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    Monitoring Dremio Nodes

    There are various approaches for operational monitoring of Dremio nodes. This topic discusses collecting JMX metrics, but Dremio administrators can other types of metrics, such as system telemetry.

    Blacklisting Nodes

    Dremio allows administrators to blacklist a node in a Dremio cluster from being used for query execution. You may wish to blacklist a node because queries are running slowly and you want to do some diagnostics or because you want to upgrade some component on the node, such as other firmware.


    Limitations: Blacklisting will not work for queries that are accelerated and when the reflections are stored on PDFS.

    To blacklist a node:

    1. From the Dremio UI, navigate to Admin > Cluster > Node Activity.
    2. Click on the Actions icon for the node.
    3. Select Avoid using this executor node.
    4. Select Yes, I am sure. to the Node status change popup.

    Alternatively, to whitelist a node that has been blacklisted:

    1. From the Dremio UI, navigate to Admin > Cluster > Node Activity.
    2. From the Actions icon for the whitelisted node, select Use this node for execution.
    3. Select Yes, I am sure. to the Node status change popup.

    Monitoring JMX Metrics

    Dremio recommends monitoring the following metrics:

    • Heap memory usage and GC frequency
    • Direct memory usage
    • Used lightweight threads

    Heap Memory Usage and GC Frequency

    Dremio uses heap memory for planning, coordination, UI serving, query management, connection management, and some types of record reading etc. type of tasks. Heap memory is expected to be higher in coordinator nodes in high concurrency deployments. When observed together, continued high garbage collection (GC) frequency and high heap memory usage would indicate an undersized cluster/node.

    Heap usage can be tracked via memory.heap.usage.

    Garbage collection can be tracked by monitoring cumulative counts and times over time: gc.PS-MarkSweep.count, gc.PS-MarkSweep.time, gc.PS-Scavenge.count, gc.PS-Scavenge.time. Please note that garbage collection logging is already enabled by default on all Dremio nodes.

    Direct Memory Usage

    Dremio uses direct memory for query execution tasks — directly affecting performance and concurrency. Dremio also uses direct memory for RPC communication between executor and coordinator nodes, as well as communicating with the end users. Direct memory is expected to be used heavily during query execution on the executor nodes. Continued high direct memory usage would indicate the cluster/node approaching it’s capacity.

    Direct memory allocated/used by the execution engine can be tracked via dremio.memory.direct_current. Total direct memory given to the JVM can be tracked via dremio.memory.jvm_direct_current.

    Used Lightweight Threads

    Depending on how much work Dremio is doing, the system might be aggressively parallel. Sometimes this can mean that Dremio is designed to allow for even a single query to use as many cores as available to the process. The number of threads running on each executor node describes the total amount of parallelization Dremio is using. This number maybe substantially more than the number of cores as Dremio is very effective at scheduling between different threads.

    If this metric goes more than 10-20 times the number of logical cores, you are probably slowing down individual queries due to contention. You can better understand the impact of contention on a per query basis by looking at the query profile and viewing “Wait Time” value under the “Thread Overview” section per phase. This describes how long each lightweight thread has work available to do but is not scheduled due to CPU contention. Note that this thread count is not directly correlated to kernel threads.

    Lightweight threads can be tracked via dremio.exec.work.running_fragments.

    Enabling Node Metrics

    Dremio enables node monitoring by default. To manually enable node monitoring, add the following properties to the dremio-env file on each Dremio node in your deployment.

    -Dcom.sun.management.jmxremote.port=<monitoring port>


    In production environments, Dremio strongly recommends using both SSL client certificates to authenticate the client host and password authentication for user management. See Monitoring and Management Using JMX Technology, Out-of-the-Box Monitoring and Management Properties section, for more configuration information.

    Available JMX Metrics

    The following table describes the JMX metrics provided by Dremio and specifies which Dremio node roles support them:

