One of the most important tasks for the administrator is to make sure that no data will be lost in the case of a system failure. Elasticsearch, in its assumptions, is a resistant and well-configured cluster of nodes and can survive even a few simultaneous disasters. However, even the most properly configured cluster is vulnerable to network splits and network partitions, which in some very rare cases can result in data corruption or loss. In such cases, being able to get data restored from the backup is the only solution that can save us from recreating our indices. You probably already know what we want to talk about: the snapshot / restore functionality provided by Elasticsearch. However, as we said earlier, we don't want to repeat ourselves—this is a book for more advanced Elasticsearch users, and basics of the snapshot and restore API were already described in Elasticsearch Server Second Edition by Packt Publishing and in the official documentation. Now, we want to focus on...