PgSQL · 最佳實踐 · pg_rman源碼淺析與使用 · 數據庫內核月報

## 背景對于商業數據庫來說，備份的功能一般都非常的全面。? 比如Oracle，它的備份工具rman是非常強大的，很多年前就已經支持全量、增量、歸檔的備份模式，支持壓縮等。? 還支持元數據存儲到數據庫中，管理也非常的方便，例如保留多少歸檔，備份集的管理也很方便，例如要恢復到什么時間點，將此前的備份清除等等。? 對于開源數據庫來說，支持向商業版本這么豐富功能的比較少，PostgreSQL算是非常完善的一個。? PostgreSQL作為最高級的開源數據庫，備份方面已經向商業數據庫看齊。? 目前PostgreSQL已經支持類似Oracle的rman備份工具的功能，支持全量、增量、歸檔三種備份模式，支持壓縮，支持備份集的管理等。? 有了塊級增量備份，對于那種非常龐大的數據庫，備份起來就不像只支持全量和歸檔的模式那么吃力了。 ## PostgreSQL增量備份是怎么做到的呢？一個數據頁的框架如下 ~~~ * +----------------+---------------------------------+ * | PageHeaderData | linp1 linp2 linp3 ... | * +-----------+----+---------------------------------+ * | ... linpN | | * +-----------+--------------------------------------+ * | ^ pd_lower | * | | * | v pd_upper | * +-------------+------------------------------------+ * | | tupleN ... | * +-------------+------------------+-----------------+ * | ... tuple3 tuple2 tuple1 | "special space" | * +--------------------------------+-----------------+ ~~~ 數據頁頭部的數據結構 ~~~ typedef struct PageHeaderData { /* XXX LSN is member of *any* block, not only page-organized ones */ PageXLogRecPtr pd_lsn; /* LSN: next byte after last byte of xlog * record for last change to this page */ uint16 pd_checksum; /* checksum */ uint16 pd_flags; /* flag bits, see below */ LocationIndex pd_lower; /* offset to start of free space */ LocationIndex pd_upper; /* offset to end of free space */ LocationIndex pd_special; /* offset to start of special space */ uint16 pd_pagesize_version; TransactionId pd_prune_xid; /* oldest prunable XID, or zero if none */ ItemIdData pd_linp[FLEXIBLE_ARRAY_MEMBER]; /* line pointer array */ } PageHeaderData; ~~~ 因為如果對象是持久化的，那么它的所有變更都會記錄REDO，數據頁頭部的pd_lsn表示該數據頁最后一次變化時，變化產生的REDO在xlog file中的結束位置.? 即如果xlog flush的xlog地址位大于或等于此頁pd_lsn，那么這個頁的更改就可以認為是可靠的。 ~~~ * pd_lsn - identifies xlog record for last change to this page. * pd_checksum - page checksum, if set. * pd_flags - flag bits. * pd_lower - offset to start of free space. * pd_upper - offset to end of free space. * pd_special - offset to start of special space. * pd_pagesize_version - size in bytes and page layout version number. * pd_prune_xid - oldest XID among potentially prunable tuples on page. ~~~ 好了，既然每次塊的變化都包含了LSN的修改，那么也即是說，我們可以通過第一次備份開始時的全局LSN，以及當前需要備份的數據的page LSN來判斷此頁是否發生過修改。如果修改了就備份，沒修改，就不需要備份，從而實現數據庫的塊級增量備份。 ## pg_rman 介紹 pg_rman是一個[開源的PostgreSQL備份管理軟件](https://github.com/ossc-db/pg_rman)，類似Oracle的RMAN。? [documentation見](http://ossc-db.github.io/pg_rman/index.html) pg_rman使用的是pg_start_backup(), copy, pg_stop_backup()的備份模式。? pg_rman跑的不是流復制協議，而是文件拷貝，所以pg_rman必須和數據庫節點跑在一起。? 如果在standby節點跑pg_rman，pg_rman則需要通過網絡連接到主節點執行pg_start_backup和pg_stop_backup。? pg_rman的用法非常簡單，支持以下幾種運行模式。 | init | Initialize a backup catalog. | | backup | Take an online backup. | | restore | Do restore. | | show | Show backup history. The detail option shows with additional information of each backups. | | validate | Validate backup files. Backups without validation cannot be used for restore and incremental backup. | | delete | Delete backup files. | | purge | Remove deleted backups from backup catalog. | ## 使用pg_rman的前提開啟歸檔? 配置csvlog? 建議的配置 ~~~ postgres=# show log_destination ; log_destination ----------------- csvlog (1 row) postgres=# SHOW log_directory ; log_directory --------------- pg_log (1 row) postgres=# SHOW archive_command ; archive_command -------------------------------------------- cp %p /data04/digoal/arc_log/%f (1 row) ~~~ ## 初始化pg_rman backup catalog 首先需要初始化一個backup catalog，實際上就是需要一個目錄，這個目錄將用于存放備份的文件。? 同時這個目錄也會存放一些元數據，例如備份的配置文件，數據庫的systemid，時間線文件歷史等等。? 初始化命令需要兩個參數，分別為備份目標目錄，以及數據庫的$PGDATA ~~~ $ mkdir /data05/digoal/pgbbk $ /home/digoal/pgsql9.5/bin/pg_rman init -B /data05/digoal/pgbbk -D /data04/digoal/pg_root INFO: ARCLOG_PATH is set to '/data04/digoal/arc_log' INFO: SRVLOG_PATH is set to '/data04/digoal/pg_root/pg_log' ~~~ 生成備份元數據如下 ~~~ [digoal@iZ28tqoemgtZ ~]$ cd /data05/digoal/pgbbk/ [digoal@iZ28tqoemgtZ pgbbk]$ ll total 16 drwx------ 4 digoal digoal 4096 Aug 26 19:29 backup -rw-rw-r-- 1 digoal digoal 82 Aug 26 19:29 pg_rman.ini -rw-rw-r-- 1 digoal digoal 40 Aug 26 19:29 system_identifier drwx------ 2 digoal digoal 4096 Aug 26 19:29 timeline_history ~~~ 生成的配置文件 ~~~ $ cat pg_rman.ini ARCLOG_PATH='/data04/digoal/arc_log' SRVLOG_PATH='/data04/digoal/pg_root/pg_log' ~~~ 你可以把將來要使用的配置寫在這個配置文件中，或者寫在pg_rman的命令行中。? 我后面的測試會直接使用命令行參數。? 生成的數據庫system id，用于區分備份的數據庫是不是一個數據庫，防止被沖。 ~~~ $ cat system_identifier SYSTEM_IDENTIFIER='6318621837015461309' ~~~ 與控制文件中存儲的system id一致。注意? pg_rman只從postgresql.conf取log_directory和archive_command參數的值。? 如果你的PostgreSQL的配置文件是include的或者配置在postgresql.auto.conf中，這兩個值將不準確。? 所以建議你僅僅把參數配置在postgresql.conf中，而不要使用其他配置文件。 ## pg_rman 命令行用法 ~~~ pg_rman manage backup/recovery of PostgreSQL database. Usage: pg_rman OPTION init pg_rman OPTION backup pg_rman OPTION restore pg_rman OPTION show [DATE] pg_rman OPTION show detail [DATE] pg_rman OPTION validate [DATE] pg_rman OPTION delete DATE pg_rman OPTION purge Common Options: -D, --pgdata=PATH location of the database storage area -A, --arclog-path=PATH location of archive WAL storage area -S, --srvlog-path=PATH location of server log storage area -B, --backup-path=PATH location of the backup storage area -c, --check show what would have been done -v, --verbose show what detail messages -P, --progress show progress of processed files Backup options: -b, --backup-mode=MODE full, incremental, or archive -s, --with-serverlog also backup server log files -Z, --compress-data compress data backup with zlib -C, --smooth-checkpoint do smooth checkpoint before backup -F, --full-backup-on-error switch to full backup mode if pg_rman cannot find validate full backup on current timeline NOTE: this option is only used in --backup-mode=incremental or archive. --keep-data-generations=NUM keep NUM generations of full data backup --keep-data-days=NUM keep enough data backup to recover to N days ago --keep-arclog-files=NUM keep NUM of archived WAL --keep-arclog-days=DAY keep archived WAL modified in DAY days --keep-srvlog-files=NUM keep NUM of serverlogs --keep-srvlog-days=DAY keep serverlog modified in DAY days --standby-host=HOSTNAME standby host when taking backup from standby --standby-port=PORT standby port when taking backup from standby Restore options: --recovery-target-time time stamp up to which recovery will proceed --recovery-target-xid transaction ID up to which recovery will proceed --recovery-target-inclusive whether we stop just after the recovery target --recovery-target-timeline recovering into a particular timeline --hard-copy copying archivelog not symbolic link Catalog options: -a, --show-all show deleted backup too Delete options: -f, --force forcibly delete backup older than given DATE Connection options: -d, --dbname=DBNAME database to connect -h, --host=HOSTNAME database server host or socket directory -p, --port=PORT database server port -U, --username=USERNAME user name to connect as -w, --no-password never prompt for password -W, --password force password prompt Generic options: -q, --quiet don't show any INFO or DEBUG messages --debug show DEBUG messages --help show this help, then exit --version output version information, then exit Read the website for details. <http://github.com/ossc-db/pg_rman> Report bugs to <http://github.com/ossc-db/pg_rman/issues>. ~~~ ## 全量備份輸入必要的參數或option ~~~ $ export PGPASSWORD=postgres $ /home/digoal/pgsql9.5/bin/pg_rman backup \ -B /data05/digoal/pgbbk \ -D /data04/digoal/pg_root \ -b full \ -s \ -Z \ -C \ --keep-data-days=10 \ --keep-arclog-files=15 \ --keep-arclog-days=10 \ --keep-srvlog-files=10 \ --keep-srvlog-days=15 \ -h 127.0.0.1 -p 1921 -U postgres -d postgres ~~~ 結果 ~~~ INFO: copying database files NOTICE: pg_stop_backup complete, all required WAL segments have been archived INFO: copying archived WAL files INFO: copying server log files INFO: backup complete HINT: Please execute 'pg_rman validate' to verify the files are correctly copied. INFO: start deleting old archived WAL files from ARCLOG_PATH (keep files = 15, keep days = 10) INFO: the threshold timestamp calculated by keep days is "2016-08-16 00:00:00" INFO: start deleting old server files from SRVLOG_PATH (keep files = 10, keep days = 15) INFO: the threshold timestamp calculated by keep days is "2016-08-11 00:00:00" INFO: start deleting old backup (keep after = 2016-08-16 00:00:00) INFO: does not include the backup just taken WARNING: backup "2016-08-26 19:39:32" is not taken int account DETAIL: This is not valid backup. ~~~ ## 校驗備份集備份時pg_rman會記錄每個備份文件的crc，以便validate進行校驗。? 例如某個備份集 ~~~ $ less /data05/digoal/pgbbk/20160826/195809/file_database.txt .s.PGSQL.1921 ? 