From aea877d1a49951165856a46b702cafd2356a26b5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= Date: Wed, 31 Aug 2016 17:10:57 +0200 Subject: Update documentation --- docs/en/cowboy/2.0/guide/resp.asciidoc | 363 ++++++++++++++------- docs/en/cowboy/2.0/guide/resp/index.html | 343 ++++++++++++------- docs/en/cowboy/2.0/guide/ws_handlers.asciidoc | 30 +- docs/en/cowboy/2.0/guide/ws_handlers/index.html | 30 +- .../cowboy/2.0/manual/cowboy_websocket/index.html | 28 +- 5 files changed, 505 insertions(+), 289 deletions(-) (limited to 'docs/en') diff --git a/docs/en/cowboy/2.0/guide/resp.asciidoc b/docs/en/cowboy/2.0/guide/resp.asciidoc index 1ffdfbd5..b8ba7d5a 100644 --- a/docs/en/cowboy/2.0/guide/resp.asciidoc +++ b/docs/en/cowboy/2.0/guide/resp.asciidoc @@ -1,201 +1,318 @@ [[resp]] == Sending a response -The Req object also allows you to send a response. +The response must be sent using the Req object. -You can only send one response. Any other attempt will -trigger a crash. The response may be sent in one go or -with its body streamed by chunks of arbitrary size. +Cowboy provides two different ways of sending responses: +either directly or by streaming the body. Response headers +and body may be set in advance. The response is sent as +soon as one of the reply or stream reply function is +called. -You can also set headers or the response body in advance -and Cowboy will use them when you finally do reply. +Cowboy also provides a simplified interface for sending +files. It can also send only specific parts of a file. + +While only one response is allowed for every request, +HTTP/2 introduced a mechanism that allows the server +to push additional resources related to the response. +This chapter also describes how this feature works in +Cowboy. === Reply -You can send a reply with no particular headers or body. -Cowboy will make sure to send the mandatory headers with -the response. +Cowboy provides three functions for sending the entire reply, +depending on whether you need to set headers and body. In all +cases, Cowboy will add any headers required by the protocol +(for example the date header will always be sent). + +When you need to set only the status code, +use `cowboy_req:reply/2`: [source,erlang] -Req2 = cowboy_req:reply(200, Req). +Req = cowboy_req:reply(200, Req0). -You can define headers to be sent with the response. Note -that header names must be lowercase. Again, Cowboy will -make sure to send the mandatory headers with the response. +When you need to set response headers at the same time, +use `cowboy_req:reply/3`: [source,erlang] ---- -Req2 = cowboy_req:reply(303, [ - {<<"location">>, <<"http://ninenines.eu">>} -], Req). +Req = cowboy_req:reply(303, #{ + <<"location">> => <<"http://ninenines.eu">> +}, Req0). ---- -You can override headers that Cowboy would send otherwise. -Any header set by the user will be used over the ones set -by Cowboy. For example, you can advertise yourself as a -different server. +Note that the header name must always be a lowercase +binary. + +When you also need to set the response body, +use `cowboy_req:reply/4`: [source,erlang] ---- -Req2 = cowboy_req:reply(200, [ - {<<"server">>, <<"yaws">>} -], Req). +Req = cowboy_req:reply(200, #{ + <<"content-type">> => <<"text/plain">> +}, "Hello world!", Req0). ---- -We also saw earlier how to force close the connection by -overriding the connection header. +You should always set the content-type header when the +response has a body. There is however no need to set +the content-length header; Cowboy does it automatically. -Finally, you can also send a body with the response. Cowboy -will automatically set the content-length header if you do. -We recommend that you set the content-type header so the -client may know how to read the body. +The response body and the header values must be either +a binary or an iolist. An iolist is a list containing +binaries, characters, strings or other iolists. This +allows you to build a response from different parts +without having to do any concatenation: [source,erlang] ---- -Req2 = cowboy_req:reply(200, [ - {<<"content-type">>, <<"text/plain">>} -], "Hello world!", Req). +Title = "Hello world!", +Body = <<"Hats off!">>, +Req = cowboy_req:reply(200, #{ + <<"content-type">> => <<"text/html">> +}, ["", Title, "", + "

", Body, "

"], Req0). ---- -Here is the same example but sending HTML this time. +This method of building responses is more efficient than +concatenating. Behind the scenes, each element of the list +is simply a pointer, and those pointers are used directly +when writing to the socket. -[source,erlang] ----- -Req2 = cowboy_req:reply(200, [ - {<<"content-type">>, <<"text/html">>} -], "Hello world!

