diff options
Diffstat (limited to 'lib/diameter')
| -rw-r--r-- | lib/diameter/doc/src/diameter_app.xml | 192 |
1 files changed, 112 insertions, 80 deletions
diff --git a/lib/diameter/doc/src/diameter_app.xml b/lib/diameter/doc/src/diameter_app.xml index 98c8b8c807..9d8a6568eb 100644 --- a/lib/diameter/doc/src/diameter_app.xml +++ b/lib/diameter/doc/src/diameter_app.xml @@ -112,7 +112,8 @@ and, for the call-specific callbacks, any extra arguments passed to <item> <p> A record containing the identities of -the local Diameter node and the remote Diameter peer having an established transport +the local Diameter node and the remote Diameter peer having an +established transport connection, as well as the capabilities as determined by capabilities exchange. Each field of the record is a 2-tuple consisting of @@ -168,13 +169,14 @@ Fields should not be set in return values except as documented.</p> <tag><c>peer_ref() = term()</c></tag> <item> <p> -A term identifying a transport connection with a Diameter peer. -Should be treated opaquely.</p> +A term identifying a transport connection with a Diameter peer.</p> </item> <marker id="peer"/> -<tag><c>peer() = {<seealso marker="#peer_ref">peer_ref()</seealso>, <seealso marker="#capabilities">capabilities()</seealso>}</c></tag> +<tag><c>peer() = + {<seealso marker="#peer_ref">peer_ref()</seealso>, + <seealso marker="#capabilities">capabilities()</seealso>}</c></tag> <item> <p> A tuple representing a Diameter peer connection.</p> @@ -219,10 +221,29 @@ process.</p> </type> <desc> <p> -Invoked when a transport connection has been established -and a successful capabilities exchange has indicated that the peer -supports the Diameter application of the application on which -the callback module in question has been configured.</p> +Invoked to signal the availability of a peer connection. +In particular, capabilities exchange with the peer has indicated +support for the application in question, the RFC 3539 watchdog state +machine for the connection has reached state <c>OKAY</c> and Diameter +messages can be both sent and received.</p> + +<note> +<p> +A watchdog state machine can reach state <c>OKAY</c> from state +<c>SUSPECT</c> without a new capabilities exchange taking place. +A new transport connection (and capabilities exchange) results in a +new peer_ref().</p> +</note> + +<note> +<p> +There is no requirement that a callback return before incoming +requests are received: <seealso +marker="#handle_request">handle_request/3</seealso> callbacks must be +handled independently of <seealso +marker="#peer_up">peer_up/3</seealso> and <seealso +marker="#peer_down">peer_down/3</seealso>.</p> +</note> <marker id="peer_down"/> </desc> @@ -238,36 +259,42 @@ the callback module in question has been configured.</p> </type> <desc> <p> -Invoked when a transport connection has been lost following a previous -call to <seealso marker="#peer_up">peer_up/3</seealso>.</p> +Invoked to signal that a peer connection is no longer available +following a previous call to <seealso +marker="#peer_up">peer_up/3</seealso>. +In particular, that the RFC 3539 watchdog state machine for the +connection has left state <c>OKAY</c> and the peer will no longer be a +candidate in <seealso marker="#pick_peer">pick_peer()</seealso> +callbacks.</p> <marker id="pick_peer"/> </desc> </func> <func> -<name>Mod:pick_peer(Candidates, Reserved, SvcName, State) - -> {ok, Peer} | {Peer, NewState} | false</name> +<name>Mod:pick_peer(Candidates, _Reserved, SvcName, State) + -> Selection | false</name> <fsummary>Select a target peer for an outgoing request.</fsummary> <type> <v>Candidates = [<seealso marker="#peer">peer()</seealso>]</v> -<v>Peer = <seealso marker="#peer">peer()</seealso> | false</v> <v>SvcName = <seealso marker="diameter#service_name">diameter:service_name()</seealso></v> <v>State = NewState = <seealso marker="#state">state()</seealso></v> +<v>Selection = {ok, Peer} | {Peer, NewState}</v> +<v>Peer = <seealso marker="#peer">peer()</seealso> | false</v> </type> <desc> <p> Invoked as a consequence of a call to <seealso marker="diameter#call">diameter:call/4</seealso> to select a destination -peer for an outgoing request, the return value indicating the selected -peer.</p> +peer for an outgoing request. +The return value indicates the selected peer.