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Diffstat (limited to 'src/bin/pg_rewind/filemap.c')
| -rw-r--r-- | src/bin/pg_rewind/filemap.c | 832 |
1 files changed, 832 insertions, 0 deletions
diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c new file mode 100644 index 0000000..2618b4c --- /dev/null +++ b/src/bin/pg_rewind/filemap.c @@ -0,0 +1,832 @@ +/*------------------------------------------------------------------------- + * + * filemap.c + * A data structure for keeping track of files that have changed. + * + * This source file contains the logic to decide what to do with different + * kinds of files, and the data structure to support it. Before modifying + * anything, pg_rewind collects information about all the files and their + * attributes in the target and source data directories. It also scans the + * WAL log in the target, and collects information about data blocks that + * were changed. All this information is stored in a hash table, using the + * file path relative to the root of the data directory as the key. + * + * After collecting all the information required, the decide_file_actions() + * function scans the hash table and decides what action needs to be taken + * for each file. Finally, it sorts the array to the final order that the + * actions should be executed in. + * + * Copyright (c) 2013-2021, PostgreSQL Global Development Group + * + *------------------------------------------------------------------------- + */ + +#include "postgres_fe.h" + +#include <sys/stat.h> +#include <unistd.h> + +#include "catalog/pg_tablespace_d.h" +#include "common/hashfn.h" +#include "common/string.h" +#include "datapagemap.h" +#include "filemap.h" +#include "pg_rewind.h" +#include "storage/fd.h" + +/* + * Define a hash table which we can use to store information about the files + * appearing in source and target systems. + */ +static uint32 hash_string_pointer(const char *s); +#define SH_PREFIX filehash +#define SH_ELEMENT_TYPE file_entry_t +#define SH_KEY_TYPE const char * +#define SH_KEY path +#define SH_HASH_KEY(tb, key) hash_string_pointer(key) +#define SH_EQUAL(tb, a, b) (strcmp(a, b) == 0) +#define SH_SCOPE static inline +#define SH_RAW_ALLOCATOR pg_malloc0 +#define SH_DECLARE +#define SH_DEFINE +#include "lib/simplehash.h" + +#define FILEHASH_INITIAL_SIZE 1000 + +static filehash_hash *filehash; + +static bool isRelDataFile(const char *path); +static char *datasegpath(RelFileNode rnode, ForkNumber forknum, + BlockNumber segno); + +static file_entry_t *insert_filehash_entry(const char *path); +static file_entry_t *lookup_filehash_entry(const char *path); +static int final_filemap_cmp(const void *a, const void *b); +static bool check_file_excluded(const char *path, bool is_source); + +/* + * Definition of one element part of an exclusion list, used to exclude + * contents when rewinding. "name" is the name of the file or path to + * check for exclusion. If "match_prefix" is true, any items matching + * the name as prefix are excluded. + */ +struct exclude_list_item +{ + const char *name; + bool match_prefix; +}; + +/* + * The contents of these directories are removed or recreated during server + * start so they are not included in data processed by pg_rewind. + * + * Note: those lists should be kept in sync with what basebackup.c provides. + * Some of the values, contrary to what basebackup.c uses, are hardcoded as + * they are defined in backend-only headers. So this list is maintained + * with a best effort in mind. + */ +static const char *excludeDirContents[] = +{ + /* + * Skip temporary statistics files. PG_STAT_TMP_DIR must be skipped even + * when stats_temp_directory is set because PGSS_TEXT_FILE is always + * created there. + */ + "pg_stat_tmp", /* defined as PG_STAT_TMP_DIR */ + + /* + * It is generally