Hats off!

", Req). ----- +=== Stream reply -Note that the reply is sent immediately. +Cowboy provides two functions for initiating a response, +and an additional function for streaming the response body. +Cowboy will add any required headers to the response. -=== Chunked reply +// @todo For HTTP/1.1 Cowboy should probably not use chunked transfer-encoding if the content-length is set. -You can also stream the response body. First, you need to -initiate the reply by sending the response status code. -Then you can send the body in chunks of arbitrary size. +When you need to set only the status code, +use `cowboy_req:stream_reply/2`: [source,erlang] -Req2 = cowboy_req:chunked_reply(200, Req), -cowboy_req:chunk("Hello...", Req2), -cowboy_req:chunk("chunked...", Req2), -cowboy_req:chunk("world!!", Req2). +---- +Req = cowboy_req:stream_reply(200, Req0), -You should make sure to match on `ok` as an error may be -returned. +cowboy_req:stream_body("Hello...", nofin, Req), +cowboy_req:stream_body("chunked...", nofin, Req), +cowboy_req:stream_body("world!!", fin, Req). +---- + +The second argument to `cowboy_req:stream_body/3` indicates +whether this data terminates the body. Use `fin` for the +final flag, and `nofin` otherwise. -While it is possible to send a chunked response without -a content-type header, it is still recommended. You can -set this header or any other just like for normal replies. +This snippet does not set a content-type header. This is +not recommended. All responses with a body should have +a content-type. The header can be set beforehand, or +using the `cowboy_req:stream_reply/3`: [source,erlang] ---- -Req2 = cowboy_req:chunked_reply(200, [ - {<<"content-type">>, <<"text/html">>} -], Req), -cowboy_req:chunk("Hello world!", Req2), -cowboy_req:chunk("

Hats off!

", Req2). +Req = cowboy_req:stream_reply(200, #{ + <<"content-type">> => <<"text/html">> +}, Req0), + +cowboy_req:stream_body("Hello world!", nofin, Req), +cowboy_req:stream_body("

Hats off!

