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| -rw-r--r-- | .gitignore | 1 | ||||
| -rw-r--r-- | LICENSE | 165 | ||||
| -rw-r--r-- | LICENSE.GPL3 | 674 | ||||
| -rw-r--r-- | Makefile | 40 | ||||
| -rw-r--r-- | README.md | 93 | ||||
| -rw-r--r-- | config.h | 16 | ||||
| -rw-r--r-- | pgbak.c | 569 | ||||
| -rw-r--r-- | test.py | 187 |
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Interpretation of Sections 15 and 16. + + If the disclaimer of warranty and limitation of liability provided +above cannot be given local legal effect according to their terms, +reviewing courts shall apply local law that most closely approximates +an absolute waiver of all civil liability in connection with the +Program, unless a warranty or assumption of liability accompanies a +copy of the Program in return for a fee. + + END OF TERMS AND CONDITIONS + + How to Apply These Terms to Your New Programs + + If you develop a new program, and you want it to be of the greatest +possible use to the public, the best way to achieve this is to make it +free software which everyone can redistribute and change under these terms. + + To do so, attach the following notices to the program. It is safest +to attach them to the start of each source file to most effectively +state the exclusion of warranty; and each file should have at least +the "copyright" line and a pointer to where the full notice is found. + + <one line to give the program's name and a brief idea of what it does.> + Copyright (C) <year> <name of author> + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. + +Also add information on how to contact you by electronic and paper mail. + + If the program does terminal interaction, make it output a short +notice like this when it starts in an interactive mode: + + <program> Copyright (C) <year> <name of author> + This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate +parts of the General Public License. Of course, your program's commands +might be different; for a GUI interface, you would use an "about box". + + You should also get your employer (if you work as a programmer) or school, +if any, to sign a "copyright disclaimer" for the program, if necessary. +For more information on this, and how to apply and follow the GNU GPL, see +<https://www.gnu.org/licenses/>. + + The GNU General Public License does not permit incorporating your program +into proprietary programs. If your program is a subroutine library, you +may consider it more useful to permit linking proprietary applications with +the library. If this is what you want to do, use the GNU Lesser General +Public License instead of this License. But first, please read +<https://www.gnu.org/licenses/why-not-lgpl.html>. diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..638e08d --- /dev/null +++ b/Makefile @@ -0,0 +1,40 @@ +CFLAGS_dev:= \ + -std=gnu17 -Wall -Wextra \ + -Werror=conversion \ + -Werror=sign-conversion \ + -Werror=float-conversion \ + -Werror=old-style-definition \ + -Werror=strict-prototypes \ + -Werror=missing-prototypes \ + -Werror=implicit-function-declaration \ + -Werror=missing-declarations \ + -Werror=return-type \ + -Werror=pointer-arith \ + -Werror=vla \ + -Werror=incompatible-pointer-types \ + -Werror=int-conversion \ + -Werror=int-conversion \ + -Werror=format=2 \ + -Werror=overflow \ + -Werror=shift-count-overflow \ + -Werror=init-self \ + -Werror=shadow \ + -Werror=redundant-decls \ + -Werror=missing-field-initializers \ + -Werror=write-strings \ + -Werror=date-time \ + -Werror=nested-externs \ + -Werror=endif-labels \ + -Werror=undef \ + -Wmissing-include-dirs \ + -Wfloat-equal \ + -Winline \ + -Wmissing-noreturn \ + -Werror=implicit-fallthrough \ + -Werror=shift-overflow + +CC?