Monitoring Cluster Metrics with Amazon CloudWatch

Interpreting Health Dashboards

The Instance health tab in the Amazon ES console uses box charts to provide at-a-glance visibility into the health of each Elasticsearch node.

• Each colored box shows the range of values for the node over the specified time period.

• Blue boxes represent values that are consistent with other nodes. Red boxes represent outliers.

• The white line within each box shows the node's current value.

• The “whiskers” on either side of each box show the minimum and maximum values for all nodes over the time period.

Amazon ES domains send performance metrics to Amazon CloudWatch every minute. If you use General Purpose or Magnetic EBS volumes, the EBS volume metrics update only every five minutes. To view these metrics, use the Cluster health and Instance health tabs in the Amazon Elasticsearch Service console. The metrics are provided at no extra charge.

If you make configuration changes to your domain, the list of individual instances in the Cluster health and Instance health tabs often double in size for a brief period before returning to the correct number. For an explanation of this behavior, see Configuration Changes.

All metrics are in the AWS/ES namespace. Metrics for individual nodes are in the ClientId, DomainName, NodeId dimension. Cluster metrics are in the Per-Domain, Per-Client Metrics dimension. Some node metrics are aggregated at the cluster level and thus included in both dimensions. The service archives metrics for two weeks before discarding them.

• Cluster Metrics

• Dedicated Master Node Metrics

• EBS Volume Metrics

• Instance Metrics

• UltraWarm Metrics

• Alerting Metrics

• SQL Metrics

• KNN Metrics

• Cross-Cluster Search Metrics

Cluster Metrics

Amazon Elasticsearch Service provides the following metrics for clusters.

