megaco_user(3erl) | Erlang Module Definition | megaco_user(3erl) |
megaco_user - Callback module for users of the Megaco application
This module defines the callback behaviour of Megaco users. A megaco_user compliant callback module must export the following functions:
The semantics of them and their exact signatures are explained below.
The user_args configuration parameter which may be used to extend the argument list of the callback functions. For example, the handle_connect function takes by default two arguments:
handle_connect(Handle, Version)
but if the user_args parameter is set to a longer list, such as [SomePid,SomeTableRef], the callback function is expected to have these (in this case two) extra arguments last in the argument list:
handle_connect(Handle, Version, SomePid, SomeTableRef)
action_request() = #'ActionRequest'{} action_reply() = #'ActionReply'{} error_desc() = #'ErrorDescriptor'{} segment_no() = integer()
conn_handle() = #megaco_conn_handle{}
The record initially returned by megaco:connect/4,5. It identifies a "virtual" connection and may be reused after a reconnect (disconnect + connect).
protocol_version() = integer()
Is the actual protocol version. In most cases the protocol version is retrieved from the processed message, but there are exceptions:
In these cases, the ProtocolVersion default version is obtained from the static connection configuration:
handle_connect(ConnHandle, ProtocolVersion) -> ok | error |
{error,ErrorDescr}
handle_connect(ConnHandle, ProtocolVersion, Extra) -> ok | error |
{error,ErrorDescr}
Types:
Invoked when a new connection is established
Connections may either be established by an explicit call to megaco:connect/4 or implicitly at the first invocation of megaco:receive_message/3.
Normally a Media Gateway (MG) connects explicitly while a Media Gateway Controller (MGC) connects implicitly.
At the Media Gateway Controller (MGC) side it is possible to reject a connection request (and send a message error reply to the gateway) by returning {error, ErrorDescr} or simply error which generates an error descriptor with code 402 (unauthorized) and reason "Connection refused by user" (this is also the case for all unknown results, such as exit signals or throw).
See note above about the Extra argument in handle_message_error/4.
handle_connect/3 (with Extra) can also be called as a result of a call to the megaco:connect/5 function (if that function is called with the Extra argument different than ignore_extra.
handle_disconnect(ConnHandle, ProtocolVersion, Reason) ->
ok
Types:
Invoked when a connection is teared down
The disconnect may either be made explicitly by a call to megaco:disconnect/2 or implicitly when the control process of the connection dies.
handle_syntax_error(ReceiveHandle, ProtocolVersion, DefaultED)
-> reply | {reply, ED} | no_reply | {no_reply, ED}
handle_syntax_error(ReceiveHandle, ProtocolVersion, DefaultED, Extra) ->
reply | {reply, ED} | no_reply | {no_reply, ED}
Types:
Invoked when a received message had syntax errors
Incoming messages is delivered by megaco:receive_message/4 and normally decoded successfully. But if the decoding failed this function is called in order to decide if the originator should get a reply message (reply) or if the reply silently should be discarded (no_reply).
Syntax errors are detected locally on this side of the protocol and may have many causes, e.g. a malfunctioning transport layer, wrong encoder/decoder selected, bad configuration of the selected encoder/decoder etc.
The error descriptor defaults to DefaultED, but can be overridden with an alternate one by returning {reply,ED} or {no_reply,ED} instead of reply and no_reply respectively.
Any other return values (including exit signals or throw) and the DefaultED will be used.
See note above about the Extra argument in handle_syntax_error/4.
handle_message_error(ConnHandle, ProtocolVersion, ErrorDescr)
-> ok
handle_message_error(ConnHandle, ProtocolVersion, ErrorDescr, Extra) ->
ok
Types:
Invoked when a received message just contains an error instead of a list of transactions.
Incoming messages is delivered by megaco:receive_message/4 and successfully decoded. Normally a message contains a list of transactions, but it may instead contain an ErrorDescriptor on top level of the message.
Message errors are detected remotely on the other side of the protocol. And you probably don't want to reply to it, but it may indicate that you have outstanding transactions that not will get any response (request -> reply; reply -> ack).
See note above about the Extra argument in handle_message_error/4.
handle_trans_request(ConnHandle, ProtocolVersion,
ActionRequests) -> pending() | reply() | ignore_trans_request
handle_trans_request(ConnHandle, ProtocolVersion, ActionRequests, Extra)
-> pending() | reply() | ignore_trans_request
Types:
Invoked for each transaction request
Incoming messages is delivered by megaco:receive_message/4 and successfully decoded. Normally a message contains a list of transactions and this function is invoked for each TransactionRequest in the message.
