sbroker behaviour (sbroker v1.1.1)
This module provides a process match making service. A process joins one of two queues and is matched with a process in the other queue. The queues are managed using sbroker_queue callback module per queue so that a different strategy can be used for both queues. Processes that die while in a queue are automatically removed to prevent matching with a process that is nolonger alive. A broker also uses an sbroker_meter callback module to monitor the queue and processing delays of the broker.
There are two functions to join a queue: ask/1 and ask_r/1. Processes that call ask/1 are matched against processes that call ask_r/1. If no match is immediately available a process is queued in the relevant queue until a match becomes available. If queue management is used processes may be dropped without a match.
Processes calling ask/1 try to match with/dequeue a process in the ask_r queue. If no process exists they are queued in the ask queue and await a process to call ask_r/1.
Similarly processes calling ask_r/1 try to match with/dequeue a process in the ask queue. If no process exists they are queued in the ask_r queue and await a process to call ask/1.
A broker requires a callback module. The callback modules implements one callback, init/1, with single argument Args. init/1 should return {ok, {AskQueueSpec, AskRQueueSpec, [MeterSpec]}) or ignore. AskQueueSpec is the queue specification for the ask queue, AskRQueueSpec is the queue specification for the ask_r queue and MeterSpec is a meter specification. There can any number of meters but a meter module can only be included once. In the case of ignore the broker is not started and start_link returns ignore. As the callback modules are defined in the init/1 callback a broker supports the dynamic modules supervisor child specification.
Both queue and meter specifcations take the form: {Module, Args}. Module is the callback module and Args are its arguments.
For example:
-module(sbroker_example).
-behaviour(sbroker).
-export([start_link/0]).
-export([ask/0]).
-export([ask_r/1]).
-export([init/1]).
start_link() ->
sbroker:start_link({local, ?MODULE}, ?MODULE, [], []).
ask() ->
sbroker:ask(?MODULE).
ask_r() ->
sbroker:ask_r(?MODULE).
init([]) ->
AskQueueSpec = {sbroker_codel_queue, #{}},
AskRQueueSpec = {sbroker_timeout_queue, #{}},
MeterSpec = {sbroker_overload_meter, #{alarm => {overload, ?MODULE}}},
{ok, {AskQueueSpec, AskRQueueSpec, [MeterSpec]}}.Link to this section Summary
Functions
Equivalent to ask(Broker, self()).
Send a match request, with value ReqValue, to try to match with a process calling ask_r/2 on the broker, Broker.
Equivalent to ask_r(Broker, self()).
ask/2 on the same broker.See also: ask/2.
Equivalent to async_ask(Broker, self()).
Monitors the broker and sends an asynchronous request to match with a process calling ask_r/2. Returns {await, Tag, Pid} or {drop, 0}.
Sends an asynchronous request to match with a process calling ask_r/2. Returns {await, Tag, Pid}.
Equivalent to async_ask_r(Broker, self()).
ask/2.See also: async_ask/2, cancel/2.
ask/2.See also: async_ask/3, cancel/2.
Await the response to an asynchronous request identified by Tag.
Equivalent to cancel(Broker, Tag, infinity).
false if no requests exist. In the later case a caller may wish to check its message queue for an existing reply.See also: async_ask/1, async_ask_r/1.
Equivalent to change_config(Broker, infinity).
Change the configuration of the broker. Returns ok on success and {error, Reason} on failure, where Reason, is the reason for failure.
Cancels an asynchronous request.
Equivalent to dynamic_ask(Broker, self()).
Tries to match with a process calling ask_r/2 on the same broker. If no immediate match available the request is converted to an async_ask/2.
Equivalent to dynamic_ask_r(Broker, self()).
ask/2 on the same broker. If no immediate match available the request is converted to an async_ask_r/2.See also: dynamic_ask/2.
Equivalent to len(Broker, infinity).
ask queue in the broker, Broker.Equivalent to len_r(Broker, infinity).
ask_r queue in the broker, Broker.Equivalent to nb_ask(Broker, self()).
Tries to match with a process calling ask_r/2 on the same broker but does not enqueue the request if no immediate match. Returns {go, Ref, Value, RelativeTime, SojournTime} on a successful match or {drop, SojournTime}.
Equivalent to nb_ask_r(Broker, self()).
ask/2 on the same broker but does not enqueue the request if no immediate match.See also: nb_ask/2.
Starts a broker with callback module Module and argument Args, and broker options Opts.
Name, callback module Module and argument Args, and broker options Opts.See also: start_link/3.
