How to troubleshoot an ERROR: Unable to connect to host http://localhost:4444/wd/hub. Contact EPSM. Message: Could not initialize class we received in application monitoring application for SharePoint Server?

Bajracharya, Prabinesh 417 Reputation points

We have an application monitoring application called Nagios XI in our organization and recently we received an alert - ** PROBLEM Service Alert: <domain>/prod: user: auth: https_<domain> is UNKNOWN** with an ERROR: Unable to connect to host http://localhost:4444/wd/hub. Contact EPSM. Message: Could not initialize class

The error message came at 12:19 PM on Monday and then at 12:57 got another alert notifying a RECOVERY.
RECOVERY: Closed session and quit window

In order to find the root cause of this issue, we have looked at the Event Logs and SharePoint Logs (Verbose) to find any reference for http://localhost:4444/wd/hub and class but with no luck.



Internet Information Services
Windows Server
Windows Server
A family of Microsoft server operating systems that support enterprise-level management, data storage, applications, and communications.
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SharePoint Server Management
SharePoint Server Management
SharePoint Server: A family of Microsoft on-premises document management and storage systems.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Limitless Technology 39,506 Reputation points


    Thanks for reaching out.

    wd is the short form of WebDriver
    hub refers to Selenium Grid configuration where the two components are:

    Selenium Grid Hub (is commonly termed as hub)

    Selenium Grid Node (is commonly termed as node)

    wd/hub is the part of the uri through which the node communicates with the hub

    Hence to troubleshoot more I would suggest you to check Selenium Gird logs from application folder.

    --If the reply was helpful, please don’t forget to upvote or accept as answer. --

  2. Bajracharya, Prabinesh 417 Reputation points

    Found the answer for my own question from our application monitoring team.

    "This is an older synthetic transaction and there are times that the check fails for an unknown reason. Normally, the error clears on the next check, but in this case it did not until Selenium services were restarted.
    When you see Unable to connect to host http://localhost:4444/wd/hub, that is a Nagios/Selenium issue, not a service issue."

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  3. Yi Lu_MSFT 17,471 Reputation points

    Hi @Anonymous
    According to the information you provided and is related to 3rd tool, this issue seems not suitable for discussion in our forums, I would suggest you to open a ticket or go to other related forums for further support.

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

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