Doing so will let us notice when the connection is gone instead
of waiting for timeouts, at least in the cases where the remote
socket was closed properly. Timeouts are still needed in case
of TCP half-open problems.
This change means that the order of stream handler commands is
more important than before because socket errors may occur
during the processing of commands.
LH: I have fixed issues in the PR and incorporated changes
from a sister PR by @djankovic (git author: Dom J). I also
made sure the UTF-8 files were readable without Chinese
fonts and added their downloading to the examples test suite.
Note: This commit makes cowboy depend on cowlib master.
Graceful shutdown for HTTP/2:
1. A GOAWAY frame with the last stream id set to 2^31-1 is sent and a
timer is started (goaway_initial_timeout, default 1000ms), to wait
for any in-flight requests sent by the client, and the status is set
to 'closing_initiated'. If the client responds with GOAWAY and closes
the connection, we're done.
2. A second GOAWAY frame is sent with the actual last stream id and the
status is set to 'closing'. If no streams exist, the connection
terminates. Otherwise a second timer (goaway_complete_timeout,
default 3000ms) is started, to wait for the streams to complete. New
streams are not accepted when status is 'closing'.
3. If all streams haven't completed after the second timeout, the
connection is forcefully terminated.
Graceful shutdown for HTTP/1.x:
1. If a request is currently being handled, it is waited for and the
response is sent back to the client with the header "Connection:
close". Then, the connection is closed.
2. If the current request handler is not finished within the time
configured in transport option 'shutdown' (default 5000ms), the
connection process is killed by its supervisor (ranch).
Implemented for HTTP/1.x and HTTP/2 in the following scenarios:
* When receiving exit signal 'shutdown' from the supervisor (e.g. when
cowboy:stop_listener/3 is called).
* When a connection process is requested to terminate using
sys:terminate/2,3.
LH: Edited tests a bit and added todos for useful tests to add.
Verb agreement error "The request process executes
middlewares which, by default, including the router
and then the execution of handlers." -> "The request
process executes middlewares. By default, the request
process executes the router and then the handlers."
Adverbial clause at beginning of sentence needs comma
"By default Cowboy comes..." -> "By default, Cowboy comes..."
When calling cowboy_req:reply/4 with a body a crash will occur
resulting in a 500 response. When calling cowboy_req:stream_reply/2,3
and then attempting to send a body a crash will occur.
