View Source Plug.Conn (Plug v1.14.0)
The Plug connection.
This module defines a struct and the main functions for working with requests and responses in an HTTP connection.
Note request headers are normalized to lowercase and response headers are expected to have lowercase keys.
request-fields
Request fields
These fields contain request information:
host
- the requested host as a binary, example:"www.example.com"
method
- the request method as a binary, example:"GET"
path_info
- the path split into segments, example:["hello", "world"]
script_name
- the initial portion of the URL's path that corresponds to the application routing, as segments, example:["sub","app"]
request_path
- the requested path, example:/trailing/and//double//slashes/
port
- the requested port as an integer, example:80
remote_ip
- the IP of the client, example:{151, 236, 219, 228}
. This field is meant to be overwritten by plugs that understand e.g. theX-Forwarded-For
header or HAProxy's PROXY protocol. It defaults to peer's IPreq_headers
- the request headers as a list, example:[{"content-type", "text/plain"}]
. Note all headers will be downcasedscheme
- the request scheme as an atom, example::http
query_string
- the request query string as a binary, example:"foo=bar"
fetchable-fields
Fetchable fields
The request information in these fields is not populated until it is fetched
using the associated fetch_
function. For example, the cookies
field uses
fetch_cookies/2
.
If you access these fields before fetching them, they will be returned as
Plug.Conn.Unfetched
structs.
cookies
- the request cookies with the response cookiesbody_params
- the request body params, populated through aPlug.Parsers
parser.query_params
- the request query params, populated throughfetch_query_params/2
path_params
- the request path params, populated by routers such asPlug.Router
params
- the request params, the result of merging the:path_params
on top of:body_params
on top of:query_params
req_cookies
- the request cookies (without the response ones)
session-vs-assigns
Session vs Assigns
HTTP is stateless.
This means that a server begins each request cycle with no knowledge about
the client except the request itself.
Its response may include one or more "Set-Cookie"
headers, asking the client
to send that value back in a "Cookie"
header on subsequent requests.
This is the basis for stateful interactions with a client, so that the server
can remember the client's name, the contents of their shopping cart, and so on.
In Plug, a "session" is a place to store data that persists from one request
to the next.
Typically, this data is stored in a cookie using Plug.Session.COOKIE
.
A minimal approach would be to store only a user's id in the session, then
use that during the request cycle to look up other information (in a database
or elsewhere).
More can be stored in a session cookie, but be careful: this makes requests
and responses heavier, and clients may reject cookies beyond a certain size.
Also, whatever is stored in a session cookie is not shared between a user's
different browsers or devices.
If the session is stored elsewhere, such as with Plug.Session.ETS
,
something like a user id would still be needed to look it up on each request.
Unlike data in a session, data in the assigns
field lasts only for a single
request.
A typical use case would be for an authentication plug to look up a
user by id and store the user's details in the assigns for later plugs to
access during the same request.
When the next request happens, this data will be gone.
To summarize: assigns
is for storing data to be accessed during the current
request, and the session is for storing data to be accessed in subsequent
requests.
response-fields
Response fields
These fields contain response information:
resp_body
- the response body, by default is an empty string. It is set to nil after the response is sent, except for test connections. The response charset used defaults to "utf-8".resp_cookies
- the response cookies with their name and optionsresp_headers
- the response headers as a list of tuples, by defaultcache-control
is set to"max-age=0, private, must-revalidate"
. Note, response headers are expected to have lowercase keys.status
- the response status
connection-fields
Connection fields
assigns
- shared user data as a mapowner
- the Elixir process that owns the connectionhalted
- the boolean status on whether the pipeline was haltedsecret_key_base
- a secret key used to verify and encrypt cookies. the field must be set manually whenever one of those features are used. This data must be kept in the connection and never used directly, always usePlug.Crypto.KeyGenerator.generate/3
to derive keys from itstate
- the connection state
The connection state is used to track the connection lifecycle. It starts as
:unset
but is changed to :set
(via resp/3
) or :set_chunked
(used only for before_send
callbacks by send_chunked/2
) or :file
(when invoked via send_file/3
). Its final result is :sent
, :file
, :chunked
or :upgraded
depending on the response model.
private-fields
Private fields
These fields are reserved for libraries/framework usage.
