Reindex

Refer to https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html

Reindex: If you want to merge different concrete indices.

Sometimes if the indices is not balance like too many tiny indices or can not shrink number of shards to suitable number.

Brief introduction

1. Create the new dest indices
2. Call _reindex action
3. Check reindex running status
4. Recover the indices setting to the new dest indices
5. Delete the old indices

Example

We want to merge qlog-fff-202105-000002, qlog-fff-202104-1

Run Step 1.

Create the dest indices with the right mappings and settings. Check the template for index name if you want to apply some default settings.

• replica and refresh_interval are for speeding up the process.

PUT  qlog-fff-202104-0000-1
{
  "settings": {
    "index": {
      "number_of_shards": 2,  // Change here depends on your case
      "number_of_replicas": 0,
      "refresh_interval": "-1"
    }
  }
}

Run Step 2.

• slices can speed up reindex process.
• By default _reindex uses scroll batches of 1000. You can change the batch size with the size field in the source element:
• Set dest indices by the previous one

POST _reindex?wait_for_completion=false&slices=auto&refresh=false
{
  "source": {
    "index": ["qlog-fff-202105-000002", "qlog-fff-202104-1"],
    "size": 5000
  },
  "dest": {
    "index": "qlog-fff-202104-0000-1"
  }
}

Run Step 3.

check reindex status

GET _tasks?detailed=true&actions=*reindex

Run Step 4.

Check the new indices doc.size whether is expected or not Recover Settings

GET qlog-fff-202104-0000-1/_settings
PUT qlog-fff-202104-0000-1/_settings
{
  "index": {
  "refresh_interval": null, // depends on your default setting value
  "number_of_replicas": 1
  }
}

Run Step 5.

Delete unnecessary indices.

GET _cat/snapshots/cs-automated?v&s=start_epoch:desc
GET _snapshot/cs-automated/2021-04-08t08-50-34.1efe36ab-ed7d-4dc7-b160-6014453d8774
## Check Snapshot before delection


DELETE qlog-fff-202105-000002
DELETE qlog-fff-202104-1"