Feature #16559

Net::HTTP#request injects "Connection: close" header if #started? is false, wasting HTTP server resources

Added by f3ndot (Justin Bull) 9 months ago. Updated 5 months ago.

Target version:



There appears to be a bug in Net::HTTP#request (and thus #get, #post, etc.) on an instance that isn't explicitly started by the programmer (by invoking #start first, or by executing #request inside a block passed to #start).

Inspecting the source code, it reveals #request will recursively call itself inside a #start block if #started? is false. This is great and as I'd expect.

However in production and in a test setup I'm observing TCP socket connections on the server-side in the "TIME_WAIT" state, indicating the socket was never properly closed. Conversely, explicitly running #request inside a #start block yields no such behaviour.

Consider the following setup, assuming you have docker:

docker run --rm -it -p 8080:80/tcp --user root ubuntu
apt-get update && apt-get install net-tools watch nginx
service nginx start
watch 'netstat -tunapl'

Running this on your host machine:

net ='localhost', 8080)
50.times { net.get('/') } # is bad

Will spawn 50 TCP connections on the server, and will all have on TIME_WAIT for 60 seconds (different *nix OSes have different times):

Every 2.0s: netstat -tunapl

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0    *               LISTEN      791/nginx: master p
tcp        0      0         TIME_WAIT   -
tcp        0      0         TIME_WAIT   -
tcp        0      0         TIME_WAIT   -
tcp        0      0         TIME_WAIT   -

However running any of these incantations have no such result:

50.times { Net::HTTP.get(URI('http://localhost:8080/')) } # is OK
net ='localhost', 8080)
50.times { net.get('/') } # is OK
net ='localhost', 8080)
50.times { net.start { net.get('/') } } # is OK

These TIME_WAIT connections matter because a server receiving many HTTP requests from clients using Net::HTTP in this fashion (as Faraday does1) the server will begin to oversaturate and timeout past a particular scale.

I've tested and reproduced this in 2.7 and 2.6.


dont-default-connection-close.patch (3.77 KB) dont-default-connection-close.patch f3ndot (Justin Bull), 01/24/2020 03:19 PM

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