Important Note:
This response is specifically applicable to the Selenium 3.x series (specifically version 3.14.1, which as of today is the latest in the Selenium 3 series). It's crucial to highlight that the architecture of Selenium 4 grid is significantly different from that of Selenium 3, hence this answer may not be directly relevant for Selenium 4 grid (given that it is yet to be released).
The concept you are inquiring about appears to require a form of self-repairing mechanism, which isn't inherently available in the standard configuration of selenium grid.
It's important to note that Selenium node lacks the ability to track active sessions running on it.
To implement this functionality, it would need to be constructed at the level of Selenium Hub (where all pertinent information is stored).
At a high level, the following steps would need to be taken:
- Create a custom proxy by extending
org.openqa.grid.selenium.proxy.DefaultRemoteProxy
with the following features:
- Incorporate an API that marks the proxy as quiesced when utilized (indicating that the node is undergoing maintenance and will no longer accept new session requests)
- Override
getNewSession(Map<String, Object> requestedCapability)
to first verify if a node is not quiesced before enabling a new session.
- Develop a customized servlet capable of performing the following functions:
- When given a node, invoke the API created in step 1.1 to mark the node as quiesced
- Provide a list of nodes without any active sessions. If your servlet extends
org.openqa.grid.web.servlet.RegistryBasedServlet
, you should be able to retrieve the URLs of free nodes using the code snippet below
List<RemoteProxy> freeProxies =
StreamSupport.stream(getRegistry().getAllProxies().spliterator(), false)
.filter(remoteProxy -> !remoteProxy.isBusy())
.collect(Collectors.toList());
List<URL> urls =
freeProxies.stream().map(RemoteProxy::getRemoteHost).collect(Collectors.toList());
With this custom Hub now equipped to handle cleanup tasks, you can use the 2.1 endpoint to initiate shutting down nodes and then continuously check the 2.2 endpoint to fetch IP and Port combinations of nodes no longer supporting test sessions, subsequently triggering
http://NODE-IP:5555/selenium-server/driver/?cmd=shutDownSeleniumServer
on them.
Generally speaking, these actions will address your requirements.
For further guidance on this topic, consider exploring the following resource links (each link directs to a blog authored on related subjects):
- Self-healing grid -
- Building a bespoke proxy -
- Developing a unique servlet for the hub -