PYRO - Errors and Troubleshooting

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## 10. Errors and Troubleshooting

The Pyro Errors section describes the various errors that can occur when using Pyro. It only describes Pyro's custom exceptions - other Python exceptions may occur due to other runtime problems.

The Troubleshooting section provides various hints and tips when you can't get things to work as expected.

### Pyro Errors

#### Pyro Exception Hierarchy

- Exception
  - PyroError
    - URIError
    - DaemonError
    - NamingError
    - NoModuleError
    - ProtocolError
      - ConnectionClosedError
        - TimeoutError
      - ConnectionDeniedError

### Pyro's exception extensions

Pyro transports a remote exception (and traceback) to the client, where it is raised again as if it occured locally. Pyro provides some powerful debugging possibilities:

- Automatically printing the remote traceback in case of an exception. The `__str__` method of the exception object is remapped so that if the exception is printed, it includes the traceback from the server. The old (client-side-only) print method is still available as `excepion.standardStr()`. See the `PYRO_PRINT_REMOTE_TRACEBACK` config item.
- Printing a very detailed traceback, including the names and values of current local variables at the moment of the exception. See the `PYRO_DETAILED_TRACEBACK` config item.

By default, both options are disabled because of security reasons.

### What error occurs where and when?

#### Initialization

`OSError`-- is raised when Pyro needs but can't create or open the storage directory specified by `PYRO_STORAGE`.

#### Name Server

`NamingError`-- The Name Server responds with the following kinds of `NamingError` exceptions (raised by the remote NS object):

Error string | raised by | description
--- | --- | ---
name already exists | register | The name you're trying to register is already present in the NS database
name not found | unregister | You're trying to unregister an unknown name.
name not found | resolve | The name you're trying to resolve is unknown by the NS.
invalid name | various methods | The object name is invalid. It must be a string with no whitespaces and only 7-bit ASCII characters.
invalid URI | various methods | The object URI that was passed is invalid.
parent is no group | register | A new name can only be registered within a group. The name is not in a correct group.
attempt to resolve groupname | resolve | A resolve was done on a group name, only object names can be resolved.
group not found | various methods | The name contains an unknown group.
is no group | deleteGroup, list | An operation was done that can only be performed on a group, not on an object name.
(parent)group not found | various methods | The name contains an unknown (parent) group.
name is not absolute | nearly all methods | Object names have to be absolute (i.e. fully specified in the namespace).
default group name is not absolute | nearly all methods | The default group name has to be absolute (i.e. fully specified in the namespace).

`PyroError`-- The `NameServerLocator` raises `PyroError` "Name Server not responding" if it failed to discover the Name Server (via the `getNS` method).

Also, the `PYROAdapter` raises `NoModuleError` "No module named XYZ" if it cannot import a Python module. See below in the table.

Also, the startup code in `configuration.py` raises `PyroError` "Error reading config file" if Pyro's configuration file cannot be read.

#### Pyro Core

`URIError`-- The `PyroURI` object raises `URIError` "illegal URI format" when you try to create a `PyroURI` object from an illegal URI. Also "unknown host" means that you supplied an unknown hostname or IP address for the URI.

`DaemonError`-- The `Daemon` object raises `DaemonError` "Couldn't start Pyro daemon" if it was unable to start. This usually means that the required network port (socket) is temporarily unavailable because another Pyro daemon is already running on it.

#### PYRO Protocol adapter

Various exceptions may be raised by the PYRO protocol code:

Exception | Error string | raised by | description
--- | --- | --- | ---
`ConnectionClosedError` | connection lost | receive code | The network connection was lost while receiving data.
`ConnectionClosedError` | connection lost | send code | The network connection was lost while sending data.
`ProtocolError` | incompatible protocol in URI | `bindToURI` method of `PYROAdapter` | You supplied an incompatible protocol ID. Use 'PYRO'.
`ProtocolError` | connection failed | `bindToURI` method of `PYROAdapter` | Network problems caused the connection to fail. Also the Pyro server may have crashed.
`ProtocolError` | invalid header | receive code | A message with an invalid header has been received.
`ProtocolError` | incompatible version | receive code | A message from an incompatible Pyro version has been received.
`ProtocolError` | unsupported protocol | `getProtocolAdapter` | You tried to get a protocol adapter for an unsupported protocol. Currently only the 'PYRO' protocol is supported.
`ProtocolError` | compression not supported | receive code | An incoming message used compression, which this Pyro setup doesn't support (most likely you don't have the `zlib` module).
`ProtocolError` | unknown object ID | receive code | Incoming method call for an unknown object (i.e. the object ID was not found in the Daemon's list of active objects).
`NoModuleError` | No module named XYZ | remote method call code | The Pyro server cannot import the Python module XYZ that contains the code for an object that was passed in a remote call. If you don't use mobile code, the Pyro server must have all `.py` files available.
`PyroError` | attempt to supply code denied | remote method call code | Either a client tried to submit code to a server that hasn't enabled mobile code, or the server had enabled mobile code but the codeValidator refused to accept it.
`ConnectionDeniedError` | unspecified reason | `bindToURI` method of `PYROAdapter` | No specific reason given for denying the connection
`ConnectionDeniedError` | server too busy | `bindToURI` method of `PYROAdapter` | The Pyro server has too many connections at this time so your request for another connection was denied.
`ConnectionDeniedError` | host blocked | `bindToURI` method of `PYROAdapter` | The server blocks your host/IP address.
`ConnectionDeniedError` | security reasons | `bindToURI` method of `PYROAdapter` | General security issue prevented a connection.
`TimeoutError` | connection timeout | while transferring data in PyroAdapter | The communication took longer that the timeout perioud that was specified. (default: off)

#### Util

`KeyError`-- The `ArgParser` will raise `KeyError` "no such option" if you try to `getOpt` an option that has not been detected in the option string and you have not supplied a default value to `getOpt` (otherwise that default value is returned).

