Solr Metrics - Andrzej Białecki, Lucidworks
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Solr metrics allow monitoring of Solr system behavior and performance optimization. Key aspects include: - Solr collects metrics using the Dropwizard Metrics framework, organizing data into registries by component like JVM, core, query handler, etc. - Metrics include counters, timers, histograms and gauges capturing values like request rates, cache sizes, commit times. - The /admin/metrics handler provides access to metrics from all registries through flexible selection criteria. - Configuration in solr.xml specifies metric reporters like JMX, Ganglia, Graphite to export data to external systems.
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Solr Metrics - Andrzej Białecki, Lucidworks
- 2. 2 whoami • Lucene / Solr user, contributor, commi2er • Author of Luke – The Index Toolbox • Lucidworks Fusion developer
- 3. 3 Agenda • MoAvaAon – why Solr needs metrics • Design – how Solr collects metrics and what data is being collected • ImplementaAon – key components • ConfiguraAon – what to collect and how to report it • Examples of metrics and integraAons with external systems • Future development
- 4. 4 Motivation
- 5. 5 Why metrics? • DevOps need tools for monitoring the system behavior • ProducAon troubleshooAng, eg. FD leaks, outlier requests - Profiling is not an opAon in producAon deployments • OpAmizaAon of the system on various levels - OS, collecAon, node, shard, doc rouAng, … • Especially useful in locked-‐down deployments
- 6. 6 JIRA • Long-‐standing request – first created in 2013! • Many contributors (and watchers!) • “metrics” JIRA component - Containing now approx. 60 issues • Key JIRAs: - SOLR-‐4735 iniAal framework - SOLR-‐9812 /admin/metrics handler • First released in Solr 6.4.0 - With important bug fixes released in 6.4.2
- 7. 7 Design
- 8. 8 Dropwizard Metrics • High-‐performance lightweight metrics framework • Metric types - counter: monotonically increasing counter - number of processed docs - meter: counter + moving average (rate), 1-‐, 5-‐ and 15-‐minute - system load average, rate of requests - histogram: histogram of values (exponenAally decaying by default) - result sizes, IO read sizes - Amer: meter and histogram of event duraAons - commit Ames, query Ames, request Ames - gauge: instantaneous reading of a value - current heap size, number of cores, TLOG buffer size
- 9. 9 Where the data is collected from? • JVM metrics - GC, heap, threads, class loading, OS load / mem / FDs, etc • Je2y / HTTP metrics - connecAons, thread pools, … • Container metrics - number of cores, data paths, admin handler metrics • Per-‐SolrCore metrics - All RequestHandler-‐s: request counters and Amers - Searcher and cache stats - ReplicaAon - Index-‐level Amers and histograms - Other components • SolrCloud metrics (opAonal) - Aggregated from SolrCloud nodes JVM Je&y / HTTP CoreContainer SolrCore … Components Solr instance
- 10. 10 Registries • Metric groups for each major aspect of a Solr instance: - jvm, jetty, node (CoreContainer), core (SolrCore) - see SolrInfoBean.Group • One registry per group, and one for each SolrCore - Easier to manage core metrics throughout core life-‐cycle • No persistence across node restarts - SolrCore metrics persist across core reloads solr.jvm solr.node solr.core.collec=on1
- 11. 11 Registry names • Hierarchical, dot-‐separated • Always prefixed with solr. • Overridable using System properAes: -Dsolr.core.collection1=solr.myCollection - This is useful eg. to collapse per-‐replica registries into one registry with aggregated metrics • SolrCloud “core” registry name example: SolrCore name: collection1_shard1_replica_n3 Registry name: solr.core.collection1.shard1.replica_n3 solr.jvm solr.node solr.core.collec=on1
