On Wed, Jan 1, 2014 at 11:53 PM, Dimitri Fontaine <dimi...@2ndquadrant.fr>wrote:
> Hi,
>
> As much as I've seen people frown upon $subject, it still happens in the
> wild, and Magnus seems to agree that the current failure mode of our
> pg_basebackup tool when confronted to the situation is a bug.
>
> So here's a fix, attached.
>
> To reproduce, mkdir -p $PGDATA/tbs/foo then CREATE TABLESPACE there, and
> then pg_basebackup your server. If doing so from the same server, as I
> did, then pick the tar format, as here:
>
> pg_basebackup -Ft -z -c fast -v -X fetch -D /tmp/backup
>
> Then use tar to see that the base backup contains the whole content of
> your foo tablespace, and if you did create another tablespace within
> $PGDATA/pg_tblspc (which is the other common way to trigger that issue)
> then add it to what you want to see:
>
> tar tzvf /tmp/backup/base.tar.gz pg_tblspc tbs/foo pg_tblspc/bar
>
> Note that empty directories are expected, so tar should output their
> entries. Those directories are where you need to be restoring the
> tablespace tarballs.
>
> When using pg_basebackup in plain mode, the error is that you get a copy
> of all your tablespaces first, then the main PGDATA is copied over and
> as the destination directories already do exists (and not empty) the
> whole backup fails there.
>
> The bug should be fixed against all revisions of pg_basebackup, though I
> didn't try to apply this very patch on all target branches.
>
I had a second round of thought about this, and I don't think this one is
going to work. Unfortunately, it's part of the advice I gave you yesterday
that was bad I think :)
We can't get away with just comparing the relative part of the pathname.
Because it will fail if there is another path with exactly the same length,
containing the tablespace.
I think we might want to store a value in the tablespaceinfo struct
indicating whether it's actually inside PGDATA (since we have the full path
at that point), and then skip it based on that instead. Or store and pass
the value of getcwd() perhaps.
Or am I thinking wrong now instead? :)
I've attached a slightly updated patch - I changed around a bit of logic
order and updated some comments during my review. And added error-checking.
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
*** a/src/backend/replication/basebackup.c
--- b/src/backend/replication/basebackup.c
***************
*** 45,51 **** typedef struct
} basebackup_options;
! static int64 sendDir(char *path, int basepathlen, bool sizeonly);
static int64 sendTablespace(char *path, bool sizeonly);
static bool sendFile(char *readfilename, char *tarfilename,
struct stat * statbuf, bool missing_ok);
--- 45,52 ----
} basebackup_options;
! static int64 sendDir(char *path, int basepathlen, int rootpathlen,
! bool sizeonly, List *tablespaces);
static int64 sendTablespace(char *path, bool sizeonly);
static bool sendFile(char *readfilename, char *tarfilename,
struct stat * statbuf, bool missing_ok);
***************
*** 100,105 **** perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
--- 101,119 ----
XLogRecPtr endptr;
TimeLineID endtli;
char *labelfile;
+ char cwd[MAXPGPATH];
+ int rootpathlen;
+
+ /*
+ * We need to compute rootpathlen to allow for skipping tablespaces
+ * installed within PGDATA.
+ */
+ if (!getcwd(cwd, MAXPGPATH))
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not determine current directory: %m")));
+
+ rootpathlen = strlen(cwd) + 1;
backup_started_in_recovery = RecoveryInProgress();
***************
*** 165,171 **** perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
/* Add a node for the base directory at the end */
ti = palloc0(sizeof(tablespaceinfo));
! ti->size = opt->progress ? sendDir(".", 1, true) : -1;
tablespaces = lappend(tablespaces, ti);
/* Send tablespace header */
--- 179,186 ----
/* Add a node for the base directory at the end */
ti = palloc0(sizeof(tablespaceinfo));
! ti->size = opt->progress ?