", fin, Req). ---- -Note that the reply and each chunk following it are sent -immediately. +HTTP provides a few different ways to stream response bodies. +Cowboy will select the most appropriate one based on the HTTP +version and the request and response headers. + +While not required by any means, it is recommended that you +set the content-length header in the response if you know it +in advance. This will ensure that the best response method +is selected and help clients understand when the response +is fully received. + +// @todo Document trailers here. === Preset response headers -You can define response headers in advance. They will be -merged into the headers given in the reply call. Headers -in the reply call override preset response headers which -override the default Cowboy headers. +Cowboy provides functions to set response headers without +immediately sending them. They are stored in the Req object +and sent as part of the response when a reply function is +called. + +To set response headers: [source,erlang] -Req2 = cowboy_req:set_resp_header(<<"allow">>, "GET", Req). +Req = cowboy_req:set_resp_header(<<"allow">>, "GET", Req0). + +Header names must be a lowercase binary. -You can check if a response header has already been set. -This will only check the response headers that you set, -and not the ones Cowboy will add when actually sending -the reply. +Do not use this function for setting cookies. Refer to +the xref:cookies[Cookies] chapter for more information. + +To check if a response header has already been set: [source,erlang] cowboy_req:has_resp_header(<<"allow">>, Req). -It will return `true` if the header is defined, and `false` -otherwise. +It returns `true` if the header was set, `false` otherwise. -Finally, you can also delete a preset response header if -needed. If you do, it will not be sent. +To delete a response header that was set previously: [source,erlang] -Req2 = cowboy_req:delete_resp_header(<<"allow">>, Req). +Req = cowboy_req:delete_resp_header(<<"allow">>, Req0). -=== Preset response body +=== Overriding headers -You can set the response body in advance. Note that this -body will be ignored if you then choose to send a chunked -reply, or if you send a reply with an explicit body. +As Cowboy provides different ways of setting response +headers and body, clashes may occur, so it's important +to understand what happens when a header is set twice. -[source,erlang] -Req2 = cowboy_req:set_resp_body("Hello world!", Req). +Headers come from five different origins: + +* Protocol-specific headers (for example HTTP/1.1's connection header) +* Other required headers (for example the date header) +* Preset headers +* Headers given to the reply function +* Set-cookie headers + +Cowboy does not allow overriding protocol-specific headers. + +Set-cookie headers will always be appended at the end of +the list of headers before sending the response. + +Headers given to the reply function will always override +preset headers and required headers. If a header is found +in two or three of these, then the one in the reply function +is picked and the others are dropped. -You can also set a fun that will be called when it is time -to send the body. There are three different ways of doing -that. +Similarly, preset headers will always override required +headers. -If you know the length of the body that needs to be sent, -you should specify it, as it will help clients determine -the remaining download time and allow them to inform the -user. +To illustrate, look at the following snippet. Cowboy by +default sends the server header with the value "Cowboy". +We can override it: [source,erlang] ---- -F = fun (Socket, Transport) -> - Transport:send(Socket, "Hello world!") -end, -Req2 = cowboy_req:set_resp_body_fun(12, F, Req). +Req = cowboy_req:reply(200, #{ + <<"server">> => <<"yaws">> +}, Req0). ---- -If you do not know the length of the body, you should use -a chunked response body fun instead. +=== Preset response body + +Cowboy provides functions to set the response body without +immediately sending it. It is stored in the Req object and +sent when the reply function is called. + +To set the response body: [source,erlang] ----- -F = fun (SendChunk) -> - Body = lists:duplicate(random:uniform(1024, $a)), - SendChunk(Body) -end, -Req2 = cowboy_req:set_resp_body_fun(chunked, F, Req). ----- +Req = cowboy_req:set_resp_body("Hello world!", Req0). + +// @todo Yeah we probably should add that function that +// also sets the content-type at the same time... -Finally, you can also send data on the socket directly, -without knowing the length in advance. Cowboy may be -forced to close the connection at the end of the response -though depending on the protocol capabilities. +To check if a response body has already been set: + +[source,erlang] +cowboy_req:has_resp_body(Req). + +It returns `true` if the body was set and is non-empty, +`false` otherwise. + +// @todo We probably should also have a function that +// properly removes the response body, including any +// content-* headers. + +The preset response body is only sent if the reply function +used is `cowboy_req:reply/2` or `cowboy_req:reply/3`. + +=== Sending files + +Cowboy provides a shortcut for sending files. When +using `cowboy_req:reply/4`, or when presetting the +response header, you can give a `sendfile` tuple to +Cowboy: + +[source,erlang] +{sendfile, Offset, Length, Filename} + +Depending on the values for `Offset` or `Length`, the +entire file may be sent, or just a part of it. + +The length is required even for sending the entire file. +Cowboy sends it in the content-length header. + +To send a file while replying: [source,erlang] ---- -F = fun (Socket, Transport) -> - Body = lists:duplicate(random:uniform(1024, $a)), - Transport:send(Socket, Body) -end, -Req2 = cowboy_req:set_resp_body_fun(F, Req). +Req = cowboy_req:reply(200, #{ + <<"content-type">> => "image/png" +}, {sendfile, 0, 12345, "path/to/logo.png"}, Req0). ---- -=== Sending files +// @todo An example of presetting a file would be useful, +// but let's wait for the function that can set the +// content-type at the same time. + +// @todo What about streaming many files? For example +// it should be possible to build a tar file on the fly +// while still using sendfile. Another example could be +// proper support for multipart byte ranges. Yet another +// example would be automatic concatenation of CSS or JS +// files. + +=== Push + +The HTTP/2 protocol introduced the ability to push resources +related to the one sent in the response. Cowboy provides two +functions for that purpose: `cowboy_req:push/3,4`. + +Push is only available for HTTP/2. Cowboy will automatically +ignore push requests if the protocol doesn't support it. + +The push function must be called before any of the reply +functions. Doing otherwise will result in a crash. + +To push a resource, you need to provide the same information +as a client performing a request would. This includes the +HTTP method, the URI and any necessary request headers. -You can send files directly from disk without having to -read them. Cowboy will use the `sendfile` syscall when -possible, which means that the file is sent to the socket -directly from the kernel, which is a lot more performant -than doing it from userland. +Cowboy by default only requires you to give the path to +the resource and the request headers. The rest of the URI +is taken from the current request (excluding the query +string, set to empty) and the method is GET by default. -Again, it is recommended to set the size of the file if it -can be known in advance. +The following snippet pushes a CSS file that is linked to +in the response: [source,erlang] ---- -F = fun (Socket, Transport) -> - Transport:sendfile(Socket, "priv/styles.css") -end, -Req2 = cowboy_req:set_resp_body_fun(FileSize, F, Req). +cowboy_req:push("/static/style.css", #{ + <<"accept">> => <<"text/css">> +}, Req0), +Req = cowboy_req:reply(200, #{ + <<"content-type">> => <<"text/html">> +}, ["My web page", + "", + "

Welcome to Erlang!