Metric	Description
ClusterStatus.green	A value of 1 indicates that all index shards are allocated to nodes in the cluster. Relevant statistics: Maximum
ClusterStatus.yellow	A value of 1 indicates that the primary shards for all indices are allocated to nodes in the cluster, but replica shards for at least one index are not. For more information, see Yellow Cluster Status. Relevant statistics: Maximum
ClusterStatus.red	A value of 1 indicates that the primary and replica shards for at least one index are not allocated to nodes in the cluster. For more information, see Red Cluster Status. Relevant statistics: Maximum
Nodes	The number of nodes in the Amazon ES cluster, including dedicated master nodes and UltraWarm nodes. For more information, see Configuration Changes. Relevant statistics: Maximum
SearchableDocuments	The total number of searchable documents across all data nodes in the cluster. Relevant statistics: Minimum, Maximum, Average
DeletedDocuments	The total number of documents marked for deletion across all data nodes in the cluster. These documents no longer appear in search results, but Elasticsearch only removes deleted documents from disk during segment merges. This metric increases after delete requests and decreases after segment merges. Relevant statistics: Minimum, Maximum, Average
CPUUtilization	The percentage of CPU usage for data nodes in the cluster. Maximum shows the node with the highest CPU usage. Average represents all nodes in the cluster. This metric is also available for individual nodes. Relevant statistics: Maximum, Average
FreeStorageSpace	The free space for data nodes in the cluster. Sum shows total free space for the cluster, but you must leave the period at one minute to get an accurate value. Minimum and Maximum show the nodes with the least and most free space, respectively. This metric is also available for individual nodes. Amazon ES throws a ClusterBlockException when this metric reaches 0. To recover, you must either delete indices, add larger instances, or add EBS-based storage to existing instances. To learn more, see Lack of Available Storage Space. The Amazon ES console displays this value in GiB. The Amazon CloudWatch console displays it in MiB. Note FreeStorageSpace will always be lower than the value that the Elasticsearch _cluster/stats API provides. Amazon ES reserves a percentage of the storage space on each instance for internal operations. Relevant statistics: Minimum, Maximum, Average, Sum
ClusterUsedSpace	The total used space for the cluster. You must leave the period at one minute to get an accurate value. The Amazon ES console displays this value in GiB. The Amazon CloudWatch console displays it in MiB. Relevant statistics: Minimum, Maximum
ClusterIndexWritesBlocked	Indicates whether your cluster is accepting or blocking incoming write requests. A value of 0 means that the cluster is accepting requests. A value of 1 means that it is blocking requests. Some common factors include the following: FreeStorageSpace is too low or JVMMemoryPressure is too high. To alleviate this issue, consider adding more disk space or scaling your cluster. Relevant statistics: Maximum
JVMMemoryPressure	The maximum percentage of the Java heap used for all data nodes in the cluster. Amazon ES uses half of an instance's RAM for the Java heap, up to a heap size of 32 GiB. You can scale instances vertically up to 64 GiB of RAM, at which point you can scale horizontally by adding instances. See Recommended CloudWatch Alarms. Relevant statistics: Maximum
AutomatedSnapshotFailure	The number of failed automated snapshots for the cluster. A value of 1 indicates that no automated snapshot was taken for the domain in the previous 36 hours. Relevant statistics: Minimum, Maximum
CPUCreditBalance	The remaining CPU credits available for data nodes in the cluster. A CPU credit provides the performance of a full CPU core for one minute. For more information, see CPU credits in the Amazon EC2 Developer Guide. This metric is available only for the T2 instance types. Relevant statistics: Minimum
KibanaHealthyNodes	A health check for Kibana. A value of 1 indicates normal behavior. A value of 0 indicates that Kibana is inaccessible. In most cases, the health of Kibana mirrors the health of the cluster. Relevant statistics: Minimum
KMSKeyError	A value of 1 indicates that the KMS customer master key used to encrypt data at rest has been disabled. To restore the domain to normal operations, re-enable the key. The console displays this metric only for domains that encrypt data at rest. Relevant statistics: Minimum, Maximum
KMSKeyInaccessible	A value of 1 indicates that the KMS customer master key used to encrypt data at rest has been deleted or revoked its grants to Amazon ES. You can't recover domains that are in this state. If you have a manual snapshot, though, you can use it to migrate the domain's data to a new domain. The console displays this metric only for domains that encrypt data at rest. Relevant statistics: Minimum, Maximum
InvalidHostHeaderRequests	The number of HTTP requests made to the Elasticsearch cluster that included an invalid (or missing) host header. Valid requests include the domain hostname as the host header value. Amazon ES rejects invalid requests for public access domains that don't have a restrictive access policy. We recommend applying a restrictive access policy to all domains. If you see large values for this metric, confirm that your Elasticsearch clients include the domain hostname (and not, for example, its IP address) in their requests. Relevant statistics: Sum
ElasticsearchRequests	The number of requests made to the Elasticsearch cluster. Relevant statistics: Sum
2xx, 3xx, 4xx, 5xx	The number of requests to the domain that resulted in the given HTTP response code (2xx, 3xx, 4xx, 5xx). Relevant statistics: Sum

Dedicated Master Node Metrics

Amazon Elasticsearch Service provides the following metrics for dedicated master nodes.

Metric	Description
MasterCPUUtilization	The maximum percentage of CPU resources used by the dedicated master nodes. We recommend increasing the size of the instance type when this metric reaches 60 percent. Relevant statistics: Average
MasterFreeStorageSpace	This metric is not relevant and can be ignored. The service does not use master nodes as data nodes.
MasterJVMMemoryPressure	The maximum percentage of the Java heap used for all dedicated master nodes in the cluster. We recommend moving to a larger instance type when this metric reaches 85 percent. Relevant statistics: Maximum
MasterCPUCreditBalance	The remaining CPU credits available for dedicated master nodes in the cluster. A CPU credit provides the performance of a full CPU core for one minute. For more information, see CPU credits in the Amazon EC2 Developer Guide. This metric is available only for the T2 instance types. Relevant statistics: Minimum
MasterReachableFromNode	A health check for MasterNotDiscovered exceptions. A value of 1 indicates normal behavior. A value of 0 indicates that /_cluster/health/ is failing. Failures mean that the master node stopped or is not reachable. They are usually the result of a network connectivity issue or AWS dependency problem. Relevant statistics: Minimum
MasterSysMemoryUtilization	The percentage of the master node's memory that is in use. Relevant statistics: Maximum

EBS Volume Metrics

Amazon Elasticsearch Service provides the following metrics for EBS volumes.

