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PYRONAME://, PYROLOC:// and PYROLOCSSL:// URIs
bin directory that will start a Pyro Name Server for you:
ns (Name Server)
rns (Restarting Name Server)
ns command but the script will restart the
name server if it quits or crashes. Do not confuse this with the -d argument,
which will start a Name Server that has its database persistent on disk. Of course it is
very useful to combine the rns with the -d switch!!!ns.bat, rns.bat
nssvc (Windows-only Name Server 'NT-service' control script)
nssvc.bat script to register it as a service.
Make sure you have Pyro properly installed in your Python's site-packages.
Or make sure to register the service using an account with the correct PYTHONPATH setting, so that Pyro can be located.
The NS service logs to C:\Pyro_NS_svc.log, and writes its URI to C:\Pyro_NS_URI.txt
(C: being your system drive).
HKLM\System\CurrentControlSet\Services\PyroNS, and
the value under that key is: PyroServiceArguments (REG_SZ, it will be asked and created
for you when doing a nssvc.bat install from a command prompt).
nsc command (explained in the Usage chapter) you can control a Name
Server that is already running.
Consider setting PYRO_CHECKSUM to 1 before starting the NS. It will communicate more reliably and the overhead is very small.
If you want to start the NS from within your own program, you can ofcourse start it by executing
the start script mentioned above. You could also use the Pyro.naming.NameServerStarter class
to start it directly (this is what the script also does). Be sure to start it
in a separate process or thread because it will run in its own endless loop.
You probably have to wait until the NS has been fully started, call the waitUntilStarted() method on
the starter object. It returns true if the NS has been started, false if it is not yet ready. You can provide a timeout
argument (in seconds).
Object names can be absolute or relative. Relative object names are searched in the default group (which has a special name, set by PYRO_NS_DEFAULTGROUP). Absolute names are always searched from the root. Absolute object names start with a special character that signifies the root; the colon (':'). Relative object names don't have this character at the start.
Object names can be simple or compound. Compound object names consist of multiple parts separated by a special group separator character: the dot ('.'). Compound names are used to search within the namespace hierarchy. Each component of the name is the name of a group. The last name component can be the name of a group or an object (usually the latter).
Object name parts can only consist of the ASCII characters in the range 33-126 ('!'-'~') and except the backslash (\), dot ('.') and colon (':'). So spaces are also illegal in names, but normal slashes ('/') are okay.
Let's finish with a few examples to clarify all this. Note that by name alone you cannot distinguish a group name or an object name.
:
| The namespace root group |
:TestObj
| The TestObj name in the root (most likely an object name) |
:Test.simple.object1
| The object1 name in the simple group in the Test group in the root. |
Test.simple.object1
| The object1 name in the simple group in the Test group in the default group (which is ":Default" if not configured otherwise. This is the Default group in the root). |
object1
| The object1 name in the default group. |
Pyro.naming.NameServer)
Pyro.naming.PersistentNameServer)
The persistent NS stores its naming database on disk. Currently this is implemented the easy
way; there is a direct mapping between the group names and directories on disk, and between
object names + URI's and files in these directories on disk. The database by default is
stored in a "Pyro_NS_database" directory that is created in the directory configured
by PYRO_STORAGE. There is a special option for the script that specifies
another location, if needed.
Usually you don't access the NameServer or PersistentNameServer classes
directly: there are scripts to start the right name server.
connect method of the daemon to connect your object
instances to the daemon on the server. The daemon will register your object with the
name server too, if you supplied a NS to the daemon and your object isn't transient (it has a name).
But, when using the persistent name server, there is a complication here: if you didn't explicitly remove your object from the NS, the entry will still be there the next time. Your connect attempt will then fail because your object cannot be registered again in the NS.
The solution is to use the connectPersistent method of the Pyro daemon.
Except for the method name, you call it exactly like the regular connect method.
It tries to find your object in the NS. If it's there already, the previous URI is used for your object
(that also means that the object's GUID is replaced by the previous GUID that was found in the
NS). If it isn't there, the regular connect call takes over.
Of course you could always play safe and explicitly unregister any possible previous occurrences from the NS before you connect new instances. This is what all examples do by the way, so you can safely run an example again and again.
For your information, the code that starts the Persistent Name Server uses connectPersistent to connect the name server object to the daemon. Why? because the name server itself
is also registered in the NS database, and it is necessary that when the NS restarts, it
uses the URI of the previous instance if found in the persistent database.
Paired mode is activated by using the -1 and -2
options when starting the NS. 1 means: this is the first one, 2 means: this is the second
one of the pair (this distinction is necessary because of a slightly different
startup procedure depending on being the first or the second).
You can add a hostname:port argument to the -1 and -2 option,
that specify the location of the other name server. So, for instance:
ns -n atlantis -p 4000 -1 atlantis:5000 to start NS #1,
ns -n atlantis -p 5000 -2 atlantis:4000 to start NS #2.
But usually just -1 or -2 is good enough.
There are three new config items dealing with paired mode NS:
PYRO_NS2_HOSTNAME, PYRO_NS2_PORT and PYRO_NS2_BC_PORT.
They can be used to specify non-default values for the hostname and port number
that the second NS will use. See the config chapter.
