megaco_user
MODULE
megaco_user
MODULE SUMMARY
Callback module for users of the Megaco application
DESCRIPTION
This module defines the callback behaviour of Megaco users. A
megaco_user compliant callback module must export the following
functions:
-
handle_connect/2,3
-
handle_disconnect/3
-
handle_syntax_error/3,4
-
handle_message_error/3,4
-
handle_trans_request/3,4
-
handle_trans_long_request/3,4
-
handle_trans_reply/4,5
-
handle_trans_ack/4,5
-
handle_unexpected_trans/3,4
-
handle_trans_request_abort/4,5
-
handle_segment_reply/5,6
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)
DATA TYPES
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 retreived from the processed message, but there
are exceptions:
-
When handle_connect/2,3 is triggered by an
explicit call to megaco:connect/4,5.
-
handle_disconnect/3
-
handle_syntax_error/3
In these cases, the ProtocolVersion default
version is obtained from the static connection
configuration:
-
megaco:conn_info(ConnHandle, protocol_version).
EXPORTS
handle_connect(ConnHandle, ProtocolVersion) -> ok | error | {error,ErrorDescr}
handle_connect(ConnHandle, ProtocolVersion, Extra]) -> ok | error | {error,ErrorDescr}
Types:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
ErrorDescr = error_desc()
Extra = term()
Invoked when a new connection is established
Connections may either be established by an explicit call to
megaco:connect/4 or implicitely at the first invokaction 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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
Reason = term()
Invoked when a connection is teared down
The disconnect may either be made explicitely by a call to
megaco:disconnect/2 or implicitely 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:
ReceiveHandle = receive_handle()
ProtocolVersion = protocol_version()
DefaultED = error_desc()
ED = error_desc()
Extra = term()
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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
ErrorDescr = error_desc()
Extra = term()
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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
ActionRequests = [action_request()]
Extra = term()
pending() = {pending, req_data()}
req_data() = term()
reply() = {ack_action(), actual_reply()} | {ack_action(), actual_reply(), send_options()}
ack_action() = discard_ack | {handle_ack, ack_data()} | {handle_pending_ack, ack_data()} | {handle_sloppy_ack, ack_data()}
actual_reply() = [action_reply()] | error_desc()
ack_data() = term()
send_options() = [send_option()]
send_option() = {reply_timer, megaco_timer()} | {send_handle, term()} | {protocol_version, integer()}
Extra = term()
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:
-
Return ignore_trans_request
-
Decide that these action requests shall be ignored
completely.
-
Return pending()
-
Decide that the processing of these action requests
will take a long time and that the originator should get
an immediate 'TransactionPending' reply as interim
response. The actual processing of these action requests
instead should be delegated to the the
handle_trans_long_request/3 callback function with the
req_data() as one of its arguments.
-
Return reply()
-
Process the action requests and either return an
error_descr() indicating some fatal error or a list of
action replies (wildcarded or not).
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:
-
discard_ack
-
Meaning that you don't care if the reply is
acknowledged or not.
-
{handle_ack, ack_data()} | {handle_ack, ack_data(), send_options()}
-
Meaning that you want an immediate acknowledgement
when the other part receives this transaction
reply. When the acknowledgement eventually is
received, the handle_trans_ack/4 callback function
will be invoked with the ack_data() as one of its
arguments. ack_data() may be any Erlang term.
-
{handle_pending_ack, ack_data()} | {handle_pending_ack, ack_data(), send_options()}
-
This has the same effect as the above,
if and only if megaco has sent atleast one
pending message for this request (during the processing
of the request). If no pending message has been sent, then
immediate acknowledgement will not be
requested.
Note that this only works as specified if the
sent_pending_limit config option has been set to
an integer value.
-
{handle_sloppy_ack, ack_data()}| {handle_sloppy_ack, ack_data(), send_options()}
-
Meaning that you want an acknowledgement sometime.
When the acknowledgement eventually is received, the
handle_trans_ack/4 callback function will be invoked with
the ack_data() as one of its arguments. ack_data() may be
any Erlang term.