"], Req0). ---- -Please see the Ranch guide for more information about -sending files. +To override the method, scheme, host, port or query string, +simply pass in a fourth argument. The following snippet +uses a different host name: + +[source,erlang] +---- +cowboy_req:push("/static/style.css", #{ + <<"accept">> => <<"text/css">> +}, #{host => <<"cdn.example.org">>}, Req), +---- + +Pushed resources don't have to be files. As long as the push +request is cacheable, safe and does not include a body, the +resource can be pushed. + +Under the hood, Cowboy handles pushed requests the same as +normal requests: a different process is created which will +ultimately send a response to the client. diff --git a/docs/en/cowboy/2.0/guide/resp/index.html b/docs/en/cowboy/2.0/guide/resp/index.html index 424a97d3..b87b1efa 100644 --- a/docs/en/cowboy/2.0/guide/resp/index.html +++ b/docs/en/cowboy/2.0/guide/resp/index.html @@ -69,219 +69,320 @@

Sending a response

-

The Req object also allows you to send a response.

-

You can only send one response. Any other attempt will -trigger a crash. The response may be sent in one go or -with its body streamed by chunks of arbitrary size.

-

You can also set headers or the response body in advance -and Cowboy will use them when you finally do reply.

+

The response must be sent using the Req object.

+

Cowboy provides two different ways of sending responses: +either directly or by streaming the body. Response headers +and body may be set in advance. The response is sent as +soon as one of the reply or stream reply function is +called.

+

Cowboy also provides a simplified interface for sending +files. It can also send only specific parts of a file.

+

While only one response is allowed for every request, +HTTP/2 introduced a mechanism that allows the server +to push additional resources related to the response. +This chapter also describes how this feature works in +Cowboy.

Reply

-

You can send a reply with no particular headers or body. -Cowboy will make sure to send the mandatory headers with -the response.

+

Cowboy provides three functions for sending the entire reply, +depending on whether you need to set headers and body. In all +cases, Cowboy will add any headers required by the protocol +(for example the date header will always be sent).

+

When you need to set only the status code, +use cowboy_req:reply/2:

-
Req2 = cowboy_req:reply(200, Req).
-

You can define headers to be sent with the response. Note -that header names must be lowercase. Again, Cowboy will -make sure to send the mandatory headers with the response.

+
Req = cowboy_req:reply(200, Req0).
+

When you need to set response headers at the same time, +use cowboy_req:reply/3:

-
Req2 = cowboy_req:reply(303, [
-    {<<"location">>, <<"http://ninenines.eu">>}
-], Req).
-

You can override headers that Cowboy would send otherwise. -Any header set by the user will be used over the ones set -by Cowboy. For example, you can advertise yourself as a -different server.

+
Req = cowboy_req:reply(303, #{
+    <<"location">> => <<"http://ninenines.eu">>
+}, Req0).
+

Note that the header name must always be a lowercase +binary.

+

When you also need to set the response body, +use cowboy_req:reply/4:

-
Req2 = cowboy_req:reply(200, [
-    {<<"server">>, <<"yaws">>}
-], Req).
-

We also saw earlier how to force close the connection by -overriding the connection header.

-

Finally, you can also send a body with the response. Cowboy -will automatically set the content-length header if you do. -We recommend that you set the content-type header so the -client may know how to read the body.

+
Req = cowboy_req:reply(200, #{
+    <<"content-type">> => <<"text/plain">>
+}, "Hello world!", Req0).
+

You should always set the content-type header when the +response has a body. There is however no need to set +the content-length header; Cowboy does it automatically.

+

The response body and the header values must be either +a binary or an iolist. An iolist is a list containing +binaries, characters, strings or other iolists. This +allows you to build a response from different parts +without having to do any concatenation:

-
Req2 = cowboy_req:reply(200, [
-    {<<"content-type">>, <<"text/plain">>}
-], "Hello world!", Req).
-

Here is the same example but sending HTML this time.