not useful to backup the contents of this directory + * even if the intention is to restore to another primary. See backup.sgml + * for a more detailed description. + */ + "pg_replslot", + + /* Contents removed on startup, see dsm_cleanup_for_mmap(). */ + "pg_dynshmem", /* defined as PG_DYNSHMEM_DIR */ + + /* Contents removed on startup, see AsyncShmemInit(). */ + "pg_notify", + + /* + * Old contents are loaded for possible debugging but are not required for + * normal operation, see SerialInit(). + */ + "pg_serial", + + /* Contents removed on startup, see DeleteAllExportedSnapshotFiles(). */ + "pg_snapshots", + + /* Contents zeroed on startup, see StartupSUBTRANS(). */ + "pg_subtrans", + + /* end of list */ + NULL +}; + +/* + * List of files excluded from filemap processing. Files are excluded + * if their prefix match. + */ +static const struct exclude_list_item excludeFiles[] = +{ + /* Skip auto conf temporary file. */ + {"postgresql.auto.conf.tmp", false}, /* defined as PG_AUTOCONF_FILENAME */ + + /* Skip current log file temporary file */ + {"current_logfiles.tmp", false}, /* defined as + * LOG_METAINFO_DATAFILE_TMP */ + + /* Skip relation cache because it is rebuilt on startup */ + {"pg_internal.init", true}, /* defined as RELCACHE_INIT_FILENAME */ + + /* + * If there's a backup_label or tablespace_map file, it belongs to a + * backup started by the user with pg_start_backup(). It is *not* correct + * for this backup. Our backup_label is written later on separately. + */ + {"backup_label", false}, /* defined as BACKUP_LABEL_FILE */ + {"tablespace_map", false}, /* defined as TABLESPACE_MAP */ + + /* + * If there's a backup_manifest, it belongs to a backup that was used to + * start this server. It is *not* correct for this backup. Our + * backup_manifest is injected into the backup separately if users want + * it. + */ + {"backup_manifest", false}, + + {"postmaster.pid", false}, + {"postmaster.opts", false}, + + /* end of list */ + {NULL, false} +}; + +/* + * Initialize the hash table for the file map. + */ +void +filehash_init(void) +{ + filehash = filehash_create(FILEHASH_INITIAL_SIZE, NULL); +} + +/* Look up entry for 'path', creating a new one if it doesn't exist */ +static file_entry_t * +insert_filehash_entry(const char *path) +{ + file_entry_t *entry; + bool found; + + entry = filehash_insert(filehash, path, &found); + if (!found) + { + entry->path = pg_strdup(path); + entry->isrelfile = isRelDataFile(path); + + entry->target_exists = false; + entry->target_type = FILE_TYPE_UNDEFINED; + entry->target_size = 0; + entry->target_link_target = NULL; + entry->target_pages_to_overwrite.bitmap = NULL; + entry->target_pages_to_overwrite.bitmapsize = 0; + + entry->source_exists = false; + entry->source_type = FILE_TYPE_UNDEFINED; + entry->source_size = 0; + entry->source_link_target = NULL; + + entry->action = FILE_ACTION_UNDECIDED; + } + + return entry; +} + +static file_entry_t * +lookup_filehash_entry(const char *path) +{ + return filehash_lookup(filehash, path); +} + +/* + * Callback for processing source file list. + * + * This is called once for every file in the source server. We record the + * type and size of the file, so that decide_file_action() can later decide what + * to do with it. + */ +void +process_source_file(const char *path, file_type_t type, size_t size, + const char *link_target) +{ + file_entry_t *entry; + + /* + * Pretend that pg_wal is a directory, even if it's really a symlink. We + * don't want to mess with the symlink itself, nor complain if it's a + * symlink in source but not in target or vice versa. + */ + if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK) + type = FILE_TYPE_DIRECTORY; + + /* + * sanity check: a filename that looks like a data file better be a + * regular file + */ + if (type != FILE_TYPE_REGULAR && isRelDataFile(path)) + pg_fatal("data file \"%s\" in source is not a regular file", path); + + /* Remember this source file */ + entry = insert_filehash_entry(path); + if (entry->source_exists) + pg_fatal("duplicate source file \"%s\"", path); + entry->source_exists = true; + entry->source_type = type; + entry->source_size = size; + entry->source_link_target = link_target ? pg_strdup(link_target) : NULL; +} + +/* + * Callback for processing target file list. + * + * Record the type and size of the file, like process_source_file() does. + */ +void +process_target_file(const char *path, file_type_t type, size_t size, + const char *link_target) +{ + file_entry_t *entry; + + /* + * Do not apply any exclusion filters here. This has advantage to remove + * from the target data folder all paths which have been filtered out from + * the source data folder when processing the source files. + */ + + /* + * Like in process_source_file, pretend that pg_wal is always a directory. + */ + if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK) + type = FILE_TYPE_DIRECTORY; + + /* Remember this target file */ + entry = insert_filehash_entry(path); + if (entry->target_exists) + pg_fatal("duplicate source file \"%s\"", path); + entry->target_exists = true; + entry->target_type = type; + entry->target_size = size; + entry->target_link_target = link_target ? pg_strdup(link_target) : NULL; +} + +/* + * This callback gets called while we read the WAL in the target, for every + * block that has changed in the target system. It decides if the given + * 'blkno' in the target relfile needs to be overwritten from the source, and + * if so, records it in 'target_pages_to_overwrite' bitmap. + * + * NOTE: All the files on both systems must have already been added to the + * hash table! + */ +void +process_target_wal_block_change(ForkNumber forknum, RelFileNode rnode, + BlockNumber blkno) +{ + char *path; + file_entry_t *entry; + BlockNumber blkno_inseg; + int segno; + + segno = blkno / RELSEG_SIZE; + blkno_inseg = blkno % RELSEG_SIZE; + + path = datasegpath(rnode, forknum, segno); + entry = lookup_filehash_entry(path); + pfree(path); + + /* + * If the block still exists in both systems, remember it. Otherwise we + * can safely ignore it. + * + * If the block is beyond the EOF in the source system, or the file + * doesn't exist in the source at all, we're going to truncate/remove it + * away from the target anyway. Likewise, if it doesn't exist in the + * target anymore, we will copy it over with the "tail" from the source + * system, anyway. + * + * It is possible to find WAL for a file that doesn't exist on either + * system anymore. It means that the relation was dropped later in the + * target system, and independently on the source system too, or that it + * was created and dropped in the target system and it never existed in + * the source. Either way, we can safely ignore it. + */ + if (entry) + { + Assert(entry->isrelfile); + + if (entry->target_exists) + { + if (entry->target_type != FILE_TYPE_REGULAR) + pg_fatal("unexpected page modification for non-regular file \"%s\"", + entry->path); + + if (entry->source_exists) + { + off_t end_offset; + + end_offset = (blkno_inseg + 1) * BLCKSZ; + if (end_offset <= entry->source_size && end_offset <= entry->target_size) + datapagemap_add(&entry->target_pages_to_overwrite, blkno_inseg); + } + } + } +} + +/* + * Is this the path of file that pg_rewind can skip copying? + */ +static bool +check_file_excluded(const char *path, bool is_source) +{ + char localpath[MAXPGPATH]; + int excludeIdx; + const char *filename; + + /* + * Skip all temporary files, .../pgsql_tmp/... and .../pgsql_tmp.