Link to this section Types
broker/0
Specs
broker() :: pid() | atom() | {atom(), node()} | {global, any()} | {via, module(), any()}.
debug_option/0
Specs
debug_option() ::
trace | log |
{log, pos_integer()} |
statistics |
{log_to_file, file:filename()} |
{install, {fun(), any()}}.
handler_spec/0
Specs
handler_spec() :: {module(), any()}.
name/0
Specs
name() :: {local, atom()} | {global, any()} | {via, module(), any()}.
start_option/0
Specs
start_option() ::
{debug, debug_option()} |
{timeout, timeout()} |
{spawn_opt, [proc_lib:spawn_option()]} |
{read_time_after, non_neg_integer() | infinity}.
start_return/0
Specs
start_return() :: {ok, pid()} | ignore | {error, any()}.
Link to this section Callbacks
init/1
Specs
init(Args :: any()) ->
{ok,
{AskQueueSpec :: handler_spec(),
AskRQueueSpec :: handler_spec(),
[MeterSpec :: handler_spec()]}} |
ignore.
Link to this section Functions
ask(Broker)
Specs
ask(Broker) -> Go | Drop
when
Broker :: broker(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
Equivalent to ask(Broker, self()).
ask(Broker, ReqValue)
Specs
ask(Broker, ReqValue) -> Go | Drop
when
Broker :: broker(),
ReqValue :: any(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
Send a match request, with value ReqValue, to try to match with a process calling ask_r/2 on the broker, Broker.
Returns {go, Ref, Value, RelativeTime, SojournTime} on a successful match or {drop, SojournTime}. value of the matched request sent by the counterparty process. RelativeTime is the approximate time differnece (in the broker's time unit) between when the request was sent and the matching request was sent. SojournTime is the approximate time spent in both the broker's message queue and internal queue.
RelativeTime represents the SojournTime without the overhead of the broker. The value measures the level of queue congestion without being effected by the load of the broker.
If RelativeTime is positive, the request was enqueued in the internal queue awaiting a match with another request sent approximately RelativeTime after this request was sent. Therefore SojournTime minus RelativeTime is the latency, or overhead, of the broker.
If RelativeTime is negative, the request dequeued a request in the internal queue that was sent approximately RelativeTime before this request was sent. Therefore SojournTime is the latency, or overhead, of the broker.
If RelativeTime is 0, the request was matched with a request sent at approximately the same time. Therefore SojournTime is the latency, or overhead, of the broker.
The sojourn time for matched process can be approximated by SojournTime minus RelativeTime.
via module sprotector returns {drop, 0} and does not send the request.
ask_r(Broker)
Specs
ask_r(Broker) -> Go | Drop
when
Broker :: broker(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
Equivalent to ask_r(Broker, self()).
ask_r(Broker, ReqValue)
Specs
ask_r(Broker, ReqValue) -> Go | Drop
when
Broker :: broker(),
ReqValue :: any(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
ask/2 on the same broker.See also: ask/2.
async_ask(Broker)
Specs
async_ask(Broker) -> {await, Tag, Process} | {drop, 0}
when Broker :: broker(), Tag :: reference(), Process :: pid() | {atom(), node()}.
Equivalent to async_ask(Broker, self()).
async_ask(Broker, ReqValue)
Specs
async_ask(Broker, ReqValue) -> {await, Tag, Process} | {drop, 0}
when
Broker :: broker(),
ReqValue :: any(),
Tag :: reference(),
Process :: pid() | {atom(), node()}.
Monitors the broker and sends an asynchronous request to match with a process calling ask_r/2. Returns {await, Tag, Pid} or {drop, 0}.
Tag is a monitor reference() that uniquely identifies the reply containing the result of the request. Process, is the pid() of the monitored broker or {atom(), node()} if the broker is registered locally in another node. To cancel the request call cancel(Process, Tag).
The reply is of the form {Tag, {go, Ref, Value, RelativeTime, SojournTime} or {Tag, {drop, SojournTime}}.
Ref is the transaction reference, which is a reference(). Value is the value of the matched process. RelativeTime is the time spent waiting for a match after discounting time spent waiting for the broker to handle requests. SojournTime is the time spent in the broker's message queue.
Multiple asynchronous requests can be made from a single process to a broker and no guarantee is made of the order of replies. A process making multiple requests can reuse the monitor reference for subsequent requests to the same broker process (Process) using async_ask/3.
via module sprotector returns {drop, 0} and does not send the request.See also: async_ask/3, cancel/2.
async_ask(Broker, ReqValue, To)
Specs
async_ask(Broker, ReqValue, To) -> {await, Tag, Process} | {drop, 0}
when
Broker :: broker(),
ReqValue :: any(),
To :: {Pid, Tag},
Pid :: pid(),
Tag :: any(),
Process :: pid() | {atom(), node()}.
Sends an asynchronous request to match with a process calling ask_r/2. Returns {await, Tag, Pid}.