0 0 0777 2016-08-26 19:27:05 .s.PGSQL.1921.lock f 55 590164837 0600 2016-08-26 19:27:05 PG_VERSION f 12 3872055064 0600 2016-07-28 10:03:42 backup_label f 167 2985542389 0600 2016-08-26 19:58:42 backup_label.old f 155 4273989468 0600 2016-08-23 19:43:32 base d 0 0 0700 2016-08-23 10:28:32 base/1 d 0 0 0700 2016-08-24 16:17:02 base/1/112 f 57 1147028285 0600 2016-07-28 10:03:42 base/1/113 f 57 1147028285 0600 2016-07-28 10:03:42 base/1/1247 F 8178 1875285513 0600 2016-07-29 13:51:29 base/1/1247_fsm f 139 3668812536 0600 2016-07-28 10:03:43 ~~~ 解釋: 路徑，文件類型，大小，CRC校驗值，權限，時間，第四列即crc校驗值? 每次備份完，必須要做一次校驗，否則備份集不可用用來恢復，增量備份時也不會用它來做增量比較。 ~~~ $ /home/digoal/pgsql9.5/bin/pg_rman validate -B /data05/digoal/pgbbk INFO: validate: "2016-08-26 19:39:50" backup, archive log files and server log files by CRC INFO: backup "2016-08-26 19:39:50" is valid ~~~ 每個備份集都包含了一個備份狀態文件，如下 ~~~ cat /data05/digoal/pgbbk/20160826/201955/backup.ini # configuration BACKUP_MODE=INCREMENTAL FULL_BACKUP_ON_ERROR=false WITH_SERVERLOG=true COMPRESS_DATA=true # result TIMELINEID=1 START_LSN=46/df000108 STOP_LSN=46/df000210 START_TIME='2016-08-26 20:19:55' END_TIME='2016-08-26 20:20:48' RECOVERY_XID=3896508593 RECOVERY_TIME='2016-08-26 20:20:47' TOTAL_DATA_BYTES=6196524307 READ_DATA_BYTES=3199287520 READ_ARCLOG_BYTES=33554754 READ_SRVLOG_BYTES=0 WRITE_BYTES=125955 BLOCK_SIZE=8192 XLOG_BLOCK_SIZE=8192 STATUS=OK ~~~ 這個文件中包含了很重要的信息，比如LSN，后面LSN將用于比對增量備份時對比數據塊的LSN是否發生了變化，是否需要備份。 ## 增量備份 ~~~ $ export PGPASSWORD=postgres $ /home/digoal/pgsql9.5/bin/pg_rman backup \ -B /data05/digoal/pgbbk \ -D /data04/digoal/pg_root \ -b incremental \ -s \ -Z \ -C \ --keep-data-days=10 \ --keep-arclog-files=15 \ --keep-arclog-days=10 \ --keep-srvlog-files=10 \ --keep-srvlog-days=15 \ -h 127.0.0.1 -p 1921 -U postgres -d postgres ~~~ 增量備份輸出 ~~~ INFO: copying database files NOTICE: pg_stop_backup complete, all required WAL segments have been archived INFO: copying archived WAL files INFO: copying server log files INFO: backup complete HINT: Please execute 'pg_rman validate' to verify the files are correctly copied. INFO: start deleting old archived WAL files from ARCLOG_PATH (keep files = 15, keep days = 10) INFO: the threshold timestamp calculated by keep days is "2016-08-16 00:00:00" INFO: start deleting old server files from SRVLOG_PATH (keep files = 10, keep days = 15) INFO: the threshold timestamp calculated by keep days is "2016-08-11 00:00:00" INFO: start deleting old backup (keep after = 2016-08-16 00:00:00) INFO: does not include the backup just taken INFO: backup "2016-08-26 19:39:50" should be kept DETAIL: This is taken after "2016-08-16 00:00:00". WARNING: backup "2016-08-26 19:39:32" is not taken int account DETAIL: This is not valid backup. ~~~ ## 校驗備份集 ~~~ $ /home/digoal/pgsql9.5/bin/pg_rman validate -B /data05/digoal/pgbbk INFO: validate: "2016-08-26 19:43:20" backup, archive log files and server log files by CRC INFO: backup "2016-08-26 19:43:20" is valid ~~~ ## 列出備份集 ~~~ $ /home/digoal/pgsql9.5/bin/pg_rman show -B /data05/digoal/pgbbk ========================================================== StartTime Mode Duration Size TLI Status ========================================================== 2016-08-26 19:43:20 INCR 0m 54kB 1 OK 2016-08-26 19:39:50 FULL 1m 245MB 1 OK ~~~ 可以看到增量非常小，因為很少變化的塊。? 接下來更新一張大表的某一條記錄，再看看。 ~~~ postgres=# \dt+ List of relations Schema | Name | Type | Owner | Size | Description --------+----------+-------+----------+---------+------------- public | hll_test | table | postgres | 208 kB | public | t | table | postgres | 3050 MB | public | tbl1 | table | postgres | 226 MB | public | tbl2 | table | postgres | 63 MB | public | test | table | postgres | 120 MB | (5 rows) postgres=# with t1 as (select id from t where id between 1 and 1000 limit 10) update t set info='new' where id in (select * from t1); UPDATE 10 ~~~ 更新后做一個增量備份 ~~~ $ /home/digoal/pgsql9.5/bin/pg_rman backup -B /data05/digoal/pgbbk -D /data04/digoal/pg_root -b incremental -s -Z -C --keep-data-days=10 --keep-arclog-files=15 --keep-arclog-days=10 --keep-srvlog-files=10 --keep-srvlog-days=15 -h 127.0.0.1 -p 1921 -U postgres -d postgres INFO: copying database files NOTICE: pg_stop_backup complete, all required WAL segments have been archived INFO: copying archived WAL files INFO: copying server log files INFO: backup complete HINT: Please execute 'pg_rman validate' to verify the files are correctly copied. INFO: start deleting old archived WAL files from ARCLOG_PATH (keep files = 15, keep days = 10) INFO: the threshold timestamp calculated by keep days is "2016-08-16 