Troubleshooting index lifecycle management errors

When ILM executes a lifecycle policy, it’s possible for errors to occur while performing the necessary index operations for a step. When this happens, ILM moves the index to an ERROR step. If ILM cannot resolve the error automatically, execution is halted until you resolve the underlying issues with the policy, index, or cluster.

For example, you might have a shrink-index policy that shrinks an index to four shards once it is at least five days old:

response = client.ilm.put_lifecycle(
  policy: 'shrink-index',
  body: {
    policy: {
      phases: {
        warm: {
          min_age: '5d',
          actions: {
            shrink: {
              number_of_shards: 4
            }
          }
        }
      }
    }
  }
)
puts response

PUT _ilm/policy/shrink-index
{
  "policy": {
    "phases": {
      "warm": {
        "min_age": "5d",
        "actions": {
          "shrink": {
            "number_of_shards": 4
          }
        }
      }
    }
  }
}

There is nothing that prevents you from applying the shrink-index policy to a new index that has only two shards:

PUT /my-index-000001
{
  "settings": {
    "index.number_of_shards": 2,
    "index.lifecycle.name": "shrink-index"
  }
}

After five days, ILM attempts to shrink my-index-000001 from two shards to four shards. Because the shrink action cannot increase the number of shards, this operation fails and ILM moves my-index-000001 to the ERROR step.

You can use the ILM Explain API to get information about what went wrong:

response = client.ilm.explain_lifecycle(
  index: 'my-index-000001'
)
puts response

GET /my-index-000001/_ilm/explain

Which returns the following information:

{
  "indices" : {
    "my-index-000001" : {
      "index" : "my-index-000001",
      "managed" : true,
      "index_creation_date_millis" : 1541717265865,
      "time_since_index_creation": "5.1d",
      "policy" : "shrink-index",                
      "lifecycle_date_millis" : 1541717265865,
      "age": "5.1d",                            
      "phase" : "warm",                         
      "phase_time_millis" : 1541717272601,
      "action" : "shrink",                      
      "action_time_millis" : 1541717272601,
      "step" : "ERROR",                         
      "step_time_millis" : 1541717272688,
      "failed_step" : "shrink",                 
      "step_info" : {
        "type" : "illegal_argument_exception",  
        "reason" : "the number of target shards [4] must be less that the number of source shards [2]"
      },
      "phase_execution" : {
        "policy" : "shrink-index",
        "phase_definition" : {                  
          "min_age" : "5d",
          "actions" : {
            "shrink" : {
              "number_of_shards" : 4
            }
          }
        },
        "version" : 1,
        "modified_date_in_millis" : 1541717264230
      }
    }
  }
}

To resolve this, you could update the policy to shrink the index to a single shard after 5 days:

response = client.ilm.put_lifecycle(
  policy: 'shrink-index',
  body: {
    policy: {
      phases: {
        warm: {
          min_age: '5d',
          actions: {
            shrink: {
              number_of_shards: 1
            }
          }
        }
      }
    }
  }
)
puts response

PUT _ilm/policy/shrink-index
{
  "policy": {
    "phases": {
      "warm": {
        "min_age": "5d",
        "actions": {
          "shrink": {
            "number_of_shards": 1
          }
        }
      }
    }
  }
}

Once you fix the problem that put an index in the ERROR step, you might need to explicitly tell ILM to retry the step:

POST /my-index-000001/_ilm/retry

ILM subsequently attempts to re-run the step that failed. You can use the ILM Explain API to monitor the progress.

Here’s how to resolve the most common errors reported in the ERROR step.

The target rollover alias is specified in an index template’s index.lifecycle.rollover_alias setting. You need to explicitly configure this alias one time when you bootstrap the initial index. The rollover action then manages setting and updating the alias to roll over to each subsequent index.

Do not explicitly configure this same alias in the aliases section of an index template.

Either the index is using the wrong alias or the alias does not exist.

Check the index.lifecycle.rollover_alias index setting. To see what aliases are configured, use _cat/aliases.

The index.lifecycle.rollover_alias setting must be configured for the rollover action to work.

Update the index settings to set index.lifecycle.rollover_alias.

Only one index can be designated as the write index for a particular alias.

Use the aliases API to set is_write_index:false for all but one index.

The index name must match the regex pattern ^.*-\d+ for the rollover action to work. The most common problem is that the index name does not contain trailing digits. For example, my-index does not match the pattern requirement.

Append a numeric value to the index name, for example my-index-000001.

This indicates that the cluster is hitting resource limits.

Before continuing to set up ILM, you’ll need to take steps to alleviate the resource issues. For more information, see Circuit breaker errors.

This indicates that the cluster is running out of disk space. This can happen when you don’t have index lifecycle management set up to roll over from hot to warm nodes.

Consider adding nodes, upgrading your hardware, or deleting unneeded indices.

This indicates the ILM action cannot be executed because the user used by ILM to perform the action doesn’t have the proper privileges. This can happen when user’s privileges has been dropped after updating the ILM policy. ILM actions are run as though they were performed by the last user who modify the policy. The account used to create or modify the policy from should have permissions to perform all operations that are part of that policy.