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authorLoïc Hoguin <[email protected]>2014-09-30 20:12:13 +0300
committerLoïc Hoguin <[email protected]>2014-09-30 20:12:13 +0300
commit0dc063ab7d94edb37c61f821b5d8e4c2da7f8ff1 (patch)
treeaaa71b552b0348fc403cc68ba8318e58f213d4fd /doc/src/manual
parent5ce4c2bfb40ecc4b687a2941e612025a1c4ff913 (diff)
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Improve handler interface and documentation
This change simplifies a little more the sub protocols mechanism. Aliases have been removed. The renaming of loop handlers as long polling handlers has been reverted. Plain HTTP handlers now simply do their work in the init/2 callback. There is no specific code for them. Loop handlers now follow the same return value as Websocket, they use ok to continue and shutdown to stop. Terminate reasons for all handler types have been documented. The terminate callback is now appropriately called in all cases (or should be). Behaviors for all handler types have been moved in the module that implement them. This means that cowboy_handler replaces the cowboy_http_handler behavior, and similarly cowboy_loop replaces cowboy_loop_handler, cowboy_websocket replaces cowboy_websocket_handler. Finally cowboy_rest now has the start of a behavior in it and will have the full list of optional callbacks defined once Erlang 18.0 gets released. The guide has been reorganized and should be easier to follow.
Diffstat (limited to 'doc/src/manual')
-rw-r--r--doc/src/manual/cowboy_handler.ezdoc88
-rw-r--r--doc/src/manual/cowboy_http_handler.ezdoc57
-rw-r--r--doc/src/manual/cowboy_loop.ezdoc100
-rw-r--r--doc/src/manual/cowboy_loop_handler.ezdoc91
-rw-r--r--doc/src/manual/cowboy_rest.ezdoc56
-rw-r--r--doc/src/manual/cowboy_websocket.ezdoc133
-rw-r--r--doc/src/manual/cowboy_websocket_handler.ezdoc133
-rw-r--r--doc/src/manual/index.ezdoc4
8 files changed, 336 insertions, 326 deletions
diff --git a/doc/src/manual/cowboy_handler.ezdoc b/doc/src/manual/cowboy_handler.ezdoc
index 0495f28..b440b60 100644
--- a/doc/src/manual/cowboy_handler.ezdoc
+++ b/doc/src/manual/cowboy_handler.ezdoc
@@ -15,10 +15,96 @@ Environment output:
* result = ok
+This module also defines the `cowboy_handler` behaviour that
+defines the basic interface for handlers. All Cowboy handlers
+implement at least the `init/2` callback, and may implement
+the `terminate/3` callback optionally.
+
:: Types
None.
+:: Terminate reasons
+
+The following values may be received as the terminate reason
+in the optional `terminate/3` callback. Different handler types
+may define additional terminate reasons.
+
+: normal
+
+The connection was closed normally.
+
+: {crash, Class, Reason}
+
+A crash occurred in the handler. `Class` and `Reason` can be
+used to obtain more information about the crash. The function
+`erlang:get_stacktrace/0` can also be called to obtain the
+stacktrace of the process when the crash occurred.
+
+:: Callbacks
+
+: init(Req, Opts)
+ -> {ok, Req, State}
+ | {Module, Req, State}
+ | {Module, Req, State, hibernate}
+ | {Module, Req, State, Timeout}
+ | {Module, Req, State, Timeout, hibernate}
+
+Types:
+
+* Req = cowboy_req:req()
+* Opts = any()
+* State = any()
+* Module = module()
+* Timeout = timeout()
+
+Process the request.
+
+This function can be used to switch to an alternate handler
+type by returning the name of the module to be used, along
+with a few options.
+
+For basic handlers this is the function where the response
+should be sent. If no response is sent, Cowboy will ensure
+that a `204 No Content` response is sent.
+
+A crash in this callback will result in `terminate/3` being
+called if it is defined, with the `State` argument set to
+the value of `Opts` originally given to the `init/2` callback.
+
+: terminate(Reason, Req, State) -> ok
+
+Types:
+
+* Reason = any()
+* Req = cowboy_req:req()
+* State = any()
+
+Perform any necessary cleanup of the state.