adapter
- holds the adapter information in a tupleprivate
- shared library data as a map
custom-status-codes
Custom status codes
Plug allows status codes to be overridden or added in order to allow new codes
not directly specified by Plug or its adapters. Adding or overriding a status
code is done through the Mix configuration of the :plug
application. For
example, to override the existing 404 reason phrase for the 404 status code
("Not Found" by default) and add a new 998 status code, the following config
can be specified:
config :plug, :statuses, %{
404 => "Actually This Was Found",
998 => "Not An RFC Status Code"
}
As this configuration is Plug specific, Plug will need to be recompiled for the changes to take place: this will not happen automatically as dependencies are not automatically recompiled when their configuration changes. To recompile Plug:
mix deps.clean --build plug
The atoms that can be used in place of the status code in many functions are inflected from the reason phrase of the status code. With the above configuration, the following will all work:
put_status(conn, :not_found) # 404
put_status(conn, :actually_this_was_found) # 404
put_status(conn, :not_an_rfc_status_code) # 998
Even though 404 has been overridden, the :not_found
atom can still be used
to set the status to 404 as well as the new atom :actually_this_was_found
inflected from the reason phrase "Actually This Was Found".
protocol-upgrades
Protocol Upgrades
Plug provides basic support for protocol upgrades via the upgrade_adapter/3
function to facilitate connection upgrades to protocols such as WebSockets.
As the name suggests, this functionality is adapter-dependent and the
functionality & requirements of a given upgrade require explicit coordination
between a Plug application & the underlying adapter. Plug provides upgrade
related functionality only to the extent necessary to allow a Plug application
to request protocol upgrades from the underlying adapter. See the documentation
for upgrade_adapter/3
for details.
Link to this section Summary
Functions
Assigns a value to a key in the connection.
Sends a chunk as part of a chunked response.
Clears the entire session.
Configures the session.
Deletes a request header if present.
Deletes a response cookie.
Deletes a response header if present.
Deletes key
from session.
Fetches cookies from the request headers.
Fetches query parameters from the query string.
Fetches the session from the session store. Will also fetch cookies.
Returns the HTTP protocol and version.
Returns the request peer data if one is present.
Returns the values of the request header specified by key
.
Returns the values of the response header specified by key
.
Returns the whole session.
Returns session value for the given key
. If key
is not set, nil
is returned.
Halts the Plug pipeline by preventing further plugs downstream from being
invoked. See the docs for Plug.Builder
for more information on halting a
Plug pipeline.
Sends an informational response to the client.
Sends an information response to a client but raises if the adapter does not support inform.
Assigns multiple values to keys in the connection.
Assigns multiple private keys and values in the connection.
Merges a series of request headers into the connection.
Merges a series of response headers into the connection.
Prepends the list of headers to the connection request headers.
Prepends the list of headers to the connection response headers.
Pushes a resource to the client.
Pushes a resource to the client but raises if the adapter does not support server push.
Assigns a new private key and value in the connection.
Adds a new request header (key
) if not present, otherwise replaces the
previous value of that header with value
.
Sets the value of the "content-type"
response header taking into account the
charset
.
Puts a response cookie in the connection.
Adds a new response header (key
) if not present, otherwise replaces the
previous value of that header with value
.
Puts the specified value
in the session for the given key
.
Stores the given status code in the connection.
Reads the request body.
Reads the body of a multipart request.
Reads the headers of a multipart request.
Registers a callback to be invoked before the response is sent.
Returns the full request URL.
Sets the response to the given status
and body
.
Sends the response headers as a chunked response.
Sends a file as the response body with the given status
and optionally starting at the given offset until the given length.
Sends a response to the client.
Sends a response with the given status and body.
Updates a request header if present, otherwise it sets it to an initial value.
Updates a response header if present, otherwise it sets it to an initial value.
Request a protocol upgrade from the underlying adapter.
