詳解Docker無(wú)法正常啟動(dòng)的原因及解決辦法

服務(wù)器

一、docker啟動(dòng)異常表現：

1.狀態(tài)反復restaring，用命令查看

$docker ps -a
CONTAINER ID  IMAGE COMMAND    CREATED   STATUS    PORTS  NAMES
21c09be88c11   docker.xxxx.cn:5000/xxx-tes/xxx_tes:1.0.6  /usr/local/tomcat...  9 days ago     Restarting (1) Less than a second ago           xxx10

2.Docker日志有明顯問(wèn)題：

$docker logs [容器名/容器ID]

二、Docker啟動(dòng)異常的可能原因：

2.1.內存不夠

Docker 啟動(dòng)至少需要2G內存，首先執行free -mh命令查看剩余內存是否足夠

直接查看內存

$free -mh
      total    used    free   shared buff/cache  available
Mem:     15G     14G     627M    195M    636M   726M
Swap:     0B     0B     0B

分析日志

有時(shí)候一瞬間內存過(guò)載溢出，導致部分進(jìn)程被殺死，看起來(lái)內存也是夠用的，事實(shí)上docker還是會(huì )反復重啟，就需要通過(guò)docker日志和系統日志信的息來(lái)進(jìn)一步分析：

分析docker日志

查看docker日志看到內存溢出的信息，要仔細翻閱才能找到信息，并不是在最下面

$docker logs [容器名/容器ID]|less 
Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x0000000769990000, 1449590784, 0) failed; error=\'Cannot allocate memory\' (errno=12)
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 1449590784 bytes for committing reserved memory.
# An error report file with more information is saved as:
# //hs_err_pid1.log
Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x0000000769990000, 1449590784, 0) failed; error=\'Cannot allocate memory\' (errno=12)
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 1449590784 bytes for committing reserved memory.
# An error report file with more information is saved as:
# /tmp/hs_err_pid1.log
Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x0000000769990000, 1449590784, 0) failed; error=\'Cannot allocate memory\' (errno=12)
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 1449590784 bytes for committing reserved memory.
# Can not save log file, dump to screen..
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 1449590784 bytes for committing reserved memory.
# Possible reasons:
#  The system is out of physical RAM or swap space
#  In 32 bit mode, the process size limit was hit
# Possible solutions:
#  Reduce memory load on the system
#  Increase physical memory or swap space
#  Check if swap backing store is full
#  Use 64 bit Java on a 64 bit OS
#  Decrease Java heap size (-Xmx/-Xms)
#  Decrease number of Java threads
#  Decrease Java thread stack sizes (-Xss)
#  Set larger code cache with -XX:ReservedCodeCacheSize=
# This output file may be truncated or incomplete.
#
# Out of Memory Error (os_linux.cpp:2756), pid=1, tid=140325689620224
#
# JRE version: (7.0_79-b15) (build )
# Java VM: Java HotSpot(TM) 64-Bit Server VM (24.79-b02 mixed mode linux-amd64 compressed oops)
# Core dump written. Default location: //core or core.1
#

分析系統日志

查看系統日志，發(fā)現有大量由于內存溢出，進(jìn)程被殺死的記錄

$grep -i \'Out of Memory\' /var/log/messages
Apr 7 10:04:02 centos106 kernel: Out of memory: Kill process 1192 (java) score 54 or sacrifice child
Apr 7 10:08:00 centos106 kernel: Out of memory: Kill process 2301 (java) score 54 or sacrifice child
Apr 7 10:09:59 centos106 kernel: Out of memory: Kill process 28145 (java) score 52 or sacrifice child
Apr 7 10:20:40 centos106 kernel: Out of memory: Kill process 2976 (java) score 54 or sacrifice child
Apr 7 10:21:08 centos106 kernel: Out of memory: Kill process 3577 (java) score 47 or sacrifice child
Apr 7 10:21:08 centos106 kernel: Out of memory: Kill process 3631 (java) score 47 or sacrifice child
Apr 7 10:21:08 centos106 kernel: Out of memory: Kill process 3634 (java) score 47 or sacrifice child
Apr 7 10:21:08 centos106 kernel: Out of memory: Kill process 3640 (java) score 47 or sacrifice child
Apr 7 10:21:08 centos106 kernel: Out of memory: Kill process 3654 (java) score 47 or sacrifice child
Apr 7 10:27:27 centos106 kernel: Out of memory: Kill process 6998 (java) score 51 or sacrifice child
Apr 7 10:27:28 centos106 kernel: Out of memory: Kill process 7027 (java) score 52 or sacrifice child
Apr 7 10:28:10 centos106 kernel: Out of memory: Kill process 7571 (java) score 42 or sacrifice child
Apr 7 10:28:10 centos106 kernel: Out of memory: Kill process 7586 (java) score 42 or sacrifice child

2.2.端口沖突

該docker監聽(tīng)端口已經(jīng)被其他進(jìn)程占用，一般此種問(wèn)題容易出現在新部署的服務(wù)，或在原有機器上部署新的后臺服務(wù)，所以在部署之前應該執行命令檢查端口是否已經(jīng)被占用，如果上線(xiàn)后發(fā)現占有則應改為可用端口再重啟之。

檢查命令：    $netstat -nltp|grep [規劃的端口號]

三、對策

3.1.內存不夠的對策：

對策1:
    3.1.1 saltstack的minion在運行過(guò)久之后，可能占用大量?jì)却?，需要將其重啟。重啟命令可能有時(shí)并不起作用。主要檢查運行狀態(tài)，如果未成功停止，則重新重啟；

對策2:
    3.2.2 ELK日志收集程序或者其他java進(jìn)程占用過(guò)高，用top和ps命令排查，謹慎確定進(jìn)程的作用，在確保不影響業(yè)務(wù)的情況下，停止相關(guān)進(jìn)程；

對策3:
   釋放被占用的內存（buff/cache）：
   $sync  #將內存數據寫(xiě)入磁盤(pán)
   $echo 3 > /proc/sys/vm/drop_caches  #釋放被占用的內存

對策4:
    有時(shí)候并不是buff/cache過(guò)高導致內存不夠用，確實(shí)是被很多必要的進(jìn)程消耗掉了內存，那就需要從機器資源分配使用的層面去考慮和解決了。

3.2 端口沖突的對策

對策1:
 一般此種問(wèn)題容易出現在新部署的服務(wù)，或在原有機器上部署新的后臺服務(wù)，所以在部署之前應該執行命令檢查端口是否已經(jīng)被占用，如果上線(xiàn)后發(fā)現占有則應改為可用端口再重啟之。
檢查命令：    $netstat -nltp|grep [規劃的端口號]

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