ALA Communication

ALA Communication

The Broker and ALA communicate using system-defined document types. All document types described are volatile with infinite time-to-live.

// Sent from Broker to ALA. ALA replies with
// Broker::ALA::label or Broker::ALA:error
Broker::ALA::lookup {
unicode_string user;
unicode_string authenticator;
unicode_string serial;
unicode_string hint;
};

// Sent from ALA to Broker, in response to
// Broker::ALA::lookup.
Broker::ALA::label {
unicode_string user;
unicode_string authenticator;
short label[];
};

// Sent from ALA to Broker, in response to
// Broker::ALA::lookup.
Broker::ALA::error {
unicode_string user;
unicode_string authenticator;
unicode_string error;
unicode_string detail;
};

// Sent from ALA to Broker.
Broker::ALA::change {
unicode_string user;
unicode_string authenticator;
unicode_string serial;
short label[];
};

The ALA can use the Broker::ALA::error document to report problems during label lookup. The error field should be one of the following:

Error Field	Meaning
unknown	The user is not known to the ALA.
internal	A temporary failure has occurred. If the client has an existing label, it is not invalidated.

If the error string is not internal, the current access label is invalidated (e.g., cleared).

You can use the detail field to record an implementation-specific error message. If the detail field is present, the Broker logs an error for the failure. In error cases, any pending lookups for the user's label will fail. If there is a non-empty detail string, it is logged to the Broker Server's error log.

The ALA can use the change document to update an access label the Broker already knows about. You can effectively revoke a label by updating it with a zero-length label. The client is not notified when its access label changes.

The Broker delivers documents to the ALA client (that is, the _env.destId field is set). The ALA should confirm that_env.pubId is set to //broker-name.

The ALA should deliver documents to the Broker using //broker-name as the destination ID. The Broker ignores published ALA documents, as well as documents not delivered from a local member of the "accessLabelAdapter" client group.