root / man / ganeti-masterd.sgml @ 9b94905f
History | View | Annotate | Download (5 kB)
1 |
<!doctype refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN" [ |
---|---|
2 |
|
3 |
<!-- Please adjust the date whenever revising the manpage. --> |
4 |
<!ENTITY dhdate "<date>February 11, 2009</date>"> |
5 |
<!-- SECTION should be 1-8, maybe w/ subsection other parameters are |
6 |
allowed: see man(7), man(1). --> |
7 |
<!ENTITY dhsection "<manvolnum>8</manvolnum>"> |
8 |
<!ENTITY dhucpackage "<refentrytitle>ganeti-masterd</refentrytitle>"> |
9 |
<!ENTITY dhpackage "ganeti-masterd"> |
10 |
|
11 |
<!ENTITY debian "<productname>Debian</productname>"> |
12 |
<!ENTITY gnu "<acronym>GNU</acronym>"> |
13 |
<!ENTITY gpl "&gnu; <acronym>GPL</acronym>"> |
14 |
<!ENTITY footer SYSTEM "footer.sgml"> |
15 |
]> |
16 |
|
17 |
<refentry> |
18 |
<refentryinfo> |
19 |
<copyright> |
20 |
<year>2008</year> |
21 |
<year>2009</year> |
22 |
<holder>Google Inc.</holder> |
23 |
</copyright> |
24 |
&dhdate; |
25 |
</refentryinfo> |
26 |
<refmeta> |
27 |
&dhucpackage; |
28 |
|
29 |
&dhsection; |
30 |
<refmiscinfo>ganeti 2.0</refmiscinfo> |
31 |
</refmeta> |
32 |
<refnamediv> |
33 |
<refname>&dhpackage;</refname> |
34 |
|
35 |
<refpurpose>ganeti master daemon</refpurpose> |
36 |
</refnamediv> |
37 |
<refsynopsisdiv> |
38 |
<cmdsynopsis> |
39 |
<command>&dhpackage; </command> |
40 |
<arg>-f</arg> |
41 |
<arg>-d</arg> |
42 |
<arg>--no-voting</arg> |
43 |
|
44 |
</cmdsynopsis> |
45 |
</refsynopsisdiv> |
46 |
<refsect1> |
47 |
<title>DESCRIPTION</title> |
48 |
|
49 |
<para> |
50 |
The <command>&dhpackage;</command> is the daemon which is |
51 |
responsible for the overall cluster coordination. Without it, no |
52 |
change can be performed on the cluster. |
53 |
</para> |
54 |
|
55 |
<para> |
56 |
For testing purposes, you can give the <option>-f</option> |
57 |
option and the program won't detach from the running terminal. |
58 |
</para> |
59 |
|
60 |
<para> |
61 |
Debug-level message can be activated by giving the |
62 |
<option>-d</option> option. |
63 |
</para> |
64 |
<refsect2> |
65 |
<title>ROLE</title> |
66 |
<para> |
67 |
The role of the master daemon is to coordinate all the actions |
68 |
that change the state of the cluster. Things like accepting |
69 |
new jobs, coordinating the changes on nodes (via RPC calls to |
70 |
the respective node daemons), maintaining the configuration |
71 |
and so on are done via this daemon. |
72 |
</para> |
73 |
|
74 |
<para> |
75 |
The only action that can be done without the master daemon is |
76 |
the failover of the master role to another node in the |
77 |
cluster, via the <command>gnt-cluster masterfailover</command> |
78 |
command. |
79 |
</para> |
80 |
|
81 |
<para> |
82 |
If the master daemon is stopped, the instances are not |
83 |
affected, but they won't be restarted automatically in case of |
84 |
failure. |
85 |
</para> |
86 |
</refsect2> |
87 |
|
88 |
<refsect2> |
89 |
<title>STARTUP</title> |
90 |
<para> |
91 |
At startup, the master daemon will confirm with the node |
92 |
daemons that the node it is running is indeed the master node |
93 |
of the cluster. It will abort if it doesn't get half plus one |
94 |
positive answers (offline nodes are queried too, just in case |
95 |
our configuration is stale). |
96 |
</para> |
97 |
|
98 |
<para> |
99 |
For small clusters with a number of nodes down, and especially |
100 |
for two-node clusters where the other has gone done, this |
101 |
creates a problem. In this case the |
102 |
<option>--no-voting</option> option can be used to skip this |
103 |
process. The option requires interactive confirmation, as |
104 |
having two masters on the same cluster is a very dangerous |
105 |
situation and will most likely lead to data loss. |
106 |
</para> |
107 |
</refsect2> |
108 |
|
109 |
<refsect2> |
110 |
<title>JOB QUEUE</title> |
111 |
<para> |
112 |
The master daemon maintains a job queue (located under |
113 |
<filename |
114 |
class="directory">@LOCALSTATEDIR@/lib/ganeti/queue</filename>) in |
115 |
which all current jobs are stored, one job per file serialized |
116 |
in JSON format; in this directory a subdirectory called |
117 |
<filename class="directory">archive</filename> holds archived |
118 |
job files. |
119 |
</para> |
120 |
|
121 |
<para> |
122 |
The moving of jobs from the current to the queue directory is |
123 |
done via a request to the master; this can be accomplished |
124 |
from the command line with the <command>gnt-job |
125 |
archive</command> or <command>gnt-job autoarchive</command> |
126 |
commands. In case of problems with the master, a job file can |
127 |
simply be moved away or deleted (but this might leave the |
128 |
cluster inconsistent). |
129 |
</para> |
130 |
|
131 |
</refsect2> |
132 |
|
133 |
<refsect2> |
134 |
<title>COMMUNICATION PROTOCOL</title> |
135 |
<para> |
136 |
The master accepts commands over a Unix socket, using JSON |
137 |
serialized messages separated by a specific byte sequence. For |
138 |
more details, see the design documentation supplied with |
139 |
Ganeti. |
140 |
</para> |
141 |
</refsect2> |
142 |
|
143 |
</refsect1> |
144 |
|
145 |
&footer; |
146 |
|
147 |
</refentry> |
148 |
|
149 |
<!-- Keep this comment at the end of the file |
150 |
Local variables: |
151 |
mode: sgml |
152 |
sgml-omittag:t |
153 |
sgml-shorttag:t |
154 |
sgml-minimize-attributes:nil |
155 |
sgml-always-quote-attributes:t |
156 |
sgml-indent-step:2 |
157 |
sgml-indent-data:t |
158 |
sgml-parent-document:nil |
159 |
sgml-default-dtd-file:nil |
160 |
sgml-exposed-tags:nil |
161 |
sgml-local-catalogs:nil |
162 |
sgml-local-ecat-files:nil |
163 |
End: |
164 |
--> |