00:00:00" INFO: start deleting old server files from SRVLOG_PATH (keep files = 10, keep days = 15) INFO: the threshold timestamp calculated by keep days is "2016-08-11 00:00:00" INFO: start deleting old backup (keep after = 2016-08-16 00:00:00) INFO: does not include the backup just taken INFO: backup "2016-08-26 19:58:09" should be kept DETAIL: This is taken after "2016-08-16 00:00:00". WARNING: backup "2016-08-26 19:56:54" is not taken int account DETAIL: This is not valid backup. INFO: backup "2016-08-26 19:43:20" should be kept DETAIL: This is taken after "2016-08-16 00:00:00". INFO: backup "2016-08-26 19:39:50" should be kept DETAIL: This is taken after "2016-08-16 00:00:00". WARNING: backup "2016-08-26 19:39:32" is not taken int account DETAIL: This is not valid backup. ~~~ 校驗備份集 ~~~ [digoal@iZ28tqoemgtZ pg_rman]$ /home/digoal/pgsql9.5/bin/pg_rman validate -B /data05/digoal/pgbbk INFO: validate: "2016-08-26 20:19:55" backup, archive log files and server log files by CRC INFO: backup "2016-08-26 20:19:55" is valid ~~~ 輸出當前備份 ~~~ [digoal@iZ28tqoemgtZ pg_rman]$ /home/digoal/pgsql9.5/bin/pg_rman show -B /data05/digoal/pgbbk ========================================================== StartTime Mode Duration Size TLI Status ========================================================== 2016-08-26 20:19:55 INCR 0m 125kB 1 OK 2016-08-26 19:58:09 FULL 11m 3094MB 1 OK 2016-08-26 19:56:54 FULL 1m 0B 0 ERROR 2016-08-26 19:43:20 INCR 0m 54kB 1 OK 2016-08-26 19:39:50 FULL 1m 245MB 1 OK 2016-08-26 19:39:32 FULL 0m 0B 0 ERROR ~~~ 增量備份的文件非常小，因為變化的數據塊很少。 ## 按指定時間從catalog刪除備份集例如我只需要我的備份集能恢復到2016-08-26 19:59:00，在這個時間點以前，不需要用來恢復到這個時間點的備份全刪掉。 ~~~ $ /home/digoal/pgsql9.5/bin/pg_rman delete "2016-08-26 19:59:00" -B /data05/digoal/pgbbk WARNING: cannot delete backup with start time "2016-08-26 19:58:09" DETAIL: This is the latest full backup necessary for successful recovery. INFO: delete the backup with start time: "2016-08-26 19:56:54" INFO: delete the backup with start time: "2016-08-26 19:43:20" INFO: delete the backup with start time: "2016-08-26 19:39:50" INFO: delete the backup with start time: "2016-08-26 19:39:32" ~~~ 保留的備份集合可以將數據庫恢復到2016-08-26 19:59:00 ~~~ $ /home/digoal/pgsql9.5/bin/pg_rman show -B /data05/digoal/pgbbk ========================================================== StartTime Mode Duration Size TLI Status ========================================================== 2016-08-26 20:19:55 INCR 0m 125kB 1 OK 2016-08-26 19:58:09 FULL 11m 3094MB 1 OK ~~~ ## 物理刪除已從catalog刪除的備份集 ~~~ $ /home/digoal/pgsql9.5/bin/pg_rman purge -B /data05/digoal/pgbbk INFO: DELETED backup "2016-08-26 19:56:54" is purged INFO: DELETED backup "2016-08-26 19:43:20" is purged INFO: DELETED backup "2016-08-26 19:39:50" is purged INFO: DELETED backup "2016-08-26 19:39:32" is purged ~~~ ## 恢復 pg_rman數據恢復時的兩個必要要素? 1\. 新的$PGDATA? 2\. 備份目錄? 命令的選項也很簡單，甚至可以不指定任何option ~~~ Restore options: The parameters which are started with –recovery are same as parameters in recovery.conf. See also “Recovery Configuration” for details. ~~~ 接下來的幾個配置，與recovery.conf的意思對齊。如果不指定時間線，則使用$PGDATA/global/pg_control，如果沒有$PGDATA/global/pg_control，則使用最新的全量備份集的時間線。 ~~~ --recovery-target-timeline TIMELINE Specifies recovering into a particular timeline. If not specified, the current timeline from ($PGDATA/global/pg_control) is used. ~~~ 如果不指定，則恢復到最新時間 ~~~ --recovery-target-time TIMESTAMP This parameter specifies the time stamp up to which recovery will proceed. If not specified, continue recovery to the latest time. ~~~ 如果不指定，則恢復到最新xid ~~~ --recovery-target-xid XID This parameter specifies the transaction ID up to which recovery will proceed. If not specified, continue recovery to the latest xid. ~~~ 如果不指定，則默認使用true，即恢復到包含恢復目標XID的commit record為止，或者第一筆commit record ts>指定ts的 commit redo record為止；? 如果是false則不apply恢復目標XID的commit record，或者不apply第一筆commit record ts>=指定ts的 commit redo record。 ~~~ --recovery-target-inclusive Specifies whether we stop just after the specified recovery target (true), or just before the recovery target (false). Default is true. ~~~ 是否使用硬鏈接復制archive log，而不需要拷貝文件 ~~~ The following parameter determines the behavior of restore. --hard-copy The archive WAL are copied to archive WAL storage area. If not specified, pg_rman makes symbolic link to archive WAL where are in the backup catalog directory. ~~~ ## 例子恢復時，需要注意，你可以選擇原地恢復（覆蓋式），或者使用新的$PGDATA作為恢復目標。