 2007 15:16:19 +0000 (15:16 +0000)
  pg_standby is a production-ready program that can be used to
  create a Warm Standby server. Other configuration is required
  as well, all of which is described in the main server manual.

Simon Riggs

contrib/pg_standby/Makefile [new file with mode: 0644]
contrib/pg_standby/README.pg_standby [new file with mode: 0644]
contrib/pg_standby/pg_standby.c [new file with mode: 0644]

diff --git a/contrib/pg_standby/Makefile b/contrib/pg_standby/Makefile
new file mode 100644 (file)
index 0000000..99abebc
--- /dev/null
@@ -0,0 +1,18 @@
+
+PROGRAM = pg_standby
+OBJS   = pg_standby.o
+
+PG_CPPFLAGS = -I$(libpq_srcdir)
+PG_LIBS = $(libpq_pgport)
+
+DOCS = README.pg_standby
+
+ifdef USE_PGXS
+PGXS := $(shell pg_config --pgxs)
+include $(PGXS)
+else
+subdir = contrib/pg_standby
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/pg_standby/README.pg_standby b/contrib/pg_standby/README.pg_standby
new file mode 100644 (file)
index 0000000..9c4ef8e
--- /dev/null
@@ -0,0 +1,164 @@
+pg_standby README              2006/12/08 Simon Riggs
+
+o What is pg_standby?
+
+  pg_standby is a production-ready program that can be used to
+  create a Warm Standby server. Other configuration is required
+  as well, all of which is described in the main server manual.
+
+  The program is designed to be a wait-for restore_command, 
+  required to turn a normal archive recovery into a Warm Standby.
+  Within the restore_command of the recovery.conf you could
+  configure pg_standby in the following way:
+
+    restore_command = 'pg_standby archiveDir %f %p'
+
+  which would be sufficient to define that files will be restored
+  from archiveDir. 
+
+o features of pg_standby
+
+  - pg_standby is written in C. So it is very portable
+    and easy to install.
+
+  - supports copy or link from a directory (only)
+
+  - source easy to modify, with specifically designated
+    sections to modify for your own needs, allowing 
+    interfaces to be written for additional Backup Archive Restore
+    (BAR) systems
+
+  - portable: tested on Linux and Windows 
+
+o How to install pg_standby
+
+ $make
+ $make install
+
+o How to use pg_standby?
+
+  pg_standby should be used within the restore_command of the
+  recovery.conf file. See the main PostgreSQL manual for details.
+
+  The basic usage should be like this:
+
+    restore_command = 'pg_standby archiveDir %f %p'
+
+  with the pg_standby command usage as
+
+    pg_standby [OPTION]... [ARCHIVELOCATION] [NEXTWALFILE] [XLOGFILEPATH]
+
+  When used within the restore_command the %f and %p macros
+  will provide the actual file and path required for the restore/recovery.
+  
+o options
+
+  pg_standby has number of options.
+
+       -c
+               use copy/cp command to restore WAL files from archive
+
+       -d
+               debug/logging option.
+
+       -k numfiles
+               Cleanup files in the archive so that we maintain no more
+               than this many files in the archive. 
+
+               You should be wary against setting this number too low,
+               since this may mean you cannot restart the standby. This
+               is because the last restartpoint marked in the WAL files
+               may be many files in the past and can vary considerably.
+               This should be set to a value exceeding the number of WAL
+               files that can be recovered in 2*checkpoint_timeout seconds,
+               according to the value in the warm standby postgresql.conf.
+               It is wholly unrelated to the setting of checkpoint_segments
+               on either primary or standby.
+
+               If in doubt, use a large value or do not set a value at all.
+
+       -l 
+               use ln command to restore WAL files from archive
+               WAL files will remain in archive
+
+               Link is more efficient, but the default is copy to 
+               allow you to maintain the WAL archive for recovery
+               purposes as well as high-availability.
+
+               This option uses the Windows Vista command mklink
+               to provide a file-to-file symbolic link. -l will
+               not work on versions of Windows prior to Vista.
