Use ZEO with Zope

ZEO will help you scale your site and give redundancy/high availability to your site too. Every Zope installation will be a Client Storage (CS) that talks to the Zope Storage Server (ZSS). Every CS will have its own object cache and will be able to work independently of other CS.

You can have the CS cache in-memory or on the file system. Every request will be taken from the cache, if available, and from the ZSS if not. Modifications and additions will be sync to the ZSS. ZSS will take care of the object validity.

Basic setup

The most basic setup is to have your ZSS and CS in the same machine. However, I will use two physically different machine to fully use ZEO capability. However, you can increase the number of physical machine to the nth.

Here, we have a machine that's acting as a ZSS and CS(the main server). We have other machines that will have a Zope instance and will be the other CSs(the client servers).

This may not be the only way to connect. This setup is quite flat, and you have a single point of failure, the ZSS. Check out the ZEO FactSheet.

Security

Installing the main server

1. You will need Zope > 2.2.0.

2. Unpack and install Zope[Zope/path/]. Test your Zope installation.

3. Get ZEO.

4. Unpack ZEO-latestversion.tgz

5. cd ZEO-latestversion

6. mv or copy ZEO to Zope/path/lib/python

7. cd Zope/path/lib/python

8. ln -s ../../ZServer .

not needed anymore

9. cd ZEO

10. ln -s ../cPickle.so

not needed anymore

11. copy custom_zodb.py.dist to your Zope installation dir [Zope/path/] or INSTANCE HOME, if you use INSTANCE HOME. With release 0.4, a sample custom_zodb.py is included in misc folder/directory. I have yet to use this, so could not comment on it yet. If you use it, please tell us what you did, changed, etc and I'll include it here.

12. edit custom_zodb.py. Add the appropriate host name and port number where you will run ZSS. The default is local host('') and port 8800.

13. rename custom_zodb.py.dist to custom_zodb.py

14. start ZSS

    cd Zope/path
    python lib/python/ZEO/start -p 8800
    
    Note: To serve to private network, use
    python lib/python/ZEO/start -p 8800 -h 192.168.1.1
    
    

    This will serve up your Data.fs

A better way to control your ZEO Server is to use the included zeo_start and zeo_stop.

• create a storage file in Zope/path/lib/python/ZEO. lets call it StorageConfig.py.

  ##StorageConfig.py
  import ZODB.FileStorage
  main_storage= ZODB.FileStorage.FileStorage('/Zope/path/var/Data.fs')
  

• Now create a zeo_start in Zope/path/

  ###zeo_start
  #!/bin/sh
  reldir=`dirname $0`
  exec python $reldir/lib/python/ZEO/start.py -S main=StorageConfig:main_storage -p 8800 -h 10.10.10.2\
    ZEO_SERVER_PID=$reldir/var/ZEO_SERVER.pid \
    STUPID_LOG_FILE=$reldir/var/ZEO_EVENTS.log \
    "$@" 

• create zeo_stop in Zope/path/

  ###stop zeo
  #!/bin/sh
  reldir=`dirname $0`
  kill `cat $reldir/var/ZEO_SERVER.pid`
  

• zeo_start and zeo_stop is available in ZEO tar ball.

15. start Zope

    If you start Zope without ZEO_CLIENT, the cache will be in-memory. To have the cache on your fs, start Zope with ZEO_CLIENT. Add ZEO_CLIENT=8800 in your start script e.g.

    #! /bin/sh
    reldir=`dirname $0`
    PYTHONHOME=`cd $reldir; pwd`
    export PYTHONHOME
    exec /usr/bin/python \
         $PYTHONHOME/z2.py  -X -w 80 STUPID_LOG_FILE='var/stupid.log' \
         -D '' "$@" ZEO_CLIENT=8800
    

    I think it is good practice to have STUPID_LOG_FILE since it will really help point out errors and help in debugging.

16. You will now have the cache in Zope/path/var

17. You can test your ZSS and first CS.