This function takes a list of 'ActionRequest' records and has three main options:
If for some reason megaco is unable to deliver the reply, the reason for this will be passed to the user via a call to the callback function handle_trans_ack, unless ack_action() = discard_ack.
The ack_action() is either:
Note that this only works as specified if the sent_pending_limit config option has been set to an integer value.
Any other return values (including exit signals or throw) will result in an error descriptor with code 500 (internal gateway error) and the module name (of the callback module) as reason.
See note above about the Extra argument in handle_trans_request/4.
handle_trans_long_request(ConnHandle, ProtocolVersion, ReqData)
-> reply()
handle_trans_long_request(ConnHandle, ProtocolVersion, ReqData, Extra)
-> reply()
Types:
Optionally invoked for a time consuming transaction request
If this function gets invoked or not is controlled by the reply from the preceding call to handle_trans_request/3. The handle_trans_request/3 function may decide to process the action requests itself or to delegate the processing to this function.
The req_data() argument to this function is the Erlang term returned by handle_trans_request/3.
Any other return values (including exit signals or throw) will result in an error descriptor with code 500 (internal gateway error) and the module name (of the callback module) as reason.
See note above about the Extra argument in handle_trans_long_request/4.
handle_trans_reply(ConnHandle, ProtocolVersion, UserReply,
ReplyData) -> ok
handle_trans_reply(ConnHandle, ProtocolVersion, UserReply, ReplyData,
Extra) -> ok
Types:
Optionally invoked for a transaction reply
The sender of a transaction request has the option of deciding, whether the originating Erlang process should synchronously wait (megaco:call/3) for a reply or if the message should be sent asynchronously (megaco:cast/3) and the processing of the reply should be delegated this callback function.
Note that if the reply is segmented (split into several smaller messages; segments), then some extra info, segment number and an indication if all segments of a reply has been received or not, is also included in the UserReply.
The ReplyData defaults to megaco:lookup(ConnHandle, reply_data), but may be explicitly overridden by a megaco:cast/3 option in order to forward info about the calling context of the originating process.
At success(), the UserReply either contains:
failure() indicates an local or external error and can be one of the following:
See note above about the Extra argument in handle_trans_reply/5.
handle_trans_ack(ConnHandle, ProtocolVersion, AckStatus,
AckData) -> ok
handle_trans_ack(ConnHandle, ProtocolVersion, AckStatus, AckData, Extra)
-> ok
Types:
Optionally invoked for a transaction acknowledgement
If this function gets invoked or not, is controlled by the reply from the preceding call to handle_trans_request/3. The handle_trans_request/3 function may decide to return {handle_ack, ack_data()} or {handle_sloppy_ack, ack_data()} meaning that you need an immediate acknowledgement of the reply and that this function should be invoked to handle the acknowledgement.
The ack_data() argument to this function is the Erlang term returned by handle_trans_request/3.
If the AckStatus is ok, it is indicating that this is a true acknowledgement of the transaction reply.
If the AckStatus is {error, Reason}, it is an indication that the acknowledgement or even the reply (for which this is an acknowledgement) was not delivered, but there is no point in waiting any longer for it to arrive. This happens when:
See note above about the Extra argument in handle_trans_ack/5.
handle_unexpected_trans(ConnHandle, ProtocolVersion, Trans)
-> ok
handle_unexpected_trans(ConnHandle, ProtocolVersion, Trans, Extra) ->
ok
Types:
Invoked when a unexpected message is received
If a reply to a request is not received in time, the megaco stack removes all info about the request from its tables. If a reply should arrive after this has been done the app has no way of knowing where to send this message. The message is delivered to the "user" by calling this function on the local node (the node which has the link).
See note above about the Extra argument in handle_unexpected_trans/4.
handle_trans_request_abort(ConnHandle, ProtocolVersion,
TransNo, Pid) -> ok
handle_trans_request_abort(ConnHandle, ProtocolVersion, TransNo, Pid,
Extra) -> ok
Types:
Invoked when a transaction request has been aborted
This function is invoked if the originating pending limit has been exceeded. This usually means that a request has taken abnormally long time to complete.
See note above about the Extra argument in handle_trans_request_abort/5.
handle_segment_reply(ConnHandle, ProtocolVersion, TransNo,
SegNo, SegCompl) -> ok
handle_segment_reply(ConnHandle, ProtocolVersion, TransNo, SegNo, SegCompl,
Extra) -> ok
Types:
This function is called when a segment reply has been received if the segment_reply_ind config option has been set to true.
This is in effect a progress report.
See note above about the Extra argument in handle_segment_reply/6.
megaco 3.19.5 | Ericsson AB |