+               Use the -c option instead.
+               see http://en.wikipedia.org/wiki/NTFS_symbolic_link
+
+       -r maxretries
+               the maximum number of times to retry the restore command if it
+               fails. After each failure, we wait for sleeptime * num_retries
+               so that the wait time increases progressively, so by default
+               we will wait 5 secs, 10 secs then 15 secs before reporting
+               the failure back to the database server. This will be
+               interpreted as and end of recovery and the Standby will come
+               up fully as a result.
+               Default=3
+
+       -s sleeptime
+               the number of seconds to sleep between testing to see
+               if the file to be restored is available in the archive yet.
+               The default setting is not necessarily recommended,
+               consult the main database server manual for discussion.
+               Default=5
+
+       -t triggerfile
+               the presence of the triggerfile will cause recovery to end
+               whether or not the next file is available
+               It is recommended that you use a structured filename to 
+               avoid confusion as to which server is being triggered
+               when multiple servers exist on same system.
+               e.g. /tmp/pgsql.trigger.5432
+
+       -w maxwaittime
+               the maximum number of seconds to wait for the next file,
+               after which recovery will end and the Standby will come up.
+               The default setting is not necessarily recommended,
+               consult the main database server manual for discussion.
+               Default=0
+
+       Note: --help is not supported since pg_standby is not intended
+               for interactive use, except during dev/test
+
+o examples
+
+       Linux
+
+       archive_command = 'cp %p ../archive/%f'
+
+       restore_command = 'pg_standby -l -d -k 255 -r 2 -s 2 -w 0 -t /tmp/pgsql.trigger.5442 $PWD/../archive %f %p 2>> standby.log' 
+
+       which will
+       - use a ln command to restore WAL files from archive
+       - produce logfile output in standby.log
+       - keep the last 255 full WAL files, plus the current one
+       - sleep for 2 seconds between checks for next WAL file is full
+       - never timeout if file not found
+       - stop waiting when a trigger file called /tmp.pgsql.trigger.5442 appears
+
+       Windows
+       
+       archive_command = 'copy %p ..\\archive\\%f'
+       Note that backslashes need to be doubled in the archive_command, but
+       *not* in the restore_command, in 8.2, 8.1, 8.0 on Windows.
+
+       restore_command = 'pg_standby -c -d -s 5 -w 0 -t C:\pgsql.trigger.5442
+..\archive %f %p 2>> standby.log'
+
+       which will
+       - use a copy command to restore WAL files from archive
+       - produce logfile output in standby.log
+       - sleep for 5 seconds between checks for next WAL file is full
+       - never timeout if file not found
+       - stop waiting when a trigger file called C:\pgsql.trigger.5442 appears
+
+o reported test success
+
+       SUSE Linux 10.2
+       Windows XP Pro
diff --git a/contrib/pg_standby/pg_standby.c b/contrib/pg_standby/pg_standby.c
new file mode 100644 (file)
index 0000000..ef732aa
--- /dev/null
@@ -0,0 +1,619 @@
+/*
+ * pg_standby.c
+ * 
+ * Production-ready example of how to create a Warm Standby
+ * database server using continuous archiving as a 
+ * replication mechanism
+ *
+ * We separate the parameters for archive and nextWALfile
+ * so that we can check the archive exists, even if the 
+ * WAL file doesn't (yet).
+ *
+ * This program will be executed once in full for each file
+ * requested by the warm standby server.
+ *
+ * It is designed to cater to a variety of needs, as well
+ * providing a customizable section.