但是請注意，不管是哪種恢復方式，如果在本機恢復的話，pg_rman可能會覆蓋原有的數據文件，arch, pg_xlog目錄中的文件，所以，如果你要保留原數據，建議先將原數據目錄重命名。? 1\. 原地恢復? 2\. 使用新的$PGDATA恢復在本機恢復的例子? 1\. 停庫 ~~~ pg_ctl stop -m fast -D /data04/digoal/pg_root_1922 ~~~ 2\. 重命名原數據相關目錄 ~~~ $PGDATA mv /data04/digoal/pg_root_1922 /data04/digoal/old_pg_root_1922 PG_XLOG mv /data05/digoal/pg_xlog_1922 /data05/digoal/old_pg_xlog_1922 表空間 mv /data02/digoal/tbs1_1922 /data02/digoal/old_tbs1_1922 歸檔目錄，除了要重命名，還需要新建一個原目錄 mv /data04/digoal/arc_log1922 /data04/digoal/old_arc_log1922 mkdir /data04/digoal/arc_log1922 ... ~~~ 3\. pg_rman restore ~~~ pg_rman restore -B /data05/digoal/pgstdbak -D /data04/digoal/pg_restore_root WARNING: could not open pg_controldata file "/data04/digoal/pg_restore_root/global/pg_control": No such file or directory WARNING: could not open pg_controldata file "/data04/digoal/pg_restore_root/global/pg_control": No such file or directory INFO: the recovery target timeline ID is not given INFO: use timeline ID of latest full backup as recovery target: 1 INFO: calculating timeline branches to be used to recovery target point INFO: searching latest full backup which can be used as restore start point INFO: found the full backup can be used as base in recovery: "2016-08-29 15:05:32" INFO: copying online WAL files and server log files INFO: clearing restore destination INFO: validate: "2016-08-29 15:05:32" backup, archive log files and server log files by SIZE INFO: backup "2016-08-29 15:05:32" is valid INFO: restoring database files from the full mode backup "2016-08-29 15:05:32" INFO: searching incremental backup to be restored INFO: validate: "2016-08-29 15:13:10" backup, archive log files and server log files by SIZE INFO: backup "2016-08-29 15:13:10" is valid INFO: restoring database files from the incremental mode backup "2016-08-29 15:13:10" INFO: searching backup which contained archived WAL files to be restored INFO: backup "2016-08-29 15:13:10" is valid INFO: restoring WAL files from backup "2016-08-29 15:13:10" INFO: restoring online WAL files and server log files INFO: generating recovery.conf INFO: restore complete HINT: Recovery will start automatically when the PostgreSQL server is started. ~~~ 4\. 修改postgresql.conf, recovery.conf? 根據實際情況調整，本例不修改 ~~~ cd /data04/digoal/pg_restore_root/ digoal@iZ28tqoemgtZ-> ll total 124K -rw------- 1 digoal digoal 193 Aug 29 17:05 backup_label.old drwx------ 7 digoal digoal 4.0K Aug 29 17:05 base drwx------ 2 digoal digoal 4.0K Aug 29 17:05 global drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_clog drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_commit_ts drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_dynshmem -rw------- 1 digoal digoal 4.4K Aug 29 17:05 pg_hba.conf -rw------- 1 digoal digoal 1.6K Aug 29 17:05 pg_ident.conf drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_log drwx------ 4 digoal digoal 4.0K Aug 29 17:05 pg_logical drwx------ 4 digoal digoal 4.0K Aug 29 17:05 pg_multixact drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_notify drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_replslot drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_serial drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_snapshots drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_stat drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_stat_tmp drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_subtrans drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_tblspc drwx------ 2 digoal digoal 4.0K Aug 29 17:05 pg_twophase -rw------- 1 digoal digoal 4 Aug 29 17:05 PG_VERSION lrwxrwxrwx 1 digoal digoal 27 Aug 29 17:05 pg_xlog -> /data05/digoal/pg_xlog_1922 -rw------- 1 digoal digoal 88 Aug 29 17:05 postgresql.auto.conf -rw------- 1 digoal digoal 22K Aug 29 17:05 postgresql.conf -rw------- 1 digoal digoal 44 Aug 29 17:05 postmaster.opts -rw-r--r-- 1 digoal digoal 130 Aug 29 17:06 recovery.conf digoal@iZ28tqoemgtZ-> cd pg_tblspc/ digoal@iZ28tqoemgtZ-> ll total 0 lrwxrwxrwx 1 digoal digoal 24 Aug 29 17:05 16719 -> /data02/digoal/tbs1_1922 cd .. vi postgresql.conf archive_command = 'cp %p /data04/digoal/arc_log1922/%f' vi recovery.conf # recovery.conf generated by pg_rman 1.3.2 restore_command = 'cp /data04/digoal/arc_log1922/%f %p' recovery_target_timeline = '1' ~~~ 5\. 