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Commitc5b5168

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pg_rewind: fsync target data directory.
Previously pg_rewind did not fsync any files. That's problematic, giventhat the target directory is modified. If the database was startedafterwards,2ce439f luckily already caused the data directory to besynced to disk at postmaster startup; reducing the scope of the problem.To fix, use initdb -S, at the end of the pg_rewind run. It doesn't seemworthwhile to duplicate the code into pg_rewind, and initdb -S isalready used that way by pg_upgrade.Reported-By: Andres FreundAuthor: Michael Paquier, somewhat edited by meDiscussion: 20160310034352.iuqgvpmg5qmnxtkz@alap3.anarazel.de CAB7nPqSytVG1o4S3S2pA1O=692ekurJ+fckW2PywEG3sNw54Ow@mail.gmail.comBackpatch: 9.5, where pg_rewind was introduced
1 parentfa5098d commitc5b5168

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2 files changed

+57
-1
lines changed

2 files changed

+57
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lines changed

‎src/bin/pg_rewind/file_ops.c

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Original file line numberDiff line numberDiff line change
@@ -79,7 +79,6 @@ close_target_file(void)
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dstpath,strerror(errno));
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dstfd=-1;
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/* fsync? */
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}
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void

‎src/bin/pg_rewind/pg_rewind.c

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Original file line numberDiff line numberDiff line change
@@ -36,6 +36,7 @@ static void createBackupLabel(XLogRecPtr startpoint, TimeLineID starttli,
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staticvoiddigestControlFile(ControlFileData*ControlFile,char*source,
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size_tsize);
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staticvoidupdateControlFile(ControlFileData*ControlFile);
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staticvoidsyncTargetDirectory(constchar*argv0);
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staticvoidsanityChecks(void);
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staticvoidfindCommonAncestorTimeline(XLogRecPtr*recptr,TimeLineID*tli);
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@@ -343,6 +344,9 @@ main(int argc, char **argv)
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ControlFile_new.state=DB_IN_ARCHIVE_RECOVERY;
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updateControlFile(&ControlFile_new);
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pg_log(PG_PROGRESS,"syncing target data directory\n");
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syncTargetDirectory(argv[0]);
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printf(_("Done!\n"));
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return0;
@@ -572,3 +576,56 @@ updateControlFile(ControlFileData *ControlFile)
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close_target_file();
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}
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/*
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* Sync target data directory to ensure that modifications are safely on disk.
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*
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* We do this once, for the whole data directory, for performance reasons. At
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* the end of pg_rewind's run, the kernel is likely to already have flushed
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* most dirty buffers to disk. Additionally initdb -S uses a two-pass approach
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* (only initiating writeback in the first pass), which often reduces the
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* overall amount of IO noticeably.
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*/
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staticvoid
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syncTargetDirectory(constchar*argv0)
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{
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intret;
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#defineMAXCMDLEN (2 * MAXPGPATH)
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charexec_path[MAXPGPATH];
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charcmd[MAXCMDLEN];
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/* locate initdb binary */
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if ((ret=find_other_exec(argv0,"initdb",
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"initdb (PostgreSQL) "PG_VERSION"\n",
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exec_path))<0)
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{
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charfull_path[MAXPGPATH];
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if (find_my_exec(argv0,full_path)<0)
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strlcpy(full_path,progname,sizeof(full_path));
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if (ret==-1)
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pg_fatal("The program \"initdb\" is needed by %s but was \n"
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"not found in the same directory as \"%s\".\n"
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"Check your installation.\n",progname,full_path);
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else
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pg_fatal("The program \"initdb\" was found by \"%s\"\n"
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"but was not the same version as %s.\n"
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"Check your installation.\n",full_path,progname);
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}
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/* only skip processing after ensuring presence of initdb */
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if (dry_run)
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return;
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/* finally run initdb -S */
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if (debug)
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snprintf(cmd,MAXCMDLEN,"\"%s\" -D \"%s\" -S",
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exec_path,datadir_target);
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else
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snprintf(cmd,MAXCMDLEN,"\"%s\" -D \"%s\" -S > \"%s\"",
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exec_path,datadir_target,DEVNULL);
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if (system(cmd)!=0)
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pg_fatal("sync of target directory failed\n");
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}

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