Query metrics MBean 

The query metrics MBean is useful for troubleshooting query performance, tuning the Solr configuration, such as the schema and caches, and tuning server resources, such as the JVM heap.

The query metrics MBean is useful for troubleshooting query performance, tuning the Solr configuration, such as the schema and caches, and tuning server resources, such as the JVM heap. The query metrics MBean records the amount of time spent to execute several main phases of a distributed query on the index.

Main operational phases 

The main phases of a distributed query operation are:

  • COORDINATE

    Comprises the total amount of time spent by the coordinator node to distribute the query and gather/process results from shards. This value is computed only on query coordinator nodes.

  • EXECUTE

    Comprises the time spent by a single shard to execute the actual index query. This value is computed on the local node executing the shard query.

  • RETRIEVE

    Comprises the time spent by a single shard to retrieve the actual data from Cassandra. This value will be computed on the local node hosting the requested data.

Query metrics MBean operations 

The query metrics MBean measures latency in microseconds. Metrics can be grouped by query, by providing an additional query.name parameter. For example, assuming you are using a Solr core named demo.solr and have indexed a field named type, this URL provides the additional query.name parameter:

http://localhost:8983/solr/demo.solr/select/?q=type:1&query.name=myquery

All metrics collected under a given query name are recorded and retrieved separately, as shown in the following list of operations. If no query name is provided, all metrics are recorded together.

Operations are:

  • setEnabled(boolean enabled)

    Enables/disables metrics recording. Enabled by default.

  • isEnabled()

    Checks if metrics recording is enabled.

  • getLatencyPercentile(String phase, String query, double percentile)

    Gets a query latency percentile by its query name, which is optional and can be null, and phase.

  • getRecordedLatencyCount(String phase, String query)

    Gets the total count of recorded latency metrics by its query name, which is optional and can be null, and phase.

  • getUnrecordedLatencyCount()

    Gets the total count of unrecorded latency values due to exceeding the maximum tracked latency, which is 10 minutes.

  • resetLatency(String query)

    Resets latency metrics for the given query name, which is optional and can be null.

  • resetLatencies()

    Resets all latency metrics.

Query metrics MBean operations use the phase names previously listed.

Using MBeans to evaluate performance 

The following example shows how to use the MBeans on Linux to obtain information about performance while running the DataStax Solr stress test demo.

  1. Start a single DSE Search node.
  2. Start jconsole using the PID of the DSE Search node: For example:
    sudo jconsole 1284
  3. Change to the demos directory.
    The default location of the demos directory depends on the type of installation:
    Installer-Services and Package installations /usr/share/dse/demos
    Installer-No Services and Tarball installations install_location/demos
  4. Make demos/solr_stress your current directory.
  5. Execute this script to create the schema:
    ./create-schema.sh [options]
    
    where the script options are:
    CQL table creation options
    --ssl use SSL for Cassandra table creation over cqlsh
    Solr HTTP options
    -e CA_CERT_FILE use HTTPS with the provided CA certificate
    -E CLIENT_CERT_FILE use the provided client certificate
    -h HOST hostname or IP for Solr HTTP requests
    -a enable Kerberos
    -u USERNAME Kerberos username
    -p PASSWORD Kerberos password
    The script creates the Cassandra schema and posts the solrconfig.xml and schema.xml files to these locations:
    • http://localhost:8983/solr/resource/demo.solr/solrconfig.xml
    • http://localhost:8983/solr/resource/demo.solr/schema.xml
    The script then creates the core/index by posting to the following location:
    • http://localhost:8983/solr/admin/cores?action=CREATE&name=demo.solr
    You can override the script defaults by specifying command line parameters:
    -x schemafile.xml -t tableCreationFile.cql -r solrCofgFile.xml -k solrCore
  6. Execute this script to run the benchmark:
    ./run-benchmark.sh [--clients=clients_count] [--loops=loops_count] [--fetch=fetch_size] [--solrCore=solr_core] [--testData=test_data_file] [--url=url1,url2,url3,...] [--qps=qps] [--stats=true|false] [--seed=seed_value]
    where the script options are:
    --clients
    The number of client threads to create.
    Default: 1
    --loops
    The number of times the commands list gets executed if running sequentially or the number of commands to run if running randomly.
    Default: 1
    --fetch
    Fetch size for CQL pagination (disabled by default). Only the first page is retrieved.
    --solrCore
    Solr core name to run the benchmark against.
    --testData
    Name of the file that contains the test data.
    --seed
    Value to set the random generator seed to.
    --qps
    Maximum number of queries per second allowed.
    --stats
    Specifies whether to gather statics during runtime and create a csv file with the recorded values.
    Default: false
    --url
    A comma delimited list of servers to run the benchmark against. For example: --url=http://localhost:8983,http://192.168.10.45:8983,http://192.168.10.46:8983
    Default: http://localhost:8983

    The demo creates a Solr core named demo.solr and indexes 50,000 documents.

    Example CQL commands:
    ./run-benchmark.sh --url=http://localhost:8983 --testData=resources/testCqlQuery.txt --solrCore=demo.solr
    ./run-benchmark.sh --url=http://localhost:8983 --testData=resources/testCqlWrite.txt --solrCore=demo.solr

    See /demos/solr_stress/README.txt for execution modes and sample script commands.

  7. In jconsole, expand com.datastax.bdp > search > demo.solr.

    The CommitMetrics and QueryMetrics MBean items appear.

  8. In jconsole, in Search > demo.solr > CommitMetrics > Operations > getLatencyPercentile, type EXECUTE in the p0 text entry box and 0.95 in the p1 text entry box. Click the getLatencyPercentile button.

    The Operation return value, 582 microseconds, appears:



  9. Click OK.
  10. Query Solr 20,000 times using the query.name parameter. For example:
    curl "http://localhost:8983/solr/demo.solr/select/?q=type:1&query.name=myquery"
    curl "http://localhost:8983/solr/demo.solr/select/?q=type:3&query.name=myquery"
  11. In jconsole, in Search > demo.solr > QueryMetrics Operations getLatencyPercentile, type EXECUTE in the p0 text entry box, myquery in the p1 text entry box, and 95.0 in the P2 text entry box.

    The Operation return value, 97 microseconds, appears.