Metric	Description
ReadLatency	The latency, in seconds, for read operations on EBS volumes. Relevant statistics: Minimum, Maximum, Average
WriteLatency	The latency, in seconds, for write operations on EBS volumes. Relevant statistics: Minimum, Maximum, Average
ReadThroughput	The throughput, in bytes per second, for read operations on EBS volumes. Relevant statistics: Minimum, Maximum, Average
WriteThroughput	The throughput, in bytes per second, for write operations on EBS volumes. Relevant statistics: Minimum, Maximum, Average
DiskQueueDepth	The number of pending input and output (I/O) requests for an EBS volume. Relevant statistics: Minimum, Maximum, Average
ReadIOPS	The number of input and output (I/O) operations per second for read operations on EBS volumes. Relevant statistics: Minimum, Maximum, Average
WriteIOPS	The number of input and output (I/O) operations per second for write operations on EBS volumes. Relevant statistics: Minimum, Maximum, Average

Instance Metrics

Amazon Elasticsearch Service provides the following metrics for each instance in a domain. Amazon ES also aggregates these instance metrics to provide insight into overall cluster health. You can verify this behavior using the Data samples statistic in the console. Note that each metric in the following table has relevant statistics for the node and the cluster.

Important

Different versions of Elasticsearch use different thread pools to process calls to the _index API. Elasticsearch 1.5 and 2.3 use the index thread pool. Elasticsearch 5.x, 6.0, and 6.2 use the bulk thread pool. 6.3 and later use the write thread pool. Currently, the Amazon ES console doesn't include a graph for the bulk thread pool.

Use GET _cluster/settings?include_defaults=true to check thread pool and queue sizes for your cluster.

