# Siren Federate User Guide

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## Cluster APIs

The cluster APIs enables the retrieval of cluster and node level information, such as statistics about off-heap memory allocation.

### Nodes statistics

The cluster nodes stats API allows to retrieve one or more (or all) of the cluster nodes statistics.

    GET /_siren/nodes/stats
    GET /_siren/nodes/nodeId1,nodeId2/stats

The first command retrieves stats of all the nodes in the cluster. The second command selectively retrieves nodes stats of only `nodeId1` and `nodeId2`.

By default, all stats are returned. You can limit this by combining any of the following stats:

`memory`

  Memory allocation statistics.

`planner`

  Statistics about the planner job and task pools.

#### Memory information

The `memory` flag can be set to retrieve information about the memory allocation:

    GET /_siren/nodes/stats/memory

The response includes memory allocation statistics for each node as follows:

    {
      "se6baEC9T4K7-14yuG2qgA": {
        "memory" : {
          "allocated_direct_memory_in_bytes" : 0,
          "allocated_root_memory_in_bytes": 0,
          "root_allocator_dump": "Allocator(ROOT) 0/0/3750232064/17179869184 (res/actual/peak/limit)"
        }
      },
      "sKnVUBo9ShGzkl4GYih7BA": {
        "memory" : {
          "allocated_direct_memory_in_bytes" : 0,
          "allocated_root_memory_in_bytes": 0,
          "root_allocator_dump": "Allocator(ROOT) 0/0/0/17179869184 (res/actual/peak/limit)"
        }
      }
    }

`allocated_direct_memory_in_bytes`

  The actual direct memory allocated by Netty in bytes.

`allocated_root_memory_in_bytes`

  The actual direct memory allocated by the root allocator in bytes.

`allocator_dump`

  Dump of the root allocator including the actual direct memory allocated, the peak and the limit.

#### Planner information

The `planner` flag can be set to retrieve information about the planner job and task pools:

    GET /_siren/nodes/stats/planner

The response includes memory allocation statistics for each node as follows:

    {
      "se6baEC9T4K7-14yuG2qgA": {
        "planner": {
          "thread_pool": {
            "job": {
              "permits": 1,
              "queue": 0,
              "active": 0,
              "largest": 1,
              "completed": 538
            },
            "task": {
              "permits": 3,
              "queue": 0,
              "active": 0,
              "largest": 3,
              "completed": 3955
            }
          }
        }
      },
      "sKnVUBo9ShGzkl4GYih7BA": {
        "planner": {
          "thread_pool": {
            "job": {
              "permits": 1,
              "queue": 0,
              "active": 0,
              "largest": 1,
              "completed": 537
            },
            "task": {
              "permits": 3,
              "queue": 0,
              "active": 0,
              "largest": 3,
              "completed": 3863
            }
          }
        }
      }
    }

### Optimizer statistics cache

The cluster optimizer cache API allows to retrieve a snapshot of the query optimizer cache for a list of the cluster nodes.

    GET /_siren/cache
    GET /_siren/nodeId1,nodeId2/cache
    GET /_siren/cache/clear
    GET /_siren/nodeId1,nodeId2/cache/clear

The first command retrieves the state of the optimizer cache for all the nodes in the cluster, while the second only for the desired list of node IDs. The third command invalidates the optimizer cache on every node, while the last command does so for only the selected nodes.

The response includes statistics about the cache use on each node:

    {
      "aQAf0tIwRtq_n4mBr9SLTw": {
        "size": 92,
        "hit_count": 32,
        "miss_count": 92,
        "eviction_count": 42,
        "load_exception_count": 0,
        "load_success_count": 92,
        "total_load_time_in_millis": 68004
      }
    }

`size`

  The estimated number of entries in the cache.

`hit_count`

  The number of cache hits.

`miss_count`

  The number of cache misses.

`eviction_count`

  The number of evicted entries.

`load_exception_count`

  The number of times a request failed to execute as its response was to be put in the cache.

`load_success_count`

  The number of times a request was executed successfully as its response was to be put in the cache.

`total_load_time_in_millis`

  The time spent in milliseconds to load request responses into the cache.

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