系統技術非業餘研究 » init_debug檢視系統boot過程
erl啟動的時候有個引數 -init_debug 作用是
Makes init write some debug information while interpreting the boot script.
參見erlang system_principles的1.3節：Boot Scripts， 我們可以知道，每個erlang vm啟動的時候，init程序都會去讀取boot檔案，來獲取系統要啟動那些服務。
如果我們不輸入任何引數的話，，預設是其他start_clean.boot檔案, 其內容如下：
$ cat ~/otp/erts/start_scripts/start_clean.script
%% script generated at {2012,12,26} {16,12,32}
{script,
{"OTP APN 181 01","R15B03"},
[{preLoaded,
[erl_prim_loader,erlang,init,otp_ring0,prim_file,prim_inet,prim_zip,
zlib]},
{progress,preloaded},
{path,["$ROOT/lib/kernel-2.15.3/ebin","$ROOT/lib/stdlib-1.18.3/ebin"]},
{primLoad,[error_handler]},
{kernel_load_completed},
{progress,kernel_load_completed},
{path,["$ROOT/lib/kernel-2.15.3/ebin"]},
{primLoad,
[application,application_controller,application_master,
application_starter,auth,code,code_server,disk_log,disk_log_1,
disk_log_server,disk_log_sup,dist_ac,dist_util,erl_boot_server,
erl_ddll,erl_distribution,erl_epmd,erl_reply,error_logger,
erts_debug,file,file_io_server,file_server,gen_sctp,gen_tcp,gen_udp,
global,global_group,global_search,group,heart,hipe_unified_loader,
inet,inet6_sctp,inet6_tcp,inet6_tcp_dist,inet6_udp,inet_config,
inet_db,inet_dns,inet_gethost_native,inet_hosts,inet_parse,inet_res,
inet_sctp,inet_tcp,inet_tcp_dist,inet_udp,kernel,kernel_config,net,
net_adm,net_kernel,os,packages,pg2,ram_file,rpc,seq_trace,
standard_error,user,user_drv,user_sup,wrap_log_reader]},
{path,["$ROOT/lib/stdlib-1.18.3/ebin"]},
{primLoad,
[array,base64,beam_lib,binary,c,calendar,dets,dets_server,dets_sup,
dets_utils,dets_v8,dets_v9,dict,digraph,digraph_utils,edlin,
edlin_expand,epp,erl_bits,erl_compile,erl_eval,erl_expand_records,
erl_internal,erl_lint,erl_parse,erl_posix_msg,erl_pp,erl_scan,
erl_tar,error_logger_file_h,error_logger_tty_h,escript,ets,
eval_bits,file_sorter,filelib,filename,gb_sets,gb_trees,gen,
gen_event,gen_fsm,gen_server,io,io_lib,io_lib_format,io_lib_fread,
io_lib_pretty,lib,lists,log_mf_h,math,ms_transform,orddict,ordsets,
otp_internal,pg,pool,proc_lib,proplists,qlc,qlc_pt,queue,random,re,
sets,shell,shell_default,slave,sofs,string,supervisor,
supervisor_bridge,sys,timer,unicode,win32reg,zip]},
{progress,modules_loaded},
{path,["$ROOT/lib/kernel-2.15.3/ebin","$ROOT/lib/stdlib-1.18.3/ebin"]},
{kernelProcess,heart,{heart,start,[]}},
{kernelProcess,error_logger,{error_logger,start_link,[]}},
{kernelProcess,application_controller,
{application_controller,start,
[{application,kernel,
[{description,"ERTS CXC 138 10"},
{vsn,"2.15.3"},
{id,[]},
{modules,
[application,application_controller,application_master,
application_starter,auth,code,packages,code_server,
dist_util,erl_boot_server,erl_distribution,erl_reply,
error_handler,error_logger,file,file_server,
file_io_server,global,global_group,global_search,
group,heart,hipe_unified_loader,inet6_tcp,
inet6_tcp_dist,inet6_udp,inet6_sctp,inet_config,
inet_hosts,inet_gethost_native,inet_tcp_dist,kernel,
kernel_config,net,net_adm,net_kernel,os,ram_file,rpc,
user,user_drv,user_sup,disk_log,disk_log_1,
disk_log_server,disk_log_sup,dist_ac,erl_ddll,
erl_epmd,erts_debug,gen_tcp,gen_udp,gen_sctp,inet,
inet_db,inet_dns,inet_parse,inet_res,inet_tcp,
inet_udp,inet_sctp,pg2,seq_trace,standard_error,
wrap_log_reader]},
{registered,
[application_controller,erl_reply,auth,boot_server,
code_server,disk_log_server,disk_log_sup,
erl_prim_loader,error_logger,file_server_2,
fixtable_server,global_group,global_name_server,heart,
init,kernel_config,kernel_sup,net_kernel,net_sup,rex,
user,os_server,ddll_server,erl_epmd,inet_db,pg2]},
{applications,[]},
{included_applications,[]},
{env,[{error_logger,tty}]},
{maxT,infinity},
{maxP,infinity},
{mod,{kernel,[]}}]}]}},
{progress,init_kernel_started},
{apply,
{application,load,
[{application,stdlib,
[{description,"ERTS CXC 138 10"},
{vsn,"1.18.3"},
{id,[]},
{modules,
[array,base64,beam_lib,binary,c,calendar,dets,
dets_server,dets_sup,dets_utils,dets_v8,dets_v9,dict,
digraph,digraph_utils,edlin,edlin_expand,epp,
eval_bits,erl_bits,erl_compile,erl_eval,
erl_expand_records,erl_internal,erl_lint,erl_parse,
erl_posix_msg,erl_pp,erl_scan,erl_tar,
error_logger_file_h,error_logger_tty_h,escript,ets,
file_sorter,filelib,filename,gb_trees,gb_sets,gen,
gen_event,gen_fsm,gen_server,io,io_lib,io_lib_format,
io_lib_fread,io_lib_pretty,lib,lists,log_mf_h,math,
ms_transform,orddict,ordsets,otp_internal,pg,pool,
proc_lib,proplists,qlc,qlc_pt,queue,random,re,sets,
shell,shell_default,slave,sofs,string,supervisor,
supervisor_bridge,sys,timer,unicode,win32reg,zip]},
{registered,
[timer_server,rsh_starter,take_over_monitor,
pool_master,dets]},
{applications,[kernel]},
{included_applications,[]},
{env,[]},
{maxT,infinity},
{maxP,infinity}]}]}},
{progress,applications_loaded},
{apply,{application,start_boot,[kernel,permanent]}},
{apply,{application,start_boot,[stdlib,permanent]}},
{apply,{c,erlangrc,[]}},
{progress,started}]}.