+
+This callback should release any resource currently in use,
+clear any active timer and reset the process to its original
+state, as it might be reused for future requests sent on the
+same connection. Typical plain HTTP handlers rarely need to
+use it.
+
+A crash in this callback or an invalid return value will
+result in the closing of the connection and the termination
+of the process.
+
:: Exports
-None.
+: terminate(Reason, Req, State, Handler) -> ok
+
+Types:
+
+* Reason = any()
+* Req = cowboy_req:req()
+* State = any()
+* Handler = module()
+
+Call the optional `terminate/3` callback if it exists.
+
+This function should always be called at the end of the execution
+of a handler, to give it a chance to clean up or perform
+miscellaneous operations.
diff --git a/doc/src/manual/cowboy_http_handler.ezdoc b/doc/src/manual/cowboy_http_handler.ezdoc
deleted file mode 100644
index 6776598..0000000
--- a/doc/src/manual/cowboy_http_handler.ezdoc
+++ /dev/null
@@ -1,57 +0,0 @@
-::: cowboy_http_handler
-
-The `cowboy_http_handler` behaviour defines the interface used
-by plain HTTP handlers.
-
-Unless noted otherwise, the callbacks will be executed sequentially.
-
-:: Types
-
-None.
-
-:: Callbacks
-
-: init({TransportName, ProtocolName}, Req, Opts)
- -> {ok, Req, State} | {shutdown, Req, State}
-
-Types:
-
-* TransportName = tcp | ssl | atom()
-* ProtocolName = http | atom()
-* Req = cowboy_req:req()
-* Opts = any()
-* State = any()
-
-Initialize the state for this request.
-
-The `shutdown` return value can be used to skip the `handle/2`
-call entirely.
-
-: handle(Req, State) -> {ok, Req, State}
-
-Types:
-
-* Req = cowboy_req:req()
-* State = any()
-
-Handle the request.
-
-This callback is where the request is handled and a response
-should be sent. If a response is not sent, Cowboy will send
-a `204 No Content` response automatically.
-
-: terminate(Reason, Req, State) -> ok
-
-Types:
-
-* Reason = {normal, shutdown} | {error, atom()}
-* Req = cowboy_req:req()
-* State = any()
-
-Perform any necessary cleanup of the state.
-
-This callback should release any resource currently in use,
-clear any active timer and reset the process to its original
-state, as it might be reused for future requests sent on the
-same connection. Typical plain HTTP handlers rarely need to
-use it.
diff --git a/doc/src/manual/cowboy_loop.ezdoc b/doc/src/manual/cowboy_loop.ezdoc
new file mode 100644
index 0000000..1f3ab9e
--- /dev/null
+++ b/doc/src/manual/cowboy_loop.ezdoc
@@ -0,0 +1,100 @@
+::: cowboy_loop
+
+The `cowboy_loop` module implements a handler interface for
+long running HTTP connections. It is the recommended interface
+for long polling and server-sent events, amongst others.
+
+This module is a sub protocol that defines three callbacks to
+be implemented by handlers. The `init/2` and `terminate/3`
+callbacks are common to all handler types and are documented
+in the manual for the ^cowboy_handler module.
+
+The `info/3` callback is specific to loop handlers and will be
+called as many times as necessary until a reply is sent.
+
+It is highly recommended to return a timeout value from the
+`init/2` callback to ensure that the process is terminated
+when no data has been received during that timespan. The
+default timeout is `infinity`, which should only be used if
+you have alternate means of ending inactive connections.
+
+:: Types
+
+None.
+
+:: Terminate reasons
+
+The following values may be received as the terminate reason
+in the optional `terminate/3` callback.
+
+: normal
+
+The connection was closed normally before switching to the
+loop sub protocol. This typically happens if an `ok` tuple is
+returned from the `init/2` callback.
+
+: shutdown
+
+The handler requested to close the connection by returning
+a `shutdown` tuple.
+
+: timeout
+
+The connection has been closed due to inactivity. The timeout
+value can be configured from `init/2`. The response sent when
+this happens is a `204 No Content`.