### Troubleshooting

Problem | Possible cause | Hint/tip
--- | --- | ---
The Name Server or my own Pyro server refuses to start, aborts with `DaemonError` | The daemon can't set up the network port (socket), probably because another daemon is already running, or another process occupies the resource. | Wait a little while and try again (sometimes it takes a while for resources to become available again). If this doesn't work, find the other daemon that is probably running and shut it down, or specify another port for the new daemon. Sorry, but your new process can't yet use the daemon of another running process - perhaps in a future Pyro version. It could also be that there is something special about your network setup, like: multiple NICs / IP addresses on a single host. Please read the "Features and Guidelines" chapter.
Name Server acts weird with names or groups | not using built-in static NS proxy | always use the `Pyro.naming.NameServerProxy` returned by the Name Server Locator.
Pyro refuses to initialize, aborts with `IOError` and/or things saying 'permission denied' or similar | You probably specified a wrong location for Pyro's storage directory and/or logfiles. Perhaps you don't have permission to write in those locations. | Fix those locations by changing the configuration items. Make sure you have permission to write to those locations. Usually `PYRO_STORAGE` must be changed to point to a correct directory.
My code can't find the Name Server, it aborts with "Name Server not responding" | The Pyro Name Server is not running or it can't be discovered automatically. The latter may be the case if your network doesn't support broadcasts or if the NS is running on a different subnet that cannot be reached by a broadcast. | Start the NS if it's not running. If the problem persists, you have to help the `NameServerLocator` by specifying the host and perhaps even the port number where the NS is running. You can also try to obtain the NS' URI string and create a proxy directly from this string, bypassing the `NameServerLocator`.
Still can't contact Name Server or my Pyro objects, but NS is active. Log has warning about local address 127.0.0.1. | NS or daemon binds on loopback address due to faulty network config. | Often it's wrong if your hostname resolves to 127.0.0.1 (the loopback address) - your servers are invisible from other hosts if they bind on this address. This usually isn't Pyro's fault, but an error in your network/DNS/resolv configuration. Pyro warns you about this, but continues, because sometimes it is correct.
'name not absolute' errors after changing default namespace group. | The default group name for the `PYRO_NS_DEFAULTGROUP` config item must be an absolute name (starting with the root char). | Change it to an absolute name.
Client can't bind to URI or find URI in Name Server. NS is running ok, server is running ok. | The URI is not registered correctly in the Name Server. | Make sure that the client accesses the correct Name Server (the one that the server used to register the object), especially if you're running multiple NS. Also make sure that the client uses the correct URI.
Client problems when accessing Pyro object attributes, client prints stuff like `<bound method DynamicProxy.__invokePYRO__ of DynamicProxy ... >` instead of attribute value | You are using regular dynamic proxy | Use attribute enabled proxy, either a static one generated by `pyroc` or the dynamic one, see `getAttrProxyForURI`.
Client crashes with "No module named ..." or similar when accessing attributes | The attribute object is an instance of a class that cannot be found/imported on the client | make the module that contains every attribute class available on the client, or write getters.
Pyro doesn't use my configuration settings! | Other settings overrule your settings. | Check if there is an environment variable that overrules your config file, or perhaps even a setting in your code..
Pyro object doesn't initialise correctly | Pyro objects cannot have a remote __init__ method | Use explicit remote initialization by using a custom init method..
My proxy acts very weird after I updated the Pyro object | Using old static proxy | Regenerate static proxy (or use dynamic proxy).
General network errors when using firewall or multiple network adapters (can't find NS, Pyro uses wrong IP address in URIs) | Firewalls need special treatment | Read the chapter Features and Guidelines.
Client cannot connect anymore after restarting the server | Pyro URIs change every time the server is restarted, and the client uses an old URI | update the URI on the client, or use the Name Server, or use Persistent Naming.
Deadlock (Pyro freezes) | Callback waits for other object (occurs in 'conversation' or 'looping' invocation) | Make sure your Daemon is running in multithreaded mode. Also consider using Oneway invocations or the Event Server.
Pyro Object created on server and returned to client doesn't work | You are probably not returning a proxy but the object itself. | Return a proxy instead: `return Obj.getAttrProxy()`
PicklingError or TypeError: can't pickle .... objects | You're passing an unpickleable object to Pyro | Remove any nonpickleable objects. You might want to try custom `__getstate__` and `__setstate__` methods.
Syntax Error exception when using mobile code | Pyro couldn't compile the downloaded code | It could be that you have old *.pyc or *.pyo files around from a different Python version. Remove these files. If not, your source has a true syntax error in it, try to import it standalone and see if it works. It could also be that your source has windows-style line endings (CR LF), this won't compile (known issue).
Other problem not mentioned here | Your code probably breaks a Pyro rule | read the the chapter Features and Guidelines.
SSL problems | ? | Sorry, I don't know much about SSL. Ask on Usenet or the mailing list.
Trouble using `object.attr.subattr.subsubattr` or calling 'nested' methods like `obj.address.getStreet()` | All classes that are used for the nested attributes must be available on the client. | See the "attributes" example.
Pyro crashes. | Most likely a bug. | Contact me.

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