* + */ + if (strstr(path, "/" PG_TEMP_FILE_PREFIX) != NULL || + strstr(path, "/" PG_TEMP_FILES_DIR "/") != NULL) + { + return true; + } + + /* check individual files... */ + for (excludeIdx = 0; excludeFiles[excludeIdx].name != NULL; excludeIdx++) + { + int cmplen = strlen(excludeFiles[excludeIdx].name); + + filename = last_dir_separator(path); + if (filename == NULL) + filename = path; + else + filename++; + + if (!excludeFiles[excludeIdx].match_prefix) + cmplen++; + if (strncmp(filename, excludeFiles[excludeIdx].name, cmplen) == 0) + { + if (is_source) + pg_log_debug("entry \"%s\" excluded from source file list", + path); + else + pg_log_debug("entry \"%s\" excluded from target file list", + path); + return true; + } + } + + /* + * ... And check some directories. Note that this includes any contents + * within the directories themselves. + */ + for (excludeIdx = 0; excludeDirContents[excludeIdx] != NULL; excludeIdx++) + { + snprintf(localpath, sizeof(localpath), "%s/", + excludeDirContents[excludeIdx]); + if (strstr(path, localpath) == path) + { + if (is_source) + pg_log_debug("entry \"%s\" excluded from source file list", + path); + else + pg_log_debug("entry \"%s\" excluded from target file list", + path); + return true; + } + } + + return false; +} + +static const char * +action_to_str(file_action_t action) +{ + switch (action) + { + case FILE_ACTION_NONE: + return "NONE"; + case FILE_ACTION_COPY: + return "COPY"; + case FILE_ACTION_TRUNCATE: + return "TRUNCATE"; + case FILE_ACTION_COPY_TAIL: + return "COPY_TAIL"; + case FILE_ACTION_CREATE: + return "CREATE"; + case FILE_ACTION_REMOVE: + return "REMOVE"; + + default: + return "unknown"; + } +} + +/* + * Calculate the totals needed for progress reports. + */ +void +calculate_totals(filemap_t *filemap) +{ + file_entry_t *entry; + int i; + + filemap->total_size = 0; + filemap->fetch_size = 0; + + for (i = 0; i < filemap->nentries; i++) + { + entry = filemap->entries[i]; + + if (entry->source_type != FILE_TYPE_REGULAR) + continue; + + filemap->total_size += entry->source_size; + + if (entry->action == FILE_ACTION_COPY) + { + filemap->fetch_size += entry->source_size; + continue; + } + + if (entry->action == FILE_ACTION_COPY_TAIL) + filemap->fetch_size += (entry->source_size - entry->target_size); + + if (entry->target_pages_to_overwrite.bitmapsize > 0) + { + datapagemap_iterator_t *iter; + BlockNumber blk; + + iter = datapagemap_iterate(&entry->target_pages_to_overwrite); + while (datapagemap_next(iter, &blk)) + filemap->fetch_size += BLCKSZ; + + pg_free(iter); + } + } +} + +void +print_filemap(filemap_t *filemap) +{ + file_entry_t *entry; + int i; + + for (i = 0; i < filemap->nentries; i++) + { + entry = filemap->entries[i]; + if (entry->action != FILE_ACTION_NONE || + entry->target_pages_to_overwrite.bitmapsize > 0) + { + pg_log_debug("%s (%s)", entry->path, + action_to_str(entry->action)); + + if (entry->target_pages_to_overwrite.bitmapsize > 0) + datapagemap_print(&entry->target_pages_to_overwrite); + } + } + fflush(stdout); +} + +/* + * Does it look like a relation data file? + * + * For our purposes, only files belonging to the main fork are considered + * relation files. Other forks are always copied in toto, because we cannot + * reliably track changes to them, because WAL only contains block references + * for the main fork. + */ +static bool +isRelDataFile(const char *path) +{ + RelFileNode rnode; + unsigned int segNo; + int nmatch; + bool matched; + + /*---- + * Relation data files can be in one of the following directories: + * + * global/ + * shared relations + * + * base/<db oid>/ + * regular relations, default tablespace + * + * pg_tblspc/<tblspc oid>/<tblspc version>/ + * within a non-default tablespace (the name of the directory + * depends on version) + * + * And the relation data files themselves have a filename like: + * + * <oid>.