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Fix some issues with WAL segment opening for pg_receivewal --compress

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The logic handling the opening of new WAL segments was fuzzy when using
--compress if a partial, non-compressed, segment with the same base name
existed in the repository storing those files.  In this case, using
--compress would cause the code to first check for the existence and the
size of a non-compressed segment, followed by the opening of a new
compressed, partial, segment.  The code was accidentally working
correctly on most platforms as the buildfarm has proved, except
bowerbird where gzflush() could fail in this code path.  It is wrong
anyway to take the code path used pre-padding when creating a new
partial, non-compressed, segment, so let's fix it.

Note that this issue exists when users mix successive runs of
pg_receivewal with or without compression, as discovered with the tests
introduced by ffc9dda.

While on it, this refactors the code so as code paths that need to know
about the ".gz" suffix are down from four to one in walmethods.c, easing
a bit the introduction of new compression methods.  This addresses a
second issue where log messages generated for an unexpected failure
would not show the compressed segment name involved, which was
confusing, printing instead the name of the non-compressed equivalent.

Reported-by: Georgios Kokolatos
Discussion: https://postgr.es/m/YPDLz2x3o1aX2wRh@paquier.xyz
Backpatch-through: 10
This commit is contained in:
Michael Paquier
2021-07-20 12:12:47 +09:00
parent e1cdf61726
commit 3a0d2d0cba
3 changed files with 78 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

79
src/bin/pg_basebackup/walmethods.c
View File

@ -68,20 +68,32 @@ dir_getlasterror(void)
return strerror(errno);
}
static char *
dir_get_file_name(const char *pathname, const char *temp_suffix)
{
char *filename = pg_malloc0(MAXPGPATH * sizeof(char));
snprintf(filename, MAXPGPATH, "%s%s%s",
pathname, dir_data->compression > 0 ? ".gz" : "",
temp_suffix ? temp_suffix : "");
return filename;
}
static Walfile
dir_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_size)
{
static char tmppath[MAXPGPATH];
char *filename;
int fd;
DirectoryMethodFile *f;
#ifdef HAVE_LIBZ
gzFile gzfp = NULL;
#endif
snprintf(tmppath, sizeof(tmppath), "%s/%s%s%s",
dir_data->basedir, pathname,
dir_data->compression > 0 ? ".gz" : "",
temp_suffix ? temp_suffix : "");
filename = dir_get_file_name(pathname, temp_suffix);
snprintf(tmppath, sizeof(tmppath), "%s/%s",
dir_data->basedir, filename);
/*
* Open a file for non-compressed as well as compressed files. Tracking
@ -232,26 +244,31 @@ dir_close(Walfile f, WalCloseMethod method)
/* Build path to the current version of the file */
if (method == CLOSE_NORMAL && df->temp_suffix)
{
char *filename;
char *filename2;
/*
* If we have a temp prefix, normal operation is to rename the
* file.
*/
snprintf(tmppath, sizeof(tmppath), "%s/%s%s%s",
dir_data->basedir, df->pathname,
dir_data->compression > 0 ? ".gz" : "",
df->temp_suffix);
snprintf(tmppath2, sizeof(tmppath2), "%s/%s%s",
dir_data->basedir, df->pathname,
dir_data->compression > 0 ? ".gz" : "");
filename = dir_get_file_name(df->pathname, df->temp_suffix);
snprintf(tmppath, sizeof(tmppath), "%s/%s",
dir_data->basedir, filename);
/* permanent name, so no need for the prefix */
filename2 = dir_get_file_name(df->pathname, NULL);
snprintf(tmppath2, sizeof(tmppath2), "%s/%s",
dir_data->basedir, filename2);
r = durable_rename(tmppath, tmppath2);
}
else if (method == CLOSE_UNLINK)
{
char *filename;
/* Unlink the file once it's closed */
snprintf(tmppath, sizeof(tmppath), "%s/%s%s%s",
dir_data->basedir, df->pathname,
dir_data->compression > 0 ? ".gz" : "",
df->temp_suffix ? df->temp_suffix : "");
filename = dir_get_file_name(df->pathname, df->temp_suffix);
snprintf(tmppath, sizeof(tmppath), "%s/%s",
dir_data->basedir, filename);
r = unlink(tmppath);
}
else
@ -313,6 +330,12 @@ dir_get_file_size(const char *pathname)
return statbuf.st_size;
}
static int
dir_compression(void)
{
return dir_data->compression;
}
static bool
dir_existsfile(const char *pathname)
{
@ -355,6 +378,8 @@ CreateWalDirectoryMethod(const char *basedir, int compression, bool sync)
method->write = dir_write;
method->get_current_pos = dir_get_current_pos;
method->get_file_size = dir_get_file_size;
method->get_file_name = dir_get_file_name;
method->compression = dir_compression;
method->close = dir_close;
method->sync = dir_sync;
method->existsfile = dir_existsfile;
@ -527,11 +552,22 @@ tar_write_padding_data(TarMethodFile *f, size_t bytes)
return true;
}
static char *
tar_get_file_name(const char *pathname, const char *temp_suffix)
{
char *filename = pg_malloc0(MAXPGPATH * sizeof(char));
snprintf(filename, MAXPGPATH, "%s%s",
pathname, temp_suffix ? temp_suffix : "");
return filename;
}
static Walfile
tar_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_size)
{
int save_errno;
static char tmppath[MAXPGPATH];
char *tmppath;
tar_clear_error();
@ -583,8 +619,7 @@ tar_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_
tar_data->currentfile = pg_malloc0(sizeof(TarMethodFile));
snprintf(tmppath, sizeof(tmppath), "%s%s",
pathname, temp_suffix ? temp_suffix : "");
tmppath = tar_get_file_name(pathname, temp_suffix);
/* Create a header with size set to 0 - we will fill out the size on close */
if (tarCreateHeader(tar_data->currentfile->header, tmppath, NULL, 0, S_IRUSR | S_IWUSR, 0, 0, time(NULL)) != TAR_OK)
@ -689,6 +724,12 @@ tar_get_file_size(const char *pathname)
return -1;
}
static int
tar_compression(void)
{
return tar_data->compression;
}
static off_t
tar_get_current_pos(Walfile f)
{
@ -994,6 +1035,8 @@ CreateWalTarMethod(const char *tarbase, int compression, bool sync)
method->write = tar_write;
method->get_current_pos = tar_get_current_pos;
method->get_file_size = tar_get_file_size;
method->get_file_name = tar_get_file_name;
method->compression = tar_compression;
method->close = tar_close;
method->sync = tar_sync;
method->existsfile = tar_existsfile;