View Source Plug.Conn.Adapter behaviour (Plug v1.14.0)

Specification of the connection adapter API implemented by webservers.

Link to this section Summary

Callbacks

Sends a chunk in the chunked response.

Returns the HTTP protocol and its version.

Returns peer information such as the address, port and ssl cert.

Send an informational response to the client.

Push a resource to the client.

Reads the request body.

Sends the given status, headers as the beginning of a chunked response to the client.

Sends the given status, headers and file as a response back to the client.

Sends the given status, headers and body as a response back to the client.

Attempt to upgrade the connection with the client.

Functions

Function used by adapters to create a new connection.

Link to this section Types

@type http_protocol() :: :"HTTP/1" | :"HTTP/1.1" | :"HTTP/2" | atom()
@type payload() :: term()
@type peer_data() :: %{
  address: :inet.ip_address(),
  port: :inet.port_number(),
  ssl_cert: binary() | nil
}

Link to this section Callbacks

@callback chunk(payload(), body :: Plug.Conn.body()) ::
  :ok | {:ok, sent_body :: binary(), payload()} | {:error, term()}

Sends a chunk in the chunked response.

If the request has method "HEAD", the adapter should not send the response to the client.

Webservers are advised to return :ok and not modify any further state for each chunk. However, the test implementation returns the actual body and payload so it can be used during testing.

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get_http_protocol(payload)

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@callback get_http_protocol(payload()) :: http_protocol()

Returns the HTTP protocol and its version.

@callback get_peer_data(payload()) :: peer_data()

Returns peer information such as the address, port and ssl cert.

Link to this callback

inform(payload, status, headers)

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@callback inform(payload(), status :: Plug.Conn.status(), headers :: Keyword.t()) ::
  :ok | {:error, term()}

Send an informational response to the client.

If the adapter does not support inform, then {:error, :not_supported} should be returned.

Link to this callback

push(payload, path, headers)

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@callback push(payload(), path :: String.t(), headers :: Keyword.t()) ::
  :ok | {:error, term()}

Push a resource to the client.

If the adapter does not support server push then {:error, :not_supported} should be returned.

Link to this callback

read_req_body(payload, options)

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@callback read_req_body(payload(), options :: Keyword.t()) ::
  {:ok, data :: binary(), payload()}
  | {:more, data :: binary(), payload()}
  | {:error, term()}

Reads the request body.

Read the docs in Plug.Conn.read_body/2 for the supported options and expected behaviour.

Link to this callback

send_chunked(payload, status, headers)

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@callback send_chunked(
  payload(),
  status :: Plug.Conn.status(),
  headers :: Plug.Conn.headers()
) ::
  {:ok, sent_body :: binary() | nil, payload()}

Sends the given status, headers as the beginning of a chunked response to the client.

Webservers are advised to return nil as the sent_body, as the body can no longer be manipulated. However, the test implementation returns the actual body so it can be used during testing.

Link to this callback

send_file(payload, status, headers, file, offset, length)

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@callback send_file(
  payload(),
  status :: Plug.Conn.status(),
  headers :: Plug.Conn.headers(),
  file :: binary(),
  offset :: integer(),
  length :: integer() | :all
) :: {:ok, sent_body :: binary() | nil, payload()}

Sends the given status, headers and file as a response back to the client.

If the request has method "HEAD", the adapter should not send the response to the client.

Webservers are advised to return nil as the sent_body, as the body can no longer be manipulated. However, the test implementation returns the actual body so it can be used during testing.

Link to this callback

send_resp(payload, status, headers, body)

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@callback send_resp(
  payload(),
  status :: Plug.Conn.status(),
  headers :: Plug.Conn.headers(),
  body :: Plug.Conn.body()
) :: {:ok, sent_body :: binary() | nil, payload()}

Sends the given status, headers and body as a response back to the client.

If the request has method "HEAD", the adapter should not send the response to the client.

Webservers are advised to return nil as the sent_body, as the body can no longer be manipulated. However, the test implementation returns the actual body so it can be used during testing.

Link to this callback

upgrade(payload, protocol, opts)

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@callback upgrade(payload(), protocol :: atom(), opts :: term()) ::
  {:ok, payload()} | {:error, term()}

Attempt to upgrade the connection with the client.

If the adapter does not support the indicated upgrade, then {:error, :not_supported} should be be returned.

If the adapter supports the indicated upgrade but is unable to proceed with it (due to a negotiation error, invalid opts being passed to this function, or some other reason), then an arbitrary error may be returned. Note that an adapter does not need to process the actual upgrade within this function; it is a wholly supported failure mode for an adapter to attempt the upgrade process later in the connection lifecycle and fail at that point.

Link to this section Functions

Link to this function

conn(adapter, method, uri, remote_ip, req_headers)

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Function used by adapters to create a new connection.