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0 说明
使用的es版本为5.6，Linux版本为CentOs 6.5.
1 Elasticsearch bootstrap checks
1.1 开发环境
如果在es的配置中没有配置network.host来指定一个可用的IP地址的话，默认情况下，就绑定到localhost上，此时es会认为用户只是在开发环境下使用es，基于开箱即用的原则，虽然es此时也会进行bootstrap checks，来检查用户的配置是否与es设定的安全值相匹配，如下：
- 如果匹配，则不会有warnning信息，此时es正常启动；
- 如果不匹配，则会有warnning信息，但因为是开发环境，es依然会正常启动；
1.2 生产环境
一旦用户配置了network.host来指定一个可用的非loopback地址，那么es就会认为用户此时是在生产环境下启动es，同样会进行检查，但一旦检查不通过，直接会将前面的warnning提升为error，所以此时es会启动失败。
2 开发环境启动时的bootstrap checks分析
不配置network.host时，直接启动es，会有下面的warnning：
[2018-12-07T04:15:44,735][INFO ][o.e.d.DiscoveryModule ] [PQ85ukj] using discovery type [zen]
[2018-12-07T04:15:45,702][INFO ][o.e.n.Node ] initialized
[2018-12-07T04:15:45,703][INFO ][o.e.n.Node ] [PQ85ukj] starting ...
[2018-12-07T04:15:46,071][INFO ][o.e.t.TransportService ] [PQ85ukj] publish_address {127.0.0.1:9300}, bound_addresses {[::1]:9300}, {127.0.0.1:9300}
[2018-12-07T04:15:46,090][WARN ][o.e.b.BootstrapChecks ] [PQ85ukj] max file descriptors [4096] for elasticsearch process is too low, increase to at least [65536]
[2018-12-07T04:15:46,090][WARN ][o.e.b.BootstrapChecks ] [PQ85ukj] max number of threads [1024] for user [hadoop] is too low, increase to at least [2048]
[2018-12-07T04:15:46,090][WARN ][o.e.b.BootstrapChecks ] [PQ85ukj] max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
[2018-12-07T04:15:46,090][WARN ][o.e.b.BootstrapChecks ] [PQ85ukj] system call filters failed to install; check the logs and fix your configuration or disable system call filters at your own risk
[2018-12-07T04:15:49,269][INFO ][o.e.c.s.ClusterService ] [PQ85ukj] new_master {PQ85ukj}{PQ85ukjdSoeVEpSpByAjMw}{Dbb3lzTWTN-eUEKXO8z-sw}{127.0.0.1}{127.0.0.1:9300}, reason: zen-disco-elected-as-master ([0] nodes joined)
[2018-12-07T04:15:49,313][INFO ][o.e.h.n.Netty4HttpServerTransport] [PQ85ukj] publish_address {127.0.0.1:9200}, bound_addresses {[::1]:9200}, {127.0.0.1:9200}
[2018-12-07T04:15:49,313][INFO ][o.e.n.Node ] [PQ85ukj] started
[2018-12-07T04:15:49,553][INFO ][o.e.g.GatewayService ] [PQ85ukj] recovered [0] indices into cluster_state
提取其waarnning信息，如下：
文件描述符：
max file descriptors [4096] for elasticsearch process is too low, increase to at least [65536]
线程数：
max number of threads [1024] for user [hadoop] is too low, increase to at least [2048]
虚拟内存：
max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
system call filters:
system call filters failed to install; check the logs and fix your configuration or disable system call filters at your own risk
可以看到有4个问题，分别为：文件描述符、线程数、虚拟内存与system call filters。
虽然有warnning，但因为es本身会认为是在开发环境下运行，基于开箱即用的特性，是仍然可以正常启动的。
3 生产环境启动时的bootstrap checks分析
绑定IP地址后再启动，发现有下面的报错信息：
ERROR: [4] bootstrap checks failed
[1]: max file descriptors [4096] for elasticsearch process is too low, increase to at least [65536]
[2]: max number of threads [1024] for user [hadoop] is too low, increase to at least [2048]
[3]: max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
[4]: system call filters failed to install; check the logs and fix your configuration or disable system call filters at your own risk
直接error，所以会启动失败，除非进行上面的设置符合安全要求。
4 生产环境正常启动配置
解决上面出现的问题，需要进行如下的配置。
4.1 文件描述符
ulimit -n 65536
但是重新登录后就会恢复成默认值了。
修改/etc/security/limits.conf配置，如下：
hadoop soft nofile 65536 # soft表示为超过这个值就会有warnning
hadoop hadr nofile 100000 # hard则表示不能超过这个值
之后再重新登录，使用ulimit -n就可以进行验证。
4.2 线程数
修改/etc/security/limits.conf配置，如下：
hadoop soft nproc 2048
hadoop hard nproc 4096
实际上，该配置文件对于nproc的说明为进程数，而不是线程数：
# -
39,1 41%
# /etc/security/limits.conf
#
#Each line describes a limit for a user in the form:
#
#
-
#
#Where:
# can be:
# - an user name
# - a group name, with @group syntax
# - the wildcard *, for default entry
# - the wildcard %, can be also used with %group syntax,
# for maxlogin limit
#
# can have the two values:
# - "soft" for enforcing the soft limits
# - "hard" for enforcing hard limits
#
#
- can be one of the following:
# - core - limits the core file size (KB)
# - data - max data size (KB)
# - fsize - maximum filesize (KB)
# - memlock - max locked-in-memory address space (KB)
# - nofile - max number of open files
# - rss - max resident set size (KB)
# - stack - max stack size (KB)
# - cpu - max CPU time (MIN)
# - nproc - max number of processes
# - as - address space limit (KB)
# - maxlogins - max number of logins for this user
# - maxsyslogins - max number of logins on the system
# - priority - the priority to run user process with
# - locks - max number of file locks the user can hold
# - sigpending - max number of pending signals
# - msgqueue - max memory used by POSIX message queues (bytes)
# - nice - max nice priority allowed to raise to values: [-20, 19]
# - rtprio - max realtime priority
#
#
-
#
#* soft core 0
#* hard rss 10000
4.3 虚拟内存
sysctl vm.max_map_count
sysctl -w vm.max_map_count=262144
但是重启系统后就会失效。
修改配置文件/etc/sysctl.conf，如下：
vm.max_map_count=262144
需要重启后才生效。
4.4 system call filters
参考：https://www.jianshu.com/p/89f8099a6d09
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