zope.app.twisted 3.4.2

Server Types

Zope 3 needs to support many server types – HTTP, FTP, HTTP with postmortem debugging, etc. All of them are registered as IServerType utilities in ZCML. This allows developers to easily develop and register new servers for Zope 3.

ServerType is an implementation of IServerType that is specific to the standard Twisted servers.. The constructor of ServerType takes three arguments: the factory that will create a Twisted IServerFactory object and the default port and IP to which to bind the server.

The factory argument should be a callable expecting one argument, the ZODB instance. It is up to the factory, to implement the necessary glue between the server and the application:

>>> class TwistedServerFactoryStub(object):
...     def doStart(self): pass

>>> def factory(db):
...     print 'ZODB: %s' %db
...     return TwistedServerFactoryStub()

For the other two constructor arguments of ServerType, the defaultPort argument specifies the default TCP port number for the server. The defaultIP argument specifies the network interface for listening on. You can specify the network interface IP address, or an empty string if you want to listen on all interfaces.

We are now ready to instantiate the server type:

>>> from zope.app.twisted.server import ServerType
>>> st = ServerType(factory, defaultPort=8080)

and let’s make sure it really implements the promised interface:

>>> from zope.interface.verify import verifyObject
>>> from zope.app.twisted.interfaces import IServerType
>>> verifyObject(IServerType, st)
True

A server type is then registered as a named utility. These utilities are used while interpreting <server> sections of zope.conf to create instances of servers listening on a specific port.

When you create an instance of a server using the create() method of the server type, you need to tell it an identifying name and a the ZODB database object. The IP address, port and backlog count can be optionally passed to the method.

>>> db = 'my database'
>>> server = st.create('Example-HTTP', db, port=0)
ZODB: my database
>>> server #doctest:+ELLIPSIS
<zope.app.twisted.server.ZopeTCPServer instance at ...>

As you can see the server type creates a Zope-specific TCP server, which is simply a standard twisted.internet.TCPServer that creates a log entry upon startup.

>>> server.startService()
>>> print log.getvalue()
-- Example-HTTP Server started.
   Hostname: localhost
   Port: 0

You can, of course, create multiple instances of the same server type, and bind them to different ports.

>>> server2 = st.create('Example-HTTP-2', db, port=0)
ZODB: my database

>>> server2.startService()
>>> print log.getvalue()
-- Example-HTTP Server started.
   Hostname: localhost
   Port: 0
-- Example-HTTP-2 Server started.
   Hostname: localhost
   Port: 0

A special type of server type is the SSL server type; it requires some additional information (private key path, certificate path, and TLS flag) to start up the server. The setup will only work, if OpenSSL is installed:

# >>> from zope.app.twisted.server import SSLServerType # >>> ssl_st = SSLServerType(factory, defaultPort=8443) # # >>> ssl_server = ssl_st.create(‘Example-HTTPS’, db, # … ‘server.pem’, ‘server.pem’) # ZODB: my database # >>> ssl_server #doctest:+ELLIPSIS # <zope.app.twisted.server.ZopeSSLServer instance at …>

Server Factories

Now, of course we do not hardwire the setup of actual servers in Python. Instead, we are using ZConfig to setup the servers. Unfortunately that means that we need yet another abstraction layer to setup the servers. ZConfig-based configuration code creates so called ServerFactory and SSLServerFactory objects that then use the server types to create the servers.

>>> from zope.interface import implements
>>> from zope.app.twisted.interfaces import IServerType
>>> class MyServerType:
...     implements(IServerType)
...     def create(self, name, db,
...                port='unknown', ip='', backlog=50):
...         if not ip:
...             ip = '*' # listen on all interfaces
...         return ('%s server on %s:%d, registered with %s, backlog %d'
...                 % (name, ip, port, db, backlog))

>>> from zope.app.testing import ztapi
>>> ztapi.provideUtility(IServerType, MyServerType(), name='HTTP')
>>> ztapi.provideUtility(IServerType, MyServerType(), name='FTP')

ServerFactory is used to hook into ZConfig and create instances of servers specified in zope.conf. It gets a section argument that contains settings specified in a ZConfig <server> section.

>>> class ServerSectionStub:
...     type = 'HTTP'
...     address = ('', 8080)
...     backlog = 30
>>> my_section = ServerSectionStub()

>>> from zope.app.twisted.server import ServerFactory
>>> sf = ServerFactory(my_section)

The server factory object knows how to create a server, given a ZODB database object. The name is a combination of type, ip, and port, so that the Twisted code can distinguish between the different HTTP servers.

>>> db = 'my db'
>>> print sf.create(db)
HTTP:localhost:8080 server on *:8080, registered with my db, backlog 30

It can create more than one, using different ports.

>>> my_section.address = ('', 8081)
>>> sf = ServerFactory(my_section)
>>> print sf.create(db)
HTTP:localhost:8081 server on *:8081, registered with my db, backlog 30

The settings should actually work with FTP as well.

>>> my_section.type = 'FTP'
>>> my_section.address = ('127.0.0.1', 8021)
>>> sf = ServerFactory(my_section)
>>> print sf.create(db)
FTP:127.0.0.1:8021 server on 127.0.0.1:8021, registered with my db, backlog 30

3.4.2 (2009-01-27)

• Fix tests. Remove unused code.

• Add zope.testbrowser to testing dependencies for ZEO tests.

• Remove unneeded dependency on ZODB3.

• Remove dependency on zope.app.zapi, substituting its uses with direct imports.

• Change “cheeseshop” to “pypi” in the package homepage.

3.4.1 (2008-02-02)

• Fix of 599 error on conflict error in request see: http://mail.zope.org/pipermail/zope-dev/2008-January/030844.html

3.4.0 (2007-10-27)

• Initial release independent of the main Zope tree.