WebDriver holds many TCP ports

[Marrowbones]

Hello,

Apologies if this isn't the right way to ask this, but I can't find much more information elsewhere.

We have written a Java WebDriver application that we run many concurrent instances of, each of which runs many multi-step Selenium tests. As the number of concurrent tests has inreased, we've occassionally been hitting "java.net.SocketException: No buffer space" exceptions. We've applied relevant OS level patches for similar problems, so it's not (just) that.

On further investigation, it seems that each WebDriver test holds dozens of ports open... and even after the driver has shut down cleanly, these are held in TIME_WAIT for some time.

Is this expected behaviour? It's causing us quite a few resource problems, with thousands of sockets stuck in TIME_WAIT.

For info, there seems to be many java > browser/driver and browser/driver connections, as well as (the more expected) browser > webpage sockets. Chrome seems to have less of the driver > Java connections than Firefox, but still has lots of the others. But generally it seems that every WebDriver interaction results in at least 3 sockets being hogged (Java > browser, browser > Java, browser <> webpage), sometimes more (example below)

Is this all expected? Might it be amended in future?

Cheers,
Marc

...
TCP 127.0.0.1:7055 COMPUTERNAME:64378 TIME_WAIT
TCP 127.0.0.1:7055 COMPUTERNAME:64380 TIME_WAIT
TCP 127.0.0.1:7055 COMPUTERNAME:64385 TIME_WAIT
TCP 127.0.0.1:7055 COMPUTERNAME:64409 ESTABLISHED
[firefox.exe]

...
TCP 127.0.0.1:64384 COMPUTERNAME:7055 TIME_WAIT
TCP 127.0.0.1:64386 COMPUTERNAME:7055 TIME_WAIT
TCP 127.0.0.1:64387 COMPUTERNAME:7055 TIME_WAIT
TCP 127.0.0.1:64409 COMPUTERNAME:7055 ESTABLISHED
[java.exe]

...
TCP 10.111.34.81:56076 webserver-02:8080 TIME_WAIT
TCP 10.111.34.81:56079 webserver-02:8080 ESTABLISHED
[firefox.exe]
TCP 10.111.34.81:56080 webserver-02:8080 ESTABLISHED
[firefox.exe]
TCP 10.111.34.81:56081 webserver-02:8080 ESTABLISHED
[firefox.exe]

[barancev]

This issue has been resolved in Java binding by migration to OkHttp library (if target driver supports keep-alive).

For other bindings see #5758