+ * 
+ * Original author:            Simon Riggs      simon@2ndquadrant.com
+ * Current maintainer:         Simon Riggs
+ */
+#include "postgres_fe.h"
+#include "pg_config_manual.h"
+
+#include <ctype.h>
+#include <dirent.h>
+#include <sys/stat.h>
+#include <signal.h>
+
+#ifdef WIN32
+#include "win32.h"
+int getopt(int argc, char * const argv[], const char *optstring);
+#else
+#include <sys/time.h>
+#include <unistd.h>
+
+#ifdef HAVE_GETOPT_H
+#include <getopt.h>
+#endif
+
+#endif   /* ! WIN32 */
+
+extern char *optarg;
+extern int     optind;
+
+/* Options and defaults */
+int sleeptime = 5;                             /* amount of time to sleep between file checks */
+int waittime = -1;                             /* how long we have been waiting, -1 no wait yet */
+int maxwaittime = 0;                   /* how long are we prepared to wait for? */
+int keepfiles = 0;                             /* number of WAL files to keep, 0 keep all */
+int maxretries = 3;                            /* number of retries on restore command */
+bool debug = false;                            /* are we debugging? */
+bool triggered = false;
+bool signaled = false;
+
+char *archiveLocation;           /* where to find the archive? */
+char *triggerPath;                       /* where to find the trigger file? */
+char *xlogFilePath;                     /* where we are going to restore to */
+char *nextWALFileName;           /* the file we need to get from archive */
+char *priorWALFileName;                  /* the file we need to get from archive */
+char WALFilePath[MAXPGPATH];/* the file path including archive */
+char restoreCommand[MAXPGPATH]; /* run this to restore */
+char inclusiveCleanupFileName[MAXPGPATH];                /* the file we need to get from archive */
+
+#define RESTORE_COMMAND_COPY 0
+#define RESTORE_COMMAND_LINK 1
+int restoreCommandType;                 
+
+#define XLOG_DATA                       0
+#define XLOG_HISTORY            1
+#define XLOG_BACKUP_LABEL       2
+int nextWALFileType;
+
+#define SET_RESTORE_COMMAND(cmd, arg1, arg2) \
+       snprintf(restoreCommand, MAXPGPATH, cmd " %s %s", arg1, arg2)
+
+struct stat stat_buf;
+
+/* =====================================================================
+ *
+ *               Customizable section
+ *
+ * =====================================================================
+ *
+ *     Currently, this section assumes that the Archive is a locally
+ *     accessible directory. If you want to make other assumptions,
+ *     such as using a vendor-specific archive and access API, these
+ *     routines are the ones you'll need to change. You're
+ *  enouraged to submit any changes to pgsql-patches@postgresql.org
+ *     or personally to the current maintainer. Those changes may be 
+ *     folded in to later versions of this program.
+ */
+
+#define XLOG_DATA_FNAME_LEN    24
+/* Reworked from access/xlog_internal.h */
+#define XLogFileName(fname, tli, log, seg)     \
+       snprintf(fname, XLOG_DATA_FNAME_LEN + 1, "%08X%08X%08X", tli, log, seg)
+
+/*
+ *  Initialize allows customized commands into the warm standby program.
+ *
+ *  As an example, and probably the common case, we use either
+ *  cp/ln commands on *nix, or copy/move command on Windows.
+ *
+ */
+static void
+CustomizableInitialize(void)
+{
+#ifdef WIN32
+       snprintf(WALFilePath, MAXPGPATH, "%s\\%s", archiveLocation, nextWALFileName);
+       switch (restoreCommandType)
+       {
+               case RESTORE_COMMAND_LINK:
+                       SET_RESTORE_COMMAND("mklink",WALFilePath, xlogFilePath);
+               case RESTORE_COMMAND_COPY:
+               default:
+                       SET_RESTORE_COMMAND("copy",WALFilePath, xlogFilePath);
+                       break;
+        }   
+#else
+       snprintf(WALFilePath, MAXPGPATH, "%s/%s", archiveLocation, nextWALFileName);
+       switch (restoreCommandType)
+       {
+               case RESTORE_COMMAND_LINK:
+#if HAVE_WORKING_LINK
+                       SET_RESTORE_COMMAND("ln -s -f",WALFilePath, xlogFilePath);
+                       break;
+#endif
+               case RESTORE_COMMAND_COPY:
+               default:
+                       SET_RESTORE_COMMAND("cp",WALFilePath, xlogFilePath);
+                       break;
+        }   
+#endif
+
+       /*
+        * This code assumes that archiveLocation is a directory
+        * You may wish to add code to check for tape libraries, etc..
