Over the selected timeframe, the Cluster Status Summary frame shows the color statuses that the Elasticsearch cluster has gone through. In this example, during the selected timeframe, the cluster was in a Green status once and in a Yellow status once during the selected timeframe.
The Active Primary Shards frame will show differing numbers depending on the number of active primary shards for the selected account’s Elasticsearch service.
From Elasticsearch: The definitive Guide [2.x]:
“In Dynamically Updatable Indices, we explained that a shard is a Lucene index and that an Elasticsearch index is a collection of shards. Your application talks to an index, and Elasticsearch routes your requests to the appropriate shards. A shard is the unit of scale. The smallest index you can have is one with a single shard. This may be more than sufficient for your needs — a single shard can hold a lot of data — but it limits your ability to scale.”
When an index is created, there are several shards created with that index. By default, five primary shards are allotted to each new index, meaning that an index can be spread across five nodes (one shard per node). There are also replica shards. These are primarily for failover. Replica shards can serve read requests.
Active Shards in Cluster - ALL primary and replica shards in an Elasticsearch cluster.
This frame will show the index name and the index color status count. Scrolling down the table, you will see the same index name with Yellow and Red color statuses. The number that follows the 27 index name is the count of the status color. If it is zero, there were no instances of the index being in that color status during these selected timeframes.
The Elasticsearch Status by node information frame shows the Elasticsearch cluster status by color, by node. This will help indicate which node in the Elasticsearch cluster is returning what status during the selected timeframe.
This Elasticsearch index information table shows the index name, what node it is on, the number of indexed documents, the index health, and the index size in MB at a particular time.
The Elasticsearch process CPU % frame shows the process CPU% by the Elasticsearch process over the selected timeframe.
Elasticsearch is a Java process. If it runs low on allocated memory, it will initiate garbage collection to free up memory. If garbage collection is frequent, it is an indication that there may be too many indices or shards for the allocated memory. There may be an opportunity to clean up the indices and shards or Elasticsearch may need more memory.
As indexes are created and updated, the index health may change.
The Elasticsearch Index Size frame indicates the index name and size across the selected timeframe. It may indicate problems with how a site is indexing.
The Elasticsearch Errors frame will display errors with Elasticsearch like running out of space, switching from Yellow to Red status, when all shards fail, when there are parameter issues with searches, version errors and when all nodes are unavailable.
Unassigned shards will cause a cluster to move from Green status to Yellow status.