Link to this section Types
@type body() :: iodata()
@type halted() :: boolean()
@type host() :: binary()
@type int_status() :: non_neg_integer() | nil
@type method() :: binary()
@type owner() :: pid()
@type port_number() :: :inet.port_number()
@type query_param() :: binary() | %{optional(binary()) => query_param()} | [query_param()]
@type query_params() :: %{optional(binary()) => query_param()}
@type query_string() :: String.t()
@type scheme() :: :http | :https
@type secret_key_base() :: binary() | nil
@type segments() :: [binary()]
@type state() ::
:unset
| :set
| :set_chunked
| :set_file
| :file
| :chunked
| :sent
| :upgraded
@type status() :: atom() | int_status()
@type t() :: %Plug.Conn{ adapter: adapter(), assigns: assigns(), body_params: params() | Plug.Conn.Unfetched.t(), cookies: cookies() | Plug.Conn.Unfetched.t(), halted: halted(), host: host(), method: method(), owner: owner(), params: params() | Plug.Conn.Unfetched.t(), path_info: segments(), path_params: query_params(), port: :inet.port_number(), private: assigns(), query_params: query_params() | Plug.Conn.Unfetched.t(), query_string: query_string(), remote_ip: :inet.ip_address(), req_cookies: req_cookies() | Plug.Conn.Unfetched.t(), req_headers: headers(), request_path: binary(), resp_body: body() | nil, resp_cookies: resp_cookies(), resp_headers: headers(), scheme: scheme(), script_name: segments(), secret_key_base: secret_key_base(), state: state(), status: int_status() }
Link to this section Functions
Assigns a value to a key in the connection.
The "assigns" storage is meant to be used to store values in the connection so that other plugs in your plug pipeline can access them. The assigns storage is a map.
examples
Examples
iex> conn.assigns[:hello]
nil
iex> conn = assign(conn, :hello, :world)
iex> conn.assigns[:hello]
:world
Sends a chunk as part of a chunked response.
It expects a connection with state :chunked
as set by
send_chunked/2
. It returns {:ok, conn}
in case of success,
otherwise {:error, reason}
.
To stream data use Enum.reduce_while/3
instead of Enum.into/2
.
Enum.reduce_while/3
allows aborting the execution if chunk/2
fails to
deliver the chunk of data.
example
Example
Enum.reduce_while(~w(each chunk as a word), conn, fn (chunk, conn) ->
case Plug.Conn.chunk(conn, chunk) do
{:ok, conn} ->
{:cont, conn}
{:error, :closed} ->
{:halt, conn}
end
end)
Clears the entire session.
This function removes every key from the session, clearing the session.
Note that, even if clear_session/1
is used, the session is still sent to the
client. If the session should be effectively dropped, configure_session/2
should be used with the :drop
option set to true
.
Configures the session.
options
Options
:renew
- Whentrue
, generates a new session id for the cookie:drop
- Whentrue
, drops the session, a session cookie will not be included in the response:ignore
- Whentrue
, ignores all changes made to the session in this request cycle
examples
Examples
configure_session(conn, renew: true)
Deletes a request header if present.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
examples
Examples
Plug.Conn.delete_req_header(conn, "content-type")
Deletes a response cookie.
Deleting a cookie requires the same options as to when the cookie was put.
Check put_resp_cookie/4
for more information.
Deletes a response header if present.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
examples
Examples
Plug.Conn.delete_resp_header(conn, "content-type")
Deletes key
from session.
The key can be a string or an atom, where atoms are automatically converted to strings.
Fetches cookies from the request headers.
options
Options
:signed
- a list of one or more cookies that are signed and must be verified accordingly:encrypted
- a list of one or more cookies that are encrypted and must be decrypted accordingly
See put_resp_cookie/4
for more information.
Fetches query parameters from the query string.
Params are decoded as "x-www-form-urlencoded"
in which key/value pairs
are separated by &
and keys are separated from values by =
.
This function does not fetch parameters from the body. To fetch
parameters from the body, use the Plug.Parsers
plug.
options
Options
:length
- the maximum query string length. Defaults to1_000_000
bytes. Keep in mind the webserver you are using may have a more strict limit. For example, for the Cowboy webserver, please read.:validate_utf8
- boolean that tells whether or not to validate the keys and values of the decoded query string are UTF-8 encoded. Defaults totrue
.
Fetches the session from the session store. Will also fetch cookies.
@spec get_http_protocol(t()) :: Plug.Conn.Adapter.http_protocol()
Returns the HTTP protocol and version.
examples
Examples
iex> get_http_protocol(conn)
:"HTTP/1.1"
@spec get_peer_data(t()) :: Plug.Conn.Adapter.peer_data()
Returns the request peer data if one is present.