+        * So, since it is a directory, we use stat to test if its accessible
+        */
+       if (stat(archiveLocation, &stat_buf) != 0)
+       {
+               fprintf(stderr, "pg_standby: archiveLocation \"%s\" does not exist\n", archiveLocation);
+               fflush(stderr);
+               exit(2);                        
+       }
+}
+
+/*
+ * CustomizableNextWALFileReady()
+ * 
+ *       Is the requested file ready yet?
+ */
+static bool 
+CustomizableNextWALFileReady()
+{
+       if (stat(WALFilePath, &stat_buf) == 0)
+       {
+               /*
+                * If its a backup file, return immediately
+                * If its a regular file return only if its the right size already
+                */
+               if (strlen(nextWALFileName) > 24 &&
+                       strspn(nextWALFileName, "0123456789ABCDEF") == 24 &&
+                       strcmp(nextWALFileName + strlen(nextWALFileName) - strlen(".backup"),
+                                  ".backup") == 0)
+               {
+                       nextWALFileType = XLOG_BACKUP_LABEL;
+                       return true;
+               }
+               else
+                       if (stat_buf.st_size == XLOG_SEG_SIZE)
+                       {
+#ifdef WIN32
+                               /*
+                                * Windows reports that the file has the right number of bytes
+                                * even though the file is still being copied and cannot be
+                                * opened by pg_standby yet. So we wait for sleeptime secs
+                                * before attempting to restore. If that is not enough, we
+                                * will rely on the retry/holdoff mechanism.
+                                */
+                           pg_usleep(sleeptime * 1000000L);
+#endif
+                               nextWALFileType = XLOG_DATA;
+                               return true;
+                       }
+
+               /*
+                * If still too small, wait until it is the correct size
+                */
+               if (stat_buf.st_size > XLOG_SEG_SIZE)
+               {
+                       if (debug)
+                       {
+                               fprintf(stderr, "file size greater than expected\n");
+                               fflush(stderr);
+                       }
+                       exit(3); 
+               }
+       }
+
+       return false;
+}
+
+#define MaxSegmentsPerLogFile ( 0xFFFFFFFF / XLOG_SEG_SIZE )
+
+static void
+CustomizableCleanupPriorWALFiles(void)
+{
+       uint32                  tli,
+                                       log,
+                                       seg;
+       int                             signed_log = 0;
+
+       if (keepfiles > 0)
+       {
+               sscanf(nextWALFileName, "%08X%08X%08X", &tli, &log, &seg);
+               signed_log = log - (keepfiles / MaxSegmentsPerLogFile);
+               if (keepfiles <= seg)
+                       seg -= keepfiles;
+               else
+               {
+                       seg = MaxSegmentsPerLogFile - (keepfiles % MaxSegmentsPerLogFile);                      
+                       signed_log--;   
+               }
+               log = (uint32) signed_log;
+       }
+
+       /*
+        * Work out name of prior file from current filename
+        */
+       if (keepfiles > 0 && signed_log >= 0 && nextWALFileType == XLOG_DATA)
+       {
+               int                     rc;
+               DIR                             *xldir;
+               struct dirent   *xlde;
+
+               XLogFileName(inclusiveCleanupFileName, tli, log, seg);
+
+               /*
+                * Assume its OK to keep failing. The failure situation may change over
+                * time, so we'd rather keep going on the main processing than fail
+                * because we couldnt clean up yet.
+                */
+               if ((xldir = opendir(archiveLocation)) != NULL)
+               {
+                       while ((xlde = readdir(xldir)) != NULL)
+                       {
+                               /*
+                                * We ignore the timeline part of the XLOG segment identifiers in
+                                * deciding whether a segment is still needed.  This ensures that we
+                                * won't prematurely remove a segment from a parent timeline. We could
+                                * probably be a little more proactive about removing segments of
+                                * non-parent timelines, but that would be a whole lot more
+                                * complicated.
+                                *
+                                * We use the alphanumeric sorting property of the filenames to decide
+                                * which ones are earlier than the inclusiveCleanupFileName file.