-
-
-
Req2 = cowboy_req:reply(200, [
-    {<<"content-type">>, <<"text/html">>}
-], "<html><head>Hello world!</head><body><p>Hats off!</p></body></html>", Req).
-

Note that the reply is sent immediately.

+
Title = "Hello world!",
+Body = <<"Hats off!">>,
+Req = cowboy_req:reply(200, #{
+    <<"content-type">> => <<"text/html">>
+}, ["<html><head><title>", Title, "</title></head>",
+        "<body><p>", Body, "</p></body></html>"], Req0).
+

This method of building responses is more efficient than +concatenating. Behind the scenes, each element of the list +is simply a pointer, and those pointers are used directly +when writing to the socket.

-

Chunked reply

+

Stream reply

-

You can also stream the response body. First, you need to -initiate the reply by sending the response status code. -Then you can send the body in chunks of arbitrary size.

+

Cowboy provides two functions for initiating a response, +and an additional function for streaming the response body. +Cowboy will add any required headers to the response.

+

When you need to set only the status code, +use cowboy_req:stream_reply/2:

-
Req2 = cowboy_req:chunked_reply(200, Req),
-cowboy_req:chunk("Hello...", Req2),
-cowboy_req:chunk("chunked...", Req2),
-cowboy_req:chunk("world!!", Req2).
-

You should make sure to match on ok as an error may be -returned.

-

While it is possible to send a chunked response without -a content-type header, it is still recommended. You can -set this header or any other just like for normal replies.

+
Req = cowboy_req:stream_reply(200, Req0),
+
+cowboy_req:stream_body("Hello...", nofin, Req),
+cowboy_req:stream_body("chunked...", nofin, Req),
+cowboy_req:stream_body("world!!", fin, Req).
+

The second argument to cowboy_req:stream_body/3 indicates +whether this data terminates the body. Use fin for the +final flag, and nofin otherwise.

+

This snippet does not set a content-type header. This is +not recommended. All responses with a body should have +a content-type. The header can be set beforehand, or +using the cowboy_req:stream_reply/3:

-
Req2 = cowboy_req:chunked_reply(200, [
-    {<<"content-type">>, <<"text/html">>}
-], Req),
-cowboy_req:chunk("<html><head>Hello world!</head>", Req2),
-cowboy_req:chunk("<body><p>Hats off!</p></body></html>", Req2).
-

Note that the reply and each chunk following it are sent -immediately.

+
Req = cowboy_req:stream_reply(200, #{
+    <<"content-type">> => <<"text/html">>
+}, Req0),
+
+cowboy_req:stream_body("<html><head>Hello world!</head>", nofin, Req),
+cowboy_req:stream_body("<body><p>Hats off!</p></body></html>", fin, Req).
+

HTTP provides a few different ways to stream response bodies. +Cowboy will select the most appropriate one based on the HTTP +version and the request and response headers.

+

While not required by any means, it is recommended that you +set the content-length header in the response if you know it +in advance. This will ensure that the best response method +is selected and help clients understand when the response +is fully received.

Preset response headers

-

You can define response headers in advance. They will be -merged into the headers given in the reply call. Headers -in the reply call override preset response headers which -override the default Cowboy headers.

+

Cowboy provides functions to set response headers without +immediately sending them. They are stored in the Req object +and sent as part of the response when a reply function is +called.

+

To set response headers:

-
Req2 = cowboy_req:set_resp_header(<<"allow">>, "GET", Req).
-

You can check if a response header has already been set. -This will only check the response headers that you set, -and not the ones Cowboy will add when actually sending -the reply.

+
Req = cowboy_req:set_resp_header(<<"allow">>, "GET", Req0).
+

Header names must be a lowercase binary.

+

Do not use this function for setting cookies. Refer to +the Cookies chapter for more information.

+

To check if a response header has already been set:

cowboy_req:has_resp_header(<<"allow">>, Req).
-

It will return true if the header is defined, and false -otherwise.

-

Finally, you can also delete a preset response header if -needed. If you do, it will not be sent.

+

It returns true if the header was set, false otherwise.

