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Diffstat (limited to 'doc/src/guide/connect.asciidoc')
| -rw-r--r-- | doc/src/guide/connect.asciidoc | 86 |
1 files changed, 46 insertions, 40 deletions
diff --git a/doc/src/guide/connect.asciidoc b/doc/src/guide/connect.asciidoc index f7983bc..dd4297d 100644 --- a/doc/src/guide/connect.asciidoc +++ b/doc/src/guide/connect.asciidoc @@ -1,3 +1,4 @@ +[[connect]] == Connection This chapter describes how to open, monitor and close @@ -26,31 +27,33 @@ to reconnect automatically. === Opening a new connection -The `gun:open/{2,3}` function must be used to open a connection. +The `gun:open/2,3` function must be used to open a connection. .Opening a connection to example.org on port 443 - [source,erlang] +---- {ok, ConnPid} = gun:open("example.org", 443). +---- If the port given is 443, Gun will attempt to connect using TLS. The protocol will be selected automatically using the ALPN extension for TLS. By default Gun supports HTTP/2 and HTTP/1.1 when connecting using TLS. -For any other port, Gun will attempt to connect using TCP -and will use the HTTP/1.1 protocol. +For any other port, Gun will attempt to connect using +plain TCP and will use the HTTP/1.1 protocol. -The transport and protocol used can be overriden using +The transport and protocol used can be overriden via options. The manual documents all available options. Options can be provided as a third argument, and take the form of a map. .Opening a TLS connection to example.org on port 8443 - [source,erlang] +---- {ok, ConnPid} = gun:open("example.org", 8443, #{transport => tls}). +---- === Waiting for the connection to be established @@ -58,22 +61,23 @@ When Gun successfully connects to the server, it sends a `gun_up` message with the protocol that has been selected for the connection. -Gun provides the functions `gun:await_up/{1,2,3}` that wait +Gun provides the functions `gun:await_up/1,2,3` that wait for the `gun_up` message. They can optionally take a monitor reference and/or timeout value. If no monitor is provided, one will be created for the duration of the function call. .Synchronous opening of a connection - [source,erlang] +---- {ok, ConnPid} = gun:open("example.org", 443), {ok, Protocol} = gun:await_up(ConnPid). +---- === Handling connection loss When the connection is lost, Gun will send a `gun_down` message indicating the current protocol, the reason the -connection was lost and two list of stream references. +connection was lost and two lists of stream references. The first list indicates open streams that _may_ have been processed by the server. The second list indicates open @@ -81,41 +85,41 @@ streams that the server did not process. === Monitoring the connection process -@todo Gun should detect the owner process being killed - Because software errors are unavoidable, it is important to detect when the Gun process crashes. It is also important to detect when it exits normally. Erlang provides two ways to do that: links and monitors. Gun leaves you the choice as to which one will be used. -However, if you use the `gun:await/{2,3}` or `gun:await_body/{2,3}` +However, if you use the `gun:await/2,3` or `gun:await_body/2,3` functions, a monitor may be used for you to avoid getting stuck waiting for a message that will never come. If you choose to monitor yourself you can do it on a permanent basis rather than on every message you will receive, saving -resources. Indeed, the `gun:await/{3,4}` and `gun:await_body/{3,4}` +resources. Indeed, the `gun:await/3,4` and `gun:await_body/3,4` functions both accept a monitor argument if you have one already. .Monitoring the connection process - [source,erlang] +---- {ok, ConnPid} = gun:open("example.org", 443). MRef = monitor(process, ConnPid). +---- This monitor reference can be kept and used until the connection process exits. .Handling `DOWN` messages - [source,erlang] +---- receive - %% Receive Gun messages here... - {'DOWN', Mref, process, ConnPid, Reason} -> - error_logger:error_msg("Oops!"), - exit(Reason); + %% Receive Gun messages here... + {'DOWN', Mref, process, ConnPid, Reason} -> + error_logger:error_msg("Oops!"), + exit(Reason) end. +---- What to do when you receive a `DOWN` message is entirely up to you. @@ -125,30 +129,32 @@ The connection can be stopped abruptly at any time by calling the `gun:close/1` function. .Immediate closing of the connection - [source,erlang] +---- gun:close(ConnPid). +---- The process is stopped immediately without having a chance to perform the protocol's closing handshake, if any. -=== Closing the connection gracefully - -The connection can also be stopped gracefully by calling the -`gun:shutdown/1` function. - -.Graceful shutdown of the connection - -[source,erlang] -gun:shutdown(ConnPid). - -Gun will refuse any new requests or messages after you call -this function. It will however continue to send you messages -for existing streams until they are all completed. - -For example if you performed a GET request just before calling -`gun:shutdown/1`, you will still receive the response before -Gun closes the connection. - -If you set a monitor beforehand, you will receive a message -when the connection has been closed. +//=== Closing the connection gracefully +// +//The connection can also be stopped gracefully by calling the +//`gun:shutdown/1` function. +// +//.Graceful shutdown of the connection +//[source,erlang] +//---- +//gun:shutdown(ConnPid). +//---- +// +//Gun will refuse any new requests or messages after you call +//this function. It will however continue to send you messages +//for existing streams until they are all completed. +// +//For example if you performed a GET request just before calling +//`gun:shutdown/1`, you will still receive the response before +//Gun closes the connection. +// +//If you set a monitor beforehand, you will receive a message +//when the connection has been closed. |