ceph代码分析之命令处理流程

一、概述：

　　查看ceph集群的基本状态，ceph -s；查看ceph命令源码(/usr/bin/ceph),这个脚本是由源码里面的ceph.in文件生成而来，哪ceph -s是如何与ceph cluster进行交互的呢？下面开始从代码（py代码）开始入手分析：

　　从该文件起初的导入部分可以得知：

　　由send_command()去与ceph cluster通信：

 1 def send_command(cluster, target=('mon', ''), cmd=None, inbuf='', timeout=0,
 2                  verbose=False):
 3     """  注释部分：使用librados的mon_command/osd_command/pg_command给daemon发送指令
 4     Send a command to a daemon using librados's
 5     mon_command, osd_command, or pg_command.  Any bulk input data
 6     comes in inbuf.
 7 
 8     Returns (ret, outbuf, outs); ret is the return code, outbuf is
 9     the outbl "bulk useful output" buffer, and outs is any status
10     or error message (intended for stderr).
11 
12     If target is osd.N, send command to that osd (except for pgid cmds)
13     """
14     cmd = cmd or []
15     try: #target[0] 用以区分发送的目标类型，mon、osd、pg、mds的
16         if target[0] == 'osd':
17             osdid = target[1]
18 
19             if verbose:
20                 print >> sys.stderr, 'submit {0} to osd.{1}'.\
21                     format(cmd, osdid)
22             ret, outbuf, outs = \
23                 cluster.osd_command(osdid, cmd, inbuf, timeout)　　#osd中消息发送主体
24 
25         elif target[0] == 'pg':
26             pgid = target[1]
27             # pgid will already be in the command for the pg <pgid>
28             # form, but for tell <pgid>, we need to put it in
29             if cmd: 
30                 cmddict = json.loads(cmd[0])
31                 cmddict['pgid'] = pgid 
32             else:
33                 cmddict = dict(pgid=pgid)
34             cmd = [json.dumps(cmddict)]
35             if verbose:
36                 print >> sys.stderr, 'submit {0} for pgid {1}'.\
37                     format(cmd, pgid)
38             ret, outbuf, outs = \
39                 cluster.pg_command(pgid, cmd, inbuf, timeout)
40 
41         elif target[0] == 'mon':
42             if verbose:
43                 print >> sys.stderr, '{0} to {1}'.\
44                     format(cmd, target[0])
45             if target[1] == '':
46                 ret, outbuf, outs = cluster.mon_command(cmd, inbuf, timeout)
47             else:
48                 ret, outbuf, outs = cluster.mon_command(cmd, inbuf, timeout, target[1])
49         elif target[0] == 'mds':
50             mds_spec = target[1]
51 
52             if verbose:
53                 print >> sys.stderr, 'submit {0} to mds.{1}'.\
54                     format(cmd, mds_spec)
55 
56             try:
57                 from cephfs import LibCephFS
58             except ImportError:
59                 raise RuntimeError("CephFS unavailable, have you installed libcephfs?")
60 
61             filesystem = LibCephFS(cluster.conf_defaults, cluster.conffile)
62             filesystem.conf_parse_argv(cluster.parsed_args)
63 
64             filesystem.init()
65             ret, outbuf, outs = \
66                 filesystem.mds_command(mds_spec, cmd, inbuf)
67             filesystem.shutdown()
68         else:
69             raise ArgumentValid("Bad target type '{0}'".format(target[0]))
70 
71     except Exception as e:
72         if not isinstance(e, ArgumentError):
73             raise RuntimeError('"{0}": exception {1}'.format(cmd, e))
74         else:
75             raise
76 
77     return ret, outbuf, outs