! sendDir(".", 1, rootpathlen, true, tablespaces) : -1;
tablespaces = lappend(tablespaces, ti);
/* Send tablespace header */
***************
*** 191,197 **** perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
sendFileWithContent(BACKUP_LABEL_FILE, labelfile);
/* ... then the bulk of the files ... */
! sendDir(".", 1, false);
/* ... and pg_control after everything else. */
if (lstat(XLOG_CONTROL_FILE, &statbuf) != 0)
--- 206,212 ----
sendFileWithContent(BACKUP_LABEL_FILE, labelfile);
/* ... then the bulk of the files ... */
! sendDir(".", 1, rootpathlen, false, tablespaces);
/* ... and pg_control after everything else. */
if (lstat(XLOG_CONTROL_FILE, &statbuf) != 0)
***************
*** 778,785 **** sendTablespace(char *path, bool sizeonly)
_tarWriteHeader(TABLESPACE_VERSION_DIRECTORY, NULL, &statbuf);
size = 512; /* Size of the header just added */
! /* Send all the files in the tablespace version directory */
! size += sendDir(pathbuf, strlen(path), sizeonly);
return size;
}
--- 793,805 ----
_tarWriteHeader(TABLESPACE_VERSION_DIRECTORY, NULL, &statbuf);
size = 512; /* Size of the header just added */
! /*
! * Send all the files in the tablespace version directory.
! * Since we don't protect against nested tablespaces anywhere
! * other than the root directory, no need to pass rootpathlen
! * and tablespaces list.
! */
! size += sendDir(pathbuf, strlen(path), 0, sizeonly, NIL);
return size;
}
***************
*** 788,796 **** sendTablespace(char *path, bool sizeonly)
* Include all files from the given directory in the output tar stream. If
* 'sizeonly' is true, we just calculate a total length and return it, without
* actually sending anything.
*/
static int64
! sendDir(char *path, int basepathlen, bool sizeonly)
{
DIR *dir;
struct dirent *de;
--- 808,820 ----
* Include all files from the given directory in the output tar stream. If
* 'sizeonly' is true, we just calculate a total length and return it, without
* actually sending anything.
+ *
+ * Omit any directory listed in tablepaces, so as to avoid backuping
+ * tablespaces twice when users created their tablespaces inside PGDATA.
*/
static int64
! sendDir(char *path, int basepathlen, int rootpathlen,
! bool sizeonly, List *tablespaces)
{
DIR *dir;
struct dirent *de;
***************
*** 931,936 **** sendDir(char *path, int basepathlen, bool sizeonly)
--- 955,964 ----
}
else if (S_ISDIR(statbuf.st_mode))
{
+ bool skip_this_dir = false;
+ int pathbuflen = strlen(pathbuf);
+ ListCell *lc;
+
/*
* Store a directory entry in the tar file so we can get the
* permissions right.
***************
*** 939,946 **** sendDir(char *path, int basepathlen, bool sizeonly)
_tarWriteHeader(pathbuf + basepathlen + 1, NULL, &statbuf);
size += 512; /* Size of the header just added */
! /* call ourselves recursively for a directory */
! size += sendDir(pathbuf, basepathlen, sizeonly);
}
else if (S_ISREG(statbuf.st_mode))
{
--- 967,1000 ----
_tarWriteHeader(pathbuf + basepathlen + 1, NULL, &statbuf);
size += 512; /* Size of the header just added */
! /*
! * call ourselves recursively for a directory, unless that
! * directory is listed in the tablespaces list (which indicates
! * that this is a tablespace that happens to be placed inside
! * PGADATA)
! */
! foreach(lc, tablespaces)
! {
! tablespaceinfo *ti = (tablespaceinfo *) lfirst(lc);
!
! /*
! * ti->path will have the complete absolute path to the
! * tablespace target, whereas pathbuf holds a relative
! * path (from the data directory, including "./").
! * Compare the relative parts only */
! */
! if (ti->path &&
! pathbuflen > 2 && /* ./ */
! strlen(ti->path) > rootpathlen &&
! strcmp(ti->path + rootpathlen, pathbuf + 2) == 0)
! {
! skip_this_dir = true;
! break;
! }
! }
! if (!skip_this_dir)
! size += sendDir(pathbuf, basepathlen, rootpathlen,
! sizeonly, tablespaces);
}
else if (S_ISREG(statbuf.st_mode))
{
--
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