报错如下MYSQL不能正常启动
2017-09-22 10:39:05 21409 [Note] InnoDB: Database was not shutdown normally! 2017-09-22 10:39:05 21409 [Note] InnoDB: Starting crash recovery. 2017-09-22 10:39:05 21409 [Note] InnoDB: Reading tablespace information from the .ibd files... 2017-09-22 10:39:05 21409 [ERROR] InnoDB: Space id in fsp header 1416128883,but in the page header 824195850
我曾经写过这样一个文章如下:
InnoDB: Error: space id and page n:o stored in the page?
http://blog.itpub.net/7728585/viewspace-2121548/
但是上面的文章只是人为模拟,实际上在生产情况中严重得多,基本是块的物理顺坏,今天又有网友问我这个问题,实际上遇到这种问题一般都涉及到块的物理损坏了,修复的可能性并不大,我们来看看源码抛错位置:
/**********************************************************************//** Reads the space id from the first page of a tablespace. @return space id, ULINT UNDEFINED if error */ ulint fsp_header_get_space_id( /*====================*/ const page_t* page) /*!< in: first page of a tablespace */ { ulint fsp_id; ulint id; fsp_id = mach_read_from_4(FSP_HEADER_OFFSET + page + FSP_SPACE_ID); id = mach_read_from_4(page + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID); DBUG_EXECUTE_IF("fsp_header_get_space_id_failure", id = ULINT_UNDEFINED;); if (id != fsp_id) { ib::error() << "Space ID in fsp header is " << fsp_id << ", but in the page header it is " << id << "."; return(ULINT_UNDEFINED); } return(id); }
File space header是每一个表空间的第一个块才会有的,存储的信息如下:
/* SPACE HEADER ============ File space header data structure: this data structure is contained in the first page of a space. The space for this header is reserved in every extent descriptor page, but used only in the first. */ /*-------------------------------------*/ #define FSP_SPACE_ID 0 /* space id */ #define FSP_NOT_USED 4 /* this field contained a value up to which we know that the modifications in the database have been flushed to the file space; not used now */ #define FSP_SIZE 8 /* Current size of the space in pages */ #define FSP_FREE_LIMIT 12 /* Minimum page number for which the free list has not been initialized: the pages >= this limit are, by definition, free; note that in a single-table tablespace where size < 64 pages, this number is 64, i.e., we have initialized the space about the first extent, but have not physically allocated those pages to the file */ #define FSP_SPACE_FLAGS 16 /* fsp_space_t.flags, similar to dict_table_t::flags */ #define FSP_FRAG_N_USED 20 /* number of used pages in the FSP_FREE_FRAG list */ #define FSP_FREE 24 /* list of free extents */ #define FSP_FREE_FRAG (24 + FLST_BASE_NODE_SIZE) /* list of partially free extents not belonging to any segment */ #define FSP_FULL_FRAG (24 + 2 * FLST_BASE_NODE_SIZE) /* list of full extents not belonging to any segment */ #define FSP_SEG_ID (24 + 3 * FLST_BASE_NODE_SIZE) /* 8 bytes which give the first unused segment id */ #define FSP_SEG_INODES_FULL (32 + 3 * FLST_BASE_NODE_SIZE) /* list of pages containing segment headers, where all the segment inode slots are reserved */ #define FSP_SEG_INODES_FREE (32 + 4 * FLST_BASE_NODE_SIZE) /* list of pages containing segment headers, where not all the segment header slots are reserved */
那么这个错误简单的说就是某个表空间ibd文件的第一个块的34后4字节和38字节后4个字节不能通过检测,但是要注意这仅仅是这8个字节一个检测。实际上这种错误基本对应着表空间文件的物理顺坏,一般来说其他字节也出现了问题,如果没有备份或者其他双机手段可能要导致这个表空间的数据丢失。好了我们回到案例。
随即我问这位朋友是否是独立表空间,他说是的,然后我们就需要找到到底哪个表空间出了问题。我曾经有一个读取二进制文件的工具,放到百度云盘:
http://pan.baidu.com/s/1num76RJ
可以直接读取这样的信息如下:
****************************************************************** This Tool Is Uesed For Find The Data In Binary format(Hexadecimal) Usage:./bcview file blocksize offset cnt-bytes! file: Is Your File Will To Find Data! blocksize: Is N kb Block.Eg: 8 Is 8 Kb Blocksize(Oracle)! Eg: 16 Is 16 Kb Blocksize(Innodb)! offset:Is Every Block Offset Your Want Start! cnt-bytes:Is After Offset,How Bytes Your Want Gets! Edtor QQ:22389860! Used gcc version 4.1.2 20080704 (Red Hat 4.1.2-46) ****************************************************************** ----Current file size is :0.109375 Mb ----Current use set blockszie is 16 Kb ----Current file name is t6.ibd current block:00000000--Offset:00036--cnt bytes:08--data is:001e0000001e0000
我们可以得到数据
current block:00000000--Offset:00036--cnt bytes:08--data is:001e0000001e0000
但是要扫描全部的ibd文件才能找到是哪个表空间检测出错,但是这个哥们shell也是比较好,写了一个如下的shell来完成:
find /opt/app/mysql5/var/ -iname \*.ibd > a for i in `cat ./a`;do ./bcview $i 16 34 8 | head -15 >> a.log;done
这样将所有表空间的第一个块的信息的34-42字节信息都提取出来了,我随即查看了一下,找到了报错的表空间:
current block:00000000--Offset:00034--cnt bytes:08--data is:31203b0a54686973
显然他们是不相等,正常情况下这8个字节4字节4字节比较是相同的,然后我查看了这个文件中块的checksum也是不相等,这个时候只有2个正常的处理方式:
显然这里也再次重申了备份的重要性,遇到这样的错误,最安全的方式还是进行数据恢复,当然某些工具可以直接提取数据文件里面的数据,但是现有的版本支持并不是太好,而且风险也是特别大。
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