HTTP ERROR 401 require authentication

HTTP Error 401 require authentication error in Apache Solr indicates that the request lacks proper authentication credentials or the provided credentials are invalid. When you encounter this error while trying to create a Solr core, it usually means that the client making the request is not authorized to perform the operation.

Here are some steps to troubleshoot and resolve the "HTTP Error 401 require authentication" issue in Solr:

1. Check Solr Authentication Configuration:
   Ensure that your Solr instance is configured for authentication, and the client is providing valid credentials. The authentication configuration is typically specified in the security.json file. You can check this file for details on authentication mechanisms and user credentials.
    
2. Check blockUnknown parameter: The blockUnknown parameter is used to control the behavior when requests are made with an unknown username. If you are using solr server inside a private network, you can set "blockUnknown" parameter to false . Open /opt/solr/server/solr/security.json file and modify the configuration to look like below:

     "authentication": {
       "blockUnknown": false,
       "class": "solr.BasicAuthPlugin",
       "credentials": {
         "solr": "scrambledsecuritycredentials"
       }

   Then restart the Solr service.
    

3. Use Correct Credentials: Verify that the credentials provided in your request (e.g., when creating a core) are correct. This includes the username and password if basic authentication is used.

4. Check Solr Logs:
   Examine the Solr logs for more details on the authentication failure. Solr logs often contain helpful information about the cause of authentication issues. Look for error messages or warnings related to authentication in the logs.
   
   By carefully reviewing your Solr configuration, checking authentication credentials, and examining Solr logs, you should be able to identify and resolve the authentication-related issues causing the HTTP Error 401 require authentication.