+
+: {crash, Class, Reason}
+
+A crash occurred in the handler. `Class` and `Reason` can be
+used to obtain more information about the crash. The function
+`erlang:get_stacktrace/0` can also be called to obtain the
+stacktrace of the process when the crash occurred.
+
+: {error, overflow}
+
+The connection is being closed and the process terminated
+because the buffer Cowboy uses to keep data sent by the
+client has reached its maximum. The buffer size can be
+configured through the environment value `loop_max_buffer`
+and defaults to 5000 bytes.
+
+If the long running request comes with a body it is recommended
+to process this body before switching to the loop sub protocol.
+
+: {error, closed}
+
+The socket has been closed brutally without a close frame being
+received first.
+
+: {error, Reason}
+
+A socket error ocurred.
+
+:: Callbacks
+
+: info(Info, Req, State)
+ -> {ok, Req, State}
+ | {ok, Req, State, hibernate}
+ | {shutdown, Req, State}
+
+Types:
+
+* Info = any()
+* Req = cowboy_req:req()
+* State = any()
+
+Handle the Erlang message received.
+
+This function will be called every time an Erlang message
+has been received. The message can be any Erlang term.
+
+The `shutdown` return value can be used to stop the receive loop,
+typically because a response has been sent.
+
+The `hibernate` option will hibernate the process until
+it receives another message.
+
+:: Exports
+
+None.
diff --git a/doc/src/manual/cowboy_loop_handler.ezdoc b/doc/src/manual/cowboy_loop_handler.ezdoc
deleted file mode 100644
index 0811a9a..0000000
--- a/doc/src/manual/cowboy_loop_handler.ezdoc
+++ /dev/null
@@ -1,91 +0,0 @@
-::: cowboy_loop_handler
-
-The `cowboy_loop_handler` behaviour defines the interface used
-by HTTP handlers that do not send a response directly, instead
-requiring a receive loop to process Erlang messages.
-
-This interface is best fit for long-polling types of requests.
-
-The `init/3` callback will always be called, followed by zero
-or more calls to `info/3`. The `terminate/3` callback will
-always be called last.
-
-:: Types
-
-None.
-
-:: Callbacks
-
-: init({TransportName, ProtocolName}, Req, Opts)
- -> {loop, Req, State}
- | {loop, Req, State, hibernate}
- | {loop, Req, State, Timeout}
- | {loop, Req, State, Timeout, hibernate}
- | {shutdown, Req, State}
-
-Types:
-
-* TransportName = tcp | ssl | atom()
-* ProtocolName = http | atom()
-* Req = cowboy_req:req()
-* Opts = any()
-* State = any()
-* Timeout = timeout()
-
-Initialize the state for this request.
-
-This callback will typically be used to register this process
-to an event manager or a message queue in order to receive
-the messages the handler wants to process.
-
-The receive loop will run for a duration of up to `Timeout`
-milliseconds after it last received data from the socket,
-at which point it will stop and send a `204 No Content` reply.
-By default this value is set to `infinity`. It is recommended
-to either set this value or ensure by any other mechanism
-that the handler will be closed after a certain period of
-inactivity.
-
-The `hibernate` option will hibernate the process until it
-starts receiving messages.
-
-The `shutdown` return value can be used to skip the receive
-loop entirely.
-
-: info(Info, Req, State) -> {ok, Req, State} | {loop, Req, State}
- | {loop, Req, State, hibernate}
-
-Types:
-
-* Info = any()
-* Req = cowboy_req:req()
-* State = any()
-
-Handle the Erlang message received.
-
-This function will be called every time an Erlang message
-has been received. The message can be any Erlang term.
-
-The `ok` return value can be used to stop the receive loop,
-typically because a response has been sent.
-
-The `hibernate` option will hibernate the process until
-it receives another message.
-
-: terminate(Reason, Req, State) -> ok
-
-Types:
-
-* Reason = {normal, shutdown} | {normal, timeout} | {error, closed} | {error, overflow} | {error, atom()}
-* Req = cowboy_req:req()
-* State = any()
-
-Perform any necessary cleanup of the state.
-
-This callback will typically unregister from any event manager
-or message queue it registered to in `init/3`.
