sauna.reload 0.3.3

Introduction

sauna.reload partially restarts Plone and reloads your changed source code every time you save a file.

• Edit your code

• Save

• Go to a browser and hit Refresh ➔ your latest changes are active

It greatly simplifies your Plone development workflow and gives back the agility of Python.

It works with any code.

sauna.reload works on OSX and Linux with Plone 4.0 and 4.1. In theory works on Windows, but no one has looked into that yet.

Installation

Here are brief installation instructions.

cd src
git clone git://github.com/epeli/sauna.reload.git

[buildout]

extends = buildout.cfg

develop +=
    src/sauna.reload

[instance]

# XXX: May conflict with existing zope-conf-additional directives
zope-conf-additional = %import sauna.reload

eggs +=
    sauna.reload

bin/buildout -c development.cfg

cd src
git clone git://github.com/gorakhargosh/watchdog.git

[buildout]

develop +=
    src/watchdog
    src/sauna.reload

set noswapfile
set nobackup
set nowritebackup

[instance]
recipe = plone.recipe.zope2instance
...
zope-conf-additional = %import sauna.reload

Usage: start Plone in reload enabled manner

To start Plone with reload functionality you need to give special environment variable RELOAD_PATH for your instance command:

RELOAD_PATH=src bin/instance fg

Or if you want to optimize load speed you can directly specify only some of your development products:

RELOAD_PATH=src/my.product:src/my.another.product bin/instance fg

When reload is active you should see something like this in your console when Zope starts up:

2011-08-10 13:28:59 INFO sauna.reload Starting file monitor on /Users/moo/code/x/plone4/src
2011-08-10 13:29:02 INFO sauna.reload We saved at least 29.8229699135 seconds from boot up time
2011-08-10 13:29:02 INFO sauna.reload Packages marked for reload are listed in here: http://127.0.0.1:8080/@@saunareload
2011-08-10 13:29:02 INFO sauna.reload Fork loop starting on process 14607
2011-08-10 13:29:02 INFO sauna.reload Booted up new new child in 0.104816913605 seconds. Pid 14608

… and when you save some file in src folder:

2011-08-10 13:29:41 INFO SignalHandler Caught signal SIGINT
2011-08-10 13:29:41 INFO Z2 Shutting down
2011-08-10 13:29:42 INFO SignalHandler Caught signal SIGCHLD
2011-08-10 13:29:42 INFO sauna.reload Booted up new new child in 0.123936891556 seconds. Pid 14609

CTRL+C should terminate Zope normally. There might be stil some kinks and error messages with shutdown.

Only eggs loaded through z3c.autoinclude. can be reloaded. Make sure you don’t use buildout.cfg zcml = directive for your eggs or sauna.reload silently ignores changes.

http://127.0.0.1:8080/@@saunareload

Debugging with sauna.reload

Regular import pdb; pdb.set_trace() will work just fine with sauna.reload. When reload happens while in pdb, though, pdb will get killed. To avoid losing your terminal echo, because of reload unexpectedly killing your pdb, you may add the following to your ~/.pdbrc:

import termios, sys
term_fd = sys.stdin.fileno()
term_echo = termios.tcgetattr(term_fd)
term_echo[3] = term_echo[3] | termios.ECHO
term_result = termios.tcsetattr(term_fd, termios.TCSADRAIN, term_echo)

sauna.reload also should work nicely with PdbTextMateSupport and PdbSublimeTextSupport. Unfortunately, we haven’t seen it working with vimpdb yet.

Background

sauna.reload is an attempt to recreate plone.reload without the issues it has. Like being unable to reload new grokked views or portlet code. This project was started on Plone Sauna Sprint 2011. There for the name, sauna.reload.

sauna.reload does reloading by using a fork loop. So actually it does not reload the code, but restarts small part of Zope2. That’s why it can it reload stuff plone.reload cannot.

It does following on Zope2 startup:

1. Defers loading of your development packages by hooking into PEP 302 loader and changing their z3c.autoinclude target module (and monkeypatching fiveconfigure/metaconfigure for legacy packages).

2. Starts a watcher thread which monitors changes in your development py-files

3. Stops loading of Zope2 in zope.processlifetime.IProcessStarting event by stepping into a infinite loop; Just before this, tries to load all non-developed dependencies of your development packages (resolved by z3c.autoinclude)

4. It forks a new child and lets it pass the loop

5. Loads all your development packages invoking z3c.autoinclude (and fiveconfigure/metaconfigure for legacy packages). This is fast!

