通过 Exit Code 定位 Pod 异常退出原因

最近更新时间：2024-02-20 14:47:52

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本文介绍如何根据 Pod 异常状态信息中的 Exit Code 进一步定位问题。  
查看 Pod 异常状态信息
执行以下命令，查看异常 Pod 状态信息。
kubectl describe pod <pod name>
返回结果如下：
Containers:
  kubedns:
    Container ID:  docker://5fb8adf9ee62afc6d3f6f3d9590041818750b392dff015d7091eaaf99cf1c945
    Image:         ccr.ccs.tencentyun.com/library/kubedns-amd64:1.14.4
    Image ID:      docker-pullable://ccr.ccs.tencentyun.com/library/kubedns-amd64@sha256:40790881bbe9ef4ae4ff7fe8b892498eecb7fe6dcc22661402f271e03f7de344
    Ports:         10053/UDP, 10053/TCP, 10055/TCP
    Host Ports:    0/UDP, 0/TCP, 0/TCP
    Args:
      --domain=cluster.local.
      --dns-port=10053
      --config-dir=/kube-dns-config
      --v=2
    State:          Running
      Started:      Tue, 27 Aug 2019 10:58:49 +0800
    Last State:     Terminated
      Reason:       Error
      Exit Code:    255
      Started:      Tue, 27 Aug 2019 10:40:42 +0800
      Finished:     Tue, 27 Aug 2019 10:58:27 +0800
    Ready:          True
    Restart Count:  1
在返回结果的容器列表 Last State 字段中， Exit Code 为程序上次退出时的状态码，该值不为0即表示程序异常退出，可根据退出状态码进一步分析异常原因。
退出状态码说明
状态码需在0 - 255之间。
0表示正常退出。
若因外界中断导致程序退出，则状态码区间为129 - 255。例如，操作系统给程序发送中断信号 kill -9 或 ctrl+c，导致程序状态变为 SIGKILL 或 SIGINT。
通常因程序自身原因导致的异常退出，状态码区间在1 - 128。在某些场景下，也允许程序设置使用129 - 255区间的状态码。
若指定的退出状态码不在0 - 255之间（例如，设置 exit(-1)），此时将会自动执行转换，最终呈现的状态码仍会在0 - 255之间。
若将退出时状态码记为 code，则不同情况下转换方式如下：
当指定的退出时状态码为负数，转换公式为：
256 - (|code| % 256)
当指定的退出时状态码为正数，转换公式为：
code % 256
常见异常状态码
137：表示程序被 SIGKILL 中断信号杀死。异常原因可能为：
通常是由于 Pod 中容器内存达到了其资源限制（resources.limits）。例如，内存溢出（OOM）。由于资源限制是通过 Linux 的 cgroup 实现的，当某个容器内存达到资源限制， cgroup 就会将其强制停止（类似于 kill -9），此时通过 describe pod 可以看到 Reason 是 OOMKilled。
宿主机本身资源不够用（OOM），则内核会选择停止一些进程来释放内存。
说明
无论是 cgroup 限制，还是因为节点机器本身资源不够导致的进程停止，都可以从系统日志中找到记录。方法如下：
Ubuntu 系统日志存储在目录 /var/log/syslog，CentOS 系统日志存储在目录 /var/log/messages 中，两者系统日志均可通过 journalctl -k 命令进行查看。
livenessProbe（存活检查）失败，使得 kubelet 停止 Pod。
被恶意木马进程停止。
1和255：通常表示一般错误，具体原因需要通过容器日志进一步定位。例如，可能是设置异常退出使用 exit(1) 或 exit(-1)导致的，而-1将会根据规则转换成255。
Linux 标准中断信号
Linux 程序被外界中断时会发送中断信号，程序退出时的状态码为中断信号值加128。例如， SIGKILL 的中断信号值为9，那么程序退出状态码则为9 + 128 = 137。更多标准信号值参考如下表：
信号 Signal
状态码 Value
动作 Action
描述 Comment
SIGHUP
1
Term
Hangup detected on controlling terminal or death of controlling process
SIGINT
2
Term
Interrupt from keyboard
SIGQUIT
3
Core
Quit from keyboard
SIGILL
4
Core
 Illegal Instruction
SIGABRT
6
Core
Abort signal from abort(3)
SIGFPE
8
Core
 Floating-point exception
SIGKILL
9
Term
Kill signal
SIGSEGV
11
Core
Invalid memory reference
SIGPIPE
13
Term
Broken pipe: write to pipe with no readers; see pipe(7)
SIGALRM
14
Term
Timer signal from alarm(2)
SIGTERM
15
Term
Termination signal
SIGUSR1
30,10,16 
Term
User-defined signal 1
SIGUSR2
31,12,17
Term
User-defined signal 2
SIGCHLD
20,17,18
Ign
Child stopped or terminated
SIGCONT
19,18,25
Cont
 Continue if stopped
SIGSTOP
17,19,23
Stop
Stop process
SIGTSTP
18,20,24
Stop
Stop typed at terminal
SIGTTIN
21,21,26
Stop
Terminal input for background process
SIGTTOU
22,22,27
Stop
Terminal output for background process
C/C++ 退出状态码
/usr/include/sysexits.h 中进行了退出状态码标准化（仅限 C/C++），如下表：
定义
状态码
描述
#define EX_OK
0
successful termination
#define EX__BASE
64
base value for error messages
#define EX_USAGE
64
command line usage error
#define EX_DATAERR
65
data format error
#define EX_NOINPUT
66
cannot open input
#define EX_NOUSER
67
addressee unknown
#define EX_NOHOST 
68
 host name unknown
#define EX_UNAVAILABLE
69
service unavailable
#define EX_SOFTWARE
70
internal software error
#define EX_OSERR 
71
system error (e.g., can't fork)
#define EX_OSFILE
72
critical OS file missing
#define EX_CANTCREAT
73
can't create (user) output file
#define EX_IOERR
74
input/output error
#define EX_TEMPFAIL
75
temp failure; user is invited to retry
#define EX_PROTOCOL
76
remote error in protocol
#define EX_NOPERM 
77
permission denied
#define EX_CONFIG
78
configuration error
#define EX__MAX 78
78
maximum listed value
状态码参考
更多状态码含义可参考以下表格：
状态码
含义
示例
描述
1
Catchall for general errors
let "var1 = 1/0"
Miscellaneous errors, such as "divide by zero" and other impermissible operations
2
Misuse of shell builtins (according to Bash documentation)
empty_function() {}
Missing keyword or command, or permission problem (and diff return code on a failed binary file comparison).
126
Command invoked cannot execute
/dev/null
Permission problem or command is not an executable
127
"command not found"
illegal_command
Possible problem with $PATH or a typo
128
Invalid argument to exit
exit 3.14159
exit takes only integer args in the range 0 - 255 (see first footnote)
128+n
Fatal error signal "n"
kill -9 $PPID of script
$? returns 137 (128 + 9)
130
Script terminated by Control-C
Ctl-C
Control-C is fatal error signal 2, (130 = 128 + 2, see above)
255*
Exit status out of range
exit -1
exit takes only integer args in the range 0 - 255
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信号 Signal	状态码 Value	动作 Action	描述 Comment
SIGHUP	1	Term	Hangup detected on controlling terminal or death of controlling process
SIGINT	2	Term	Interrupt from keyboard
SIGQUIT	3	Core	Quit from keyboard
SIGILL	4	Core	Illegal Instruction
SIGABRT	6	Core	Abort signal from abort(3)
SIGFPE	8	Core	Floating-point exception
SIGKILL	9	Term	Kill signal
SIGSEGV	11	Core	Invalid memory reference
SIGPIPE	13	Term	Broken pipe: write to pipe with no readers; see pipe(7)
SIGALRM	14	Term	Timer signal from alarm(2)
SIGTERM	15	Term	Termination signal
SIGUSR1	30,10,16	Term	User-defined signal 1
SIGUSR2	31,12,17	Term	User-defined signal 2
SIGCHLD	20,17,18	Ign	Child stopped or terminated
SIGCONT	19,18,25	Cont	Continue if stopped
SIGSTOP	17,19,23	Stop	Stop process
SIGTSTP	18,20,24	Stop	Stop typed at terminal
SIGTTIN	21,21,26	Stop	Terminal input for background process
SIGTTOU	22,22,27	Stop	Terminal output for background process