+                                */
+                               if (strlen(xlde->d_name) == XLOG_DATA_FNAME_LEN &&
+                                       strspn(xlde->d_name, "0123456789ABCDEF") == XLOG_DATA_FNAME_LEN &&
+                                       strcmp(xlde->d_name + 8, inclusiveCleanupFileName + 8) <= 0)
+                               {
+#ifdef WIN32
+                                       snprintf(WALFilePath, MAXPGPATH, "%s\\%s", archiveLocation, xlde->d_name);
+#else
+                                       snprintf(WALFilePath, MAXPGPATH, "%s/%s", archiveLocation, xlde->d_name);
+#endif
+                                       rc = unlink(WALFilePath);
+
+                                       if (debug)
+                                               fprintf(stderr, "\npg_standby: removed \"%s\"\n", WALFilePath);
+                               }
+                       }
+               }
+               else
+                       fprintf(stderr, "pg_standby: archiveLocation \"%s\" open error\n", archiveLocation);
+
+               closedir(xldir);
+       }
+       fflush(stderr);
+}
+
+/* =====================================================================
+ *               End of Customizable section
+ * =====================================================================
+ */
+
+/*
+ * CheckForExternalTrigger()
+ * 
+ *       Is there a trigger file?
+ */
+static bool 
+CheckForExternalTrigger(void)
+{
+       int rc;
+
+       /*
+        *  Look for a trigger file, if that option has been selected
+        *
+        *  We use stat() here because triggerPath is always a file
+        *  rather than potentially being in an archive
+        */
+       if (triggerPath && stat(triggerPath, &stat_buf) == 0)
+       {
+               fprintf(stderr, "trigger file found\n");
+               fflush(stderr);
+
+               /*
+                * If trigger file found, we *must* delete it. Here's why:
+                * When recovery completes, we will be asked again
+                * for the same file from the archive using pg_standby
+                * so must remove trigger file so we can reload file again
+                * and come up correctly.
+                */
+               rc = unlink(triggerPath);
+               if (rc != 0)
+               {
+                       fprintf(stderr, "\n ERROR: unable to remove \"%s\", rc=%d", triggerPath, rc);
+                       fflush(stderr);
+                       exit(rc);
+               }
+               return true;
+       }
+
+       return false;
+}
+
+/*
+ * RestoreWALFileForRecovery()
+ * 
+ *       Perform the action required to restore the file from archive
+ */
+static bool
+RestoreWALFileForRecovery(void)
+{
+       int rc = 0;
+       int numretries = 0;
+
+       if (debug)
+       {
+               fprintf(stderr, "\nrunning restore              :");
+               fflush(stderr);
+       }
+
+       while (numretries < maxretries)
+       {
+               rc = system(restoreCommand);
+               if (rc == 0)
+               {
+                       if (debug)
+                       {
+                               fprintf(stderr, " success\n");
+                               fflush(stderr);
+                       }
+                       return true;
+               }
+        pg_usleep(numretries++ * sleeptime * 1000000L);
+       }
+
+       /*
+        * Allow caller to add additional info
+        */
+       if (debug)
+               fprintf(stderr, "not restored           : ");
+       return false;
+}
+
+static void
+usage()
+{
+       fprintf(stderr, "\npg_standby allows Warm Standby servers to be configured\n");
+       fprintf(stderr, "Usage:\n");
+       fprintf(stderr, "  pg_standby [OPTION]... [ARCHIVELOCATION] [NEXTWALFILE] [XLOGFILEPATH]\n");
+       fprintf(stderr, "                                                 note space between [ARCHIVELOCATION] and [NEXTWALFILE]\n");
+       fprintf(stderr, "with main intended use via restore_command in the recovery.conf\n");
+       fprintf(stderr, "        restore_command = 'pg_standby [OPTION]... [ARCHIVELOCATION] %%f %%p'\n");
+       fprintf(stderr, "e.g. restore_command = 'pg_standby -l -u /mnt/server/archiverdir %%f %%p'\n");
+       fprintf(stderr, "\nOptions:\n");
+       fprintf(stderr, "  -c                   copies file from archive (default)\n");
+       fprintf(stderr, "  -d                   generate lots of debugging output (testing only)\n");