Returns the values of the request header specified by key
.
examples
Examples
iex> get_req_header(conn, "accept")
["application/json"]
Returns the values of the response header specified by key
.
examples
Examples
iex> conn = %{conn | resp_headers: [{"content-type", "text/plain"}]}
iex> get_resp_header(conn, "content-type")
["text/plain"]
Returns the whole session.
Although get_session/2
and put_session/3
allow atom keys,
they are always normalized to strings. So this function always
returns a map with string keys.
Raises if the session was not yet fetched.
Returns session value for the given key
. If key
is not set, nil
is returned.
The key can be a string or an atom, where atoms are automatically converted to strings.
Halts the Plug pipeline by preventing further plugs downstream from being
invoked. See the docs for Plug.Builder
for more information on halting a
Plug pipeline.
Sends an informational response to the client.
An informational response, such as an early hint, must happen prior to a response
being sent. If an informational request is attempted after a response is sent then
a Plug.Conn.AlreadySentError
will be raised. Only status codes from 100-199 are valid.
To use inform for early hints send one or more informs with a status of 103.
If the adapter does not support informational responses then this is a noop.
Most HTTP/1.1 clients do not properly support informational responses but some
proxies require it to support server push for HTTP/2. You can call
get_http_protocol/1
to retrieve the protocol and version.
Sends an information response to a client but raises if the adapter does not support inform.
See inform/3
for more information.
Assigns multiple values to keys in the connection.
Equivalent to multiple calls to assign/3
.
examples
Examples
iex> conn.assigns[:hello]
nil
iex> conn = merge_assigns(conn, hello: :world)
iex> conn.assigns[:hello]
:world
Assigns multiple private keys and values in the connection.
Equivalent to multiple put_private/3
calls.
examples
Examples
iex> conn.private[:my_plug_hello]
nil
iex> conn = merge_private(conn, my_plug_hello: :world)
iex> conn.private[:my_plug_hello]
:world
Merges a series of request headers into the connection.
The "host" header will be overridden by conn.host
and should not be set
with this method. Instead, do %Plug.Conn{conn | host: value}
.
Because header keys are case-insensitive in both HTTP/1.1 and HTTP/2,
it is recommended for header keys to be in lowercase, to avoid sending
duplicate keys in a request.
Additionally, requests with mixed-case headers served over HTTP/2 are not
considered valid by common clients, resulting in dropped requests.
As a convenience, when using the Plug.Adapters.Conn.Test
adapter, any
headers that aren't lowercase will raise a Plug.Conn.InvalidHeaderError
.
example
Example
Plug.Conn.merge_req_headers(conn, [{"accept", "text/plain"}, {"X-1337", "5P34K"}])
Merges a series of response headers into the connection.
It is recommended for header keys to be in lowercase, to avoid sending
duplicate keys in a request.
Additionally, responses with mixed-case headers served over HTTP/2 are not
considered valid by common clients, resulting in dropped responses.
As a convenience, when using the Plug.Adapters.Conn.Test
adapter, any
headers that aren't lowercase will raise a Plug.Conn.InvalidHeaderError
.
example
Example
Plug.Conn.merge_resp_headers(conn, [{"content-type", "text/plain"}, {"X-1337", "5P34K"}])
Prepends the list of headers to the connection request headers.
Similar to put_req_header
this functions adds a new request header
(key
) but rather than replacing the existing one it prepends another
header with the same key
.
The "host" header will be overridden by conn.host
and should not be set
with this method. Instead, do %Plug.Conn{conn | host: value}
.
Because header keys are case-insensitive in both HTTP/1.1 and HTTP/2,
it is recommended for header keys to be in lowercase, to avoid sending
duplicate keys in a request.
Additionally, requests with mixed-case headers served over HTTP/2 are not
considered valid by common clients, resulting in dropped requests.
As a convenience, when using the Plug.Adapters.Conn.Test
adapter, any
headers that aren't lowercase will raise a Plug.Conn.InvalidHeaderError
.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
examples
Examples
Plug.Conn.prepend_req_headers(conn, [{"accept", "application/json"}])
Prepends the list of headers to the connection response headers.
Similar to put_resp_header
this functions adds a new response header
(key
) but rather than replacing the existing one it prepends another header
with the same key
.
It is recommended for header keys to be in lowercase, to avoid sending
duplicate keys in a request.
Additionally, responses with mixed-case headers served over HTTP/2 are not
considered valid by common clients, resulting in dropped responses.
