RemoteWebdriver binds on a non ephemeral port

[phyllipecesar]

Meta -

OS: Linux
Selenium Version: any
Browser: chrome, probably firefox as well
Browser Version: Any

How currently works

Once we create a webdriver.Remote selenium server tries to find an acceptable port to start the "new driver"(I'm not that familiar with the terms).

Digging into the code I noticed that we explicitly avoid ephemeral ports, probably to avoid race conditions with other systems binding on port 0.
This is the code path that does this:

selenium/java/client/src/org/openqa/selenium/net/PortProber.java

Line 80 in 02a0df9

private static int createAcceptablePort() {

Other systems that have full control of the host might have fixed ports for isolation, but selenium races with them.

The same thing happens with chromedriver, they have a similar approach but at least they have a fixed range that we can avoid:
https://cs.chromium.org/chromium/src/chrome/test/chromedriver/server/http_handler.cc?l=88

I think it is great the selenium actually finds a random non-ephemeral port, but this might have side effects on other distributed systems.

My proposal is to add a new capability to Remote:

selenium/java/client/src/org/openqa/selenium/remote/CapabilityType.java

Line 23 in 3cd7889

public interface CapabilityType {

It could be a port capability that would allow others to actually specify selenium which port it should run the new driver, another solution I'd like is to actually provide selenium server a range which we consider acceptable, the latter wouldn't require adding a new capability and we could control when starting the server.

[barancev]

Quite contrary, Selenium attempts to find a free ephemeral port, createAcceptablePort uses a system-dependent ephemeral port range detector.

Do you suggest to restrict port range from the standard ephemeral port range (for a given OS) to a narrower range? What motivates this decision?

[barancev]

Closing the issue as the intention is not clear. We're ready to reopen it if you provide a better explanation.