+       fprintf(stderr, "  -k [NUMFILESTOKEEP]  keeps history of # files in archives; unlinks/removes files beyond that\n");
+       fprintf(stderr, "  -l                   links into archive (leaves file in archive)\n");
+       fprintf(stderr, "  -t [TRIGGERFILE]     defines a trigger file to initiate failover (no default)\n");
+       fprintf(stderr, "  -r [MAXRETRIES]      maximum number of times to retry, with progressive wait (default=3)\n");
+       fprintf(stderr, "  -s [SLEEPTIME]       number of seconds to wait between file checks (default=5)\n");
+       fprintf(stderr, "  -w [MAXWAITTIME]     max number of seconds to wait for a file (0 disables)(default=0)\n");
+       fflush(stderr);
+}
+
+static void
+sighandler(int sig)
+{
+       triggered = true;
+       signaled = true;
+}
+
+/*------------ MAIN ----------------------------------------*/
+int 
+main(int argc, char **argv)
+{
+       int                     c;
+
+       (void) signal(SIGINT,   sighandler);
+       (void) signal(SIGQUIT,  sighandler);
+
+       while ((c = getopt(argc, argv, "cdk:lr:s:t:w:")) != -1)
+       {
+               switch (c)
+               {
+                       case 'c':                       /* Use copy */
+                               restoreCommandType = RESTORE_COMMAND_COPY;
+                               break;
+                       case 'd':                       /* Debug mode */
+                               debug = true;
+                               break;
+                       case 'k':                       /* keepfiles */
+                               keepfiles = atoi(optarg);
+                               if (keepfiles <= 0)
+                               {
+                                       fprintf(stderr, "usage: pg_standby -k keepfiles must be > 0\n");
+                                       usage();
+                                       exit(2);
+                               }
+                               break;
+                       case 'l':                       /* Use link */
+                               restoreCommandType = RESTORE_COMMAND_LINK;
+                               break;
+                       case 'r':                       /* Retries */
+                               maxretries = atoi(optarg);
+                               if (maxretries < 0)
+                               {
+                                       fprintf(stderr, "usage: pg_standby -r maxretries must be > 0\n");
+                                       usage();
+                                       exit(2);
+                               }
+                               break;
+                       case 's':                       /* Sleep time */
+                               sleeptime = atoi(optarg);
+                               if (sleeptime <= 0 || sleeptime > 60)
+                               {
+                                       fprintf(stderr, "usage: pg_standby -s sleeptime incorrectly set\n");
+                                       usage();
+                                       exit(2);
+                               }
+                               break;
+                       case 't':                       /* Trigger file */
+                               triggerPath = optarg;
+                               if (CheckForExternalTrigger())
+                                       exit(1);         /* Normal exit, with non-zero */
+                               break;
+                       case 'w':                       /* Max wait time */
+                               maxwaittime = atoi(optarg);
+                               if (maxwaittime < 0)
+                               {
+                                       fprintf(stderr, "usage: pg_standby -w maxwaittime incorrectly set\n");
+                                       usage();
+                                       exit(2);
+                               }
+                               break;
+                       default:
+                               usage();
+                               exit(2);
+                               break;
+               }
+       }
+
+       /* 
+        * Parameter checking - after checking to see if trigger file present
+        */
+       if (argc == 1)
+       {
+               usage();
+               exit(2);
+       }
+
+       /*
+        * We will go to the archiveLocation to get nextWALFileName.