To is a tuple containing the process, pid(), to send the reply to and Tag, any(), that identifies the reply containing the result of the request. Process is the pid() of the broker or {atom(), node()} if the broker is registered locally on a different node. To cancel all requests identified by Tag on broker Process call cancel(Process, Tag).
The reply is of the form {Tag, {go, Ref, Value, RelativeTime, SojournTime} or {Tag, {drop, SojournTime}}.
Ref is the transaction reference, which is a reference(). Value is the value of the matched process. RelativeTime is the time spent waiting for a match after discounting time spent waiting for the broker to handle requests. SojournTime is the time spent in the broker's message queue.
Multiple asynchronous requests can be made from a single process to a broker and no guarantee is made of the order of replies. If the broker exits or is on a disconnected node there is no guarantee of a reply and so the caller should take appropriate steps to handle this scenario.
If the request is dropped when usingvia module sprotector, returns {drop, 0} and does not send the request.See also: cancel/2.
async_ask_r(Broker)
Specs
async_ask_r(Broker) -> {await, Tag, Process} | {drop, 0}
when Broker :: broker(), Tag :: reference(), Process :: pid() | {atom(), node()}.
Equivalent to async_ask_r(Broker, self()).
async_ask_r(Broker, ReqValue)
Specs
async_ask_r(Broker, ReqValue) -> {await, Tag, Process} | {drop, 0}
when
Broker :: broker(),
ReqValue :: any(),
Tag :: reference(),
Process :: pid() | {atom(), node()}.
ask/2.See also: async_ask/2, cancel/2.
async_ask_r(Broker, ReqValue, To)
Specs
async_ask_r(Broker, ReqValue, To) -> {await, Tag, Process} | {drop, 0}
when
Broker :: broker(),
ReqValue :: any(),
To :: {Pid, Tag},
Pid :: pid(),
Tag :: any(),
Process :: pid() | {atom(), node()}.
ask/2.See also: async_ask/3, cancel/2.
await(Tag, Timeout)
Specs
await(Tag, Timeout) -> Go | Drop
when
Tag :: any(),
Timeout :: timeout(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
Await the response to an asynchronous request identified by Tag.
Exits if a response is not received after Timeout milliseconds.
DOWN message is received with the reference Tag.See also: async_ask/2, async_ask_r/2.
cancel(Broker, Tag)
Specs
cancel(Broker, Tag) -> Count | false when Broker :: broker(), Tag :: any(), Count :: pos_integer().
Equivalent to cancel(Broker, Tag, infinity).
cancel(Broker, Tag, Timeout)
Specs
cancel(Broker, Tag, Timeout) -> Count | false
when Broker :: broker(), Tag :: any(), Timeout :: timeout(), Count :: pos_integer().
false if no requests exist. In the later case a caller may wish to check its message queue for an existing reply.See also: async_ask/1, async_ask_r/1.
change_config(Broker)
Specs
change_config(Broker) -> ok | {error, Reason} when Broker :: broker(), Reason :: any().
Equivalent to change_config(Broker, infinity).
change_config(Broker, Timeout)
Specs
change_config(Broker, Timeout) -> ok | {error, Reason}
when Broker :: broker(), Timeout :: timeout(), Reason :: any().
Change the configuration of the broker. Returns ok on success and {error, Reason} on failure, where Reason, is the reason for failure.
init/1 callback to get the new configuration. If init/1 returns ignore the config does not change.
dirty_cancel(Broker, Tag)
Specs
dirty_cancel(Broker, Tag) -> ok when Broker :: broker(), Tag :: any().
Cancels an asynchronous request.
Returnsok without waiting for the broker to cancel requests.See also: cancel/3.
dynamic_ask(Broker)
Specs
dynamic_ask(Broker) -> Go | Await | Drop
when
Broker :: broker(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: 0 | neg_integer(),
SojournTime :: non_neg_integer(),
Await :: {await, Tag, Pid},
Tag :: reference(),
Pid :: pid(),
Drop :: {drop, SojournTime}.
Equivalent to dynamic_ask(Broker, self()).
dynamic_ask(Broker, ReqValue)
Specs
dynamic_ask(Broker, ReqValue) -> Go | Await | Drop
when
Broker :: broker(),
ReqValue :: any(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: 0 | neg_integer(),
SojournTime :: non_neg_integer(),
Await :: {await, Tag, Pid},
Tag :: reference(),
Pid :: pid(),
Drop :: {drop, SojournTime}.
Tries to match with a process calling ask_r/2 on the same broker. If no immediate match available the request is converted to an async_ask/2.
Returns {go, Ref, Value, RelativeTime, SojournTime} on a successful match or {await, Tag, BrokerPid}.