定义	状态码	描述
#define EX_OK	0	successful termination
#define EX__BASE	64	base value for error messages
#define EX_USAGE	64	command line usage error
#define EX_DATAERR	65	data format error
#define EX_NOINPUT	66	cannot open input
#define EX_NOUSER	67	addressee unknown
#define EX_NOHOST	68	host name unknown
#define EX_UNAVAILABLE	69	service unavailable
#define EX_SOFTWARE	70	internal software error
#define EX_OSERR	71	system error (e.g., can't fork)
#define EX_OSFILE	72	critical OS file missing
#define EX_CANTCREAT	73	can't create (user) output file
#define EX_IOERR	74	input/output error
#define EX_TEMPFAIL	75	temp failure; user is invited to retry
#define EX_PROTOCOL	76	remote error in protocol
#define EX_NOPERM	77	permission denied
#define EX_CONFIG	78	configuration error
#define EX__MAX 78	78	maximum listed value

状态码	含义	示例	描述
1	Catchall for general errors	let "var1 = 1/0"	Miscellaneous errors, such as "divide by zero" and other impermissible operations
2	Misuse of shell builtins (according to Bash documentation)	empty_function() {}	Missing keyword or command, or permission problem (and diff return code on a failed binary file comparison).
126	Command invoked cannot execute	/dev/null	Permission problem or command is not an executable
127	"command not found"	illegal_command	Possible problem with $PATH or a typo
128	Invalid argument to exit	exit 3.14159	exit takes only integer args in the range 0 - 255 (see first footnote)
128+n	Fatal error signal "n"	kill -9 $PPID of script	$? returns 137 (128 + 9)
130	Script terminated by Control-C	Ctl-C	Control-C is fatal error signal 2, (130 = 128 + 2, see above)
255*	Exit status out of range	exit -1	exit takes only integer args in the range 0 - 255