The Examples

A Spring Boot 4.1 application with Spring Data JPA and H2 over an orders and customers domain, on port 8082. It has a slow report endpoint whose JPQL runs over a large table, a lazy-loading N+1 page, a checkout that fails with a business exception, and a flaky endpoint that fails 20% of the time. One endpoint calls silk-bookstore over HTTP, so a trace spans two services. Spring Boot Actuator is on, and its Micrometer meters, from http.server.requests and the HikariCP pool to Spring Data repository invocations, Tomcat sessions and Logback events, reach Spider Sense through the agent’s Micrometer bridge, so the metrics explorer shows about ninety metrics for this one service. The bridge is off in the OpenTelemetry agent by default; -Dotel.instrumentation.micrometer.enabled=true turns it on, and bootRun and the demo scripts pass it.

A Jakarta Servlet application on embedded Tomcat 11, with plain JDBC over Tomcat’s own pool and H2, on port 8083. There is no framework between the servlets and the agent, so it shows what a classic Servlet stack looks like: endpoints are named after servlet mappings, so every item page is GET /items/*, a filter runs inside the server span, and the exception behind a 500 is what Tomcat’s error page received. It has a full-scan search, an N+1 item page, a slow report, a flaky endpoint, and an async servlet whose span lasts until the request completes on another thread, or times out into a 503.

A plain Java program with HikariCP, Logback and H2 that runs scheduled jobs and serves no HTTP at all. It exists for the questions the web applications cannot raise: a service with zero requests that still has a JVM, logs and jobs, and the findings the other three never produce. A reconciliation job scans 300,000 unindexed rows, which is a slow query inside a job, and a report job streams every row into memory, which is a slow job. A reminder job catches a gateway failure and logs it at ERROR, so the span is fine and only the log knows, which is a log-error. An archive job holds a connection while it sleeps through a slow upload, eight tasks over a pool of three, so the pool runs dry, the last tasks fail on the connection timeout, and the job is slow as well. Every reminder starts a thread that waits for an acknowledgement that never comes, so the thread count climbs until a cap.

A Spider Silk application with jte pages and a JSON API, over spring-jdbc and an H2 file database, on port 8081. About 200,000 rows are seeded, so an unindexed LIKE '%…%' search is a real slow query. An SLEEP alias makes one query slow by decree, one page runs N+1 queries, one endpoint throws, and one endpoint sleeps without running any SQL.

A plain Java program that hits the three web applications at a randomised rate, so the dashboards fill without manual clicking. It is instrumented too, through java.net.http, so some traces start at the client. The worker needs no traffic; its jobs run on their own.