    Metric NameDescriptionMaster CoordinatorSecondary CoordinatorExecutor
    jobs.activeCurrently active jobsYesYesNo
    jobs.command_pool.active_threadsCurrently active commandsYesYesYes
    jobs.command_pool.queue_sizeCurrent size of queued commandsYesYesYes
    jobs.long_runningTop 25 longest running queries (minimum 10s in length) with periodic decayYesNoNo
    jobs.active_15mNumber of jobs in 15 minute periodYesNoNo
    jobs.failedNumber of failed jobs in 15 minute periodYesNoNo
    jobs.active_1dNumber of active jobs in one day periodYesNoNo
    jobs.failed_1dNumber of failed jobs in one day periodYesNoNo
    jobs.queue.<queue_name>.waitingNumber of current waiting jobsYesNoNo
    fragments.activeCurrently active fragmentsNoNoYes
    buffer-pool.direct.capacityTotal capacity of the buffers in the direct poolYesYesYes
    buffer-pool.direct.countNumber of buffers in the direct poolYesYesYes
    buffer-pool.direct.usedMemory used for the direct buffer poolYesYesYes
    buffer-pool.mapped.capacityTotal capacity of the buffers in the mapped poolYesYesYes
    buffer-pool.mapped.countNumber of buffers in the mapped poolYesYesYes
    buffer-pool.mapped.usedMemory used for the mapped buffer poolYesYesYes
    dremio.memory.direct_currentDirect memory allocated/used by the execution engineYesYesYes
    dremio.memory.jvm_direct_currentTotal direct memory given to the JVMYesYesYes
    dremio.memory.remaining_heap_allocationsRemaining heap allocation space for DremioYesYesYes
    dremio.G1-Young-Generation.countYoung generation of garbage collection objectsYesYes
    dremio.G1-Young-Generation.timeTime target for young generation of garbage collection objectsYesYesYes
    gc.G1-Old-Generation.countOld Generation of Garbage collected objectsYesYesYes
    gc.G1-Old-Generation.timeTime target for old generation of GC objectsYesYesYes
    kvstore.*Merics related to the KVStoreYesNoNo
    maestro.activeMaestro activeYesYesNo
    memory.heap.committedAmount of heap memory that is committedYesYesYes
    memory.heap.initAmount of heap memory requested at initializationYesYesYes
    memory.heap.maxMaximum amount of heap memory that can be usedYesYesYes
    memory.heap.usageRatio of memory.heap.used to memory.heap.maxYesYesYes
    memory.heap.usedAmount of used heap memoryYesYesYes
    memory.non-heap.committedAmount of non-heap memory that is committedYesYesYes
    memory.non-heap.initAmount of non-heap memory requested at initializationYesYesYes
    memory.non-heap.maxMaximum amount of non-heap memory that can be usedYesYesYes
    memory.non-heap.usageRatio of memory.non-heap.used to memory.non-heap.maxYesYesYes
    memory.non-heap.usedAmount of used non-heap memoryYesYesYes
    memory.pools.Code-Cache.initMemory committed at initialization from the memory pool used for compilation and storage of native codeYesYesYes
    memory.pools.Code-Cache.usageRatio of memory.pools.Code-Cache.used to memory.pools.Code-Cache.maxYesYesYes
    memory.pools.Compressed-Class-Space.committedMemory committed from the memory pool used for class metadataYesYesYes
    memory.pools.Compressed-Class-Space.initMemory requested at initialization from the memory pool used for class metadataYesYesYes
    memory.pools.Compressed-Class-Space.maxMaximum size of the memory pool used for class metadataYesYesYes
    memory.pools.Compressed-Class-Space.usageCollection usage from the memory pool used for class metadataYesYesYes
    memory.pools.Compressed-Class-Space.usedMemory used by the memory pool used for class metadataYesYesYes
    memory.pools.PS-Eden-Space.usageRatio of PS-Eden-Space.used to PS-Eden-Space.maxYesYesNo
    memory.pools.PS-Old-Gen.usageRatio of PS-Old-Gen.used to PS-Old-Gen.maxYesYesNo
    memory.pools.PS-Survivor-Space.usageRatio of PS-Survivor-Space.used to PS-Survivor-Space.maxYesYesNo
    memory.total.committedAmount of memory that is committed to useYesYesYes
    memory.total.initAmount of memory requested at initialization in bytes.YesYesYes
    memory.total.maxMaximum amount of memory that can be usedYesYesYes
    memory.total.usedAmount of used memoryYesYesYes
    reflections.failedCurrently failed data reflectionsYesNoNo
    reflections.unknownData reflections with currently unknown statusYesNoNo
    reflections.activeCurrently active data reflectionsYesNoNo
    reflections.refreshingData reflections currently refreshing or pending a refreshYesNoNo
    rpc.bit.data.currentMaximum amount of memory used by all RPC connectionsNoNoYes
    rpc.bit.data.peakPeak amount of memory used by all RPC connectionsNoNoYes
    rpc.data.currentMaximum amount of memory used by all RPC connectionsNoNoYes
    rpc.failure_15mRPC connection failures in 15 minute periodYesYesYes
    rpc.failure_1dRPC connection failures in 1 day periodYesYesYes
    rpc.peersNumber of active peer connectionsYesYesYes
    threads.blocked.countNumber of currently blocked threadsYesYesYes
    threads.countCurrent number of active and idle threadsYesYesYes
    threads.daemon.countNumber of currently available active daemon threadsYesYesYes
    threads.deadlock.countNumber of currently deadlocked threadsYesYesYes
    threads.deadlocksCollection of information about the currently deadlocked threadsYesYesYes
    threads.new.countCurrent number of threads in new state (not yet started)YesYesYes
    threads.runnable.countCurrent number of threads in runnable state (executing)YesYesYes
    threads.terminated.countCurrent number of threads in terminated state (completed execution)YesYesYes
    threads.timed_waiting.countCurrent number of threads in the timed_waiting stateYesYesYes
    threads.waiting.countCurrent number of threads in the waiting stateYesYesYes

    Accessing Node Metrics

    You can access your Dremio node metrics using jconsole or another Java Agent that collects JMX metrics.

    To access node metrics with jconsole:

    1. Run the following command on a Dremio host machine:

    2. In the JConsole: New Connection modal, double-click com.dremio.dac.daemon.DremioDaemon.

    3. In the Java Monitoring & Management Console, click the MBeans tab.

    4. Click metrics, then click gauges.

    5. Click the metric that you want to view.

    6. Click Attributes, then click Value.

      jconsole displays the value for the selected metric.