Metric	Description
IndexingLatency	The average time, in milliseconds, that it takes a shard to complete an indexing operation. Relevant node statistics: Average Relevant cluster statistics: Average, Maximum
IndexingRate	The number of indexing operations per minute. A single call to the _bulk API that adds two documents and updates two counts as four operations, which might be spread across one or more nodes. If that index has one or more replicas, other nodes in the cluster also record a total of four indexing operations. Document deletions do not count towards this metric. Relevant node statistics: Average Relevant cluster statistics: Average, Maximum, Sum
SearchLatency	The average time, in milliseconds, that it takes a shard on a data node to complete a search operation. Relevant node statistics: Average Relevant cluster statistics: Average, Maximum
SearchRate	The total number of search requests per minute for all shards on a data node. A single call to the _search API might return results from many different shards. If five of these shards are on one node, the node would report 5 for this metric, even though the client only made one request. Relevant node statistics: Average Relevant cluster statistics: Average, Maximum, Sum
SysMemoryUtilization	The percentage of the instance's memory that is in use. High values for this metric are normal and usually do not represent a problem with your cluster. For a better indicator of potential performance and stability issues, see the JVMMemoryPressure metric. Relevant node statistics: Minimum, Maximum, Average Relevant cluster statistics: Minimum, Maximum, Average
JVMGCYoungCollectionCount	The number of times that "young generation" garbage collection has run. A large, ever-growing number of runs is a normal part of cluster operations. Relevant node statistics: Maximum Relevant cluster statistics: Sum, Maximum, Average
JVMGCYoungCollectionTime	The amount of time, in milliseconds, that the cluster has spent performing "young generation" garbage collection. Relevant node statistics: Maximum Relevant cluster statistics: Sum, Maximum, Average
JVMGCOldCollectionCount	The number of times that "old generation" garbage collection has run. In a cluster with sufficient resources, this number should remain small and grow infrequently. Relevant node statistics: Maximum Relevant cluster statistics: Sum, Maximum, Average
JVMGCOldCollectionTime	The amount of time, in milliseconds, that the cluster has spent performing "old generation" garbage collection. Relevant node statistics: Maximum Relevant cluster statistics: Sum, Maximum, Average
ThreadpoolForce_mergeQueue	The number of queued tasks in the force merge thread pool. If the queue size is consistently high, consider scaling your cluster. Relevant node statistics: Maximum Relevant cluster statistics: Sum, Maximum, Average
ThreadpoolForce_mergeRejected	The number of rejected tasks in the force merge thread pool. If this number continually grows, consider scaling your cluster. Relevant node statistics: Maximum Relevant cluster statistics: Sum
ThreadpoolForce_mergeThreads	The size of the force merge thread pool. Relevant node statistics: Maximum Relevant cluster statistics: Average, Sum
ThreadpoolIndexQueue	The number of queued tasks in the index thread pool. If the queue size is consistently high, consider scaling your cluster. The maximum index queue size is 200. Relevant node statistics: Maximum Relevant cluster statistics: Sum, Maximum, Average
ThreadpoolIndexRejected	The number of rejected tasks in the index thread pool. If this number continually grows, consider scaling your cluster. Relevant node statistics: Maximum Relevant cluster statistics: Sum
ThreadpoolIndexThreads	The size of the index thread pool. Relevant node statistics: Maximum Relevant cluster statistics: Average, Sum
ThreadpoolSearchQueue	The number of queued tasks in the search thread pool. If the queue size is consistently high, consider scaling your cluster. The maximum search queue size is 1,000. Relevant node statistics: Maximum Relevant cluster statistics: Sum, Maximum, Average
ThreadpoolSearchRejected	The number of rejected tasks in the search thread pool. If this number continually grows, consider scaling your cluster. Relevant node statistics: Maximum Relevant cluster statistics: Sum
ThreadpoolSearchThreads	The size of the search thread pool. Relevant node statistics: Maximum Relevant cluster statistics: Average, Sum
ThreadpoolBulkQueue	The number of queued tasks in the bulk thread pool. If the queue size is consistently high, consider scaling your cluster. Relevant node statistics: Maximum Relevant cluster statistics: Sum, Maximum, Average
ThreadpoolBulkRejected	The number of rejected tasks in the bulk thread pool. If this number continually grows, consider scaling your cluster. Relevant node statistics: Maximum Relevant cluster statistics: Sum
ThreadpoolBulkThreads	The size of the bulk thread pool. Relevant node statistics: Maximum Relevant cluster statistics: Average, Sum
ThreadpoolWriteThreads	The size of the write thread pool. Relevant node statistics: Maximum Relevant cluster statistics: Average, Sum
ThreadpoolWriteRejected	The number of rejected tasks in the write thread pool. Relevant node statistics: Maximum Relevant cluster statistics: Average, Sum
ThreadpoolWriteQueue	The number of queued tasks in the write thread pool. Relevant node statistics: Maximum Relevant cluster statistics: Average, Sum

UltraWarm Metrics

Amazon Elasticsearch Service provides the following metrics for UltraWarm nodes.