+        * nextWALFileName may not exist yet, which would not be an error,
+        * so we separate the archiveLocation and nextWALFileName so we can check
+        * separately whether archiveLocation exists, if not that is an error
+        */
+       if (optind < argc)
+       {
+               archiveLocation = argv[optind];
+               optind++;
+       }
+       else
+       {
+               fprintf(stderr, "pg_standby: must specify archiveLocation\n");
+               usage();
+               exit(2);
+       }
+
+       if (optind < argc)
+       {
+               nextWALFileName = argv[optind];
+               optind++;
+       }
+       else
+       {
+               fprintf(stderr, "pg_standby: use %%f to specify nextWALFileName\n");
+               usage();
+               exit(2);
+       }
+
+       if (optind < argc)
+       {
+               xlogFilePath = argv[optind];
+               optind++;
+       }
+       else
+       {
+               fprintf(stderr, "pg_standby: use %%p to specify xlogFilePath\n");
+               usage();
+               exit(2);
+       }
+
+       CustomizableInitialize();
+
+       if (debug)
+       {
+        fprintf(stderr, "\nTrigger file                : %s", triggerPath ? triggerPath : "<not set>");
+               fprintf(stderr, "\nWaiting for WAL file : %s", WALFilePath);
+               fprintf(stderr, "\nWAL file path                : %s", nextWALFileName);
+               fprintf(stderr, "\nRestoring to...              : %s", xlogFilePath);
+               fprintf(stderr, "\nSleep interval               : %d second%s", 
+                                       sleeptime, (sleeptime > 1 ? "s" : " "));
+               fprintf(stderr, "\nMax wait interval    : %d %s", 
+                                       maxwaittime, (maxwaittime > 0 ? "seconds" : "forever"));
+               fprintf(stderr, "\nCommand for restore  : %s", restoreCommand);
+               if (keepfiles > 0)
+                       fprintf(stderr, "\nNum archived files kept      : last %d files", keepfiles);
+               else
+                       fprintf(stderr, "\nNum archived files kept      : all files");
+               fflush(stderr);
+       }
+
+       /*
+        * Check for initial history file: always the first file to be requested
+        * It's OK if the file isn't there - all other files need to wait
+        */
+       if (strlen(nextWALFileName) > 8 &&
+               strspn(nextWALFileName, "0123456789ABCDEF") == 8 &&
+               strcmp(nextWALFileName + strlen(nextWALFileName) - strlen(".history"),
+                          ".history") == 0)
+       {
+               nextWALFileType = XLOG_HISTORY;
+               if (RestoreWALFileForRecovery())
+                       exit(0);
+               else
+               {
+                       if (debug)
+                       {
+                               fprintf(stderr, "history file not found\n");
+                               fflush(stderr);
+                       }
+                       exit(1);
+               }
+       }
+
+       /* 
+        * Main wait loop
+        */
+       while (!CustomizableNextWALFileReady() && !triggered)
+       {
+               if (sleeptime <= 60)
+               pg_usleep(sleeptime * 1000000L);
+
+               if (signaled)
+               {
+                       if (debug)
+                       {
+                               fprintf(stderr, "\nsignaled to exit\n");
+                               fflush(stderr);
+                       }
+               }
+               else
+               {
+
+                       if (debug)
+                       {
+                               fprintf(stderr, "\nWAL file not present yet.");
+                               if (triggerPath)
+                                       fprintf(stderr, " Checking for trigger file...");
+                               fflush(stderr);
+                       }
+
+                       waittime += sleeptime;
+                       
+                       if (!triggered && (CheckForExternalTrigger() || (waittime >= maxwaittime && maxwaittime > 0)))
+                       {
+                               triggered = true;
+                               if (debug && waittime >= maxwaittime && maxwaittime > 0)
+                                       fprintf(stderr, "\nTimed out after %d seconds\n",waittime);
+                       }
+               }
+       }
+
+       /* 
+        * Action on exit 
+        */
+       if (triggered)
+               exit(1);                        /* Normal exit, with non-zero */
+       else
+       {
+               /* 
+                * Once we have restored this file successfully we
+                * can remove some prior WAL files.
+                * If this restore fails we musn't remove any
+                * file because some of them will be requested again
+                * immediately after the failed restore, or when
+                * we restart recovery.
+                */
+               if (RestoreWALFileForRecovery())
+                       CustomizableCleanupPriorWALFiles();
+               exit(0);
+       }
+}