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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
ReqData = req_data()
Extra = term()
req_data() = term()
reply() = {ack_action(), actual_reply()} | {ack_action(), actual_reply(), send_options()}
ack_action() = discard_ack | {handle_ack, ack_data()} | {handle_sloppy_ack, ack_data()}
actual_reply() = [action_reply()] | error_desc()
ack_data() = term()
send_options() = [send_option()]
send_option() = {reply_timer, megaco_timer()} | {send_handle, term()} | {protocol_version, integer()}
Extra = term()
Optionally invoked for a time consuming transaction request
If this function gets invoked or not is controlled by the
reply from the preceeding 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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
UserReply = success() | failure()
success() = {ok, result()}
result() = transaction_result() | segment_result()
transaction_result() = action_reps()
segment_result() = {segment_no(), last_segment(), action_reps()}
action_reps() = [action_reply()]
failure() = {error, reason()}
reason() = transaction_reason() | segment_reason() | user_cancel_reason() | send_reason() | other_reason()
transaction_reason() = error_desc()
segment_reason() = {segment_no(), last_segment(), error_desc()}
other_reason() = timeout | {segment_timeout, missing_segments()} | exceeded_recv_pending_limit | term()
last_segment() = bool()
missing_segments() = [segment_no()]
user_cancel_reason() = {user_cancel, reason_for_user_cancel()}
reason_for_user_cancel() = term()
send_reason() = send_cancelled_reason() | send_failed_reason()
send_cancelled_reason() = {send_message_cancelled, reason_for_send_cancel()}
reason_for_send_cancel() = term()
send_failed_reason() = {send_message_failed, reason_for_send_failure()}
reason_for_send_failure() = term()
ReplyData = reply_data()
reply_data() = term()
Extra = term()
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 explicitely 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:
-
A list of 'ActionReply' records possibly containing
error indications.
-
A tuple of size three containing:
the segment number,
the last segment indicator and finally
a list of 'ActionReply' records possibly containing error
indications. This is ofcourse only possible if the
reply was segmented.
failure() indicates an local or external error and
can be one of the following:
-
A transaction_reason(), indicates that the remote
user has replied with an explicit transactionError.
-
A segment_reason(), indicates that the remote user
has replied with an explicit transactionError for this
segment. This is ofcourse only possible if the reply was
segmented.
-
A user_cancel_reason(), indicates that the request
has been canceled by the user. reason_for_user_cancel()
is the reason given in the call to the
cancel
function.
-
A send_reason(), indicates that the transport module
send_message
function did not send the message. The reason for this can be:
-
send_cancelled_reason() - the message sending was
deliberately cancelled. reason_for_send_cancel()
is the reason given in the cancel return
from the
send_message
function.
-
send_failed_reason() - an error occured while attempting to
send the message.
-
An other_reason(), indicates some other error such
as:
-
timeout - the reply failed to arrive before the
request timer expired.
-
{segment_timeout, missing_segments()} -
one or more segments
was not delivered before the expire of the segment
timer.
-
exceeded_recv_pending_limit - the pending
limit was exceeded for this request.
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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
AckStatus = ok | {error, reason()}
reason() = user_cancel_reason() | send_reason() | other_reason()
user_cancel_reason() = {user_cancel, reason_for_user_cancel()}
send_reason() = send_cancelled_reason() | send_failed_reason()
send_cancelled_reason() = {send_message_cancelled, reason_for_send_cancel()}
reason_for_send_cancel() = term()
send_failed_reason() = {send_message_failed, reason_for_send_failure()}
reason_for_send_failure() = term()
other_reason() = term()
AckData = ack_data()
ack_data() = term()
Extra = term()
Optionally invoked for a transaction acknowledgement
If this function gets invoked or not, is controlled by the
reply from the preceeding 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:
-
reply_timer
-
The reply_timer eventually times out.
-
reply send failure
-
When megaco failes to send the reply (see
handle_trans_reply),
for whatever reason.
-
cancel
-
The user has explicitly cancelled the wait
(megaco:cancel/2).
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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
Trans = #'TransactionPending'{} | #'TransactionReply'{} | #'TransactionResponseAck'{}
Extra = term()
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
it's 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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
TransNo = integer()
Pid = undefined | pid()
Extra = term()
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:
ConnHandle = conn_handle()
ProtocolVersion = protocol_version()
TransNo = integer()
SegNo = integer()
SegCompl = asn1_NOVALUE | 'NULL'
Extra = term()
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 3.10.1
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Ericsson AB