k-NN settings
The k-NN plugin adds several new cluster settings. To learn more about static and dynamic settings, see Configuring OpenSearch.
Cluster settings
The following table lists all available cluster-level k-NN settings. For more information about cluster settings, see Configuring OpenSearch and Updating cluster settings using the API.
| Setting | Static/Dynamic | Default | Description |
|---|---|---|---|
knn.plugin.enabled | Dynamic | true | Enables or disables the k-NN plugin. |
knn.algo_param.index_thread_qty | Dynamic | 1 | The number of threads used for native library index creation. Keeping this value low reduces the CPU impact of the k-NN plugin but also reduces indexing performance. |
knn.cache.item.expiry.enabled | Dynamic | false | Whether to remove native library indexes that have not been accessed for a certain duration from memory. |
knn.cache.item.expiry.minutes | Dynamic | 3h | If enabled, the amount of idle time before a native library index is removed from memory. |
knn.circuit_breaker.unset.percentage | Dynamic | 75 | The native memory usage threshold for the circuit breaker. Memory usage must be lower than this percentage of knn.memory.circuit_breaker.limit in order for knn.circuit_breaker.triggered to remain false. |
knn.circuit_breaker.triggered | Dynamic | false | True when memory usage exceeds the knn.circuit_breaker.unset.percentage value. |
knn.memory.circuit_breaker.limit | Dynamic | 50% | The native memory limit for native library indexes. At the default value, if a machine has 100 GB of memory and the JVM uses 32 GB, then the k-NN plugin uses 50% of the remaining 68 GB (34 GB). If memory usage exceeds this value, then the plugin removes the native library indexes used least recently. |
knn.memory.circuit_breaker.enabled | Dynamic | true | Whether to enable the k-NN memory circuit breaker. |
knn.model.index.number_of_shards | Dynamic | 1 | The number of shards to use for the model system index, which is the OpenSearch index that stores the models used for approximate nearest neighbor (ANN) search. |
knn.model.index.number_of_replicas | Dynamic | 1 | The number of replica shards to use for the model system index. Generally, in a multi-node cluster, this value should be at least 1 in order to increase stability. |
knn.model.cache.size.limit | Dynamic | 10% | The model cache limit cannot exceed 25% of the JVM heap. |
knn.faiss.avx2.disabled | Static | false | A static setting that specifies whether to disable the SIMD-based libopensearchknn_faiss_avx2.so library and load the non-optimized libopensearchknn_faiss.so library for the Faiss engine on machines with x64 architecture. For more information, see SIMD optimization for the Faiss engine. |
Index settings
The following table lists all available index-level k-NN settings. All settings are static. For information about updating static index-level settings, see Updating a static index setting.
| Setting | Default | Description |
|---|---|---|
index.knn.advanced.filtered_exact_search_threshold | null | The filtered ID threshold value used to switch to exact search during filtered ANN search. If the number of filtered IDs in a segment is lower than this setting’s value, then exact search will be performed on the filtered IDs. |
index.knn.algo_param.ef_search | 100 | ef (or efSearch) represents the size of the dynamic list for the nearest neighbors used during a search. Higher ef values lead to a more accurate but slower search. ef cannot be set to a value lower than the number of queried nearest neighbors, k. ef can take any value between k and the size of the dataset. |