Flushing an index

For performance reasons, Elasticsearch stores some data in memory and on a transaction log. If we want to free memory, we need to empty the transaction log, and to ensure that our data is safely written on disk, we need to flush an index.

Elasticsearch automatically provides periodic flushing on disk, but forcing flushing can be useful in the following situations:

• When we need to shut down a node to prevent stale data
• When we need to have all the data in a safe state (for example, after a big indexing operation so that all the data can be flushed and refreshed)

Getting ready

You will need an up-and-running Elasticsearch installation, as we described in the Downloading and installing Elasticsearch recipe of Chapter 1, Getting Started.

To execute the commands in this recipe, you can use any HTTP client, such as curl (https://curl.haxx.se/), Postman (https://www.getpostman.com/), or others. I suggest using the Kibana console as it provides...