WordPress powers 40% of the web but has no native observability story. Here's how to instrument it end-to-end with OpenTelemetry - PHP, browser RUM, and errors.

Last9 is a  blog focusing on DevOps practices, cloud architecture, and software engineering methodologies. Through insightful articles, tutorials, and case studies, Last9 addresses various aspects of modern software development, including continuous integration and continuous delivery (CI/CD), infrastructure as code (IaC), containerization, and microservices architecture. By sharing best practices, real-world experiences, and expert insights, Last9 equips developers, DevOps engineers, and IT professionals with the knowledge and tools needed to build, deploy, and manage resilient and scalable cloud-native applications.

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A deep-dive into instrumenting WordPress with OpenTelemetry, covering PHP distributed tracing, database query instrumentation, browser RUM, error capture, and security event tracking. The post walks through a modular WordPress plugin architecture with five components: a PHP tracer using the OTel PHP SDK, an error handler capturing fatals and wp_die() calls, browser RUM via the OTel JavaScript SDK with Core Web Vitals collection, user context enrichment, and a hierarchical configuration system. Production considerations include performance benchmarks (3.3% overhead without sampling, ~0% with 10% sampling), sampling strategies, GDPR handling for user PII, and graceful degradation. Known limitations include missing outbound traceparent injection and lack of metrics/logs signals.

Instrumenting WordPress with OpenTelemetry: PHP Tracing, Browser RUM, and Error Capture in Production

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