最近一項目壓力比較大，502超多，PHP進程coredump比較頻繁于是學習了下coredump的調試講下PHP ?coredump的調試，coredump先準備代碼比較好，因為PHP是開源的，這點好辦。我的是存在/usr/local/src//usr/local/src/php-5.3.10/ 下第一種當然是通用的調試gdb /usr/local/php/sbin/php-fpm -c /data/core_files/core-php-fpm-28436-1370008094第二種是PHP特有的調試獲得一個PHP正在運行的進程#ps -ef|grep php-fpm|head #gdb --pid=$PID >source /usr/local/src//usr/local/src/php-5.3.10/.gdbinit這種方式能調試一些PHP特有的東西，比如包括參數的函數調用棧的信息.先講通用方式調試(gdb) bt #0 0x00007ffed0603a75 in raise () from /lib/libc.so.6 #1 0x00007ffed06075c0 in abort () from /lib/libc.so.6 #2 0x00007ffed342ef7c in memcached_io_slurp (ptr=0x2ef9f50) at libmemcached/io.cc:510 #3 0x00007ffed3431da6 in memcached_quit_server (ptr=0x2ef9f50, io_death=false) at libmemcached/quit.cc:95 #4 0x00007ffed3431eed in send_quit (ptr=0x2d34e90) at libmemcached/quit.cc:137 #5 0x00007ffed342ff39 in _free (ptr=0x2d34e90, release_st=true) at libmemcached/memcached.cc:130 #6 0x00007ffed3430397 in memcached_free (ptr=0x2d34e90) at libmemcached/memcached.cc:284 #7 0x00000000005d00e0 in php_memc_destroy (m_obj=0x2e3bf60, persistent=0 '\000') at /usr/local/src/php-5.3.10/ext/memcached/php_memcached.c:2519 #8 0x00000000005d145f in php_memc_free_storage (i_obj=0x2dea580) at /usr/local/src/php-5.3.10/ext/memcached/php_memcached.c:2530 #9 0x000000000081817a in zend_objects_store_del_ref_by_handle_ex (handle=<value optimized out>, handlers=<value optimized out>) at /usr/local/src/php-5.3.10/Zend/zend_objects_API.c:220 #10 0x0000000000818193 in zend_objects_store_del_ref (zobject=0x2dea620) at /usr/local/src/php-5.3.10/Zend/zend_objects_API.c:172 #11 0x00000000007e9fb5 in _zval_dtor (zval_ptr=<value optimized out>) at /usr/local/src/php-5.3.10/Zend/zend_variables.h:35 #12 _zval_ptr_dtor (zval_ptr=<value optimized out>) at /usr/local/src/php-5.3.10/Zend/zend_execute_API.c:447 #13 0x00000000008020eb in zend_hash_destroy (ht=0x2d21e20) at /usr/local/src/php-5.3.10/Zend/zend_hash.c:529 #14 0x00000000007f5416 in _zval_dtor_func (zvalue=0x2d21df0) at /usr/local/src/php-5.3.10/Zend/zend_variables.c:43 #15 0x00000000007e9fb5 in _zval_dtor (zval_ptr=<value optimized out>) at /usr/local/src/php-5.3.10/Zend/zend_variables.h:35 #16 _zval_ptr_dtor (zval_ptr=<value optimized out>) at /usr/local/src/php-5.3.10/Zend/zend_execute_API.c:447 #17 0x00000000008023f3 in zend_hash_clean (ht=0x2d21cb0) at /usr/local/src/php-5.3.10/Zend/zend_hash.c:561 #18 0x00000000007ee2cb in zend_cleanup_op_array_data (function=<value optimized out>) at /usr/local/src/php-5.3.10/Zend/zend_opcode.c:133 #19 zend_cleanup_function_data (function=<value optimized out>) at /usr/local/src/php-5.3.10/Zend/zend_opcode.c:140 #20 0x0000000000801ea4 in zend_hash_reverse_apply (ht=0x29e5c30, apply_func=0x7ee2a0 <zend_cleanup_function_data>) at /usr/local/src/php-5.3.10/Zend/zend_hash.c:757 #21 0x00000000007ea2f3 in shutdown_executor () at /usr/local/src/php-5.3.10/Zend/zend_execute_API.c:296 #22 0x00000000007f6563 in zend_deactivate () at /usr/local/src/php-5.3.10/Zend/zend.c:891 #23 0x00000000007a47a0 in php_request_shutdown (dummy=<value optimized out>) at /usr/local/src/php-5.3.10/main/main.c:1661 #24 0x0000000000884442 in main (argc=<value optimized out>, argv=<value optimized out>) at /usr/local/src/php-5.3.10/sapi/fpm/fpm/fpm_main.c:1886 (gdb) f 2 #2 0x00007ffed342ef7c in memcached_io_slurp (ptr=0x2ef9f50) at libmemcached/io.cc:510 510 libmemcached/io.cc: No such file or directory.in libmemcached/io.cc為了調試memcached，會碰到了提示說 libmemcached/io.cc不存在，于是也把libmemcached的源碼也下載回來。注意版本得配對，否則容易造成找代碼行數找不準，就白瞎了。warning: Source file is more recent than executable.