如果備份集的時間線發生了變化，需要先手工拷貝到歸檔目錄，再執行restore ~~~ digoal@iZ28tqoemgtZ-> pg_rman restore -B /data05/digoal/pgstdbak -D /data04/digoal/pg_restore_root WARNING: could not open pg_controldata file "/data04/digoal/pg_restore_root/global/pg_control": No such file or directory WARNING: could not open pg_controldata file "/data04/digoal/pg_restore_root/global/pg_control": No such file or directory INFO: the recovery target timeline ID is not given INFO: use timeline ID of latest full backup as recovery target: 2 INFO: calculating timeline branches to be used to recovery target point ERROR: could not open destination file "/data04/digoal/arc_log1922/00000002.history": No such file or directory digoal@iZ28tqoemgtZ-> mkdir /data04/digoal/arc_log1922 digoal@iZ28tqoemgtZ-> cp /data05/digoal/pgstdbak/timeline_history/00000002.history /data04/digoal/arc_log1922/ digoal@iZ28tqoemgtZ-> pg_rman restore -B /data05/digoal/pgstdbak -D /data04/digoal/pg_restore_root WARNING: could not open pg_controldata file "/data04/digoal/pg_restore_root/global/pg_control": No such file or directory WARNING: could not open pg_controldata file "/data04/digoal/pg_restore_root/global/pg_control": No such file or directory INFO: the recovery target timeline ID is not given INFO: use timeline ID of latest full backup as recovery target: 2 INFO: calculating timeline branches to be used to recovery target point INFO: searching latest full backup which can be used as restore start point INFO: found the full backup can be used as base in recovery: "2016-08-29 17:14:20" INFO: copying online WAL files and server log files INFO: clearing restore destination INFO: validate: "2016-08-29 17:14:20" backup and archive log files by SIZE INFO: backup "2016-08-29 17:14:20" is valid INFO: restoring database files from the full mode backup "2016-08-29 17:14:20" INFO: searching incremental backup to be restored INFO: searching backup which contained archived WAL files to be restored INFO: backup "2016-08-29 17:14:20" is valid INFO: restoring WAL files from backup "2016-08-29 17:14:20" INFO: restoring online WAL files and server log files INFO: generating recovery.conf INFO: restore complete HINT: Recovery will start automatically when the PostgreSQL server is started. digoal@iZ28tqoemgtZ-> cd /data04/digoal/arc_log1922 digoal@iZ28tqoemgtZ-> ll total 16K lrwxrwxrwx 1 digoal digoal 71 Aug 29 17:18 00000002000000470000000C -> /data05/digoal/pgstdbak/20160829/171420/arclog/00000002000000470000000C lrwxrwxrwx 1 digoal digoal 71 Aug 29 17:18 00000002000000470000000D -> /data05/digoal/pgstdbak/20160829/171420/arclog/00000002000000470000000D lrwxrwxrwx 1 digoal digoal 87 Aug 29 17:18 00000002000000470000000D.00000028.backup -> /data05/digoal/pgstdbak/20160829/171420/arclog/00000002000000470000000D.00000028.backup -rw------- 1 digoal digoal 42 Aug 29 17:18 00000002.history ~~~ 6\. 啟動恢復目標數據庫 ~~~ digoal@iZ28tqoemgtZ-> pg_ctl start -D /data04/digoal/pg_restore_root server starting digoal@iZ28tqoemgtZ-> LOG: 00000: redirecting log output to logging collector process HINT: Future log output will appear in directory "pg_log". LOCATION: SysLogger_Start, syslogger.c:622 digoal@iZ28tqoemgtZ-> psql -h 127.0.0.1 -p 1922 psql (9.5.3) Type "help" for help. postgres=# select pg_is_in_recovery(); pg_is_in_recovery ------------------- f (1 row) postgres=# \l+ List of databases Name | Owner | Encoding | Collate | Ctype | Access privileges | Size | Tablespace | Description --------------------+----------+----------+---------+-------+-----------------------+---------+------------+-------------------------------------------- contrib_regression | postgres | UTF8 | C | C | | 7137 kB | pg_default | db1 | postgres | UTF8 | C | C | | 111 MB | tbs1 | postgres | postgres | UTF8 | C | C | | 797 MB | pg_default | default administrative connection database template0 | postgres | UTF8 | C | C | =c/postgres +| 7137 kB | pg_default | unmodifiable empty database | | | | | postgres=CTc/postgres | | | template1 | postgres | UTF8 | C | C | =c/postgres +| 7137 kB | pg_default | default template for new databases | | | | | postgres=CTc/postgres | | | (5 rows) ~~~ ## 注意事項 1. 小心覆蓋原有的部分 2. 建議先將原有的目錄重命名，或者在其他機器恢復， 3. 軟鏈接的處理，會恢復到目標，并且重新建立軟鏈接，所以目錄結構必須與備份時保持一致。 4. 用戶可以指定$PGDATA，恢復到新的目標目錄，但是arch_log, 表空間, pg_xlog目錄無法指定新的位置，所以原地還原時，必須注意這些目錄可能被覆蓋，先重命名是比較好的手段。 ## pg_rman 可以優化的地方 1. 檢查哪些要恢復的塊與目標塊的CRC是否一致，如果一致，不需要拷貝，減少WRITE。 ## pg_rman 軟件限制 ### pg_rman的使用限制 pg_rman has the following restrictions. 