Metric	Description
WarmCPUUtilization	The percentage of CPU usage for UltraWarm nodes in the cluster. Maximum shows the node with the highest CPU usage. Average represents all UltraWarm nodes in the cluster. This metric is also available for individual UltraWarm nodes. Relevant statistics: Maximum, Average
WarmFreeStorageSpace	The amount of free warm storage space in MiB. Because UltraWarm uses Amazon S3 rather than attached disks, Sum is the only relevant statistic. You must leave the period at one minute to get an accurate value. Relevant statistics: Sum
WarmJVMMemoryPressure	The maximum percentage of the Java heap used for the UltraWarm nodes. Relevant statistics: Maximum
WarmSearchableDocuments	The total number of searchable documents across all warm indices in the cluster. You must leave the period at one minute to get an accurate value. Relevant statistics: Sum
WarmSearchLatency	The average time, in milliseconds, that it takes a shard on an UltraWarm node to complete a search operation. Relevant node statistics: Average Relevant cluster statistics: Average, Maximum
WarmSearchRate	The total number of search requests per minute for all shards on an UltraWarm node. A single call to the _search API might return results from many different shards. If five of these shards are on one node, the node would report 5 for this metric, even though the client only made one request. Relevant node statistics: Average Relevant cluster statistics: Average, Maximum, Sum
WarmStorageSpaceUtilization	The total amount of warm storage space that the cluster is using. The Amazon ES console displays this value in GiB. The Amazon CloudWatch console displays it in MiB. Relevant statistics: Maximum
HotStorageSpaceUtilization	The total amount of hot storage space that the cluster is using. Relevant statistics: Maximum
WarmSysMemoryUtilization	The percentage of the warm node's memory that is in use. Relevant statistics: Maximum
HotToWarmMigrationQueueSize	The number of indices currently waiting to migrate from hot to warm storage. Relevant statistics: Maximum
WarmToHotMigrationQueueSize	The number of indices currently waiting to migrate from warm to hot storage. Relevant statistics: Maximum
HotToWarmMigrationFailureCount	The total number of failed hot to warm migrations. Relevant statistics: Sum
HotToWarmMigrationForceMergeLatency	The average latency of the force merge stage of the migration process. If this stage consistently takes too long, consider increasing index.ultrawarm.migration.force_merge.max_num_segments. Relevant statistics: Average
HotToWarmMigrationSnapshotLatency	The average latency of the snapshot stage of the migration process. If this stage consistently takes too long, ensure that your shards are appropriately sized and distributed throughout the cluster. Relevant statistics: Average
HotToWarmMigrationProcessingLatency	The average latency of successful hot to warm migrations, not including time spent in the queue. This value is the sum of the amount of time it takes to complete the force merge, snapshot, and shard relocation stages of the migration process. Relevant statistics: Average
HotToWarmMigrationSuccessCount	The total number of successful hot to warm migrations. Relevant statistics: Sum
HotToWarmMigrationSuccessLatency	The average latency of successful hot to warm migrations, including time spent in the queue. Relevant statistics: Average

Alerting Metrics

Amazon Elasticsearch Service provides the following metrics for the alerting feature.

Metric	Description
AlertingDegraded	A value of 1 means that either the alerting index is red or one or more nodes is not on schedule. A value of 0 indicates normal behavior. Relevant statistics: Maximum
AlertingIndexExists	A value of 1 means the .opendistro-alerting-config index exists. A value of 0 means it does not. Until you use the alerting feature for the first time, this value remains 0. Relevant statistics: Maximum
AlertingIndexStatus.green	The health of the index. A value of 1 means green. A value of 0 means that the index either doesn't exist or isn't green. Relevant statistics: Maximum
AlertingIndexStatus.red	The health of the index. A value of 1 means red. A value of 0 means that the index either doesn't exist or isn't red. Relevant statistics: Maximum
AlertingIndexStatus.yellow	The health of the index. A value of 1 means yellow. A value of 0 means that the index either doesn't exist or isn't yellow. Relevant statistics: Maximum
AlertingNodesNotOnSchedule	A value of 1 means some jobs are not running on schedule. A value of 0 means that all alerting jobs are running on schedule (or that no alerting jobs exist). Check the Amazon ES console or make a _nodes/stats request to see if any nodes show high resource usage. Relevant statistics: Maximum
AlertingNodesOnSchedule	A value of 1 means that all alerting jobs are running on schedule (or that no alerting jobs exist). A value of 0 means some jobs are not running on schedule. Relevant statistics: Maximum
AlertingScheduledJobEnabled	A value of 1 means that the opendistro.scheduled_jobs.enabled cluster setting is true. A value of 0 means it is false, and scheduled jobs are disabled. Relevant statistics: Maximum

Anomaly Detection Metrics

Amazon Elasticsearch Service provides the following metrics for the anomaly detection feature.

