SaltStack 的远程执行机制

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SaltStack 的远程执行特点：

SaltStack 在设计之初的定位就是远程执行工具，远程执行对于 Salt 而言是十分频繁的操作，其具有如下特点。

(1).Salt 命令是跨操作系统、跨平台的。例如：salt '*' pkg.install git 将在不同的操作系统及平台上调用 yum、apt、pacman 甚至 Salt windows 包仓库等工具。

(2).所有 Salt 命令的返回结果都是以统一的数据结构保存，这使得检查结果正确性以及存入结果至数据库十分方便。

(3).Salt minion 在执行作业上几乎是同时开始的。

(4). Salt 可以调用成本上千种的 Python 模块，以执行远程管理。同时，Salt 也可以轻易地加入其它的自定义模块。

SaltStack 的远程执行机制：

例如：执行命令 salt '*' test.rand_sleep 120 时，其执行过程如下：

(1).命令通过发布者（publisher）端口，分发至所有已连接的 Salt minion；

(2).每个 Salt minion 都需要检查命令，评估是否应该在节点上运行命令；

(3).目标系统将会运行命令，并将结果返回至请求服务器。

当 Salt minion 接收到命令时，其执行过程如下：

(1).每条命令都将被分拆为一个独立的工作进程，从而 Salt minion 才能在同一时刻处理多项作业。

(2).针对 Salt 命令（结构如下图），找到正确的 module，随后以提供的 arguments 作为参数，调用 function。注意：Salt 实际上可以看做是 Python 函数的抽象层。