gun - Asynchronous HTTP client
The gun module provides an asynchronous interface for connecting and communicating with Web servers over HTTP, HTTP/2 or Websocket.
Connection:
Requests:
Proxies:
Messages:
Streams:
Websocket:
Gun will inform the calling process of events asynchronously by sending any of the following messages:
Connection:
Responses:
Websocket:
The response messages will be sent to the process that opened the connection by default. The reply_to request option can be used to redirect request-specific messages to a different process.
connect_destination() :: #{
host := inet:hostname() | inet:ip_address(),
port := inet:port_number(),
username => iodata(),
password => iodata(),
protocols => protocols(),
transport => tcp | tls,
tls_opts => [ssl:tls_client_option()],
tls_handshake_timeout => timeout()
}
Destination of a CONNECT request.
The default value, if any, is given next to the option name:
Destination hostname and port number. Mandatory.
Upon successful completion of the CONNECT request, Gun will begin using these as the host and port of the origin server for subsequent requests.
Proxy authorization credentials. They are only sent when both options are provided.
Ordered list of preferred protocols. Please refer to the protocols() type documentation for details.
Defaults to [http] when the transport is tcp, and [http2, http] when the transport is tls.
Transport that will be used for tunneled requests.
Options to use for tunneled TLS connections.
Handshake timeout for tunneled TLS connections.
http_opts() :: #{
closing_timeout => timeout(),
cookie_ignore_informational => boolean(),
flow => pos_integer(),
keepalive => timeout(),
transform_header_name => fun((binary()) -> binary()),
version => 'HTTP/1.1' | 'HTTP/1.0'
}
Configuration for the HTTP protocol.
The default value is given next to the option name:
Time to wait before brutally closing the connection when a graceful shutdown was requested via a call to gun:shutdown(3).
Whether cookies received inside informational responses (1xx status code) must be ignored.
The initial flow control value for all HTTP/1.1 streams. By default flow control is disabled.
Time between pings in milliseconds. Since the HTTP protocol has no standardized way to ping the server, Gun will simply send an empty line when the connection is idle. Gun only makes a best effort here as servers usually have configurable limits to drop idle connections. Disabled by default due to potential incompatibilities.
A function that will be applied to all header names before they are sent to the server. Gun assumes that all header names are in lower case. This function is useful if you, for example, need to re-case header names in the event that the server incorrectly considers the case of header names to be significant.
'HTTP/1.1')HTTP version to use.
http2_opts() :: #{
closing_timeout => timeout(),
cookie_ignore_informational => boolean(),
flow => pos_integer(),
keepalive => timeout(),
keepalive_tolerance => non_neg_integer(),
%% HTTP/2 state machine configuration.
connection_window_margin_size => 0..16#7fffffff,
connection_window_update_threshold => 0..16#7fffffff,
enable_connect_protocol => boolean(),
initial_connection_window_size => 65535..16#7fffffff,
initial_stream_window_size => 0..16#7fffffff,
max_concurrent_streams => non_neg_integer() | infinity,
max_connection_window_size => 0..16#7fffffff,
max_decode_table_size => non_neg_integer(),
max_encode_table_size => non_neg_integer(),
max_frame_size_received => 16384..16777215,
max_frame_size_sent => 16384..16777215 | infinity,
max_stream_buffer_size => non_neg_integer(),
max_stream_window_size => 0..16#7fffffff,
preface_timeout => timeout(),
settings_timeout => timeout(),
stream_window_margin_size => 0..16#7fffffff,
stream_window_update_threshold => 0..16#7fffffff
}
Configuration for the HTTP/2 protocol.
The default value is given next to the option name:
Time to wait before brutally closing the connection when a graceful shutdown was requested either via a call to gun:shutdown(3) or by the server.
Whether cookies received inside informational responses (1xx status code) must be ignored.
The initial flow control value for all HTTP/2 streams. By default flow control is disabled.
Time between pings in milliseconds.
The number of unacknowledged pings in flight that are tolerated before the connection is closed. By default this mechanism is disabled even if keepalive is enabled.
opts() :: #{
connect_timeout => timeout(),
cookie_store => gun_cookies:store(),
domain_lookup_timeout => timeout(),
http_opts => http_opts(),
http2_opts => http2_opts(),
protocols => protocols(),
retry => non_neg_integer(),
retry_fun => fun(),
retry_timeout => pos_integer(),
supervise => boolean(),
tcp_opts => [gen_tcp:connect_option()],
tls_handshake_timeout => timeout(),
tls_opts => [ssl:tls_client_option()],
trace => boolean(),
transport => tcp | tls,
ws_opts => ws_opts()
}
Configuration for the connection.
The default value is given next to the option name:
Connection timeout.
The cookie store that Gun will use for this connection. When configured, Gun will query the store for cookies and include them in the request headers; and add cookies found in response headers to the store.
By default no cookie store will be used.
Domain lookup timeout.
Options specific to the HTTP protocol.
Options specific to the HTTP/2 protocol.
Ordered list of preferred protocols. Please refer to the protocols() type documentation for details.
Defaults to [http] when the transport is tcp, and [http2, http] when the transport is tls.
Number of times Gun will try to reconnect on failure before giving up.
A fun that will be called before every reconnect attempt. It receives the current number of retries left and the Gun options. It returns the next number of retries left and the timeout to apply before reconnecting.