=gcc +CFLAGS?=-O2 -flto -ggdb + +pgbak: pgbak.c + $(CC) $(CFLAGS_dev) $(CFLAGS) $< -o $@ diff --git a/README.md b/README.md new file mode 100644 index 0000000..3040ca0 --- /dev/null +++ b/README.md @@ -0,0 +1,93 @@ +# pgbak + +## Overview + +`pgbak` is a utility for PostgreSQL backups based on WAL archiving. Data is stored in a local directory provided through the `PGBAK` environment variable. + +Note that `pgbak` itself does not back up the data to any remote location. Instead the user must provide a script at `$PGBAK/scripts/backup` which is invoked when a backup needs to be performed. If no remote backups are desired, it can simply be a symlink to `/bin/true`. + +## Backup directory structure + +- `$PGBAK/TIMESTAMP/` — One or more directories containing base backups and WAL segments. The `TIMESTAMP` is when the base backup was taken. + - `$PGBAK/TIMESTAMP/base.tzst` — A compressed tarball containing a full database backup as created by `pg_basebackup`. + - `$PGBAK/TIMESTAMP/pg_wal/NNN.zst` — One or more compressed WAL segments following the full backup. +- `$PGBAK/current` — Symlink to the latest backup directory. +- `$PGBAK/scripts/` — Directory for user-provided scripts. + - `$PGBAK/scripts/backup` — script called after one or more WAL files were archived; required +- `$PGBAK/pgbak.lock` — Lock/state file. Locking is done through `fcntl()`, so deleting this file should never be necessary. + +Currently `pgbak` never deletes old backup directories. + +## Usage + +The following subcommands are provided: + +- `pgbak wal PATH` — Archive the given WAL file and exit. A background sync process will be started if one isn't running. +- `pgbak sync` — Run sync in the foreground if necessary. +- `pgbak force-sync` — Run sync in the foreground. The `backup` script is always invoked. +- `pgbak wait [TIMEOUT]` — If a sync is running, wait for it to finish. The `TIMEOUT` is in seconds and defaults to infinity. Exits with non-zero status on error or timeout. + +The sync process is responsible for maintaining the `$PGBAK` directory. In particular, it + +- creates a new full backup every now and again +- calls `$PGBAK/scripts/backup` + +### Writing `$PGBAK/scripts/backup` + +When the `backup` script is started, the current directory is set to the subdirectory of `$PGBAK` that needs to be backed up. The script is given the following arguments: + +- the timestamp of the base backup +- the current timestamp + +Existing files will never disappear/change, provided the base backup timestamp is the same. However, new compressed WAL files may appear at any time. If this happens while the `backup` script is running, it will be called again with a refreshed current timestamp. + +On failure, the `backup` script will be retried indefinitely. The timestamps will be the same if no new WAL files have appeared. + +### Restoring