</p> <p> -The candidate peers list will only include those -which are selected by any <c>filter</c> option specified in the call to -<seealso marker="diameter#call">diameter:call/4</seealso>, and only -those which have indicated support for the Diameter application in -question. +The candidate list contains only those peers that have advertised +support for the Diameter application in question during capabilities +exchange, that have not be excluded by a <c>filter</c> option in +the call to <seealso marker="diameter#call">diameter:call/4</seealso> +and whose watchdog state machine is in the <c>OKAY</c> state. The order of the elements is unspecified except that any peers whose Origin-Host and Origin-Realm matches that of the outgoing request (in the sense of a <c>{filter, {all, [host, realm]}}</c> @@ -275,36 +302,40 @@ option to <seealso marker="diameter#call">diameter:call/4</seealso>) will be placed at the head of the list.</p> <p> -The return values <c>false</c> and <c>{false, State}</c> are -equivalent when callback state is mutable, as are -<c>{ok, Peer}</c> and <c>{Peer, State}</c>. -Returning a peer as <c>false</c> causes <c>{error, no_connection}</c> -to be returned from <seealso marker="diameter#call">diameter:call/4</seealso>. -Returning a <seealso marker="#peer">peer()</seealso> from an initial -pick_peer/4 callback will result in a -<seealso marker="#prepare_request">prepare_request/3</seealso> callback -followed by either <seealso -marker="#handle_answer">handle_answer/4</seealso> +A callback that returns a peer() will be followed by a +<seealso marker="#prepare_request">prepare_request/3</seealso> +callback and, if the latter indicates that the request should be sent, +by either <seealso marker="#handle_answer">handle_answer/4</seealso> or <seealso marker="#handle_error">handle_error/4</seealso> depending on whether or not an answer message is received from the peer. -If transport with the peer is lost before this then a new <seealso -marker="#pick_peer">pick_peer/4</seealso> callback takes place to -select an alternate peer.</p> - -<p> -Note that there is no guarantee that a <seealso +If the transport becomes unavailable after <seealso +marker="prepare_request">prepare_request/3</seealso> then a new <seealso +marker="#pick_peer">pick_peer/4</seealso> callback may take place to +failover to an alternate peer, after which <seealso +marker="#prepare_retransmit">prepare_retransmit/3</seealso> takes the +place of <seealso +marker="prepare_request">prepare_request/3</seealso> in resending the +request. +There is no guarantee that a <seealso marker="#pick_peer">pick_peer/4</seealso> callback to select -an alternate peer will be followed by any additional callbacks, only -that the initial <seealso -marker="#pick_peer">pick_peer/4</seealso> will be, since a +an alternate peer will be followed by any additional callbacks since a retransmission to an alternate peer is abandoned if an answer is received from a previously selected peer.</p> +<p> +Returning <c>false</c> or <c>{false, NewState}</c> causes <c>{error, +no_connection}</c> to be returned from <seealso +marker="diameter#call">diameter:call/4</seealso>.</p> + +<p> +The return values <c>false</c> and <c>{false, State}</c> (that is, +<c>NewState = State</c>) are equivalent, as are <c>{ok, Peer}</c> and +<c>{Peer, State}</c>.</p> + <note> <p> -<c>{Peer, NewState}</c> and its equivalents can only be returned if -the Diameter application in question was -configured with the <seealso +The return value <c>{Peer, NewState}</c> is only allowed if +the Diameter application in question was configured with the <seealso marker="diameter#application_opt">diameter:application_opt()</seealso> <c>{call_mutates_state, true}</c>. Otherwise, the <c>State</c> argument is always @@ -360,7 +391,7 @@ ignored.</p> <p> A returned <c>PostF</c> will be evaluated on any encoded <c>#diameter_packet{}</c> prior to transmission, the <c>bin</c> field -of this record containing the encoded binary. +containing the encoded binary. The return value is ignored.</p> <p> @@ -395,8 +426,9 @@ Invoked to return a request for encoding and retransmission. Has the same role as <seealso marker="#prepare_request">prepare_request/3</seealso> in the case that a peer connection is lost an an alternate peer selected but the -argument <seealso marker="#packet">packet()</seealso> is as returned by the initial -<c>prepare_request/3</c>.</p> +argument <seealso marker="#packet">packet()</seealso> is as returned +by the initial <seealso +marker="#prepare_request">prepare_request/3</seealso>.</p> <p> Returning <c>{discard, Reason}</c> causes the request to be aborted @@ -423,40 +455,41 @@ discarded}</c>.</p> <desc> <p> Invoked when an answer message is received from a peer. -The return value is returned from the call to <seealso -marker="diameter#call">diameter:call/4</seealso> for which the -callback takes place unless the <c>detach</c> option was -specified.