1 [[rcs/git]] and other distributed version control systems are all about
2 making it easy to create and maintain copies and branches of a project. And
3 this can be used for all sorts of interesting stuff. Since ikiwiki can use
4 git, let's explore some possibilities for distributed wikis.
10 There are three possible level of decentralisation:
12 0. [[default setup|rcs/git]], no decentralisation
13 1. [[a simple HTML mirror|tips/Git_repository_and_web_server_on_different_hosts/]]
14 2. separate `srcdir`, still requires a central bare repo - uses [[plugins/pinger]]
15 3. completely distinct ikiwiki installs, synchronised with [[plugins/contrib/gitpush]]
17 Here's a graphic overview of those:
19 ### Default setup - one central server
21 [[!img rcs/git/wiki_edit_flow.svg size=400x]]
23 In the default setup, all the resources are stored on the central
24 servers. Users can still clone and edit the git repo by hand and
25 contribute by git, but otherwise all the changes happen on a single
26 web interface. This basic setup is best described in [[rcs/git]].
28 ### Separate webserver and git repository
30 [[!img tips/Git_repository_and_web_server_on_different_hosts/separate-webserver.svg size=400x]]
32 This is the configuration described in
33 [[tips/Git_repository_and_web_server_on_different_hosts]]. The webserver part
34 hosts the HTML files, the ikiwiki [[cgi]] but everything else is on
37 ### Decentralised pinger setup
39 [[!img ping-setup.svg size=400x]]
41 In this configuration, the mirrors all have their own `srcdir`, but
42 still need to push and pull from the same central bare git repo. The
43 [[plugins/pinger]] plugin is used to ping the mirrors from the central
46 Step by step setup instructions for this are detailed below.
48 ### Fully decentralised setup
50 [[!img decentralized_wikis.svg size=400x]]
52 In this configuration, each wiki is fully independent and pushes its
53 changes to other wikis using the [[plugins/contrib/gitpush]] plugin.
55 ## Step by step setup instructions
57 The first two ways of setting up ikiwiki are better described in [[setup]] or [[tips/Git_repository_and_web_server_on_different_hosts]]. The remainder of this page describes the latter two more complex distributed setups.
59 Say you have a friend that has already configured a shiny ikiwiki site, and you want to help by creating a mirror. You still need to figure out how to install ikiwiki and everything, hopefully this section will help you with that.
61 ### Installing ikiwiki
63 You need to install the ikiwiki package for the mirror to work. You can use ikiwiki to publish the actual HTML pages elsewhere if you don't plan on letting people edit the wiki, but generally you want the package to be installed on the webserver for editing to work.
65 apt-get install ikiwiki
67 ### Setting up the wiki
69 (!) Optionnally: create a user just for this wiki. Otherwise the wiki will run as your user from here on.
71 We assume your username is `user` and that you will host the wiki under the hostname `mirror.example.com`. The original wiki is at `wiki.example.com`. We also assume that your friend was nice enough to provide a copy of the `.setup` file in the `setup` branch, which is the case for any wiki hosted on [branchable.com](http://branchable.com).
74 # setup srcdir, named source
75 git clone git://wiki.example.com/ source
76 # convenience copy of the setup file
77 git clone -b origin/setup source setup
79 edit ikiwiki.setup # adapt configuration
81 When editing ikiwiki.setup, make sure you change the following entries:
83 cgiurl: http://mirror.example.com/ikiwiki.cgi
84 cgi_wrapper: /var/www/ikiwiki.cgi
85 srcdir: /home/user/source
86 destdir: /var/www/mirror.example.com
87 libdir: /home/user/source/.ikiwiki
88 git_wrapper: /home/user/source/.git/hooks/post-commit
89 git_test_receive_wrapper: /home/user/source/.git/hooks/pre-receive
91 TMPDIR: /home/user/tmp
93 This assumes that your /var/www directory is writable by your user.
95 ### Basic HTML rendering
97 You should already be able to make a plain HTML rendering of the wiki:
99 ikiwiki --setup ikiwiki.setup
101 ### Webserver configuration
103 You will also need a webserver to serve the content in the `destdir`
104 defined above. We assume you will configure a virtual host named `mirror.example.com`. Here are some examples on how to do those, see [[!iki setup]] and [[!iki tips/dot_cgi]] for complete documentation.
106 Note that this will also configure CGI so that people can edit the wiki. Note that this configuration may involve timeouts if the main site is down, as ikiwiki will attempt to push to the central git repository at every change.
