Merge lp:~kim0/pyjuju/adding-hook-traces-to-readme-for-bashified-example into lp:~jimbaker/pyjuju/bashified-wordpress-mysql-examples

[Ahmed Kamal]

[Gustavo Niemeyer (niemeyer)]

That's a nice way to visualize the communication, but there's a small issue
related to one of the hooks:

[1]

+ mysql/0(db-relation-chaned): Does DB setup, calls relation-set setting variables, which triggers another run of

The mysql formula doesn't have the db-relation-changed hook, and has the db-relation-joined one.

review: Needs Fixing

[Gustavo Niemeyer (niemeyer)]

Also note that this is targeting the "bashified" branch, while it should be targeting trunk by now.

[lp:~kim0/pyjuju/adding-hook-traces-to-readme-for-bashified-example]

187. By Ahmed Kamal on 2011-05-26

Fixing docs to match hook changes (joined)

188. By Ahmed Kamal on 2011-05-27

Updating hook trace, changed always gets fired after joined

[Gustavo Niemeyer (niemeyer)]

review: Disapprove

Unmerged revisions

188. By Ahmed Kamal on 2011-05-27

Updating hook trace, changed always gets fired after joined

187. By Ahmed Kamal on 2011-05-26

Fixing docs to match hook changes (joined)

186. By Ahmed Kamal on 2011-04-14

Adding a sample hook execution trace to readme to better understand execution dynamics

=== modified file 'examples/readme.txt'
--- examples/readme.txt	2011-02-23 19:08:28 +0000
+++ examples/readme.txt	2011-05-27 15:29:32 +0000
@@ -1,7 +1,6 @@
 Examples
 ========
 
-
 These are some example formulas that can be deployed together to create some connected services.
 
 Many more formulas of greater functionality and utility exist in the Principia project, which
@@ -9,7 +8,6 @@
 
 http://launchpad.net/principia
 
-
 Deploying
 =========
 
@@ -22,3 +20,35 @@
   $ ensemble status
 
 The status command will show the address of the newly deployed wordpress service.
+
+Hooks Triggering Sequence
+=========================
+
+To better understand the above deployment dynamics, let's trace through hook execution
+
+  $ ensemble deploy --repository=examples mysql
+  mysql/0(install)
+  mysql/0(start)
+  $ ensemble deploy --repository=examples wordpress
+  wordpress/0(install)
+  wordpress/0(start)
+  $ ensemble add-relation wordpress mysql
+  Two joined hooks are fired in parallel
+  wordpress/0(db-relation-joined): Hook doesn't exist, skipped
+  mysql/0(db-relation-joined): Does DB setup, might consume some time
+  After joined hooks, changed hooks always get fired regardless
+  wordpress/0(db-relation-changed): Hook finds out database is still being created, early exits
+  mysql/0(db-relation-changed): Hook doesn't exist, skipped
+  At end of mysql/0(db-relation-joined) relation-set is called, triggering a run of
+  wordpress/0(db-relation-changed): Read DB settings from relation, applies config
+
+Assuming another wordpress service unit is to be added
+  $ ensemble add-unit wordpress
+  wordpress/1(install)
+  wordpress/1(start)
+  Two joins in no particular order
+  wordpress/1(db-relation-joined): Hook doesn't exist, skipped
+  mysql/0(db-relation-joined): Hook detects DB already exists, does early exit
+  Two db-relation-changed in no particular order
+  mysql/0(db-relation-changed): Hook doesn't exist, skipped
+  wordpress/1(db-relation-changed): Read DB settings from relation, applies config