from a backup + +In order to restore from a backup, simply extract `base.tzst` to an empty `$PGDATA` directory and uncompress all WAL files into `$PGDATA/pg_wal`. + +Recovery can take quite a while if many WAL files need to be replayed. It may be beneficial to do it without `fsync` and instead `sync` later: + +```sh +mkdir -m700 data +tar -C data -xf backup/base.tzst +zstd -d --output-dir-flat data/pg_wal backup/pg_wal/* +postgres --single -FD data < /dev/null +sync -f data +``` + +## Example configuration + +`postgresql.conf`: +```ini +archive_mode = on +archive_command = 'pgbak wal %p' +archive_timeout = 1h +``` + +`postgresql.service`: +```ini +[Unit] +# Make sure DNS works while postgres/pgbak is running +After=nss-lookup.target + +[Service] +Environment=PGBAK=/media/backup/pgsql +# Wait up to 2 minutes for pgbak sync to finish after postgres is stopped. +ExecStopPost=pgbak wait 120 +``` + +`$PGBAK/scripts/backup`: +```sh +#!/bin/sh +exec rsync -r ./ "backup@host.example:pg-$1/" +``` + +To make your first backup, simply restart postgres and call `pg_switch_wal()`. + +## Misc + +`pgbak` uses [Zstandard](http://www.zstd.net/)'s command-line tool for compression. The compression options may be tweaked in `config.h`. + +Currently only Linux is supported because of `O_TMPFILE` and `F_OFD_SETLK`. diff --git a/config.h b/config.h new file mode 100644 index 0000000..0dcd86b --- /dev/null +++ b/config.h @@ -0,0 +1,16 @@ +static const char *const BASE_OUT = "base.tzst"; +static const char *const BASE_BACKUP_ARGV[] = { + "pg_basebackup", + "-F", "t", + "-X", "none", + "-D", "-", + NULL, +}; +static const char *const BASE_COMPRESS_ARGV[] = { + "zstd", "-12", "-T0", NULL, +}; + +static const char *const WAL_EXT = ".zst"; +static const char *const WAL_COMPRESS_ARGV[] = { + "zstd", "-19", "--single-thread", NULL, +}; @@ -0,0 +1,569 @@ +// SPDX-License-Identifier: LGPL-3.0-or-later +// +// Copyright 2021 Hristo Venev + +#define _GNU_SOURCE +#include <dirent.h> +#include <errno.h> +#include <fcntl.h> +#include <limits.h> +#include <stdbool.h> +#include <stddef.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/file.h> +#include <sys/stat.h> +#include <sys/wait.h> +#include <time.h> +#include <unistd.h> + +#include "config.h" + +static int backup_dfd; +static int lck_fd; + + +static const char *const LOCK_KIND[] = { + // The `state` lock must be held while doing state-related updates, for + // example modifying the "archive needed" flag. + "state", + + // The `backup` lock is held by the archiver process. + "backup", + + // The `wait` lock is acquired by the archiver process after the `backup` + // lock. It is also acquired by processes that wait for the archiver to + // finish. + "wait", +}; + +static void lck_release(int pos) { + struct flock l = { + .l_type = F_UNLCK, + .l_whence = SEEK_SET, + .l_start = pos, + .l_len = 1, + }; + while(true) { + if(fcntl(lck_fd, F_OFD_SETLKW, &l) >= 0) return; + if(errno == EINTR) continue; + fprintf(stderr, "Failed to release %s lock: %m\n", LOCK_KIND[pos]); + abort(); + } +} + +static void lck_wait(int pos) { + struct flock l = { + .l_type = F_WRLCK, + .l_whence = SEEK_SET, + .l_start = pos, + .l_len = 1, + }; + while(true) { + if(fcntl(lck_fd, F_OFD_SETLKW, &l) >= 0) return; + if(errno == EINTR) continue; + fprintf(stderr, "Failed to acquire %s lock: %m\n", LOCK_KIND[pos]); + abort(); + } +} + +static bool lck_try(int pos) { + struct flock l = { + .l_type = F_WRLCK, + .l_whence = SEEK_SET, + .l_start = pos, + .l_len = 1, + }; + while(true) { + if(fcntl(lck_fd, F_OFD_SETLK, &l) >= 0) return true; + if(errno == EINTR) continue; + if(errno == EAGAIN || errno == EACCES) return false; + fprintf(stderr, "Failed to acquire %s lock: %m\n", LOCK_KIND[pos]); + abort(); + } +} + +static int lck_read(int pos) { + unsigned char b; + ssize_t r = pread(lck_fd, &b, 1, pos); + if(r < 0) { + fprintf(stderr, "Failed to read lock file: %m\n"); + abort(); + } + if(r >= 1) return b; + return -1; +} + +static void lck_write(int pos, unsigned char b) { + ssize_t r = pwrite(lck_fd, &b, 1, pos); + if(r < 0) { + fprintf(stderr, "Failed to read lock file: %m\n"); + abort(); + } + if(r == 0) { + fprintf(stderr, "Failed to write lock file: Empty write\n"); + abort(); + } +} + +static pid_t cld_spawn(int in_fd, int out_fd, int chdir_fd, const char *const *argv) { + pid_t child = fork(); + if(child < 0) { + fprintf(stderr, "fork(): %m\n"); + abort(); + } + if(child == 0) { + if(chdir_fd >= 0 && fchdir(chdir_fd) < 0) _exit(1); + if(in_fd >= 0 && dup2(in_fd, 0) < 0) _exit(1); + if(out_fd >= 0 && dup2(out_fd, 1) < 0) _exit(1); + execvpe(argv[0], (char*const*)argv, environ); + _exit(1); + } + return child; +} + +static int cld_wait(pid_t child, const char *cld) { + int status; + if(waitpid(child, &status, 0) < 0) { + fprintf(stderr, "waitpid(): %m\n"); + abort(); + } + + if(WIFEXITED(status)) { + int r = WEXITSTATUS(status); + if(r) { + fprintf(stderr, "Child process '%s' exited with status %d\n", cld, r); + } + return r; + } else if(WIFSIGNALED(status)) { + int r = WTERMSIG(status); + fprintf(stderr, "Child process '%s' killed by signal %d\n", cld, r); + return 128 + r; + } else { + fprintf(stderr, "waitpid(): Unknown status\n"); + abort(); + } +} + +static int cld_pipe(int in_fd, int out_fd, const char *const *argv) { + pid_t child = cld_spawn(in_fd, out_fd, -1, argv); + if(in_fd >= 0) close(in_fd); + + int r = cld_wait(child, argv[0]); + if(r == 0 && out_fd >= 0 && fsync(out_fd) < 0) { + fprintf(stderr, "fsync(): %m\n"); + r = -1; + } + return r; +} + + +static int bak_snapshot(char *name) { + { + struct timespec ts; + if(clock_gettime(CLOCK_REALTIME, &ts) < 0) { + fprintf(stderr, "clock_gettime(CLOCK_REALTIME): %m\n"); + abort(); + } + sprintf(name, "%lld", (long long)ts.tv_sec); + } + + if(mkdirat(backup_dfd, name, 0700) < 0) { + fprintf(stderr, "Failed to create $PGBAK/%s: %m\n", name); + return -1; + } + + int subdfd = openat(backup_dfd, name, O_RDONLY | O_DIRECTORY | O_CLOEXEC); + if(subdfd < 0) { + fprintf(stderr, "Failed to open $PGBAK/%s: %m\n", name); + goto fail_rmdir; + } + + if(mkdirat(subdfd, "pg_wal", 0700) < 0) { + fprintf(stderr, "Failed to create $PGBAK/%s/pg_wal: %m\n", name); + goto fail_close; + } + + int out_fd = -1; + out_fd = openat(subdfd, ".", O_WRONLY | O_TMPFILE | O_CLOEXEC, 0600); + if(out_fd < 0) { + fprintf(stderr, "Failed to create $PGBAK/%s/%s: %m\n", name, BASE_OUT); + goto fail_clean; + } + + (void)unlinkat(backup_dfd, "current", 0); + if(symlinkat(name, backup_dfd, "current") < 0) { + fprintf(stderr, "Failed to update $PGBAK/current: %m\n"); + goto fail; + } + + int pfd[2]; + if(pipe(pfd) < 0) { + fprintf(stderr, "pipe(): %m\n"); + goto fail; + } + + fprintf(stderr, "Creating full backup in $PGBAK/%s/%s\n", name, BASE_OUT); + + pid_t pid_backup = cld_spawn(-1, pfd[1], -1, BASE_BACKUP_ARGV); + close(pfd[1]); + + if(cld_pipe(pfd[0], out_fd, BASE_COMPRESS_ARGV)) { + (void)kill(pid_backup, SIGKILL); + (void)waitpid(pid_backup, NULL, 0); + goto fail; + } + if(cld_wait(pid_backup, BASE_BACKUP_ARGV[0])) { + goto fail; + } + + char fd_path[32]; + sprintf(fd_path, "/proc/self/fd/%d", out_fd); + if(linkat(AT_FDCWD, fd_path, subdfd, BASE_OUT, AT_SYMLINK_FOLLOW) < 0) { + fprintf(stderr, "Failed to link base backup: %m\n"); + goto fail; + } + + close(out_fd); + if(fsync(subdfd) < 0 || fsync(backup_dfd) < 0) { + fprintf(stderr, "fsync(): %m\n"); + abort(); + } + return subdfd; + +fail: + close(out_fd); +fail_clean: + (void)unlinkat(subdfd, "pg_wal", AT_REMOVEDIR); +fail_close: + close(subdfd); +fail_rmdir: + (void)unlinkat(backup_dfd, name, AT_REMOVEDIR); + return -1; +} + +static bool should_pgbasebackup(int subdfd) { + struct stat st; + + if(fstatat(subdfd, BASE_OUT, &st, AT_SYMLINK_NOFOLLOW) < 0) { + fprintf(stderr, "Failed to stat %s: %m\n", BASE_OUT); + return true; + } + if(!S_ISREG(st.st_mode)) { + fprintf(stderr, "Expected regular file at %s\n", BASE_OUT); + return true; + } + + off_t base_size = st.st_size; + off_t wal_size = 0; + off_t wal_count = 0; + + int wal_dfd = openat(subdfd, "pg_wal", O_RDONLY | O_DIRECTORY | O_CLOEXEC); + if(wal_dfd < 0) { + fprintf(stderr, "Failed to open $PGBAK/current/pg_wal: %m\n"); + return true; + } + + DIR *wal_dir = fdopendir(wal_dfd); + if(!wal_dir) { + fprintf(stderr, "fdopendir(): %m\n"); + abort(); + } + + while(true) { + errno = 0; + struct dirent *ent = readdir(wal_dir); + if(!ent) { + if(errno == 0) break; + fprintf(stderr, "readdir(): %m\n"); + abort(); + } + if(!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, "..")) continue; + + wal_count += 1; + if(fstatat(wal_dfd, ent->d_name, &st, AT_SYMLINK_NOFOLLOW) < 0) continue; + wal_size += st.st_size; + } + closedir(wal_dir); + + return wal_count > 8 && (wal_size >> 1) >= base_size; +} + +// Should we become an archiver? If so, acquire `backup` and `wait` locks. +static bool bak_begin(bool force) { + bool r = false; + lck_wait(0); + + if(!lck_try(1)) { + if(force) lck_write(0, 2); + goto end; + } + + if(!force && lck_read(0) <= 0) { + lck_release(1); + goto end; + } + + lck_wait(2); + r = true; + +end: + lck_release(0); + return r; +} + +// Archiver +static void bak_work(void) { + unsigned int backoff = 4 * 512; + char name[32]; + char ts_s[32]; + const char *const cmd[] = { + "../scripts/backup", name, ts_s, NULL, + }; + + int subdfd = -1; + + { + ssize_t r = readlinkat(backup_dfd, "current", name, sizeof(name)); + if(r < 0) { + if(errno != ENOENT) { + fprintf(stderr, "Failed to readlink() $PGBAK/current: %m\n"); + exit(1); + } + } else if((size_t)r >= sizeof(name)) { + fprintf(stderr, "Symlink $PGBAK/current target too long\n"); + exit(1); + } else { + name[r] = 0; + subdfd = openat(backup_dfd, name, O_RDONLY | O_DIRECTORY | O_CLOEXEC); + } + } + + bool want_ts = true; + while(true) { + lck_write(0, 1); + + bool want_snapshot = false; + const char *failed = NULL; + if(subdfd >= 0) { + if(want_ts) { + struct timespec ts; + if(clock_gettime(CLOCK_REALTIME, &ts) < 0) { + fprintf(stderr, "clock_gettime(CLOCK_REALTIME): %m\n"); + abort(); + } + sprintf(ts_s, "%lld", (long long)ts.tv_sec); + want_ts = false; + } + + pid_t child = cld_spawn(-1, -1, subdfd, cmd); + if(cld_wait(child, cmd[0])) { + failed = "backup script"; + } else { + fprintf(stderr, "Finished backup %s-%s\n", name, ts_s); + } + + if(should_pgbasebackup(subdfd)) { + close(subdfd); + want_snapshot = true; + } + } else { + want_snapshot = true; + } + + if(want_snapshot) { + subdfd = bak_snapshot(name); + if(subdfd < 0) { + failed = "pg_basebackup"; + } + } + + lck_wait(0); + int r = lck_read(0); + if(r < 0) { + fprintf(stderr, "Lock file truncated: %m\n"); + abort(); + } + if(r > 1) { + want_ts = true; + } else if(!failed) { + lck_write(0, 0); + break; + } + lck_release(0); + + if(failed) { + backoff += backoff >> 2; + if(backoff > 153600) backoff = 153600; + unsigned rnd; + (void)getentropy(&rnd, sizeof(rnd)); + backoff += rnd & 1023; + + struct timespec tv = { + .tv_sec = backoff / 512, + .tv_nsec = backoff % 512 * 1953125, + }; + fprintf(stderr, "Error in %s, retrying in %u.%09u seconds\n", failed, (unsigned)tv.tv_sec, (unsigned)tv.tv_nsec); + (void)nanosleep(&tv, NULL); + } else { + backoff = 4 * 512; + } + } +} + +static void on_sigalrm(int) { + _Exit(1); +} + +static int cmd_wait(long timeout) { + if(timeout == 0) { + if(lck_try(2)) return 0; + return 1; + } + if(timeout > 0 && (unsigned long)timeout <= UINT_MAX) { + signal(SIGALRM, on_sigalrm); + alarm((unsigned)timeout); + } + lck_wait(2); + return 0; +} + +static int cmd_wal(const char *name) { + size_t name_len = strlen(name); + if(name_len < 8 || name_len >= 192 || !!memcmp(name, "pg_wal/", 7) || memchr(name + 7, '/', name_len - 7)) { + fprintf(stderr, "Invalid WAL file name '%s'\n", name); + return 1; + } + + int wal_dfd = openat(backup_dfd, "current/pg_wal", O_RDONLY | O_DIRECTORY | O_CLOEXEC); + if(wal_dfd < 0) { + if(errno == ENOENT) goto do_full; + fprintf(stderr, "Failed to open $PGBAK/current/pg_wal: %m\n"); + return 1; + } + + char name_out[256]; + memcpy(name_out, name + 7, name_len - 7); + memcpy(name_out + name_len - 7, WAL_EXT, strlen(WAL_EXT) + 1); + + if(faccessat(wal_dfd, name_out, R_OK, AT_SYMLINK_NOFOLLOW) >= 0) { + fprintf(stderr, "WAL backup exists at $PGBAK/current/%s, skipping\n", name_out); + return 0; + } + + int out_fd = openat(wal_dfd, ".", O_WRONLY | O_TMPFILE | O_CLOEXEC, 0600); + if(out_fd < 0) { + fprintf(stderr, "Failed to create WAL backup file at $PGBAK/current: %m\n"); + goto fail_dir; + } + + int in_fd = open(name, O_RDONLY | O_CLOEXEC); + if(in_fd < 0) { + fprintf(stderr, "Failed to open WAL file %s: %m\n", name); + goto fail; + } + + fprintf(stderr, "Archiving %s\n", name); + + if(cld_pipe(in_fd, out_fd, WAL_COMPRESS_ARGV)) { + fprintf(stderr, "Failed to create WAL backup\n"); + goto fail; + } + + char fd_path[32]; + sprintf(fd_path, "/proc/self/fd/%d", out_fd); + if(linkat(AT_FDCWD, fd_path, wal_dfd, name_out, AT_SYMLINK_FOLLOW) < 0) { + fprintf(stderr, "Failed to link WAL backup: %m\n"); + goto fail; + } + close(out_fd); + + if(fsync(wal_dfd) < 0) { + fprintf(stderr, "fsync(): %m\n"); + goto fail_dir; + } + close(wal_dfd); + +do_full: + if(!bak_begin(true)) return 0; + + pid_t r = fork(); + if(r < 0) { + fprintf(stderr, "fork(): %m\n"); + abort(); + } + if(r != 0) return 0; + + bak_work(); + exit(0); + +fail: + close(out_fd); +fail_dir: + close(wal_dfd); + return 1; +} + +int main(int argc, char **argv) { + if(argc == 1) goto usage; + + const char *backup_dir = getenv("PGBAK"); + if(!backup_dir || backup_dir[0] != '/') { + fprintf(stderr, "$PGBAK not set to an absolute path\n"); + return 1; + } + + backup_dfd = open(backup_dir, O_RDONLY | O_DIRECTORY | O_CLOEXEC); + if(backup_dfd < 0) { + fprintf(stderr, "Failed to open $PGBAK directory '%s': %m\n", backup_dir); + return 1; + } + + lck_fd = openat(backup_dfd, "pgbak.lock", O_RDWR | O_CREAT | O_CLOEXEC, 0600); + if(lck_fd < 0) { + fprintf(stderr, "Failed to open $PGBAK/pgbak.lock: %m\n"); + return 1; + } + + const char *op = argv[1]; + + if(!strcmp(op, "wal")) { + if(argc != 3) goto usage; + return cmd_wal(argv[2]); + } + + if(!strcmp(op, "sync")) { + if(argc != 2) goto usage; + if(bak_begin(false)) { + bak_work(); + return 0; + } + return cmd_wait(-1); + } + + if(!strcmp(op, "force-sync")) { + if(argc != 2) goto usage; + if(bak_begin(true)) { + bak_work(); + return 0; + } + return cmd_wait(-1); + } + + if(!strcmp(op, "wait")) { + if(argc != 2 && argc != 3) goto usage; + long timeout = -1; + if(argc > 2) { + char *ep = NULL; + timeout = strtol(argv[2], &ep, 10); + if(timeout < 0 || ep == argv[2] || *ep != 0) goto usage; + } + return cmd_wait(timeout); + } + +usage: + char *arg0 = argv[0]; + fprintf(stderr, "Usage:\n\t%s wal PATH\n\t%s sync\n\t%s force-sync\n\t%s wait [TIMEOUT_SEC]\n", arg0, arg0, arg0, arg0); + return 1; +} @@ -0,0 +1,187 @@ +import os +import random +import re +import select +import shlex +import shutil +import socket +import subprocess +import tarfile +import tempfile +import threading +import time +import unittest + +def unzst(data): + return subprocess.run(['zstd', '-d'], stdout=subprocess.PIPE, input=data).stdout + +class Test(unittest.TestCase): + def setUp(self): + self._done = False + + self._wal_lock = threading.Lock() + self._wal_k = -1 + self._wal_i = 0 + self._wal_req = threading.Condition(self._wal_lock) + self._wal_done = threading.Condition(self._wal_lock) + + self._bak_relax = False + self._bak_list = [] + + self._prog = os.path.realpath('./pgbak') + self._sock,self._sock_prog = socket.socketpair(socket.AF_UNIX) + + self._tmpdir = tempfile.mkdtemp() + self._bin_path = os.path.join(self._tmpdir, 'bin') + os.mkdir(self._bin_path) + self._bak_path = os.path.join(self._tmpdir, 'bak') + os.mkdir(self._bak_path) + os.mkdir(os.path.join(self._bak_path, 'scripts')) + self._db_path = os.path.join(self._tmpdir, 'db') + os.mkdir(self._db_path) + os.mkdir(os.path.join(self._db_path, 'pg_wal')) + + with open(os.path.join(self._bin_path, 'pg_basebackup'), 'w') as f: + f.write('#!/bin/sh\necho -n r >&0; read t; cat base; sleep "$t"; [ "$((RANDOM%200))" != 0 ]\n') + os.fchmod(f.fileno(), 0o755) + + with open(os.path.join(self._bak_path, 'scripts', 'backup'), 'w') as f: + shp = shlex.quote(self._tmpdir) + f.write(f'#!