108 #### Apache configuration
111 ServerName mirror.example.com:80
112 DocumentRoot /var/www/mirror.example.com
113 <Directory /var/www/mirror.example.com>
114 Options Indexes MultiViews ExecCGI
119 ScriptAlias /ikiwiki.cgi /var/www/ikiwiki.cgi
120 ErrorDocument 404 "/ikiwiki.cgi"
123 #### Nginx configuration
126 root /var/www/mirror.example.com/;
127 index index.html index.htm;
128 server_name mirror.example.com;
131 try_files $uri $uri/ /index.html;
133 location /ikiwiki.cgi {
134 fastcgi_pass unix:/tmp/fcgi.socket;
135 fastcgi_index ikiwiki.cgi;
136 fastcgi_param SCRIPT_FILENAME /var/www/ikiwiki.cgi;
137 fastcgi_param DOCUMENT_ROOT /var/www/mirror.example.com;
138 include /etc/nginx/fastcgi_params;
142 Start this process as your own user (or the user that has write access
143 to `srcdir`, `destdir`, etc):
145 spawn-fcgi -s /tmp/fcgi.socket -n -- /usr/sbin/fcgiwrap
149 chmod a+w /tmp/fcgi.socket
151 ### Enable the pinger functionality
153 At this point, you need to enable the pinger functionality to make sure that changes on the central server propagate to your mirror.
155 This assumes a central wiki that exposes its git
156 repository and has the [[plugins/pinger]] plugin enabled. Enable the
157 [[plugins/pingee]] plugin in your configuration, and edit the origin wiki,
158 adding a ping directive for your mirror:
160 \[[!ping from="http://thewiki.com/"
161 to="http://mymirror.com/ikiwiki.cgi?do=ping"]]
163 The "from" parameter needs to be the url to the origin wiki. The "to" parameter
164 is the url to ping on your mirror. This can be done basically in any page.
166 Now whenever the main wiki is edited, it will ping your mirror, which will
167 pull the changes from "origin" using git, and update itself. It could, in
168 turn ping another mirror, etc.
170 And if someone edits a page on your mirror, it will "git push origin",
171 committing the changes back to the origin git repository, and updating the
172 origin mirror. Assuming you can push to that git repository. If you can't,
173 and you want a mirror, and not a branch, you should disable web edits on
174 your mirror. (You could also point the cgiurl for your mirror at the origin
175 wiki if you do not want to incur that overhead or do not want to, or can't, run a CGI.)
177 ### Fully decentralized configuration
179 In the above configuration, the master git repository is still on the main site. If that site goes down, there will be delays when editing the wiki mirror. It could also simply fail because it will not be able to push the changes to the master git repo. An alternative is to setup a local bare repository that is synced with the master.
181 At the setup step, you need to create *two* git repositories on the mirror:
184 # setup base repository, named source.git
185 git clone --bare git://wiki.example.com/ source.git
186 # setup srcdir, named source
188 # convenience copy of the setup file
189 git clone -b origin/setup source.git setup
191 edit ikiwiki.setup # adapt configuration
193 The following entries will be different from the above setup file:
195 git_wrapper: /home/user/source.git/hooks/post-commit
196 git_test_receive_wrapper: /home/user/source.git/hooks/pre-receive
198 To do this, the mirror needs to push back to the master, using the [[plugins/contrib/gitpush]] plugin:
201 - git://wiki.example.com/
203 This will ensure that commits done on the mirror will propagate back to the master.
207 Another guide is the [[tips/laptop_wiki_with_git]] guide. To get a
208 better understanding of how ikiwiki works, see [[rcs/git]].
210 [This](http://piny.be/jrayhawk/notes/ikiwiki_creation/) may also be of
211 use if the above doesn't work.
213 ### Announcing the mirror
215 Once your mirror works, you can also add it to the list of mirrors. You can ask the mirror where you take it from (and why not, all mirrors) to add it to their setup file. As an example, here's the configuration for the first mirror:
218 example: https://wiki.example.com/
220 The [[plugins/mirrorlist]] plugin of course needs to be enabled for this to work.
224 It follows that setting up a branch of a wiki is just like the fully decentralised mirror above, except
225 we don't want it to push changes back to the origin. The easy way to
226 accomplish this is to clone the origin git repository using a readonly
227 protocol (ie, "git://"). Then you can't push to it.
229 If a page on your branch is modified and other modifications are made to
230 the same page in the origin, a conflict might occur when that change is
231 pulled in. How well will this be dealt with and how to resolve it? I think
232 that the conflict markers will just appear on the page as it's rendered in
233 the wiki, and if you could even resolve the conflict using the web
234 interface. Not 100% sure as I've not gotten into this situation yet.