<segment number> + * + *---- + */ + rnode.spcNode = InvalidOid; + rnode.dbNode = InvalidOid; + rnode.relNode = InvalidOid; + segNo = 0; + matched = false; + + nmatch = sscanf(path, "global/%u.%u", &rnode.relNode, &segNo); + if (nmatch == 1 || nmatch == 2) + { + rnode.spcNode = GLOBALTABLESPACE_OID; + rnode.dbNode = 0; + matched = true; + } + else + { + nmatch = sscanf(path, "base/%u/%u.%u", + &rnode.dbNode, &rnode.relNode, &segNo); + if (nmatch == 2 || nmatch == 3) + { + rnode.spcNode = DEFAULTTABLESPACE_OID; + matched = true; + } + else + { + nmatch = sscanf(path, "pg_tblspc/%u/" TABLESPACE_VERSION_DIRECTORY "/%u/%u.%u", + &rnode.spcNode, &rnode.dbNode, &rnode.relNode, + &segNo); + if (nmatch == 3 || nmatch == 4) + matched = true; + } + } + + /* + * The sscanf tests above can match files that have extra characters at + * the end. To eliminate such cases, cross-check that GetRelationPath + * creates the exact same filename, when passed the RelFileNode + * information we extracted from the filename. + */ + if (matched) + { + char *check_path = datasegpath(rnode, MAIN_FORKNUM, segNo); + + if (strcmp(check_path, path) != 0) + matched = false; + + pfree(check_path); + } + + return matched; +} + +/* + * A helper function to create the path of a relation file and segment. + * + * The returned path is palloc'd + */ +static char * +datasegpath(RelFileNode rnode, ForkNumber forknum, BlockNumber segno) +{ + char *path; + char *segpath; + + path = relpathperm(rnode, forknum); + if (segno > 0) + { + segpath = psprintf("%s.%u", path, segno); + pfree(path); + return segpath; + } + else + return path; +} + +/* + * In the final stage, the filemap is sorted so that removals come last. + * From disk space usage point of view, it would be better to do removals + * first, but for now, safety first. If a whole directory is deleted, all + * files and subdirectories inside it need to removed first. On creation, + * parent directory needs to be created before files and directories inside + * it. To achieve that, the file_action_t enum is ordered so that we can + * just sort on that first. Furthermore, sort REMOVE entries in reverse + * path order, so that "foo/bar" subdirectory is removed before "foo". + */ +static int +final_filemap_cmp(const void *a, const void *b) +{ + file_entry_t *fa = *((file_entry_t **) a); + file_entry_t *fb = *((file_entry_t **) b); + + if (fa->action > fb->action) + return 1; + if (fa->action < fb->action) + return -1; + + if (fa->action == FILE_ACTION_REMOVE) + return strcmp(fb->path, fa->path); + else + return strcmp(fa->path, fb->path); +} + +/* + * Decide what action to perform to a file. + */ +static file_action_t +decide_file_action(file_entry_t *entry) +{ + const char *path = entry->path; + + /* + * Don't touch the control file. It is handled specially, after copying + * all the other files. + */ + if (strcmp(path, "global/pg_control") == 0) + return FILE_ACTION_NONE; + + /* + * Remove all files matching the exclusion filters in the target. + */ + if (check_file_excluded(path, true)) + { + if (entry->target_exists) + return FILE_ACTION_REMOVE; + else + return FILE_ACTION_NONE; + } + + /* + * Handle cases where the file is missing from one of the systems. + */ + if (!entry->target_exists && entry->source_exists) + { + /* + * File exists in source, but not in target. Copy it in toto. (If it's + * a relation data file, WAL replay after rewinding should re-create + * it anyway. But there's no harm in copying it now.) + */ + switch (entry->source_type) + { + case FILE_TYPE_DIRECTORY: + case FILE_TYPE_SYMLINK: + return FILE_ACTION_CREATE; + case FILE_TYPE_REGULAR: + return FILE_ACTION_COPY; + case FILE_TYPE_UNDEFINED: + pg_fatal("unknown file type for \"%s\"", entry->path); + break; + } + } + else if (entry->target_exists && !entry->source_exists) + { + /* File exists in