1. Requires to read database cluster directory and write backup catalog directory.? For example, you need to mount the disk where backup catalog is placed with NFS from database server.? 實際上不是必須的，如果沒有指定原來的$PGDATA，則使用備份集的元數據。 2. Block sizes of pg_rman and server should be matched. BLCKSZ and XLOG_BLCKSZ also should be matched.? 編譯pg_rman時，最好使用啟動數據集的集群軟件的pg_config。確保塊大小一致。? 因為需要做塊的校驗。讀取LSN等，都與塊大小有關。 3. If there are some unreadable files/directories in database cluster directory, WAL directory or archived WAL directory, the backup or restore would be failed. 4. When taking an incremental backup, pg_rman check the timeline ID of the target database whether it is the same with the one of the full backup in backup list.? But, pg_rman does not check whether the data itself is same with the full backup in backup list.? So, you can take an incremental backup over the full backup against the database which has the same timeline ID but has different data. ### 從standby備份時的軟件限制 Getting backup from standby-site, pg_rman has the follow restrictions too. 1. The environment of replication should be built right, or the backup will not finish. 2. You can’t get backups on master and standby at the same time.? 因為pg_rman使用的是exclusive bakcup，（pg_start_backup），所以同一時間，只能跑一次pg_start_backup。? pg_basebackup則使用的是shared backup，可以跑多個。 3. You can’t get backups on multi standbys at the same time too.? 道理同上 4. Basically, the backup from standby-site is used for restoring on MASTER.? pg_rman doesn’t treat the backup as restoring on standby automatically. 5. If you want to restore the backup on STANDBY, you have to manage archive logs with your self.? 因為備庫不歸檔，所以從standby備份時，需要解決歸檔備份的問題。? 我在前面的文檔中已經提及，包括解決思路。 ### 如果使用快照備份，有哪些軟件限制 When using storage snapshot, pg_rman has the following restrictions too. 1. If your snapshot does not have any file update time, incremental backup is same with full backup. 2. Because pg_rman judges performing full backup or incremental backup by update time for files.? If files don’t have update time because of storage snapshot specification, pg_rman performs full backup every time. 3. You can’t backup for one side works storage with split mirror snapshot. 4. Before you execute pg_rman, you should perform storage “RESYNC”. 5. After pg_rman performs backup with split mirror snapshot, storeage will be “SPLITTED”(works on one side).? pg_rman perform SPLIT command for getting snapshot, but doesn’t perform RESYNC command. 6. You cant’t get snapshot from different vendor storages in a time. 7. You cant’t use some vendor storages which have different commands for getting snapshot. 8. The script and commands for getting storage snapshot should be executable. 9. It’s expected to have authority of root for getting snapshot or mounting volumes.? So a user, performs pg_rman, is granted to execute any commands in the script. 10. If you use LVM(Logical Volume Manager), it’s needed root authority for mount, umount, lvcreate, lvremove, lvscan commands.? You should granted to these commands with sudo command to non-password executable. ## pg_rman 源碼淺析 1. 增量備份代碼上次備份以來，數據塊的LSN是否發生了變化，如果自從上次備份的start_lsn以來沒有發生變化，則不備份。代碼舉例 ~~~ else { pgBackupGetPath(prev_backup, prev_file_txt, lengthof(prev_file_txt), DATABASE_FILE_LIST); prev_files = dir_read_file_list(pgdata, prev_file_txt); /* * Do backup only pages having larger LSN than previous backup. */ lsn = &prev_backup->start_lsn; xlogid = (uint32) (*lsn >> 32); xrecoff = (uint32) *lsn; elog(DEBUG, _("backup only the page updated after LSN(%X/%08X)"), xlogid, xrecoff); } ... /* backup files from non-snapshot */ pgBackupGetPath(&current, path, lengthof(path), DATABASE_DIR); backup_files(pgdata, path, files, prev_files, lsn, current.compress_data, NULL); ~~~ 1. 備份結果backup.ini相關代碼 ~~~ # configuration BACKUP_MODE=FULL FULL_BACKUP_ON_ERROR=false WITH_SERVERLOG=true COMPRESS_DATA=true # result TIMELINEID=1 START_LSN=43/d5000028 STOP_LSN=43/d5000168 START_TIME='2016-08-26 15:43:39' END_TIME='2016-08-26 15:44:27' RECOVERY_XID=3896508572 RECOVERY_TIME='2016-08-26 15:44:18' TOTAL_DATA_BYTES=823571731 READ_DATA_BYTES=823571731 READ_ARCLOG_BYTES=234881668 READ_SRVLOG_BYTES=218248 WRITE_BYTES=206009921 BLOCK_SIZE=8192 XLOG_BLOCK_SIZE=8192 STATUS=OK ~~~ 對應的數據結構 ~~~ /* * pg_rman takes backup into the directory $BACKUP_PATH/<date>/<time>. * * status == -1 indicates the pgBackup is invalid. */ typedef struct pgBackup { /* Backup Level */ BackupMode backup_mode; bool with_serverlog; bool