As a convenience, when using the Plug.Adapters.Conn.Test
adapter, any
headers that aren't lowercase will raise a Plug.Conn.InvalidHeaderError
.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
Raises a Plug.Conn.InvalidHeaderError
if the header value contains control
feed (\r
) or newline (\n
) characters.
examples
Examples
Plug.Conn.prepend_resp_headers(conn, [{"content-type", "application/json"}])
Pushes a resource to the client.
Server pushes must happen prior to a response being sent. If a server
push is attempted after a response is sent then a Plug.Conn.AlreadySentError
will be raised.
If the adapter does not support server push then this is a noop.
Note that certain browsers (such as Google Chrome) will not accept a pushed resource if your certificate is not trusted. In the case of Chrome this means a valid cert with a SAN. See https://www.chromestatus.com/feature/4981025180483584
Pushes a resource to the client but raises if the adapter does not support server push.
Assigns a new private key and value in the connection.
This storage is meant to be used by libraries and frameworks to avoid writing
to the user storage (the :assigns
field). It is recommended for
libraries/frameworks to prefix the keys with the library name.
For example, if a plug called my_plug
needs to store a :hello
key, it would store it as :my_plug_hello
:
iex> conn.private[:my_plug_hello]
nil
iex> conn = put_private(conn, :my_plug_hello, :world)
iex> conn.private[:my_plug_hello]
:world
Adds a new request header (key
) if not present, otherwise replaces the
previous value of that header with value
.
The "host" header will be overridden by conn.host
and should not be set
with this method. Instead, do %Plug.Conn{conn | host: value}
.
Because header keys are case-insensitive in both HTTP/1.1 and HTTP/2,
it is recommended for header keys to be in lowercase, to avoid sending
duplicate keys in a request.
Additionally, requests with mixed-case headers served over HTTP/2 are not
considered valid by common clients, resulting in dropped requests.
As a convenience, when using the Plug.Adapters.Conn.Test
adapter, any
headers that aren't lowercase will raise a Plug.Conn.InvalidHeaderError
.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
examples
Examples
Plug.Conn.put_req_header(conn, "accept", "application/json")
Sets the value of the "content-type"
response header taking into account the
charset
.
If charset
is nil
, the value of the "content-type"
response header won't
specify a charset.
examples
Examples
iex> conn = put_resp_content_type(conn, "application/json")
iex> get_resp_header(conn, "content-type")
["application/json; charset=utf-8"]
Puts a response cookie in the connection.
If the :sign
or :encrypt
flag are given, then the cookie
value can be any term.
If the cookie is not signed nor encrypted, then the value must be a binary.
Note the value is not automatically escaped. Therefore if you want to store
values with non-alphanumeric characters, you must either sign or encrypt
the cookie or consider explicitly escaping the cookie value by using a
function such as Base.encode64(value, padding: false)
when writing and
Base.decode64(encoded, padding: false)
when reading the cookie.
It is important for padding to be disabled since =
is not a valid
character in cookie values.
signing-and-encrypting-cookies
Signing and encrypting cookies
This function allows you to automatically sign and encrypt cookies.
When signing or encryption is enabled, then any Elixir value can be
stored in the cookie (except anonymous functions for security reasons).
Once a value is signed or encrypted, you must also call fetch_cookies/2
with the name of the cookies that are either signed or encrypted.
To sign, you would do:
put_resp_cookie(conn, "my-cookie", %{user_id: user.id}, sign: true)
and then:
fetch_cookies(conn, signed: ~w(my-cookie))
To encrypt, you would do:
put_resp_cookie(conn, "my-cookie", %{user_id: user.id}, encrypt: true)
and then:
fetch_cookies(conn, encrypted: ~w(my-cookie))
By default a signed or encrypted cookie is only valid for a day, unless
a :max_age
is specified.
The signing and encryption keys are derived from the connection's
secret_key_base
using a salt that is built by appending "_cookie" to
the cookie name. Care should be taken not to derive other keys using
this value as the salt. Similarly do not use the same cookie name to
store different values with distinct purposes.
options
Options
:domain
- the domain the cookie applies to:max_age
- the cookie max-age, in seconds. Providing a value for this option will set both the max-age and expires cookie attributes.:path
- the path the cookie applies to:http_only
- whenfalse
, the cookie is accessible beyond HTTP:secure
- if the cookie must be sent only over https. Defaults to true when the connection is HTTPS:extra
- string to append to cookie. Use this to take advantage of non-standard cookie attributes.:sign
- when true, signs the cookie:encrypt
- when true, encrypts the cookie:same_site
- set the cookie SameSite attribute to a string value. If no string value is set, the attribute is omitted.