-
-This callback should release any resource currently in use,
-clear any active timer and reset the process to its original
-state, as it might be reused for future requests sent on the
-same connection.
diff --git a/doc/src/manual/cowboy_rest.ezdoc b/doc/src/manual/cowboy_rest.ezdoc
index 9fe5c77..f128a22 100644
--- a/doc/src/manual/cowboy_rest.ezdoc
+++ b/doc/src/manual/cowboy_rest.ezdoc
@@ -3,12 +3,13 @@
The `cowboy_rest` module implements REST semantics on top of
the HTTP protocol.
-This module cannot be described as a behaviour due to most of
-the callbacks it defines being optional. It has the same
-semantics as a behaviour otherwise.
+This module is a sub protocol that defines many callbacks
+be implemented by handlers. The `init/2` and `terminate/3`
+callbacks are common to all handler types and are documented
+in the manual for the ^cowboy_handler module.
-The only mandatory callback is `init/3`, needed to perform
-the protocol upgrade.
+All other callbacks are optional, though some may become
+required depending on the return value of previous callbacks.
:: Types
@@ -43,46 +44,23 @@ The media-type is the content-type, excluding the charset.
This value is always defined after the call to
`content_types_provided/2`.
-:: Callbacks
-
-: init({TransportName, ProtocolName}, Req, Opts)
- -> {upgrade, protocol, cowboy_rest}
- | {upgrade, protocol, cowboy_rest, Req, Opts}
-
-Types:
-
-* TransportName = tcp | ssl | atom()
-* ProtocolName = http | atom()
-* Req = cowboy_req:req()
-* Opts = any()
-
-Upgrade the protocol to `cowboy_rest`.
-
-This is the only mandatory callback.
-
-: rest_init(Req, Opts) -> {ok, Req, State}
+:: Terminate reasons
-Types:
+The following values may be received as the terminate reason
+in the optional `terminate/3` callback.
-* Req = cowboy_req:req()
-* Opts = any()
-* State = any()
+: normal
-Initialize the state for this request.
+The connection was closed normally.
-: rest_terminate(Req, State) -> ok
+: {crash, Class, Reason}
-Types:
+A crash occurred in the handler. `Class` and `Reason` can be
+used to obtain more information about the crash. The function
+`erlang:get_stacktrace/0` can also be called to obtain the
+stacktrace of the process when the crash occurred.
-* Req = cowboy_req:req()
-* State = any()
-
-Perform any necessary cleanup of the state.
-
-This callback should release any resource currently in use,
-clear any active timer and reset the process to its original
-state, as it might be reused for future requests sent on the
-same connection.
+:: Callbacks
: Callback(Req, State) -> {Value, Req, State} | {halt, Req, State}
diff --git a/doc/src/manual/cowboy_websocket.ezdoc b/doc/src/manual/cowboy_websocket.ezdoc
index 59a6248..889ddd7 100644
--- a/doc/src/manual/cowboy_websocket.ezdoc
+++ b/doc/src/manual/cowboy_websocket.ezdoc
@@ -2,8 +2,25 @@
The `cowboy_websocket` module implements the Websocket protocol.
-The callbacks for websocket handlers are defined in the manual
-for the `cowboy_websocket_handler` behaviour.
+This module is a sub protocol that defines four callbacks to
+be implemented by handlers. The `init/2` and `terminate/3`
+callbacks are common to all handler types and are documented
+in the manual for the ^cowboy_handler module.
+
+The `websocket_handle/3` and `websocket_info/3` callbacks are
+specific to Websocket handlers and will be called as many times
+as necessary until the Websocket connection is closed.
+
+The `init/2` callback can be used to negotiate Websocket protocol
+extensions with the client. It is highly recommended to return a
+timeout value from this callback to ensure that the process is
+terminated when no data has been received during that timespan.
+The default timeout is `infinity`, which should only be used if
+you have alternate means of ending inactive connections.
+
+Cowboy will terminate the process right after closing the
+Websocket connection. This means that there is no real need to
+perform any cleanup in the optional `terminate/3` callback.
:: Types
@@ -31,6 +48,118 @@ Type: 7 | 8 | 13
The version of the Websocket protocol being used.