compress_data; bool full_backup_on_error; /* Status - one of BACKUP_STATUS_xxx */ BackupStatus status; /* Timestamp, etc. */ TimeLineID tli; XLogRecPtr start_lsn; XLogRecPtr stop_lsn; time_t start_time; time_t end_time; time_t recovery_time; uint32 recovery_xid; /* Size (-1 means not-backup'ed) */ int64 total_data_bytes; int64 read_data_bytes; int64 read_arclog_bytes; int64 read_srvlog_bytes; int64 write_bytes; /* data/wal block size for compatibility check */ uint32 block_size; uint32 wal_block_size; /* if backup from standby or not */ bool is_from_standby; } pgBackup; ~~~ 備份開始時記錄pg_start_backup調用返回的lsn，寫入backup->start_lsn ~~~ /* * Notify start of backup to PostgreSQL server. */ static void pg_start_backup(const char *label, bool smooth, pgBackup *backup) { PGresult *res; const char *params[2]; params[0] = label; elog(DEBUG, "executing pg_start_backup()"); reconnect(); /* Assumes PG version >= 8.4 */ /* 2nd argument is 'fast' (IOW, !smooth) */ params[1] = smooth ? "false" : "true"; res = execute("SELECT * from pg_xlogfile_name_offset(pg_start_backup($1, $2))", 2, params); if (backup != NULL) get_lsn(res, &backup->tli, &backup->start_lsn); elog(DEBUG, "backup start point is (WAL file: %s, xrecoff: %s)", PQgetvalue(res, 0, 0), PQgetvalue(res, 0, 1)); PQclear(res); disconnect(); } ~~~ 備份停止，調用pg_stop_backup，從返回結果中取出LSN，寫入backup->stop_lsn ~~~ /* * Notify end of backup to PostgreSQL server. */ static void pg_stop_backup(pgBackup *backup) { elog(DEBUG, "executing pg_stop_backup()"); wait_for_archive(backup, "SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup())"); } static void wait_for_archive(pgBackup *backup, const char *sql) { PGresult *res; char ready_path[MAXPGPATH]; int try_count; reconnect(); res = execute(sql, 0, NULL); if (backup != NULL) { get_lsn(res, &backup->tli, &backup->stop_lsn); elog(DEBUG, "backup end point is (WAL file: %s, xrecoff: %s)", PQgetvalue(res, 0, 0), PQgetvalue(res, 0, 1)); } /* get filename from the result of pg_xlogfile_name_offset() */ elog(DEBUG, "waiting for %s is archived", PQgetvalue(res, 0, 0)); snprintf(ready_path, lengthof(ready_path), "%s/pg_xlog/archive_status/%s.ready", pgdata, PQgetvalue(res, 0, 0)); PQclear(res); res = execute(TXID_CURRENT_SQL, 0, NULL); if(backup != NULL) { get_xid(res, &backup->recovery_xid); backup->recovery_time = time(NULL); } disconnect(); /* wait until switched WAL is archived */ try_count = 0; while (fileExists(ready_path)) { sleep(1); if (interrupted) ereport(FATAL, (errcode(ERROR_INTERRUPTED), errmsg("interrupted during waiting for WAL archiving"))); try_count++; if (try_count > TIMEOUT_ARCHIVE) ereport(ERROR, (errcode(ERROR_ARCHIVE_FAILED), errmsg("switched WAL could not be archived in %d seconds", TIMEOUT_ARCHIVE))); } elog(DEBUG, "WAL file contains backup end point is archived after %d seconds waiting", try_count); } ~~~ validate 時，改backup.ini的STATUS字段 ~~~ validate.c for (i = 0; i < parray_num(backup_list); i++) { pgBackup *backup = (pgBackup *)parray_get(backup_list, i); /* clean extra backups (switch STATUS to ERROR) */ if(!another_pg_rman && (backup->status == BACKUP_STATUS_RUNNING || backup->status == BACKUP_STATUS_DELETING)) { backup->status = BACKUP_STATUS_ERROR; pgBackupWriteIni(backup); } /* Validate completed backups only. */ if (backup->status != BACKUP_STATUS_DONE) continue; /* validate with CRC value and update status to OK */ pgBackupValidate(backup, false, false, (HAVE_DATABASE(backup))); } ... /* update status to OK */ if (corrupted) backup->status = BACKUP_STATUS_CORRUPT; else backup->status = BACKUP_STATUS_OK; pgBackupWriteIni(backup); ~~~ ## 注意 1.備份參數 -C 表示無縫checkpoint, 所以可能很慢，視checkpoint_completion_target和segment_size的配置。? 如果你發現pg_rman開始很慢，可以把-C去掉，速度就快了，但是可能在高峰時，造成沖擊。? 建議高峰是不要備份。? 2.BUG? unix socket 是$PGDATA時, validate會報錯 ~~~ pg_rman validate INFO: validate: "2016-08-26 16:19:25" backup, archive log files and server log files by CRC ERROR: invalid type '?' found in "/data05/digoal/pgbak/20160826/161925/file_database.txt" vi /data05/digoal/pgbak/20160826/161925/file_database.txt .s.PGSQL.1921 ? 0 0 0777 2016-08-26 15:35:05 ~~~ 修改一下dir.c的代碼即可修復這個問題，修改如下 ~~~ if (strncmp(path, ".s.PGSQL", 7) != 0 && type != 'f' && type != 'F' && type != 'd' && type != 'l') ereport(ERROR, (errcode(ERROR_CORRUPTED), errmsg("invalid type '%c' found in \"%s\"", type, file_txt))); ~~~ 祝大家玩得開心，歡迎隨時來?阿里云促膝長談業務需求?，恭候光臨。阿里云的小伙伴們加油，努力?做好內核與服務，打造最貼地氣的云數據庫?。