Resync mechanism: Start A, then B. B remembers A's location (either discovered trough NS lookup or via command line URL). B notifies A that it has started, provides own location, and gets a copy of A's namespace database. A remembers B's location. Any namespace change in A is replicated in B and vice versa, using ONEWAY calls. If an error occurs, the reference to the faulty NS is discarded. If you discover that somehow the namespaces get out-of-sync, just kill the one that is faulty and restart it. It will automatically resync with the 'good' one.
With Identification: If you want to use paired mode together with identification (-i), you must supply the same identification argument to both name servers.
Pyro.naming package.
This object gets a Pyro proxy for the NS for you.
Because this is the recommended (and easiest way) to gain access to the Name Server,
you're not interested in the internal name Pyro uses for the Name Server.
But for consistency, it is defined, and the Name Server object itself is known
in the Name Server's namespace under the name available in Pyro.constants.NAMESERVER_NAME.
There are essentially three ways to get a reference to the Name Server:
NameServerLocator's broadcast mechanism. This only works if your network supports broadcasting and the NS is reachable by a broadcast request.
locator = Pyro.naming.NameServerLocator() ns = locator.getNS()If your network doesn't allow broadcasts, or the broadcast can't reach the NS, this mechanism doesn't work. There is a simple workaround: just set the
PYRO_NS_HOSTNAME config option to the hostname
on which your NS can be found. This disables the broadcast lookup
and uses the one below instead.
NameServerLocator's direct host mechanism. This only works if you know the host on which the NS is located.
The port argument is optional. If the NS has been started using a non-default port number you can use it to specify the port number.
locator = Pyro.naming.NameServerLocator() ns = locator.getNS(host='hostname', port=7777)If you specify the hostname yourself, the locator doesn't attempt to find the NS with the broadcast mechanism, and therefore there is no lookup delay. Also you can specify a port number different from the default port. If you set the
PYRO_NS_HOSTNAME config option, the locator
automatically uses the specified host for a direct lookup. You don't
have to pass Pyro.config.PYRO_NS_HOSTNAME to the getNS method.
Pyro_NS_URI':
uri = open('Pyro_NS_URI','r').read()
uri = Pyro.core.PyroURI(uri) # convert string to real URI object
ns = Pyro.naming.NameServerProxy(uri) # create a proxy for the NS
... you can now invoke methods, such as ns.ping() ...
Note: The URI changes every time a Pyro server or object is created. You cannot use a previously written URI when you have restarted the server.
Pyro.naming.NameServerProxy) contains all necessary logic already. So just use that one. If you use the locator (see above) you will get a correct proxy automatically.
NameServerProxy has an optional second argument: the connection authentication information.
PYRONAME://, PYROLOC:// and PYROLOCSSL:// URIsPYRO:// URIs that the Name Server returns,
and where you then get a proxy object for, you use another URI format.
This format is as follows:
PYRONAME://nshostname:port/objectname (PYRONAMESSL is not yet implemented)
nshostname is the name of the host the Name Server is running on,
and port may be a non-default port the Name Server is listening on.
Both may be omitted.
objectname is the name of the object you want to find!
So, the next code fragment will find the NS using the default lookup mechanism, resolve the object name to a real URI,
create a proxy for that, and call a method:
Pyro.core.getProxyForURI('PYRONAME://:Test.MyObject').getQuote()
So we now have remote object method invocation in one statement :-)
There is one important point: each time a PYRONAME:// URI is used,
a lookup for the Name Server has to be performed, and then a lookup for the object name.
This is much slower than the regular method. However, once you've constructed
a proxy for this URI, no more lookups are performed.
There is another special URI, that bypasses the Name Server completely:
PYROLOC://hostname:port/objectname
PYROLOCSSL://hostname:port/objectname (use this if the server is running in SSL mode)
This time hostname is required and is the name of the host that
your target Pyro object runs on. port may be a non-default port
the Pyro daemon is running on, and may be omitted.
objectname is the internal name for the Pyro object you want to access.
When you use this URI, the Name Server is bypassed and the target server is
contacted directly to get the regular URI for the desired object.
The advantage of this is that you don't have to have a Pyro Name Server running.
The disatvantages are obvious; you miss all the features of the Name Server
and you have to administrate server object names yourself somehow.
You must use the name that is passed to the connect method of the Daemon.
There is no hierarchical naming scheme because the Name Server is not used at all.
Once the object is found, the real URI is stored and no more lookups need to be done.
The next code fragment shows how to call a remote object, without requiring a Name Server to be present:
Pyro.core.getProxyForURI('PYROLOC://localhost/MyObject').getQuote()
(Use PYROLOCSSL:// if the server is running in SSL mode)
Remember that your server does not have to rely on a Name Server when you want to use this mechanism.
When you enable Pyro logging, you might get a WARN that a Name Server is not specified. You can ignore this.
Please also see the "noNS" example, that shows how to use this URI,
and also how you could connect directly by using an URI string that comes off
the server.
resolve.
There are more methods, see below. One very important thing to realize:
all names you supply must be absolute, i.e. ":Group.Objectname"
instead of just "Objectname". The NameServerProxy
that you'll usually be working with has some logic that takes care of this.
resolve(name)
register(name, URI)
unregister(name)
ping()
list(groupname)
flatlist()
createGroup(name)
deleteGroup(name)
fullName(name)
setMeta(name, meta)
getMeta(name)
nsc.py / xnsc.py) for more info.
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