+

To delete a response header that was set previously:

-
Req2 = cowboy_req:delete_resp_header(<<"allow">>, Req).
+
Req = cowboy_req:delete_resp_header(<<"allow">>, Req0).
+ + +
+

Overriding headers

+
+

As Cowboy provides different ways of setting response +headers and body, clashes may occur, so it’s important +to understand what happens when a header is set twice.

+

Headers come from five different origins:

+
    +
  • +

    +Protocol-specific headers (for example HTTP/1.1’s connection header) +

    +
    • +
  • +

    +Other required headers (for example the date header) +

    +
    • +
  • +

    +Preset headers +

    +
    • +
  • +

    +Headers given to the reply function +

    +
    • +
  • +

    +Set-cookie headers +

    +
    • +
+

Cowboy does not allow overriding protocol-specific headers.

+

Set-cookie headers will always be appended at the end of +the list of headers before sending the response.

+

Headers given to the reply function will always override +preset headers and required headers. If a header is found +in two or three of these, then the one in the reply function +is picked and the others are dropped.

+

Similarly, preset headers will always override required +headers.

+

To illustrate, look at the following snippet. Cowboy by +default sends the server header with the value "Cowboy". +We can override it:

+
+
+
Req = cowboy_req:reply(200, #{
+    <<"server">> => <<"yaws">>
+}, Req0).

Preset response body

-

You can set the response body in advance. Note that this -body will be ignored if you then choose to send a chunked -reply, or if you send a reply with an explicit body.

+

Cowboy provides functions to set the response body without +immediately sending it. It is stored in the Req object and +sent when the reply function is called.

+

To set the response body:

-
Req2 = cowboy_req:set_resp_body("Hello world!", Req).
-

You can also set a fun that will be called when it is time -to send the body. There are three different ways of doing -that.

-

If you know the length of the body that needs to be sent, -you should specify it, as it will help clients determine -the remaining download time and allow them to inform the -user.

+
Req = cowboy_req:set_resp_body("Hello world!", Req0).
+

To check if a response body has already been set:

-
F = fun (Socket, Transport) ->
-    Transport:send(Socket, "Hello world!")
-end,
-Req2 = cowboy_req:set_resp_body_fun(12, F, Req).
-

If you do not know the length of the body, you should use -a chunked response body fun instead.

+
cowboy_req:has_resp_body(Req).
+

It returns true if the body was set and is non-empty, +false otherwise.

+

The preset response body is only sent if the reply function +used is cowboy_req:reply/2 or cowboy_req:reply/3.

+ + +
+

Sending files

+
+

Cowboy provides a shortcut for sending files. When +using cowboy_req:reply/4, or when presetting the +response header, you can give a sendfile tuple to +Cowboy:

-
F = fun (SendChunk) ->
-    Body = lists:duplicate(random:uniform(1024, $a)),
-    SendChunk(Body)
-end,
-Req2 = cowboy_req:set_resp_body_fun(chunked, F, Req).
-

Finally, you can also send data on the socket directly, -without knowing the length in advance. Cowboy may be -forced to close the connection at the end of the response -though depending on the protocol capabilities.

+
{sendfile, Offset, Length, Filename}
+

Depending on the values for Offset or Length, the +entire file may be sent, or just a part of it.

+

The length is required even for sending the entire file. +Cowboy sends it in the content-length header.

+

To send a file while replying:

-
F = fun (Socket, Transport) ->
-    Body = lists:duplicate(random:uniform(1024, $a)),
-    Transport:send(Socket, Body)
-end,
-Req2 = cowboy_req:set_resp_body_fun(F, Req).
+
Req = cowboy_req:reply(200, #{
+        <<"content-type">> => "image/png"
+}, {sendfile, 0, 12345, "path/to/logo.png"}, Req0).
-

Sending files

+

Push

-

You can send files directly from disk without having to -read them. Cowboy will use the sendfile syscall when -possible, which means that the file is sent to the socket -directly from the kernel, which is a lot more performant -than doing it from userland.

-

Again, it is recommended to set the size of the file if it -can be known in advance.

+

The HTTP/2 protocol introduced the ability to push resources +related to the one sent in the response. Cowboy provides two +functions for that purpose: cowboy_req:push/3,4.

+

Push is only available for HTTP/2. Cowboy will automatically +ignore push requests if the protocol doesn’t support it.

+

The push function must be called before any of the reply +functions. Doing otherwise will result in a crash.

+

To push a resource, you need to provide the same information +as a client performing a request would. This includes the +HTTP method, the URI and any necessary request headers.