Adds a new response header (key
) if not present, otherwise replaces the
previous value of that header with value
.
Because header keys are case-insensitive in both HTTP/1.1 and HTTP/2,
it is recommended for header keys to be in lowercase, to avoid sending
duplicate keys in a request.
Additionally, responses with mixed-case headers served over HTTP/2 are not
considered valid by common clients, resulting in dropped responses.
As a convenience, when using the Plug.Adapters.Conn.Test
adapter, any
headers that aren't lowercase will raise a Plug.Conn.InvalidHeaderError
.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
Raises a Plug.Conn.InvalidHeaderError
if the header value contains control
feed (\r
) or newline (\n
) characters.
examples
Examples
Plug.Conn.put_resp_header(conn, "content-type", "application/json")
Puts the specified value
in the session for the given key
.
The key can be a string or an atom, where atoms are
automatically converted to strings. Can only be invoked
on unsent conn
s. Will raise otherwise.
Stores the given status code in the connection.
The status code can be nil
, an integer, or an atom. The list of allowed
atoms is available in Plug.Conn.Status
.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
examples
Examples
Plug.Conn.put_status(conn, :not_found)
Plug.Conn.put_status(conn, 200)
@spec read_body(t(), Keyword.t()) :: {:ok, binary(), t()} | {:more, binary(), t()} | {:error, term()}
Reads the request body.
This function reads a chunk of the request body up to a given length (specified
by the :length
option). If there is more data to be read, then
{:more, partial_body, conn}
is returned. Otherwise {:ok, body, conn}
is
returned. In case of an error reading the socket, {:error, reason}
is
returned as per :gen_tcp.recv/2
.
Like all functions in this module, the conn
returned by read_body
must
be passed to the next stage of your pipeline and should not be ignored.
In order to, for instance, support slower clients you can tune the
:read_length
and :read_timeout
options. These specify how much time should
be allowed to pass for each read from the underlying socket.
Because the request body can be of any size, reading the body will only
work once, as Plug will not cache the result of these operations. If you
need to access the body multiple times, it is your responsibility to store
it. Finally keep in mind some plugs like Plug.Parsers
may read the body,
so the body may be unavailable after being accessed by such plugs.
This function is able to handle both chunked and identity transfer-encoding by default.
options
Options
:length
- sets the maximum number of bytes to read from the body on every call, defaults to8_000_000
bytes:read_length
- sets the amount of bytes to read at one time from the underlying socket to fill the chunk, defaults to1_000_000
bytes:read_timeout
- sets the timeout for each socket read, defaults to15_000
milliseconds
The values above are not meant to be exact. For example, setting the
length to 8_000_000
may end up reading some hundred bytes more from
the socket until we halt.
examples
Examples
{:ok, body, conn} = Plug.Conn.read_body(conn, length: 1_000_000)
@spec read_part_body(t(), Keyword.t()) :: {:ok, binary(), t()} | {:more, binary(), t()} | {:done, t()}
Reads the body of a multipart request.
Returns {:ok, body, conn}
if all body has been read,
{:more, binary, conn}
otherwise, and {:done, conn}
if there is no more body.
It accepts the same options as read_body/2
.
Reads the headers of a multipart request.
It returns {:ok, headers, conn}
with the headers or
{:done, conn}
if there are no more parts.
Once read_part_headers/2
is invoked, you may call
read_part_body/2
to read the body associated to the headers.
If read_part_headers/2
is called instead, the body is automatically
skipped until the next part headers.
options
Options
:length
- sets the maximum number of bytes to read from the body for each chunk, defaults to64_000
bytes:read_length
- sets the amount of bytes to read at one time from the underlying socket to fill the chunk, defaults to64_000
bytes:read_timeout
- sets the timeout for each socket read, defaults to5_000
milliseconds
Registers a callback to be invoked before the response is sent.
