Issue #16559 has been updated by f3ndot (Justin Bull).

ruby -v changed from 2.7.0-preview to 2.8.0-dev, 2.7.0, 2.6.5
File dont-default-connection-close.patch added

I have chased this down to an opportunistic setting of 'Connection: close' header if-and-only-if #request is called when #started? is false.

Attached is a patchfile where I remove this header setting, with the rationale laid out in the description. Hopefully you agree :-)

----------------------------------------
Bug #16559: Net::HTTP#request does not properly close TCP socket if #started? is false
https://bugs.ruby-lang.org/issues/16559#change-84047

* Author: f3ndot (Justin Bull)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.8.0-dev, 2.7.0, 2.6.5
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
Hello,

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:

``` ruby
net = Net::HTTP.new('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 0.0.0.0:80              0.0.0.0:*               LISTEN      791/nginx: master p
tcp        0      0 172.17.0.2:80           172.17.0.1:60772        TIME_WAIT   -
tcp        0      0 172.17.0.2:80           172.17.0.1:60732        TIME_WAIT   -
tcp        0      0 172.17.0.2:80           172.17.0.1:60812        TIME_WAIT   -
tcp        0      0 172.17.0.2:80           172.17.0.1:60778        TIME_WAIT   -
...
```

However running any of these incantations have no such result:

``` ruby
50.times { Net::HTTP.get(URI('http://localhost:8080/')) } # is OK
```

``` ruby
net = Net::HTTP.new('localhost', 8080)
net.start
50.times { net.get('/') } # is OK
net.finish
```

``` ruby
net = Net::HTTP.new('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 does[1]) the server will begin to oversaturate and timeout past a particular scale.

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

[1]: https://github.com/lostisland/faraday/pull/1117

---Files--------------------------------
dont-default-connection-close.patch (3.77 KB)


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