+

Cowboy by default only requires you to give the path to +the resource and the request headers. The rest of the URI +is taken from the current request (excluding the query +string, set to empty) and the method is GET by default.

+

The following snippet pushes a CSS file that is linked to +in the response:

+
+
+
cowboy_req:push("/static/style.css", #{
+        <<"accept">> => <<"text/css">>
+}, Req0),
+Req = cowboy_req:reply(200, #{
+        <<"content-type">> => <<"text/html">>
+}, ["<html><head><title>My web page</title>",
+        "<link rel='stylesheet' type='text/css' href='/static/style.css'>",
+        "<body><p>Welcome to Erlang!</p></body></html>"], Req0).
+

To override the method, scheme, host, port or query string, +simply pass in a fourth argument. The following snippet +uses a different host name:

-
F = fun (Socket, Transport) ->
-    Transport:sendfile(Socket, "priv/styles.css")
-end,
-Req2 = cowboy_req:set_resp_body_fun(FileSize, F, Req).
-

Please see the Ranch guide for more information about -sending files.

+
cowboy_req:push("/static/style.css", #{
+        <<"accept">> => <<"text/css">>
+}, #{host => <<"cdn.example.org">>}, Req),
+

Pushed resources don’t have to be files. As long as the push +request is cacheable, safe and does not include a body, the +resource can be pushed.

+

Under the hood, Cowboy handles pushed requests the same as +normal requests: a different process is created which will +ultimately send a response to the client.

diff --git a/docs/en/cowboy/2.0/guide/ws_handlers.asciidoc b/docs/en/cowboy/2.0/guide/ws_handlers.asciidoc index b280fd86..1411ab6c 100644 --- a/docs/en/cowboy/2.0/guide/ws_handlers.asciidoc +++ b/docs/en/cowboy/2.0/guide/ws_handlers.asciidoc @@ -69,14 +69,14 @@ init(Req, State) -> %% Register process here... {cowboy_websocket, Req, State}. -websocket_info(post_init, Req, State) -> +websocket_info(post_init, State) -> %% Perform post_init initialization here... - {ok, Req, State}. + {ok, State}. ---- === Handling frames from the client -Cowboy will call `websocket_handle/3` whenever a text, binary, +Cowboy will call `websocket_handle/2` whenever a text, binary, ping or pong frame arrives from the client. Note that in the case of ping and pong frames, no action is expected as Cowboy automatically replies to ping frames. @@ -89,15 +89,15 @@ ignores all others. [source,erlang] ---- -websocket_handle(Frame = {text, _}, Req, State) -> - {reply, Frame, Req, State}; -websocket_handle(_Frame, Req, State) -> - {ok, Req, State}. +websocket_handle(Frame = {text, _}, State) -> + {reply, Frame, State}; +websocket_handle(_Frame, State) -> + {ok, State}. ---- === Handling Erlang messages -Cowboy will call `websocket_info/3` whenever an Erlang message +Cowboy will call `websocket_info/2` whenever an Erlang message arrives. The handler can decide to send frames to the socket, stop @@ -108,10 +108,10 @@ and ignores all others. [source,erlang] ---- -websocket_info({log, Text}, Req, State) -> - {reply, {text, Text}, Req, State}; -websocket_info(_Info, Req, State) -> - {ok, Req, State}. +websocket_info({log, Text}, State) -> + {reply, {text, Text}, State}; +websocket_info(_Info, State) -> + {ok, State}. ---- === Sending frames to the socket @@ -126,13 +126,13 @@ tuple. [source,erlang] ---- -websocket_info(hello_world, Req, State) -> +websocket_info(hello_world, State) -> {reply, [ {text, "Hello"}, {text, <<"world!">>}, {binary, <<0:8000>>} - ], Req, State}; -%% More websocket_info/3 clauses here... + ], State}; +%% More websocket_info/2 clauses here... ---- Note that the payload for text and binary frames is of type diff --git a/docs/en/cowboy/2.0/guide/ws_handlers/index.html b/docs/en/cowboy/2.0/guide/ws_handlers/index.html index 2b0e30a2..29feb4a1 100644 --- a/docs/en/cowboy/2.0/guide/ws_handlers/index.html +++ b/docs/en/cowboy/2.0/guide/ws_handlers/index.html @@ -134,15 +134,15 @@ http://www.gnu.org/software/src-highlite --> %% Register process here... {cowboy_websocket, Req, State}. -websocket_info(post_init, Req, State) -> +websocket_info(post_init, State) -> %% Perform post_init initialization here... - {ok, Req, State}. + {ok, State}.