6. And now every time when the watcher thread detects a change in development files it will signal the child to shutdown and the child will signal the parent to fork a new child when it is just about to close itself

7. Just before dying, the child saves Data.fs.index to help the new child to see the changes in ZODB (by loading the saved index)

8. GOTO 4

Internally sauna.reload uses WatchDog Python component for monitoring file-system change events.

See also Ruby guys on fork trick.

Events

sauna.reload emits couple of events during reloading.

sauna.reload.events.INewChildForked

Emited immediately after new process is forked. No development packages have been yet installed. Useful if you want to do something before your code gets loaded. Note that you cannot listen this event on a package that is marked for reloading as it is not yet installed when this is fired.

sauna.reload.events.INewChildIsReady

Emitted when all the development packages has been installed to the new forked child. Useful for notifications etc.

Limitations

sauna.reload has a major pitfall. Because it depends on deferring loading of packages to be watched and reloaded, also every package depending on those packages should be defined to be reloaded (in RELOAD_PATH). And sauna.reload doesn’t resolve those dependencies automatically!

An another potential troublemaker is that sauna.reload performs implicit <includeDependencies package="." /> for every package in RELOAD_PATH (to preload dependencies for those packages to speed up the reload).

We are sorry that sauna.reload may not work for everyone. For example, reloading of core Plone packages could be tricky, if not impossible, because many of them are explicitly included by configure.zcml of CMFPlone and are not using z3c.autoincude at all. You would have to remove the dependency from CMFPlone for development to make it work…

Also because the product installation order is altered (by all the above) you may find some issue if your product does something funky on installation or at import time.

Currently only FileStorage (ZODB) is supported.

Please report any other issues at: https://github.com/epeli/sauna.reload/issues.

Troubleshooting

Report all issues on GitHub.

2011-08-13 09:38:12 ERROR sauna.reload.child Failed to defer
src/sauna.reload/sauna/reload/configure.zcml. IT WILL NOT BE RELOADABLE.

[instance]
recipe = plone.recipe.zope2instance
...
site-zcml =
  <configure xmlns="http://namespaces.zope.org/zope"
             xmlns:meta="http://namespaces.zope.org/meta"
             xmlns:five="http://namespaces.zope.org/five">
    <include package="Products.Five" />
    <meta:redefinePermission from="zope2.Public" to="zope.Public" />
    <five:loadProducts file="meta.zcml"/>

    <!-- Add include for your package's meta.zcml here: -->
    <include package="my.product" file="meta.zcml" />

    <five:loadProducts />
    <five:loadProductsOverrides />
    <securityPolicy component="Products.Five.security.FiveSecurityPolicy" />
  </configure>

[instance]
recipe = plone.recipe.zope2instance
...
site-zcml =
  <configure xmlns="http://namespaces.zope.org/zope"
             xmlns:meta="http://namespaces.zope.org/meta"
             xmlns:five="http://namespaces.zope.org/five">
    <include package="Products.Five" />
    <meta:redefinePermission from="zope2.Public" to="zope.Public" />
    <five:loadProducts file="meta.zcml"/>

    <!-- Add autoinclude-directive for deferred meta.zcml here: -->
    <includePlugins package="sauna.reload" file="meta.zcml" />

    <five:loadProducts />
    <five:loadProductsOverrides />
    <securityPolicy component="Products.Five.security.FiveSecurityPolicy" />
  </configure>

bin/buildout -c development.cfg

Source

On GitHub.

Credits

• Esa-Matti Suuronen [esa-matti aet suuronen.org]

• Asko Soukka [asko.soukka aet iki.fi]

• Mikko Ohtamaa (idea, doccing)

• Vilmos Somogyi (logo). The logo was originally the logo of Sauna Sprint 2011 and it was created by Vilmos Somogyi.

• Martijn Pieters for teaching us PEP 302 -loader trick at Sauna Sprint 2011.

• Yesudeep Mangalapilly for creating WatchDog component and providing support for Sauna Sprint team using it

Thanks to all happy hackers on Sauna Sprint 2011!

300 kg of beer was consumed to create this package (at least). Also several kilos of firewood, one axe, one chainsaw and one boat.

We still need testers and contributors. You are very welcome!

Changelog