Elasticsearch Error: Invalid alias name - Common Causes & Fixes

Brief Explanation

The "Invalid alias name" error in Elasticsearch occurs when attempting to create or modify an index alias using a name that doesn't comply with Elasticsearch's naming conventions or restrictions for aliases.

Common Causes

1. Using reserved characters in the alias name
2. Starting the alias name with underscores, periods, or plus signs
3. Using uppercase letters in the alias name
4. Exceeding the maximum length for alias names
5. Using system-reserved names or patterns

Troubleshooting and Resolution Steps

1. Review the alias name for any invalid characters or patterns:

   • Avoid using: , , *, ", \, <, >, |, /, ?, #,
   • Don't start with: _, ., +
   • Use only lowercase letters, numbers, and hyphens

2. Ensure the alias name is all lowercase.

3. Check that the alias name doesn't exceed 255 bytes.

4. Verify that the alias name isn't a system-reserved name or pattern.

5. Rename the alias using a valid name that follows Elasticsearch naming conventions.

6. If modifying an existing alias, use the _aliases API to rename it:

   POST /_aliases
   {
     "actions": [
       {
         "remove": {
           "index": "your_index",
           "alias": "old_invalid_alias"
         }
       },
       {
         "add": {
           "index": "your_index",
           "alias": "new_valid_alias"
         }
       }
     ]
   }
   

Best Practices

1. Use descriptive, lowercase names for aliases.
2. Stick to alphanumeric characters and hyphens.
3. Prefix aliases with a common identifier for easier management.
4. Document your alias naming conventions for consistency.
5. Regularly audit your aliases to ensure they follow best practices.

Frequently Asked Questions

Q: Can I use uppercase letters in my Elasticsearch alias names?
A: No, Elasticsearch alias names should only contain lowercase letters. Using uppercase letters will result in an "Invalid alias name" error.

Q: What characters are allowed in Elasticsearch alias names?
A: Elasticsearch alias names can contain lowercase letters, numbers, and hyphens. Avoid using special characters, spaces, or starting the name with underscores, periods, or plus signs.

Q: Is there a length limit for Elasticsearch alias names?
A: Yes, Elasticsearch alias names are limited to 255 bytes in length. It's best to keep names concise while still being descriptive.

Q: Can I rename an existing alias without downtime?
A: Yes, you can rename an existing alias without downtime using the _aliases API. This allows you to add the new alias and remove the old one in a single atomic operation.

Q: Are there any reserved names I should avoid for aliases?
A: Yes, avoid using system-reserved names or patterns for aliases. These include names starting with a period (.) and certain keywords used by Elasticsearch internally. Always check the current Elasticsearch documentation for the most up-to-date list of reserved names.