Plugin coverage gaps

Shipped Plugins cover common stacks, not every client or reactive path. This page lists frequent gaps so empty tabs look like coverage limits, not a broken agent.

For intentional product non-features (no sampling %, no URL→name regex, ...) see What Glowroot does not do.

• OTP / Vert.x / Netty-only apps — JVM gauges can look fine while Web stays empty: there is no Servlet request for the servlet plugins to name. Use Instrumentation (or a framework entry the netty / other plugins already cover) to start transactions.
• Servlet vs Jakarta Servlet — javax.servlet vs jakarta.servlet are different plugins. Spring Boot 3 needs a current agent and the Jakarta plugin path.

• Queries = JDBC weaves of java.sql.* (Jdbc plugin), not “any database traffic.”
• Vert.x SQL Client and similar non-JDBC APIs often bypass that → empty Queries even with custom pointcuts on your repository classes.
• Custom Instrumentation can time your methods; it does not populate the Queries store the way Jdbc does.

Covered examples live under the http-client plugin (Apache HttpClient sync/async variants, OkHttp, HttpURLConnection, ...). Still incomplete:

• JDK java.net.http.HttpClient — not woven today → no Service Call entry from that client alone.
• Apache HttpAsyncClient execute(producer, consumer, callback) — advice may only attach an aux thread context to the callback (no Service Call entry). Other execute(...) overloads that start async service-call entries still apply. Issue tracker: #968.

Workaround when you need visibility: Instrumentation on your wrapper that performs the call, or use a client the plugin already advises.

• Spring MVC / Web controllers — Spring plugin (ControllerAspect, ...).
• WebFlux — weaker / different naming and timer richness vs MVC; raw URI-style names are a common report (#945). Prefer Instrumentation for critical routes if MVC-style names matter.

• Disabling the Executor plugin often detaches work submitted to pools from the parent trace — looks like “missing” spans, not a coverage gap in the HTTP plugin.
• Callback-only paths (see async HTTP above) need either plugin support or your own transaction/entry boundaries.

1. Confirm the relevant plugin is enabled (Plugins).
2. Check this page + What Glowroot does not do before filing “agent broken.”
3. For app-specific types: Instrumentation or Batch application instrumentation.
4. To extend Glowroot itself: Plugin and Pointcut basics + For contributors.
5. Product change requests: Discussions → Ideas (or an issue with a clear repro if you believe it is a defect in an existing weave).

• Plugins
• Instrumentation
• Transaction tabs
• What Glowroot does not do
• Troubleshooting Tips
• Plugin and Pointcut basics