Ref is the transaction reference, which is a reference(). Value is the value of the matched process. RelativeTime is the time spent waiting for a match after discounting time spent waiting for the broker to handle requests. SojournTime is the time spent in the broker's message queue. Tag is a monitor reference and BrokerPid the pid() of the broker, as returned by async_ask/2.
via module sprotector returns {drop, 0} and does not send the request.See also: async_ask/2, nb_ask/2.
dynamic_ask_r(Broker)
Specs
dynamic_ask_r(Broker) -> Go | Await | Drop
when
Broker :: broker(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: 0 | neg_integer(),
SojournTime :: non_neg_integer(),
Await :: {await, Tag, Pid},
Tag :: reference(),
Pid :: pid(),
Drop :: {drop, SojournTime}.
Equivalent to dynamic_ask_r(Broker, self()).
dynamic_ask_r(Broker, ReqValue)
Specs
dynamic_ask_r(Broker, ReqValue) -> Go | Await | Drop
when
Broker :: broker(),
ReqValue :: any(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: 0 | neg_integer(),
SojournTime :: non_neg_integer(),
Await :: {await, Tag, Pid},
Tag :: reference(),
Pid :: pid(),
Drop :: {drop, SojournTime}.
ask/2 on the same broker. If no immediate match available the request is converted to an async_ask_r/2.See also: dynamic_ask/2.
len(Broker)
Specs
len(Broker) -> Length when Broker :: broker(), Length :: non_neg_integer().
Equivalent to len(Broker, infinity).
len(Broker, Timeout)
Specs
len(Broker, Timeout) -> Length
when Broker :: broker(), Timeout :: timeout(), Length :: non_neg_integer().
ask queue in the broker, Broker.
len_r(Broker)
Specs
len_r(Broker) -> Length when Broker :: broker(), Length :: non_neg_integer().
Equivalent to len_r(Broker, infinity).
len_r(Broker, Timeout)
Specs
len_r(Broker, Timeout) -> Length
when Broker :: broker(), Timeout :: timeout(), Length :: non_neg_integer().
ask_r queue in the broker, Broker.
nb_ask(Broker)
Specs
nb_ask(Broker) -> Go | Drop
when
Broker :: broker(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: 0 | neg_integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
Equivalent to nb_ask(Broker, self()).
nb_ask(Broker, ReqValue)
Specs
nb_ask(Broker, ReqValue) -> Go | Drop
when
Broker :: broker(),
ReqValue :: any(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: 0 | neg_integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
Tries to match with a process calling ask_r/2 on the same broker but does not enqueue the request if no immediate match. Returns {go, Ref, Value, RelativeTime, SojournTime} on a successful match or {drop, SojournTime}.
Ref is the transaction reference, which is a reference(). Value is the value of the matched process. RelativeTime is the time spent waiting for a match after discounting time spent waiting for the broker to handle requests. SojournTime is the time spent in the broker's message queue.
via module sprotector returns {drop, 0} and does not send the request.See also: ask/2.
nb_ask_r(Broker)
Specs
nb_ask_r(Broker) -> Go | Drop
when
Broker :: broker(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: 0 | neg_integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
Equivalent to nb_ask_r(Broker, self()).
nb_ask_r(Broker, ReqValue)
Specs
nb_ask_r(Broker, ReqValue) -> Go | Drop
when
Broker :: broker(),
ReqValue :: any(),
Go :: {go, Ref, Value, RelativeTime, SojournTime},
Ref :: reference(),
Value :: any(),
RelativeTime :: 0 | neg_integer(),
SojournTime :: non_neg_integer(),
Drop :: {drop, SojournTime}.
ask/2 on the same broker but does not enqueue the request if no immediate match.See also: nb_ask/2.
start_link(Module, Args, Opts)
Specs
start_link(Module, Args, Opts) -> StartReturn
when
Module :: module(),
Args :: any(),
Opts :: [start_option()],
StartReturn :: start_return().
Starts a broker with callback module Module and argument Args, and broker options Opts.
Opts is a proplist and supports debug, timeout and spawn_opt used by gen_server and gen_fsm. read_time_after sets the number of requests when a cached time is stale and the time is read again. Its value is non_neg_integer() or infinity and defaults to 16.See also: gen_server:start_link/3.
start_link(Name, Module, Args, Opts)
Specs
start_link(Name, Module, Args, Opts) -> StartReturn
when
Name :: name(),
Module :: module(),
Args :: any(),
Opts :: [start_option()],
StartReturn :: start_return().
Name, callback module Module and argument Args, and broker options Opts.See also: start_link/3.
timeout(Broker)
Specs
timeout(Broker) -> ok when Broker :: broker().