- 12. 12 Metric names • Hierarchical dot-‐separated • By convenAon names start with component category - eg. CONTAINER, CORE, QUERY … - see SolrInfoBean.Category • Request handler metrics follow this naming: <category> . <handler name or scope> . <metric name> • Examples: QUERY./select.requestTimes UPDATE.updateShardHandler.threadPool.recoveryExecutor.completed solr.jvm solr.node solr.core.collec=on1 CORE.fs.totalSpace SEARCHER.new QUERY./get.requests CACHE.core.fieldCache
- 13. 13 Metric properties • Simple numeric / string value, or nested JSON maps - Numeric counter: QUERY./select.requests - Timer: QUERY./select.requestTimes - ProperAes: count, meanRate, 1minRate, 5minRate, 15minRate, min_ms, max_ms, mean_ms, p75_ms, … - A data structure: CACHE.core.fieldCache - ProperAes: total_size, entries_count, entry#0, entry#1, … - Arbitrary map: system.properties • It’s possible to retrieve only selected properAes via / admin/metrics handler - Eg. key=solr.jvm:system.properties:user.name solr.jvm solr.node solr.core.collec=on1 CORE.fs.totalSpace SEARCHER.new QUERY./get.requests CACHE.core.fieldCache total_size entries_count entry#0
- 15. 15 Components • SolrMetricManager - One central component to manage registries and reporters • MetricRegistry (Dropwizard API) - Type-‐safe Map keeping related metric instances and their names • SolrMetricProducer (interface) - Creates and registers metric instances - Many exisAng Solr components now implement this interface • SolrMetricReporter (abstract class) - Reports collected metrics to external agents and/or files - Several implementaAons available out of the box • MetricsHandler (at /admin/metrics) - Provides access to all local metric registries
- 16. 16 SolrMetricManager Solr instance solr.core.collec=on1 solr.core.collec=on2 solr.core.collec=on3 CoreContainer SolrCore1 SolrCore2 SolrCore3 solr.je&y SolrMetricReporter /admin/metrics Ganglia Graphite SLF4j JMX solr.node UI and other reporAng tools solr.jvm
- 17. 17 /admin/metrics handler • Shows metrics from all or selected registries • Flexible selecAon criteria: - registry by: group (e.g. jetty, node), or registry name (e.g. solr.core.collection1) - filter metrics by a list of prefixes (or regexes) - retrieve only some properAes using property parameter - Retrieve single metrics / properAes using fully-‐qualified key (7.1)
- 18. 18 Example /admin/metrics http://localhost:8983 /solr/admin/metrics ?group=core &prefix=SEARCHER
- 20. 20 Example /admin/metrics http://localhost:8983 /solr/admin/metrics ?group=node &prefix=CONTAINER
- 21. 21 Metrics vs. Solr 6.x MBeans • Naming of categories and groups has slightly changed - More fiqng categories for some components • Solr 6.x sAll uses independent implementaAons for Metrics and MBeans - Some staAsAcs are either unavailable in each API or reported differently • Solr 7.x uses only Metrics API to report MBean stats - This includes also nested and non-‐numeric values - <jmx> element in solrconfig.xml is no longer supported – instead use SolrJMXReporter in solr.xml - AutomaAcally added if missing and when an MBeanServer is detected
- 22. 22 Admin UI in 7.x
- 23. 23 Configuration
- 24. 24 Metrics collection • Already happening J - Minimal overhead, in the order of μs/req and < 0.5 MB / core • New secAon in solr.xml: <solr><metrics> - Reporter configuraAon - Custom metric implementaAons - Some debug configuraAon - Detailed histograms of index and TLOG processing Ames, per core
- 25. 25 Reporters • Extend SolrMetricReporter • Configured in solr.xml <solr><metrics><reporter> • Several implementaAons provided: - JMX: fully hierarchical view in e.g. JConsole - Ganglia, Graphite, SLF4J: send periodic reports of selected metrics - Easy API – create new ones! - h2ps://github.com/vthacker/solr-‐metrics-‐influxdb • Created for each selected registry, using group and/or registry list a2ributes - If neither is present the reporter is created for all registries