target, but not source. Remove it. */ + return FILE_ACTION_REMOVE; + } + else if (!entry->target_exists && !entry->source_exists) + { + /* + * Doesn't exist in either server. Why does it have an entry in the + * first place?? + */ + Assert(false); + return FILE_ACTION_NONE; + } + + /* + * Otherwise, the file exists on both systems + */ + Assert(entry->target_exists && entry->source_exists); + + if (entry->source_type != entry->target_type) + { + /* But it's a different kind of object. Strange.. */ + pg_fatal("file \"%s\" is of different type in source and target", entry->path); + } + + /* + * PG_VERSION files should be identical on both systems, but avoid + * overwriting them for paranoia. + */ + if (pg_str_endswith(entry->path, "PG_VERSION")) + return FILE_ACTION_NONE; + + switch (entry->source_type) + { + case FILE_TYPE_DIRECTORY: + return FILE_ACTION_NONE; + + case FILE_TYPE_SYMLINK: + + /* + * XXX: Should we check if it points to the same target? + */ + return FILE_ACTION_NONE; + + case FILE_TYPE_REGULAR: + if (!entry->isrelfile) + { + /* + * It's a non-data file that we have no special processing + * for. Copy it in toto. + */ + return FILE_ACTION_COPY; + } + else + { + /* + * It's a data file that exists in both systems. + * + * If it's larger in target, we can truncate it. There will + * also be a WAL record of the truncation in the source + * system, so WAL replay would eventually truncate the target + * too, but we might as well do it now. + * + * If it's smaller in the target, it means that it has been + * truncated in the target, or enlarged in the source, or + * both. If it was truncated in the target, we need to copy + * the missing tail from the source system. If it was enlarged + * in the source system, there will be WAL records in the + * source system for the new blocks, so we wouldn't need to + * copy them here. But we don't know which scenario we're + * dealing with, and there's no harm in copying the missing + * blocks now, so do it now. + * + * If it's the same size, do nothing here. Any blocks modified + * in the target will be copied based on parsing the target + * system's WAL, and any blocks modified in the source will be + * updated after rewinding, when the source system's WAL is + * replayed. + */ + if (entry->target_size < entry->source_size) + return FILE_ACTION_COPY_TAIL; + else if (entry->target_size > entry->source_size) + return FILE_ACTION_TRUNCATE; + else + return FILE_ACTION_NONE; + } + break; + + case FILE_TYPE_UNDEFINED: + pg_fatal("unknown file type for \"%s\"", path); + break; + } + + /* unreachable */ + pg_fatal("could not decide what to do with file \"%s\"", path); +} + +/* + * Decide what to do with each file. + * + * Returns a 'filemap' with the entries in the order that their actions + * should be executed. + */ +filemap_t * +decide_file_actions(void) +{ + int i; + filehash_iterator it; + file_entry_t *entry; + filemap_t *filemap; + + filehash_start_iterate(filehash, &it); + while ((entry = filehash_iterate(filehash, &it)) != NULL) + { + entry->action = decide_file_action(entry); + } + + /* + * Turn the hash table into an array, and sort in the order that the + * actions should be performed. + */ + filemap = pg_malloc(offsetof(filemap_t, entries) + + filehash->members * sizeof(file_entry_t *)); + filemap->nentries = filehash->members; + filehash_start_iterate(filehash, &it); + i = 0; + while ((entry = filehash_iterate(filehash, &it)) != NULL) + { + filemap->entries[i++] = entry; + } + + qsort(&filemap->entries, filemap->nentries, sizeof(file_entry_t *), + final_filemap_cmp); + + return filemap; +} + + +/* + * Helper function for filemap hash table. + */ +static uint32 +hash_string_pointer(const char *s) +{ + unsigned char *ss = (unsigned char *) s; + + return hash_bytes(ss, strlen(s)); +} |