而boot檔案是script檔案的term_to_binary版本，演示下init載入過程：
$ erl -init_debug
{progress,preloaded}
{progress,kernel_load_completed}
{progress,modules_loaded}
{start,heart}
{start,error_logger}
{start,application_controller}
{progress,init_kernel_started}
{apply,{application,load,[{application,stdlib,[{description,"ERTS CXC 138 10"},{vsn,"1.19.1"},{id,[]},{modules,[array,base64,beam_lib,binary,c,calendar,dets,dets_server,dets_sup,dets_utils,dets_v8,dets_v9,dict,digraph,digraph_utils,edlin,edlin_expand,epp,eval_bits,erl_bits,erl_compile,erl_eval,erl_expand_records,erl_internal,erl_lint,erl_parse,erl_posix_msg,erl_pp,erl_scan,erl_tar,error_logger_file_h,error_logger_tty_h,escript,ets,file_sorter,filelib,filename,gb_trees,gb_sets,gen,gen_event,gen_fsm,gen_server,io,io_lib,io_lib_format,io_lib_fread,io_lib_pretty,lib,lists,log_mf_h,math,ms_transform,orddict,ordsets,otp_internal,pg,pool,proc_lib,proplists,qlc,qlc_pt,queue,random,re,sets,shell,shell_default,slave,sofs,string,supervisor,supervisor_bridge,sys,timer,unicode,win32reg,zip]},{registered,[timer_server,rsh_starter,take_over_monitor,pool_master,dets]},{applications,[kernel]},{included_applications,[]},{env,[]},{maxT,infinity},{maxP,infinity}]}]}}
{progress,applications_loaded}
{apply,{application,start_boot,[kernel,permanent]}}
Erlang R16B (erts-5.10.1) [64-bit] [smp:16:16] [async-threads:10] [hipe] [kernel-poll:false]
{apply,{application,start_boot,[stdlib,permanent]}}
{apply,{c,erlangrc,[]}}
{progress,started}
Eshell V5.10.1 (abort with ^G)
1>
當然如果只是簡單的boot不會有什麼問題，但是真實地情況是reltool在打包的時候，會把 xxx.app 檔案裡面，依賴的application都打進去，順便啟動起來。
比如：
{applications,[kernel,stdlib,sasl,os_mon,mnesia,ump_lib,ump_log,
ump_zk,ump_mq]}]}.
我們在填寫.app檔案的時候，可能會漏掉幾個，結果發現系統不正常運作，這時候init_debug就能幫上大忙。
摘抄一段診斷：
{running_on_load_handler,ump_la_nifs}
ump_la_nifs on load result: ok
{on_load_handler_returned_ok,ump_la_nifs}
{running_on_load_handler,dyntrace}
{on_load_handler_returned_ok,dyntrace}
{running_on_load_handler,erlsha2}
{on_load_handler_returned_ok,erlsha2}
{running_on_load_handler,crypto}
{on_load_handler_returned_ok,crypto}
{running_on_load_handler,asn1rt_nif}
{on_load_handler_returned_ok,asn1rt_nif}
{apply,{application,start_boot,[stdlib,permanent]}}
{apply,{application,start_boot,[sasl,permanent]}}
{apply,{application,start_boot,[os_mon,permanent]}}
{apply,{application,start_boot,[mnesia,permanent]}}=INFO REPORT==== 24-Jun-2013::17:24:34 ===
alarm_handler: {set,{{disk_almost_full,”/usr”},[]}}=ERROR REPORT==== 24-Jun-2013::17:24:34 ===
Mnesia(‘[email protected]’): ** ERROR ** mnesia_event got {inconsistent_database, starting_partitioned_network, ‘[email protected]’}=ERROR REPORT==== 24-Jun-2013::17:24:34 ===
Mnesia(‘[email protected]’): ** ERROR ** mnesia_event got {inconsistent_database, starting_partitioned_network, ‘[email protected]’}
{apply,{application,start_boot,[ump_lib,permanent]}}
{apply,{application,start_boot,[lager,permanent]}}
{apply,{application,start_boot,[syslog,permanent]}}
{apply,{application,start_boot,[ump_log,permanent]}}
17:24:34.755 [info] Application lager started on node ‘[email protected]’
{apply,{application,start_boot,[erlzk,permanent]}}
{apply,{application,start_boot,[ump_zk,permanent]}}
我們很清楚的看到,這些依賴的application是如何啟動的，按照什麼樣的順序。問題馬上就能定位出來。
祝玩的開心。
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