- 26. 26 Reporter configuration details • Required a2ributes: name (unique per registry), class (FQCN) • OpAonal a2ributes: - group – comma-‐separated list of registry groups, eg. core,jvm - registry – comma-‐separated list of registry prefixes, eg. solr.node,solr.core.coll • OpAonal initArgs: - filter -‐ report only metrics with that prefix, e.g. QUERY./select - period -‐ how oven metrics will be reported, in seconds - ... other, depending on implementaAon, e.g. logger name for SLF4j * NOTE: for a given configuraAon, separate reporter instances are created for each matching registry
- 27. 27 solr.xml <solr> ... <metrics> <reporter name="global" class="org.apache.solr.metrics.reporters.SolrJmxReporter"/> <reporter name="perCore" group="core" class="org.apache.solr.metrics.reporters.SolrSlf4jReporter”> <int name=“period”>60</int> <str name=“logger”>metricsLogger</str> </reporter> </metrics> </solr>
- 28. 28 Advanced configuration • LimitaAons of default histogram / Amer in Dropwizard Metrics - Uses ExponenAallyDecayingReservoir (EDR) sampling BUT assumes normal distribuAon - If distribuAon is skewed then rare outliers may never be captured or retained long enough - EDR is tuned to prefer last 5 minutes of data – but keeps only 1028 random samples - May LOSE criAcal min / max / percenAle data under higher rate of updates - May report obsolete values to snapshot because retained data is replaced randomly - Internal values are “decayed” only during updates – no updates means values are stuck! ≠
- 29. 29 Advanced configuration • Custom parameters and implementaAons for metrics - <solr><metrics><suppliers> secAon in solr.xml - Users can provide their own implementaAons of counters, meters, Amers and histograms • Solving the issue with EDR - Use different reservoir size, or different reservoir implementaAon - Several other implementaAons available, with tradeoffs, eg. SlidingTimeWindowReservoir - Use your own histogram implementaAons - h2p://github.com/vladimir-‐bukhtoyarov/rolling-‐metrics * NOTE: metric reporters retrieve metric snapshots concurrently and at arbitrary :mes, DO NOT use implementa:ons that reset to 0 a>er each snapshot!
- 30. 30 Example advanced configuration (solr.xml) • Different reservoir implementaAon: <solr> <metrics> <suppliers> <histogram> <int name=“window”>300</int> <str name=“reservoir”>com.codahale.metrics.SlidingTimeWindowReservoir</str> </histogram> </suppliers> </metrics> </solr>
- 31. 31 SolrCloud metrics (7.x) • Shard metrics - Reported from replicas to shard leaders • Node metrics - Reported from mulAple registries on each node to Overseer • ParAally aggregated (simple sum, avg, mean, stddev, string lists) - Some aggregaAons wouldn’t make sense, eg. Histograms • AutomaAcally collected by /metrics/collector handler • Configured in solr.xml using special shard and cluster groups
- 34. 34 Example JConsole view in 6.x
- 38. 38 Future
- 39. 39 Metrics in 7.x • Adding more configurability • Be2er defaults for reservoirs • Autoscaling framework - Autoscaling acAons are largely based on metrics, eg. - freedisk, sysLoadAvg, cores, heapUsage, system properAes - May use any metric value eg. metrics:solr.node:CONTAINER.fs.usableSpace • Using metrics for feedback control in Solr clusters - Support for modeling and simulaAon of dynamic behavior (SOLR-‐11285)
- 40. 40 Summary • Metrics are a lightweight mechanism for collecAng detailed insights into Solr operaAon - Provided now by most Solr components - Easy to add new metrics • Metrics can be reported to external systems in mulAple formats and protocols - Several popular systems already supported - Easy to add new reporters • Metrics provide key data for SolrCloud autoscaling • How do you want to use metrics?
- 41. 41 Q & A
- 42. Thank You