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core.messaging.handlers.message_context

MessageContext Objects​

class MessageContext()

An execution context for messages dispatched by the message bus.

When a message handler gets executed (i.e., called by the message bus dispatchers), an instance of MessageContext (or a subclass) is passed to the handler. This context can be seen as a unit of work that exists during the execution of the handler. Its main task is to hold data that is specific to this single execution.

A message context is used as a context manager. In its __exit__ method, any exceptions will be catched, printed and passed on. This makes tracing of errors that occur during message handling easier.

It is also possible to have message handlers receive custom subtypes of this class. See Component and its create_service method for details.

__init__​

def __init__(msg_meta: MessageMetaInformation, msg_origin: UnitID,
             msg_builder: MessageBuilder, *, logger: LoggerProtocol,
             config: Configuration)

Arguments:

  • msg_builder - A MessageBuilder to be assigned to this context.
  • msg_origin - The origin of the message.
  • msg_meta - The meta information of the message.
  • logger - A logger that is configured to automatically print the trace belonging to the message that caused the handler to be executed.
  • config - The global component configuration.

is_entrypoint_local​

@property
def is_entrypoint_local() -> bool

Whether the message entered locally.

is_entrypoint_server​

@property
def is_entrypoint_server() -> bool

Whether the message entered through the server.

is_entrypoint_client​

@property
def is_entrypoint_client() -> bool

Whether the message entered through the client.

origin​

@property
def origin() -> UnitID

The origin of the message.

message_builder​

@property
def message_builder() -> MessageBuilder

The message builder to be used within this context.

logger​

@property
def logger() -> LoggerProtocol

The logger to be used within this context.

config​

@property
def config() -> Configuration

The global component configuration.

api_key​

@property
def api_key() -> str

The API key configured in the global settings.