+:: Terminate reasons
+
+The following values may be received as the terminate reason
+in the optional `terminate/3` callback.
+
+: normal
+
+The connection was closed normally before establishing a Websocket
+connection. This typically happens if an `ok` tuple is returned
+from the `init/2` callback.
+
+: remote
+
+The remote endpoint closed the connection without giving any
+further details.
+
+: {remote, Code, Payload}
+
+The remote endpoint closed the connection with the given
+`Code` and `Payload` as the reason.
+
+: shutdown
+
+The handler requested to close the connection, either by returning
+a `shutdown` tuple or by sending a `close` frame.
+
+: timeout
+
+The connection has been closed due to inactivity. The timeout
+value can be configured from `init/2`.
+
+: {crash, Class, Reason}
+
+A crash occurred in the handler. `Class` and `Reason` can be
+used to obtain more information about the crash. The function
+`erlang:get_stacktrace/0` can also be called to obtain the
+stacktrace of the process when the crash occurred.
+
+: {error, badencoding}
+
+A text frame was sent by the client with invalid encoding. All
+text frames must be valid UTF-8.
+
+: {error, badframe}
+
+A protocol error has been detected.
+
+: {error, closed}
+
+The socket has been closed brutally without a close frame being
+received first.
+
+: {error, Reason}
+
+A socket error ocurred.
+
+:: Callbacks
+
+: websocket_handle(InFrame, Req, State)
+ -> {ok, Req, State}
+ | {ok, Req, State, hibernate}
+ | {reply, OutFrame | [OutFrame], Req, State}
+ | {reply, OutFrame | [OutFrame], Req, State, hibernate}
+ | {shutdown, Req, State}
+
+Types:
+
+* InFrame = {text | binary | ping | pong, binary()}
+* Req = cowboy_req:req()
+* State = any()
+* OutFrame = frame()
+
+Handle the data received from the Websocket connection.
+
+This function will be called every time data is received
+from the Websocket connection.
+
+The `shutdown` return value can be used to close the
+connection. A close reply will also result in the connection
+being closed.
+
+The `hibernate` option will hibernate the process until
+it receives new data from the Websocket connection or an
+Erlang message.
+
+: websocket_info(Info, Req, State)
+ -> {ok, Req, State}
+ | {ok, Req, State, hibernate}
+ | {reply, OutFrame | [OutFrame], Req, State}
+ | {reply, OutFrame | [OutFrame], Req, State, hibernate}
+ | {shutdown, Req, State}
+
+Types:
+
+* Info = any()
+* Req = cowboy_req:req()
+* State = any()
+* OutFrame = frame()
+
+Handle the Erlang message received.
+
+This function will be called every time an Erlang message
+has been received. The message can be any Erlang term.
+
+The `shutdown` return value can be used to close the
+connection. A close reply will also result in the connection
+being closed.
+
+The `hibernate` option will hibernate the process until
+it receives another message or new data from the Websocket
+connection.
+
:: Exports
None.
diff --git a/doc/src/manual/cowboy_websocket_handler.ezdoc b/doc/src/manual/cowboy_websocket_handler.ezdoc
deleted file mode 100644
index 0d31a54..0000000
--- a/doc/src/manual/cowboy_websocket_handler.ezdoc
+++ /dev/null
@@ -1,133 +0,0 @@
-::: cowboy_websocket_handler
-
-The `cowboy_websocket_handler` behaviour defines the interface used
-by Websocket handlers.
-
-The `init/3` and `websocket_init/3` callbacks will always be called,
-followed by zero or more calls to `websocket_handle/3` and
-`websocket_info/3`. The `websocket_terminate/3` will always
-be called last.
-
-:: Types
-
-None.
-
-:: Callbacks
-
-: init({TransportName, ProtocolName}, Req, Opts)
- -> {upgrade, protocol, cowboy_websocket}
- | {upgrade, protocol, cowboy_websocket, Req, Opts}
-
-Types:
-
-* TransportName = tcp | ssl | atom()
-* ProtocolName = http | atom()
-* Req = cowboy_req:req()
-* Opts = any()
-
-Upgrade the protocol to `cowboy_websocket`.