看版本用 -i來看 #/usr/local/php/sbin/php-fpm -i|grep libmemcachedlibmemcached version => 1.0.4 #wget https://launchpad.net/libmemcached/1.0/1.0.4/+download/libmemcached-1.0.4.tar.gz把代碼解壓到php源碼目錄下 ?，如果出錯可能是路徑不對繼續回來gdb(gdb) f 2 #2 0x00007ffed342ef7c in memcached_io_slurp (ptr=0x2ef9f50) at libmemcached/io.cc:510 510 in libmemcached/io.cc看到是libmemcached/io.cc ?的510行報錯#vim ?libmemcached/io.cc +510看到代碼如下：memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr) {assert_msg(ptr, "Programmer error, invalid memcached_server_write_instance_st");assert(memcached_is_udp(ptr->root) == false);if (ptr->fd == INVALID_SOCKET){assert_msg(int(ptr->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO), "Invalid socket state"); #line 510return MEMCACHED_CONNECTION_FAILURE;}ssize_t data_read;這是一個無效的連接？ 除非說是網絡非常繁忙，或壓力很大。往下看看吧(gdb) f 3 #3 0x00007ffed3431da6 in memcached_quit_server (ptr=0x2ef9f50, io_death=false) at libmemcached/quit.cc:95 warning: Source file is more recent than executable. 95 while (memcached_continue(rc_slurp= memcached_io_slurp(ptr))) {} ;是在quit函數中，進代碼看看WATCHPOINT_ASSERT(rc == MEMCACHED_SUCCESS or rc == MEMCACHED_FETCH_NOTFINISHED);/* read until socket is closed, or there is an error* closing the socket before all data is read* results in server throwing away all data which is* not read** In .40 we began to only do this if we had been doing buffered* requests of had replication enabled.*/if (ptr->root->flags.buffer_requests or ptr->root->number_of_replicas){memcached_return_t rc_slurp;while (memcached_continue(rc_slurp= memcached_io_slurp(ptr))) {} ; #line 95WATCHPOINT_ASSERT(rc_slurp == MEMCACHED_CONNECTION_FAILURE);}/** memcached_io_read may call memcached_quit_server with io_death if* it encounters problems, but we don't care about those occurences.* The intention of that loop is to drain the data sent from the* server to ensure that the server processed all of the data we* sent to the server.*/ptr->server_failure_counter= 0;}memcached_io_close(ptr);}slurp的意思是：大量讀取看看注釋的意思：等待socket 正常關閉或沒有讀完數據但是出現了錯誤引起的異常關閉，結果是服務器扔掉了所有沒有讀完的數據。95行的代碼是一個條件循環，條件是memcached_io_slurp 的結果繼續分析函數 ?memcached_io_slurp發現是等待讀完buffer的過程總體的意思是說服務端開啟了buffer，PHP發送了退出請求，所以memcached擴展也被要求退出，然而buffer可能沒有讀完，所以memcached等待buffer讀完，而php等待memcached退出后才能退出(gdb) f 7 #7 0x00000000005d00e0 in php_memc_destroy (m_obj=0x2e3bf60, persistent=0 '\000') at /usr/local/src/php-5.3.10/ext/memcached/php_memcached.c:2519 2519 in /usr/local/src/php-5.3.10/ext/memcached/php_memcached.c 一路往后f (gdb) f 24 #24 0x0000000000884442 in main (argc=<value optimized out>, argv=<value optimized out>) at /usr/local/src/php-5.3.10/sapi/fpm/fpm/fpm_main.c:1886 1886 php_request_shutdown((void *) 0);看到是 fpm請求退出進程 php_request_shutdownfastcgi_request_done:if (primary_script) {efree(primary_script);}if (request_body_fd != -1) {close(request_body_fd);}request_body_fd = -2;if (EG(exit_status) == 255) {if (CGIG(error_header) && *CGIG(error_header)) {sapi_header_line ctr = {0};ctr.line = CGIG(error_header);ctr.line_len = strlen(CGIG(error_header));sapi_header_op(SAPI_HEADER_REPLACE, &ctr TSRMLS_CC);}}fpm_request_end(TSRMLS_C);fpm_log_write(NULL TSRMLS_CC);STR_FREE(SG(request_info).path_translated);SG(request_info).path_translated = NULL;php_request_shutdown((void *) 0); #line 1886if (exit_status == 0) {exit_status = EG(exit_status);}requests++;if (max_requests && (requests == max_requests)) {fcgi_finish_request(&request, 1);if (max_requests != 1) {/* no need to return exit_status of the last request */exit_status = 0;好像還沒有結果。雖然還沒查到具體的原因，大概問題歸結在memcached擴展和memcached服務器通訊的時候，數據還未傳完，PHP進程就要結束，導致coredump。

轉載于:https://blog.51cto.com/gavins/1353446

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