March 2026 monthly summary for apache/solr. Focused on reliability and traceability improvements in CloudSolrClient with a concrete fix to deleteById routing behavior under directUpdatesToLeadersOnly. This work reduced runtime exceptions and improved observability for misconfigurations while enhancing routing efficiency for leader-focused updates.

In 2026-01, delivered OTEL-integrated disk-space metrics for shard splitting in solrbot/apache-_-solr, enabling accurate Prometheus metric reads on the correct node, improving reliability and observability during shard operations. Implemented robust error handling for missing index/ free size metrics and restored shard-splitting capability after OTEL migration.

Month: 2025-11. Focused on enhancing observability and stabilizing metrics delivery for solrbot/apache-_-solr. Delivered OpenTelemetry-based observability enhancements, migrating metrics collection from Dropwizard to OpenTelemetry with native Prometheus and OTLP exports, plus a configurable OTLP endpoint (gRPC or HTTP). Also addressed test stability by upgrading OTEL dependencies to fix flaky tests. Documentation updates accompany migration and usage guidance (SOLR-17856).

2025-10 monthly summary for apache/solr focused on modernizing the metrics stack, improving observability, and stabilizing metric-related workflows across the cluster. Key work centered on migrating to OpenTelemetry and Prometheus metrics, removing Dropwizard dependencies, and implementing node-level aggregation of core metrics across the Solr cluster. Also extended Prometheus coverage to the Plugins/Stats UI, while addressing test stability during core unload/reload and hardening metric management configurations.

September 2025 monthly summary for apache/solr focused on observability enhancements, telemetry standardization, and test stability. Delivered targeted improvements to metrics collection and processing, migrated to a unified OpenTelemetry-based pipeline, and stabilized test suites to ensure reliable builds and metrics formatting across components. These efforts reduce operational toil, accelerate issue diagnosis, and align telemetry with modern standards, enabling deeper business insights and more predictable performance.

OpenTelemetry-based metrics modernization across Solr in 2025-08: consolidated instrumentation, removal of legacy reporters, and enhanced observability enabling standardized, actionable metrics; foundational work for reliable dashboards and faster root-cause analysis.

July 2025 monthly summary: Completed the OpenTelemetry (OTEL) migration for Solr metrics across core components, replacing the legacy Codahale/Dropwizard metrics with OTEL. Implemented granular per-request metrics (errors and timeouts) and refactored metrics reporting in SolrCore, DirectUpdateHandler2, and PeerSync to use OTEL instruments. This lays the groundwork for unified observability, faster diagnostics, and data-driven capacity planning. The changes were delivered through a series of commits across the repo (e.g., fcfb995949ee365cfc3ac138223883c3deab0ab7, d3e23eac4ceb7228194c57c6fe07801df8ee11ef, 8f34855115769842920d5dfecb5a060cb2075c71, ed7f2d116ade9af13ec79ba2bea4de8cb610f225).

June 2025: OpenTelemetry-based observability modernization for Solr. Implemented end-to-end OTEL integration across core initialization, instrumentation, and per-core MeterProvider management. Replaced PrometheusMetricReader usage with OTEL instrumentation, improving isolation across cores. Delivered dedicated SdkMeterProviders for Solr core metrics, laying the foundation for robust tracing and performance insights. No explicit bug fixes were recorded this month; primary focus on feature delivery and architectural improvements with clear business value.