-
-: websocket_init(TransportName, Req, Opts)
- -> {ok, Req, State}
- | {ok, Req, State, hibernate}
- | {ok, Req, State, Timeout}
- | {ok, Req, State, Timeout, hibernate}
- | {shutdown, Req}
-
-Types:
-
-* TransportName = tcp | ssl | atom()
-* Req = cowboy_req:req()
-* Opts = any()
-* State = any()
-* Timeout = timeout()
-
-Initialize the state for this session.
-
-This function is called before the upgrade to Websocket occurs.
-It can be used to negotiate Websocket protocol extensions
-with the client. It will typically be used to register this process
-to an event manager or a message queue in order to receive
-the messages the handler wants to process.
-
-The connection will stay up for a duration of up to `Timeout`
-milliseconds after it last received data from the socket,
-at which point it will stop and close the connection.
-By default this value is set to `infinity`. It is recommended
-to either set this value or ensure by any other mechanism
-that the handler will be closed after a certain period of
-inactivity.
-
-The `hibernate` option will hibernate the process until it
-starts receiving either data from the Websocket connection
-or Erlang messages.
-
-The `shutdown` return value can be used to close the connection
-before upgrading to Websocket.
-
-: websocket_handle(InFrame, Req, State)
- -> {ok, Req, State}
- | {ok, Req, State, hibernate}
- | {reply, OutFrame | [OutFrame], Req, State}
- | {reply, OutFrame | [OutFrame], Req, State, hibernate}
- | {shutdown, Req, State}
-
-Types:
-
-* InFrame = {text | binary | ping | pong, binary()}
-* Req = cowboy_req:req()
-* State = any()
-* OutFrame = cowboy_websocket:frame()
-
-Handle the data received from the Websocket connection.
-
-This function will be called every time data is received
-from the Websocket connection.
-
-The `shutdown` return value can be used to close the
-connection. A close reply will also result in the connection
-being closed.
-
-The `hibernate` option will hibernate the process until
-it receives new data from the Websocket connection or an
-Erlang message.
-
-: websocket_info(Info, Req, State)
- -> {ok, Req, State}
- | {ok, Req, State, hibernate}
- | {reply, OutFrame | [OutFrame], Req, State}
- | {reply, OutFrame | [OutFrame], Req, State, hibernate}
- | {shutdown, Req, State}
-
-Types:
-
-* Info = any()
-* Req = cowboy_req:req()
-* State = any()
-* OutFrame = cowboy_websocket:frame()
-
-Handle the Erlang message received.
-
-This function will be called every time an Erlang message
-has been received. The message can be any Erlang term.
-
-The `shutdown` return value can be used to close the
-connection. A close reply will also result in the connection
-being closed.
-
-The `hibernate` option will hibernate the process until
-it receives another message or new data from the Websocket
-connection.
-
-: websocket_terminate(Reason, Req, State) -> ok
-
-Types:
-
-* Reason = {normal, shutdown | timeout} | {remote, closed} | {remote, cowboy_websocket:close_code(), binary()} | {error, badencoding | badframe | closed | atom()}
-* Req = cowboy_req:req()
-* State = any()
-
-Perform any necessary cleanup of the state.
-
-The connection will be closed and the process stopped right
-after this call.
diff --git a/doc/src/manual/index.ezdoc b/doc/src/manual/index.ezdoc
index e364e90..133a341 100644
--- a/doc/src/manual/index.ezdoc
+++ b/doc/src/manual/index.ezdoc
@@ -5,8 +5,7 @@ The function reference documents the public interface of Cowboy.
* ^"The Cowboy Application^cowboy_app
* ^cowboy
* ^cowboy_handler
-* ^cowboy_http_handler
-* ^cowboy_loop_handler
+* ^cowboy_loop
* ^cowboy_middleware
* ^cowboy_protocol
* ^cowboy_req
@@ -16,5 +15,4 @@ The function reference documents the public interface of Cowboy.
* ^cowboy_static
* ^cowboy_sub_protocol
* ^cowboy_websocket
-* ^cowboy_websocket_handler
* ^"HTTP status codes^http_status_codes