Callbacks are invoked in the reverse order they are defined (callbacks defined first are invoked last).
examples
Examples
To log the status of response being sent:
require Logger
Plug.Conn.register_before_send(conn, fn conn ->
Logger.info("Sent a #{conn.status} response")
conn
end)
Returns the full request URL.
Sets the response to the given status
and body
.
It sets the connection state to :set
(if not already :set
)
and raises Plug.Conn.AlreadySentError
if it was already :sent
, :chunked
or :upgraded
.
If you also want to send the response, use send_resp/1
after this
or use send_resp/3
.
The status can be an integer, an atom, or nil
. See Plug.Conn.Status
for more information.
examples
Examples
Plug.Conn.resp(conn, 404, "Not found")
Sends the response headers as a chunked response.
It expects a connection that has not been :sent
or :upgraded
yet and sets its
state to :chunked
afterwards. Otherwise, raises Plug.Conn.AlreadySentError
.
After send_chunked/2
is called, chunks can be sent to the client via
the chunk/2
function.
HTTP/2 does not support chunking and will instead stream the response without a
transfer encoding. When using HTTP/1.1, the Cowboy adapter will stream the response
instead of emitting chunks if the content-length
header has been set before calling
send_chunked/2
.
@spec send_file( t(), status(), filename :: binary(), offset :: integer(), length :: integer() | :all ) :: t() | no_return()
Sends a file as the response body with the given status
and optionally starting at the given offset until the given length.
If available, the file is sent directly over the socket using
the operating system sendfile
operation.
It expects a connection that has not been :sent
, :chunked
or :upgraded
yet and sets its
state to :file
afterwards. Otherwise raises Plug.Conn.AlreadySentError
.
examples
Examples
Plug.Conn.send_file(conn, 200, "README.md")
Sends a response to the client.
It expects the connection state to be :set
, otherwise raises an
ArgumentError
for :unset
connections or a Plug.Conn.AlreadySentError
for
already :sent
, :chunked
or :upgraded
connections.
At the end sets the connection state to :sent
.
Note that this function does not halt the connection, so if
subsequent plugs try to send another response, it will error out.
Use halt/1
after this function if you want to halt the plug pipeline.
examples
Examples
conn
|> Plug.Conn.resp(404, "Not found")
|> Plug.Conn.send_resp()
Sends a response with the given status and body.
This is equivalent to setting the status and the body and then
calling send_resp/1
.
Note that this function does not halt the connection, so if
subsequent plugs try to send another response, it will error out.
Use halt/1
after this function if you want to halt the plug pipeline.
examples
Examples
Plug.Conn.send_resp(conn, 404, "Not found")
Updates a request header if present, otherwise it sets it to an initial value.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
Only the first value of the header key
is updated if present.
examples
Examples
Plug.Conn.update_req_header(
conn,
"accept",
"application/json; charset=utf-8",
&(&1 <> "; charset=utf-8")
)
Updates a response header if present, otherwise it sets it to an initial value.
Raises a Plug.Conn.AlreadySentError
if the connection has already been
:sent
, :chunked
or :upgraded
.
Only the first value of the header key
is updated if present.
examples
Examples
Plug.Conn.update_resp_header(
conn,
"content-type",
"application/json; charset=utf-8",
&(&1 <> "; charset=utf-8")
)
Request a protocol upgrade from the underlying adapter.
The precise semantics of an upgrade are deliberately left unspecified here in order to support arbitrary upgrades, even to protocols which may not exist today. The primary intent of this function is solely to allow an application to issue an upgrade request, not to manage how a given protocol upgrade takes place or what APIs the application must support in order to serve this updated protocol. For details in this regard, consult the documentation of the underlying adapter (such a Plug.Cowboy or Bandit).
Takes an argument describing the requested upgrade (for example, :websocket
), and an argument
which contains arbitrary data which the underlying adapter is expected to interpret in the
context of the requested upgrade.
If the upgrade is accepted by the adapter, the returned Plug.Conn
will have a state
of
:upgraded
. This state is considered equivalently to a 'sent' state, and is subject to the same
limitation on subsequent mutating operations. Note that there is no guarantee or expectation
that the actual upgrade process is undertaken within this function; it is entirely possible that
the server will only do the actual upgrade later in the connection lifecycle.
If the adapter does not support the requested upgrade then this is a noop and the returned
Plug.Conn
will be unchanged. The application can detect this and operate on the conn as it
normally would in order to indicate an upgrade failure to the client.