Error handling

Introduction

When remote procedures are executed, errors can be caused by almost anything: invalid request payload, arguments deserialization or result serialization error, exception in method execution, etc. All errors must be handled properly for 2 reasons :

1. An error response must be returned to RPC client (with an error code and a textual message)

2. Developers should be able to detect such errors (using logs, error reporting tool like Sentry, etc.)

For that reasons, django-modern-rpc handle all errors with Python builtin exception system. This allows for very flexible error handling and allows to define custom exceptions with fixed error code and message.

Builtin exceptions

Hopefully, error codes for both JSON-RPC and XML-RPC are pretty similar. The following errors are fully supported in django-modern-rpc.

Code	Message
-32700	parse error. not well formed
-32600	Invalid request
-32601	Method not found
-32602	Invalid params
-32603	Internal error

Additional errors from XML-RPC specs are less relevant in modern web application, and have not been implemented.

Custom exceptions

When any exception is raised from a remote procedure, the client will get a default Internal Error as response. If you want to return a custom error code and message instead, simply define a custom exception. Create an RPCException sub-classes and set a faultCode to RPC_CUSTOM_ERROR_BASE + N with N a unique number.

Here is an example:

class MyException1(RPCException):
    def __init__(self, message):
        super().__init__(RPC_CUSTOM_ERROR_BASE + 1, message)

class MyException2(RPCException):
    def __init__(self, message):
        super().__init__(RPC_CUSTOM_ERROR_BASE + 2, message)

Such exceptions raised from your remote procedure will be properly returned to client.

Log errors

New in version 1.0.

By default, when an exception is caught from modernrpc code, a stacktrace of the error will be printed in the default log output. This allows developer to detect such case and fix the issue if needed.

To disable this behavior, set MODERNRPC_LOG_EXCEPTIONS to False.