/bin/sh\nset -e; sleep 0.1; [ "$((RANDOM%200))" == 0 ] && exit 1; tar -c . > {shp}/bak-dir.tar; echo -n w >&0; read t\n') + os.fchmod(f.fileno(), 0o755) + + self._wal_thr = threading.Thread(target=self._run_wal) + self._sock_thr = threading.Thread(target=self._run_sock) + + self._wal_thr.start() + self._sock_thr.start() + + self._wal_wait(-1) + + def _run_wal(self): + i = 0 + while True: + with open(os.path.join(self._db_path, 'pg_wal', f'{i}'), 'wb') as f: + f.write(f'wal {i}\n'.encode() + os.urandom(4096)) + + with self._wal_lock: + self._wal_k = i + self._wal_done.notify_all() + while self._wal_i == i: + self._wal_req.wait() + if self._done: + return + + time.sleep(random.random() * 0.2) + self._run('wal', f'pg_wal/{i}') + i += 1 + + def _run_sock(self): + while True: + op = self._sock.recv(1) + if not op: + break + + if op == b'w': + self._bak_read() + self._sock.send(b'.\n') + continue + + if op == b'r': + i = self._wal_make() + with open(os.path.join(self._db_path, 'base'), 'wb') as f: + f.write(f'up to {i}\n'.encode() + os.urandom(20480)) + t = random.random() * 0.2 + self._wal_make() + self._sock.send(f'{t}\n'.encode()) + continue + + raise RuntimeError(f'bad command {op!r}') + + def _wal_wait(self, i): + with self._wal_lock: + while self._wal_k <= i: + self._wal_done.wait() + + def _wal_gen(self): + with self._wal_lock: + self._wal_i = (i := self._wal_i) + 1 + self._wal_req.notify() + return i + + def tearDown(self): + with self._wal_lock: + self._done = True + self._wal_req.notify() + self._sock_prog.close() + + self._wal_thr.join() + self._sock_thr.join() + + self._sock.close() + shutil.rmtree(self._tmpdir) + + def _wal_make(self): + i = self._wal_gen() + self._wal_wait(i) + return i + + def _bak_read(self): + with tarfile.TarFile(os.path.join(self._tmpdir, 'bak-dir.tar')) as tf: + data = unzst(tf.extractfile('./base.tzst').read()).split(b'\n')[0].decode() + m = re.fullmatch('up to ([0-9]+)', data) + if m is None: + raise ValueError(f'bad base data') + begin = int(m.group(1)) + + wals = set() + for i in tf.getmembers(): + if i.name in {'.', './base.tzst', './pg_wal'}: + continue + m = re.fullmatch('\./pg_wal/(0|[1-9][0-9]*)\.zst', i.name) + if m is None: + raise ValueError(f'bad archive member {i.name!r}') + data = unzst(tf.extractfile(i).read()).split(b'\n')[0].decode() + m = re.fullmatch('wal ([0-9]+)', data) + if m is None: + raise ValueError(f'bad WAL data in {i.name!r}') + wals.add(int(m.group(1))) + + print('>>> got backup', begin,sorted(wals)) + + end = begin + while end in wals: + end += 1 + end -= 1 + if end < begin + 1 and not self._bak_relax: + raise RuntimeError('missing first WAL') + + self._bak_list.append(end) + + def _run(self, *args): + env = {**os.environ} + env['PATH'] = f"{self._bin_path}:{env['PATH']}" + env['PGBAK'] = self._bak_path + subprocess.run([self._prog, *args], env=env, cwd=self._db_path, stdin=self._sock_prog, check=True) + + def testArchiving(self): + for _ in range(1000): + i = self._wal_make() + if random.randrange(20) == 0: + self._run('wait') + if not self._bak_relax: + self.assertGreaterEqual(self._bak_list[-1], i) + self._bak_relax = False + + if random.randrange(30) == 0: + # Relax the backup consistency requirement until the end of the next sync + self._bak_relax = True + try: + os.unlink(os.path.join(self._bak_path, 'current')) + except FileNotFoundError: + pass + else: + print('>>> forcing full backup') + +if __name__ == '__main__': + unittest.main() |