Metric	Description
AnomalyDetectionPluginUnhealthy	A value of 1 means that the anomaly detection plugin is not functioning properly, either because of a high number of failures or because one of the indices that it uses is red. A value of 0 indicates the plugin is working as expected. Relevant statistics: Maximum
AnomalyDetectionRequestCount	The number of requests to detect anomalies. Relevant statistics: Sum
AnomalyDetectionFailureCount	The number of failed requests to detect anomalies. Relevant statistics: Sum
AnomalyResultsIndexStatusIndexExists	A value of 1 means the index that the .opendistro-anomaly-results alias points to exists. Until you use the anomaly detection feature for the first time, this value remains 0. Relevant statistics: Maximum
AnomalyResultsIndexStatus.red	A value of 1 means the index that the .opendistro-anomaly-results alias points to is red. A value of 0 means it is not. Until you use the anomaly detection feature for the first time, this value remains 0. Relevant statistics: Maximum
AnomalyDetectorsIndexStatusIndexExists	A value of 1 means that the .opendistro-anomaly-detectors index exists. A value of 0 means it does not. Until you use the anomaly detection feature for the first time, this value remains 0. Relevant statistics: Maximum
AnomalyDetectorsIndexStatus.red	A value of 1 means that the .opendistro-anomaly-detectors index is red. A value of 0 means it is not. Until you use the anomaly detection feature for the first time, this value remains 0. Relevant statistics: Maximum
ModelsCheckpointIndexStatusIndexExists	A value of 1 means that the .opendistro-anomaly-checkpoints index exists. A value of 0 means it does not. Until you use the anomaly detection feature for the first time, this value remains 0. Relevant statistics: Maximum
ModelsCheckpointIndexStatus.red	A value of 1 means that the .opendistro-anomaly-checkpoints index is red. A value of 0 means it is not. Until you use the anomaly detection feature for the first time, this value remains 0. Relevant statistics: Maximum

SQL Metrics

Amazon Elasticsearch Service provides the following metrics for SQL support.

Metric	Description
SQLFailedRequestCountByCusErr	The number of requests to the _opendistro/_sql API that failed due to a client issue. For example, a request might return HTTP status code 400 due to an IndexNotFoundException. Relevant statistics: Sum
SQLFailedRequestCountBySysErr	The number of requests to the _opendistro/_sql API that failed due to a server problem or feature limitation. For example, a request might return HTTP status code 503 due to a VerificationException. Relevant statistics: Sum
SQLRequestCount	The number of requests to the _opendistro/_sql API. Relevant statistics: Sum
SQLDefaultCursorRequestCount	Similar to SQLRequestCount but only counts pagination requests. Relevant statistics: Sum
SQLUnhealthy	A value of 1 indicates that, in response to certain requests, the SQL plugin is returning 5xx response codes or passing invalid query DSL to Elasticsearch. Other requests should continue to succeed. A value of 0 indicates no recent failures. If you see a sustained value of 1, troubleshoot the requests your clients are making to the plugin. Relevant statistics: Maximum

KNN Metrics

Amazon Elasticsearch Service includes metrics for KNN.

