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Add missing deflateEnd() for server-side gzip base backups

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The gzip basebackup sink called deflateInit2() in begin_archive() but
never called deflateEnd(), leaking zlib's internal compression state
(~256KB per archive) until the memory context of the base backup is
destroyed.

The code tree has already a matching deflateEnd() call for each
deflateInit[2]() call (pgrypto, etc.), except for the file touched in
this commit, so this brings more consistency for all the compression
methods.  The server-side LZ4 and zstd implementations require a
dedicated cleanup callback as they allocate their state outside the
context of a palloc().

As currently used, deflateInit2() is called once per tablespace in a
single backup.  Memory would slightly bloat only when dealing with many
tablespaces at once, not across multiple base backups so this is not
worth a backpatch.  This change could matter for future uses of this
code.

zlib allows the definition of memory allocation and free callbacks in
the z_stream object given to a deflateInit[2]().  The base backup
backend code relies on palloc() for the allocations and deflateEnd()
internally only cleans up memory (no fd allocation for example).

Author: Jianghua Yang <yjhjstz@gmail.com>
Discussion: https://postgr.es/m/CAAZLFmQNJ0QNArpWEOZXwv=vbumcWKEHz-b1me5gBqRqG67EwQ@mail.gmail.com
This commit is contained in:
Michael Paquier 2026-03-23 09:04:44 +09:00
parent 69c57466a7
commit ded9754804
1 changed files with 26 additions and 1 deletions
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27
src/backend/backup/basebackup_gzip.c
View file

@ -32,6 +32,9 @@ typedef struct bbsink_gzip
/* Number of bytes staged in output buffer. */
size_t bytes_written;
/* Has the zstream been initialized? */
bool zstream_initialized;
} bbsink_gzip;
static void bbsink_gzip_begin_backup(bbsink *sink);
@ -39,6 +42,7 @@ static void bbsink_gzip_begin_archive(bbsink *sink, const char *archive_name);
static void bbsink_gzip_archive_contents(bbsink *sink, size_t len);
static void bbsink_gzip_manifest_contents(bbsink *sink, size_t len);
static void bbsink_gzip_end_archive(bbsink *sink);
static void bbsink_gzip_cleanup(bbsink *sink);
static void *gzip_palloc(void *opaque, unsigned items, unsigned size);
static void gzip_pfree(void *opaque, void *address);
@ -51,7 +55,7 @@ static const bbsink_ops bbsink_gzip_ops = {
.manifest_contents = bbsink_gzip_manifest_contents,
.end_manifest = bbsink_forward_end_manifest,
.end_backup = bbsink_forward_end_backup,
.cleanup = bbsink_forward_cleanup
.cleanup = bbsink_gzip_cleanup
};
#endif
@ -141,6 +145,7 @@ bbsink_gzip_begin_archive(bbsink *sink, const char *archive_name)
ereport(ERROR,
errcode(ERRCODE_INTERNAL_ERROR),
errmsg("could not initialize compression library"));
mysink->zstream_initialized = true;
/*
* Add ".gz" to the archive name. Note that the pg_basebackup -z produces
@ -266,6 +271,10 @@ bbsink_gzip_end_archive(bbsink *sink)
mysink->bytes_written = 0;
}
/* Release the compression resources. */
deflateEnd(zs);
mysink->zstream_initialized = false;
/* Must also pass on the information that this archive has ended. */
bbsink_forward_end_archive(sink);
}
@ -301,4 +310,20 @@ gzip_pfree(void *opaque, void *address)
pfree(address);
}
/*
* In case the backup fails, make sure we free the compression context by
* calling deflateEnd() if needed to avoid a resource leak.
*/
static void
bbsink_gzip_cleanup(bbsink *sink)
{
bbsink_gzip *mysink = (bbsink_gzip *) sink;
if (mysink->zstream_initialized)
{
deflateEnd(&mysink->zstream);
mysink->zstream_initialized = false;
}
}
#endif