Handling frames from the client

-

Cowboy will call websocket_handle/3 whenever a text, binary, +

Cowboy will call websocket_handle/2 whenever a text, binary, ping or pong frame arrives from the client. Note that in the case of ping and pong frames, no action is expected as Cowboy automatically replies to ping frames.

@@ -155,16 +155,16 @@ ignores all others.

by Lorenzo Bettini http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> -
websocket_handle(Frame = {text, _}, Req, State) ->
-        {reply, Frame, Req, State};
-websocket_handle(_Frame, Req, State) ->
-        {ok, Req, State}.
+
websocket_handle(Frame = {text, _}, State) ->
+        {reply, Frame, State};
+websocket_handle(_Frame, State) ->
+        {ok, State}.

Handling Erlang messages

-

Cowboy will call websocket_info/3 whenever an Erlang message +

Cowboy will call websocket_info/2 whenever an Erlang message arrives.

The handler can decide to send frames to the socket, stop or just continue without sending anything.

@@ -175,10 +175,10 @@ and ignores all others.

by Lorenzo Bettini http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> -
websocket_info({log, Text}, Req, State) ->
-        {reply, {text, Text}, Req, State};
-websocket_info(_Info, Req, State) ->
-        {ok, Req, State}.
+
websocket_info({log, Text}, State) ->
+        {reply, {text, Text}, State};
+websocket_info(_Info, State) ->
+        {ok, State}.
@@ -195,13 +195,13 @@ tuple.

by Lorenzo Bettini http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> -
websocket_info(hello_world, Req, State) ->
+
websocket_info(hello_world, State) ->
         {reply, [
                 {text, "Hello"},
                 {text, <<"world!">>},
                 {binary, <<0:8000>>}
-        ], Req, State};
-%% More websocket_info/3 clauses here...

+        ], State};
+%% More websocket_info/2 clauses here...

Note that the payload for text and binary frames is of type iodata(), meaning it can be either a binary() or an iolist().

diff --git a/docs/en/cowboy/2.0/manual/cowboy_websocket/index.html b/docs/en/cowboy/2.0/manual/cowboy_websocket/index.html index 8359987a..abba7a1c 100644 --- a/docs/en/cowboy/2.0/manual/cowboy_websocket/index.html +++ b/docs/en/cowboy/2.0/manual/cowboy_websocket/index.html @@ -83,7 +83,7 @@ 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 +

The websocket_handle/2 and websocket_info/2 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 @@ -224,20 +224,19 @@ timeout

Callbacks

-

websocket_handle(InFrame, Req, State) → Ret

+

websocket_handle(InFrame, State) → Ret

-
Ret = {ok, Req, State}
-        | {ok, Req, State, hibernate}
-        | {reply, OutFrame | [OutFrame], Req, State}
-        | {reply, OutFrame | [OutFrame], Req, State, hibernate}
-        | {stop, Req, State}
+
Ret = {ok, State}
+        | {ok, State, hibernate}
+        | {reply, OutFrame | [OutFrame], State}
+        | {reply, OutFrame | [OutFrame], State, hibernate}
+        | {stop, State}
 
 InFrame = {text | binary | ping | pong, binary()}
-Req = cowboy_req:req()
 State = any()
 OutFrame = cow_ws:frame()

Handle the data received from the Websocket connection.

@@ -251,20 +250,19 @@ it receives new data from the Websocket connection or an Erlang message.

-

websocket_info(Info, Req, State) → Ret

+

websocket_info(Info, State) → Ret

-
Ret = {ok, Req, State}
-        | {ok, Req, State, hibernate}
-        | {reply, OutFrame | [OutFrame], Req, State}
-        | {reply, OutFrame | [OutFrame], Req, State, hibernate}
-        | {stop, Req, State}
+
Ret = {ok, State}
+        | {ok, State, hibernate}
+        | {reply, OutFrame | [OutFrame], State}
+        | {reply, OutFrame | [OutFrame], State, hibernate}
+        | {stop, State}
 
 Info = any()
-Req = cowboy_req:req()
 State = any()
 OutFrame = cow_ws:frame()

Handle the Erlang message received.

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