Metric	Description
KNNCacheCapacityReached	Per-node metric for whether cache capacity has been reached. This metric is only relevant to approximate KNN search. Relevant statistics: Maximum
KNNCircuitBreakerTriggered	Per-cluster metric for whether the circuit breaker is triggered. If any nodes return a value of 1 for KNNCacheCapacityReached, this value will also return 1. This metric is only relevant to approximate KNN search. Relevant statistics: Maximum
KNNEvictionCount	Per-node metric for the number of graphs that have been evicted from the cache due to memory constraints or idle time. Explicit evictions that occur because of index deletion are not counted. This metric is only relevant to approximate KNN search. Relevant statistics: Sum
KNNGraphIndexErrors	Per-node metric for the number of requests to add the knn_vector field of a document to a graph that produced an error. Relevant statistics: Sum
KNNGraphIndexRequests	Per-node metric for the number of requests to add the knn_vector field of a document to a graph. Relevant statistics: Sum
KNNGraphMemoryUsage	Per-node metric for the current cache size (total size of all graphs in memory) in kilobytes. This metric is only relevant to approximate KNN search. Relevant statistics: Average
KNNGraphQueryErrors	Per-node metric for the number of graph queries that produced an error. Relevant statistics: Sum
KNNGraphQueryRequests	Per-node metric for the number of graph queries. Relevant statistics: Sum
KNNHitCount	Per-node metric for the number of cache hits. A cache hit occurs when a user queries a graph that is already loaded into memory. This metric is only relevant to approximate KNN search. Relevant statistics: Sum
KNNLoadExceptionCount	Per-node metric for the number of times an exception occurred while trying to load a graph into the cache. This metric is only relevant to approximate KNN search. Relevant statistics: Sum
KNNLoadSuccessCount	Per-node metric for the number of times the plugin successfully loaded a graph into the cache. This metric is only relevant to approximate KNN search. Relevant statistics: Sum
KNNMissCount	Per-node metric for the number of cache misses. A cache miss occurs when a user queries a graph that is not yet loaded into memory. This metric is only relevant to approximate KNN search. Relevant statistics: Sum
KNNQueryRequests	Per-node metric for the number of query requests the KNN plugin received. Relevant statistics: Sum
KNNScriptCompilationErrors	Per-node metric for the number of errors during script compilation. This statistic is only relevant to KNN score script search. Relevant statistics: Sum
KNNScriptCompilations	Per-node metric for the number of times the KNN script has been compiled. This value should usually be 1 or 0, but if the cache containing the compiled scripts is filled, the KNN script might be recompiled. This statistic is only relevant to KNN score script search. Relevant statistics: Sum
KNNScriptQueryErrors	Per-node metric for the number of errors during script queries. This statistic is only relevant to KNN score script search. Relevant statistics: Sum
KNNScriptQueryRequests	Per-node metric for the total number of script queries. This statistic is only relevant to KNN score script search. Relevant statistics: Sum
KNNTotalLoadTime	The time in nanoseconds that KNN has taken to load graphs into the cache. This metric is only relevant to approximate KNN search. Relevant statistics: Sum

Cross-Cluster Search Metrics

Amazon Elasticsearch Service provides the following metrics for Cross-cluster search.

Source domain metrics

Metric	Dimension	Description
CrossClusterOutboundConnections	ConnectionId	Number of connected nodes. If your response includes one or more skipped domains, use this metric to trace any unhealthy connections. If this number drops to 0, then the connection is unhealthy.
CrossClusterOutboundRequests	ConnectionId	Number of search requests sent to the destination domain. Use to check if the load of cross-cluster search requests are overwhelming your domain, correlate any spike in this metric with any JVM/CPU spike.

Destination domain metric

Metric	Dimension	Description
CrossClusterInboundRequests	ConnectionId	Number of incoming connection requests received from the source domain.

Add a CloudWatch alarm in the event that you lose a connection unexpectedly. For steps to create an alarm, see Create a CloudWatch Alarm Based on a Static Threshold.

Learning to Rank Metrics

Amazon Elasticsearch Service provides the following metrics for Learning to Rank.

Metric	Description
LTRRequestTotalCount	Total count of ranking requests.
LTRRequestErrorCount	Total count of unsuccessful requests.
LTRStoreIndexIsRed	Tracks if one of the indices needed to run the plugin is red.
LTRMemoryUsage	Total memory used by the plugin.