The default fun will remove one to the number of retries and set the timeout to the retry_timeout value.
The fun must be defined as follow:
fun ((non_neg_integer(), opts()) -> #{
retries => non_neg_integer(),
timeout => pos_integer()
})
The fun will never be called when the retry option is set to 0. When this function returns 0 in the retries value, Gun will do one last reconnect attempt before giving up.
Time between retries in milliseconds.
Whether the Gun process should be started under the gun_sup supervisor. Set to false to use your own supervisor.
TCP options used when establishing the connection. By default Gun enables send timeouts with the options [{send_timeout, 15000}, {send_timeout_close, true}].
TLS handshake timeout.
TLS options used for the TLS handshake after the connection has been established, when the transport is set to tls.
Whether to enable dbg tracing of the connection process. Should only be used during debugging.
Whether to use TLS or plain TCP. The default varies depending on the port used. Port 443 defaults to tls. All other ports default to tcp.
Options specific to the Websocket protocol.
Protocol :: http | {http, http_opts()}
| http2 | {http2, http2_opts()}
| raw | {raw, raw_opts()}
| socks | {socks, socks_opts()}
protocols() :: [Protocol]
Ordered list of preferred protocols. When the transport is tcp, this list must contain exactly one protocol. When the transport is tls, this list must contain at least one protocol and will be used to negotiate a protocol via ALPN. When the server does not support ALPN then http will be used, except when the list of preferred protocols is set to only accept socks.
Defaults to [http] when the transport is tcp, and [http2, http] when the transport is tls.
raw_opts() :: #{
}
Configuration for the "raw" protocol.
req_headers() :: [{binary() | string() | atom(), iodata()}]
| #{binary() | string() | atom() => iodata()}
Request headers.
req_opts() :: #{
flow => pos_integer(),
reply_to => pid()
}
Configuration for a particular request.
The default value is given next to the option name:
The initial flow control value for the stream. By default flow control is disabled.
self())The pid of the process that will receive the response messages.
socks_opts() :: #{
host := inet:hostname() | inet:ip_address(),
port := inet:port_number(),
auth => [{username_password, binary(), binary()} | none],
protocols => protocols(),
transport => tcp | tls,
version => 5,
tls_opts => [ssl:tls_client_option()],
tls_handshake_timeout => timeout()
}
Configuration for the Socks protocol.
The default value, if any, is given next to the option name:
Destination hostname and port number. Mandatory.
Upon successful completion of the Socks connection, Gun will begin using these as the host and port of the origin server for subsequent requests.
Authentication methods Gun advertises to the Socks proxy.
Ordered list of preferred protocols. Please refer to the protocols() type documentation for details.
Defaults to [http] when the transport is tcp, and [http2, http] when the transport is tls.
Transport that will be used for tunneled requests.
Options to use for tunneled TLS connections.
Handshake timeout for tunneled TLS connections.
Version of the Socks protocol to use.
stream_ref() - see below
Unique identifier for a stream.
The exact type is considered to be an implementation detail.
ws_opts() :: #{
closing_timeout => timeout(),
compress => boolean(),
default_protocol => module(),
flow => pos_integer(),
keepalive => timeout(),
protocols => [{binary(), module()}],
silence_pings => boolean(),
user_opts => any()
}
Configuration for the Websocket protocol.
The default value is given next to the option name:
Time to wait before brutally closing the connection when a graceful shutdown was requested either via a call to gun:shutdown(3) or by the server.
Whether to enable permessage-deflate compression. This does not guarantee that compression will be used as it is the server that ultimately decides. Defaults to false.
Default protocol module when no Websocket subprotocol is negotiated.
The initial flow control value for the Websocket connection. By default flow control is disabled.
Time between pings in milliseconds.
A non-empty list enables Websocket protocol negotiation. The list of protocols will be sent in the sec-websocket-protocol request header. The given module must follow the gun_ws_protocol(3) interface. Gun comes with a default interface in gun_ws_h that may be reused for negotiated protocols.
Whether the ping and pong frames should be sent to the user. In all cases Gun will automatically send a pong frame back when receiving a ping.
Additional options that are not in use by Gun unless a custom Websocket subprotocol is configured and negotiated. By default no user option is defined.
default_protocol and user_opts Websocket options were added.
stream_ref() type was added.
cookie_store was added. It can be used to configure a cookie store that Gun will use automatically. A related option, cookie_ignore_informational, was added to both http_opts() and http2_opts().
protocols() and socks_opts() have been added. Support for the Socks protocol has been added in every places where protocol selection is available. In addition it is now possible to specify separate HTTP options for the CONNECT proxy and the origin server.
connect_timeout option has been split into three options: domain_lookup_timeout, connect_timeout and when applicable tls_handshake_timeout.
retry_fun was added. It can be used to implement different reconnect strategies.
transport_opts option has been split into two options: tcp_opts and tls_opts.
gun:update_flow/3 introduced. The flow option was added to request options and HTTP/1.1, HTTP/2 and Websocket options as well.
req_headers() and extend the types accepted for header names for greater interoperability. Header names are automatically lowercased as well.
gun:headers/4,5 introduced.
keepalive option is now set to infinity by default for all protocols. This means it is disabled.
keepalive and silence_pings introduced.
protocol option from connect_destination().
protocols option and deprecate the previously introduced protocol option.
connect_destination().
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