Keepalived 1.2.3 发布，服务器状态监控
2012-07-14 09:59:03   来源：   评论：0 点击：

Keepalived 1.2.3 发布，该版本主要是合并之前的几个补丁。而上一个版本 1.2.2 发布已经是一年前的事了。

1.2.3变更说明：

* Please look at git repo for credits.
* VRRP : allow group to use priority with 'global_tracking'
  group keyword（group可通过global_tracking指令设置优先级）
* VRRP : Adjust TOS values. The TOS value used by other
  vendors is ip precedence 6, so change that. Use socket
  priority option to force packets into band 0 of pfifo_fast.（调整TOS值，其他厂商使用的TOS值中ip优先级是6,使用socket优先级选项强制包进入pfifo_fast 0带）
* VRRP : Fix sync-group thrashing.The sync group implementation
  was not very robust. If one synced instance lost communication
  without going to fault state then all synced intances would
  transition to master. Following this all instances would
  transition back to backup because they heard higher priority
  advertisements. This thrashing would continue indefinitely.
  To fix this the sync-group code was made to prefer backup state.
  That is, the sync-groups don't sync to master state unless
  every instance wants to be master.（修复sync-group抖动问题。组同步的实现不是很健壮，若某一同步实例丢失通讯而转入失效状态，则所有同步实例会切换到master上。进而，由于他们侦听到更高优先级的宣告，所有的实例会切换回backup上。这个抖动会无限制的持续下去。为修复sync-group抖动，代码修改为优先置为backup,这样，同步组不会与master同步，除非每个实例都希望成为master）
* VRRP : Fix dst lladdr in IPv6 Unsollicited NA.
* VRRP : fix pid display in syslog messages.
* Fix configure script to correctly identify kernel version.
* check : handle unspecified sockaddr_storage when comparing
* VRRP : ensure VRRP script interval and GARP delay is not 0.
* check: ensure non 0 default values for timeouts.
* VRRP : Fix priority not changing on reload.
* check : Fix IPv4 address comparison routine.
* Don't use bind() with AF_UNSPEC.
* check : enable the use of fwmark with IPv6 virtual servers.
* Fix modprobe arguments.
* Fix double ntohs() in SMTP checker.
* Pretty-print IP:port as [%s]:%d.
* check : keep retry in case of early TCP failures in checks.
* when specifying an IPv6 range, range is hexadecimal value.
* Only define kernel types for ip_vs.h header to avoid problems
  when loading other headers.
* When respawning VRRP or check process, use LOG_ALERT.
* Do not set reload flag in the main process.
* Set correct rights on PID file.
* fix 'gratuitous' typos.
* ipvs: don't include linux/types.h or asm/types.h.
* configure: check for nl_socket_modify_cb for libnl.
* configure: don't check for IPVS support with kernel 2.6.x.
* VRRP : On shutdown, release sockets later to be able to send
  shutdown packet.
* fix documentation on linkbeat_use_polling keyword.
* Fix a typo for healthchecker.
* fix syslog message if bogous vrrp packet (wrong auth type)
  received.
* manpage update.

keepalived是一个类似于layer3, 4 & 5交换机制的软件，也就是我们平时说的第3层、第4层和第5层交换。Keepalived的作用是检测web服务器的状态，如果有一台web服务器死机， 或工作出现故障，Keepalived将检测到，并将有故障的web服务器从系统中剔除，当web服务器工作正常后Keepalived自动将web服务 器加入到服务器群中，这些工作全部自动完成，不需要人工干涉，需要人工做的只是修复故障的web服务器。

Layer3,4&5工作在IP/TCP协议栈的IP层，TCP层，及应用层,原理分别如下：

Layer3：Keepalived使用Layer3的方式工作式时，Keepalived会定期向服务器群中的服务器

发送一个ICMP的数据包（既我们平时用的Ping程序）,如果发现某台服务的IP地址没有激活，Keepalived便报告这台服务器失效，并将它从服务器群中剔除，这种情况的典型例子是某台服务器被非法关机。Layer3的方式是以服务器的IP地址是否有效作为服务器工作正常与否的标准。在本文中将采用这种方式。

Layer4:如果您理解了Layer3的方式，Layer4就容易了。Layer4主要以TCP端口的状态来决定服务器工作正常与否。如web server的服务端口一般是80，如果Keepalived检测到80端口没有启动，则Keepalived将把这台服务器从服务器群中剔除。

Layer5：Layer5就是工作在具体的应用层了，比Layer3,Layer4要复杂一点，在网络上占用的带宽也要大一些。Keepalived将根据用户的设定检查服务器程序的运行是否正常，如果与用户的设定不相符，则Keepalived将把服务器从服务器群中剔除。