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+++ b/src/source/zodb.rst Sun Jan 14 11:48:51 2018 +0100
@@ -0,0 +1,158 @@
+.. _zodb:
+
+Creating ZODB
+=============
+
+PyAMS primarily relies on a ZODB (Zope Objects DataBase) to store it's configuration. Other packages may
+rely on other database(s), but *PyAMS_content* package also stores it's contents in a ZODB.
+
+As some PyAMS packages start several processes ("synchronization" is done via **ØMQ**), concurrent accesses are
+required on the ZODB (even when you start your application in "single process" mode); several ZODB storages
+implementations providing a shared access are available: `ZEO`_, `RelStorage`_ and `Newt.DB`_.
+
+
+.. _ZEO:
+
+Installing a ZEO server
++++++++++++++++++++++++
+
+ZEO (Zope Enterprise Objects) is the first available implementation available for concurrent access to a
+FileStorage, provided through the ZEO package.
+
+ZEO package documentation and complete configuration settings are available on PyPI.
+
+Creating initial buildout
+-------------------------
+
+PyAMS provides a ZEO server scaffold, called *zeo_server*, generated via a *cookiecutter* template.
+
+A simple option to create a ZEO server is to create a buildout environment including *ZEO* and *ZODB* packages:
+
+.. code-block:: bash
+
+ # mkdir /var/local/
+ # pip3 install virtualenv
+ # virtualenv --python=python3.5 env
+ # cd env
+ # . bin/activate
+ (env) # pip3.5 install cookiecutter
+ (env) # cookiecutter hg+http://hg.ztfy.org/pyams/scaffolds/zeo_server
+
+*CookieCutter* will ask you for a small set of input variables that you can change or not:
+
+- **pyams_release**: version of PyAMS configuration file to use. "latest" (default value) will point to last release;
+ you can also choose to point to a given release ("0.1.4" for example)
+
+- **project_name**: current environment name in "human form"
+
+- **project_slug**: "technical" package name, based on project name
+
+- **eggs_directory**: relative or absolute path to directory containing downloaded eggs; this directory can be
+ shared with other projects ("eggs" as default)
+
+- **run_user**: user name under which ZEO process will run ("zeoadm" as default)
+
+- **run_group**: group name under which ZEO process will run ("zeo" as default)
+
+- **zeo_server_port**: listening port of ZEO server ("8100" as default)
+
+- **zeo_monitor_port**: listening port of ZEO monitor ("8101" as default)
+
+- **zeo_storage**: name of first ZEO storage; default value is based on project name
+
+- **use_zeo_auth**: specify if ZEO authentication should be used
+
+- **zeo_auth_user**: name of ZEO authenticated user (if ZEO authentication is used)
+
+- **zeo_auth_password**: password of ZEO authenticated user (if ZEO authentication is used)
+
+- **zeo_pack_report**: email address to which pack reports should be sent
+
+- **logs_directory**: absolute path to directory containing ZEO's log files.
+
+A message is displayed after initialization to finalize environment creation:
+
+.. code::
+
+ Your ZEO environment is initialized.
+ To finalize it''s creation, just type:
+ - cd zeo_server
+ - python3.5 bootstrap.py
+ - ./bin/buildout
+
+ To initialize authentication database, please run following command after buildout:
+ ./bin/zeopasswd -f etc/auth.db -p digest -r "ZEO_server" zeouser xxxx
+
+ZEO server configuration
+------------------------
+
+All ZEO configuration files are generated in "etc" subdirectory. These includes:
+
+- **etc/zeo_server-zdaemon.conf**: ZDaemon configuration file
+
+- **etc/zeo_server-zeo.conf**: ZEO server configuration file
+
+- **etc/auth.db**: ZEO authentication file; WARNING: this file is not created automatically, you have to create it
+ after buildout.
+
+In these file names, always replace "zeo_server" with the value which was given to "project_slug" variable during
+*CookieCutter* template creation.
+
+ZEO server tools
+----------------
+
+A set of system configuration files are produced to handle your ZEO environment. These includes:
+
+- **etc/init.d/zeo-zeo_server**: ZEO server start/stop script in Init-D format. Create a link to this file in
+ */etc/init.d* and update Init.d scripts (*update-rc.d zeo-zeo_server defaults*) to include ZEO in server start/stop
+ process. You can also use this script to start/stop ZEO by hand with *start* and *stop* arguments.
+
+- **etc/systemd/zeo-zeo_server.service**: SystemD service configuration file for ZEO server. Create a link to this
+ file in */etc/systemd/system* and reload SystemD daemon (*systemctl daemon-reload*) before activating ZEO service
+ (*systemctl enable zeo-zeo_server.service* and *systemctl start zeo-zeo_server.service*).
+
+- **etc/logrotate.d/zeo-zeo_server**: LogRotate configuration file for ZEO log files. Create a link to this file in
+ */etc/logrotate.d* to activate log rotation for ZEO server.
+
+- **etc/cron.d/pack-zeo-zeo_server**: Cron configuration file for ZEO database packing. Just create a link to this
+ file in */etc/cron.d* directory to enable ZODB packing on a weekly basis (by default).
+
+In these file names, always replace "zeo_server" with the value which was given to "project_slug" variable during
+*CookieCutter* template creation. All directory names are those used on a Debian GNU/Linux distribution and may have
+to be changed on other distributions.
+
+
+.. _RelStorage:
+
+Installing a RelStorage server
+++++++++++++++++++++++++++++++
+
+RelStorage (http://relstorage.readthedocs.io/en/latest) is an alternate ZODB storage implementation, that stores
+Python pickles in a relational database; PostgreSQL (>= 9.0), MySQL (>= 5.0.32) and Oracle (> 10g) databases are
+supported.
+
+To create a database compatible with RelStorage, you just have to install the database server and create a database
+dedicated to RelStorage; schema initialization is then completely done by RelStorage on application startup.
+
+RelStorage is supposed to provide better performances than ZEO, notably under high load. RelStorage can also get
+benefit from many extensions (clustering, fail-over, hot-standby...) provided by these databases.
+
+
+.. _Newt.DB:
+
+Installing a NewtDB server
+++++++++++++++++++++++++++
+
+NewtDB (http://www.newtdb.org/en/latest) is another ZODB storage implementation. It's using RelStorage but is
+dedicated to PostgreSQL (>= 9.5).
+
+NewtDB adds conversion of data from the native serialization used by ZODB to JSON, stored in a PostgreSQL JSONB
+column. The JSON data supplements the native data to support indexing, search, and access from non-Python application.
+Because the JSON format is lossy, compared to the native format, the native format is still used for loading
+objects from the database. For this reason, the JSON data are read-only.
+
+Newt adds a search API for searching the Postgres JSON data and returning persistent objects. It also provides a
+convenient API for raw data searches.
+
+Database creation is done as with RelStorage, but NewtDB add several schema objects. Migration scripts are available
+if you need to switch from a classic RelStorage database to a Newt database.