</p> +The return value is returned from <seealso +marker="diameter#call">diameter:call/4</seealso> unless the +<c>detach</c> option was specified.</p> <p> -The decoded answer record is in the <c>msg</c> field of the argument -<seealso marker="#packet">packet()</seealso>, -the undecoded binary in the <c>packet</c> field. +The decoded answer record and undecoded binary are in the <c>msg</c> +and <c>bin</c> fields of the argument +<seealso marker="#packet">packet()</seealso> respectively. <c>Request</c> is the outgoing request message as was returned from <seealso marker="#prepare_request">prepare_request/3</seealso> or -<seealso marker="#prepare_retransmit">prepare_retransmit/3</seealso> -before the request was passed to the transport.</p> +<seealso + marker="#prepare_retransmit">prepare_retransmit/3</seealso>.</p> <p> For any given call to <seealso marker="diameter#call">diameter:call/4</seealso> there is at most one -call to the handle_answer callback of the application in question: any +<seealso marker="#handle_answer">handle_answer/4</seealso> callback: any duplicate answer (due to retransmission or otherwise) is discarded. -Similarly, only one of <c>handle_answer/4</c> or <c>handle_error/4</c> is -called for any given request.</p> +Similarly, only one of <seealso +marker="#handle_answer">handle_answer/4</seealso> or +<seealso marker="#handle_error">handle_error/4</seealso> is +called.</p> <p> By default, an incoming answer message that cannot be successfully -decoded causes the request process in question to fail, causing the -relevant call to <seealso -marker="diameter#call">diameter:call/4</seealso> -to return <c>{error, failure} (unless the <c>detach</c> option was -specified)</c>. -In particular, there is no <c>handle_error/4</c> callback in this +decoded causes the request process to fail, causing +<seealso marker="diameter#call">diameter:call/4</seealso> +to return <c>{error, failure}</c> unless the <c>detach</c> option was +specified. +In particular, there is no <seealso +marker="#handle_error">handle_error/4</seealso> callback in this case. -Application configuration may change this behaviour as described for -<seealso -marker="diameter#start_service">diameter:start_service/2</seealso>.</p> +The <seealso +marker="diameter#application_opt">diameter:application_opt()</seealso> +<c>answer_errors</c> can be set to change this behaviour.</p> <marker id="handle_error"/> </desc> @@ -474,21 +507,20 @@ marker="diameter#start_service">diameter:start_service/2</seealso>.</p> </type> <desc> <p> -Invoked when an error occurs before an answer message is received from -a peer in response to an outgoing request. -The return value is returned from the call to <seealso -marker="diameter#call">diameter:call/4</seealso> for which the -callback takes place (unless the <c>detach</c> option was -specified).</p> +Invoked when an error occurs before an answer message is received +in response to an outgoing request. +The return value is returned from <seealso +marker="diameter#call">diameter:call/4</seealso> unless the +<c>detach</c> option was specified.</p> <p> Reason <c>timeout</c> indicates that an answer message has not been -received within the required time. +received within the time specified with the corresponding <seealso +marker="diameter#call_opt">diameter:call_opt()</seealso>. Reason <c>failover</c> indicates that the transport connection to the peer to which the request has -been sent has been lost but that not alternate node was available, -possibly because a <seealso marker="#pick_peer">pick_peer/4</seealso> -callback returned false.</p> +been sent has become unavailable and that not alternate peer was +not selected.</p> <marker id="handle_request"/> </desc> @@ -504,8 +536,7 @@ callback returned false.</p> <v>Action = Reply | {relay, [Opt]} | discard - | {eval, Action, PostF} - | {eval_packet, Action, PostF}</v> + | {eval|eval_packet, Action, PostF}</v> <v>Reply = {reply, <seealso marker="#message">message()</seealso>} | {protocol_error, 3000..3999}</v> <v>Opt = <seealso marker="diameter#call_opt">diameter:call_opt()</seealso></v> @@ -624,7 +655,8 @@ causes the request to be answered with 3002 (DIAMETER_UNABLE_TO_DELIVER).</p> <tag><c>discard</c></tag> <item> <p> -Discard the request.</p> +Discard the request. +No answer message is sent to the peer.</p> </item> <tag><c>{eval, Action, PostF}</c></tag> @@ -640,7 +672,7 @@ The return value is ignored.</p> <p> Like <c>eval</c> but evaluate <c>PostF</c> on any encoded <c>#diameter_packet{}</c> prior to transmission, the <c>bin</c> field -of this record containing the encoded binary. +containing the encoded binary. The return value is ignored.</p> </item> |