Middleware: understand and operate the chain

Objectives and progression

Twelve modules connect request architecture with middleware diagnosis and recovery. Lessons distinguish heap from total memory, pools from useful capacity, delivery confirmation from business completion, and local metrics from global health. Original questions and twenty fictional cases exercise decisions in financial operations. Open Liberty and HotSpot references have explicit scope and are not equivalent instructions for traditional WebSphere. Includes native memory, containers, OpenJ9 javacores, JFR, connection budgets, transaction-state diagnosis, message recovery, and operational release acceptance. It teaches operating foundations and decisions; it is not an executable lab or hands-on validation of product administration.

Audience: Application support, middleware administrators, and technical infrastructure managers.

Prerequisites: Basic Linux, networking, application, and database knowledge. Cases do not require production access.

460 estimated study minutes

• Relate symptoms to hops, dependencies, and request context.
• Distinguish memory, thread, pool, and dependency-capacity limits.
• Plan TLS, messaging, and retries while preserving identity and outcomes.
• Use metrics and release criteria to decide continuation and recovery.

Modules

1. Map the request path
2. Investigate the JVM, heap, and pauses
3. Connect threads, pools, and dependencies
4. Operate TLS, certificates, and configuration
5. Manage queues, acknowledgements, and retries
6. Release, observe, and recover middleware
7. Retries, idempotency, and limits
8. Measure the service and locate degradation
9. JVM diagnosis and resource boundaries
10. JDBC pools and transactions under pressure
11. Messaging: delivery and controlled recovery
12. Releases, configuration, and operational acceptance

Continue learning

Technical assessments

• Linux Administration
• Production Support L3
• DNS
• TLS and Certificates

References and version

DR Middleware 2026.4; HotSpot JDK 25; JDBC 25; PostgreSQL 18; RabbitMQ 4.3; OpenSSL 3.5; explicitly scoped runtime references

• HTTP Semantics · 2026-09-29
• Context propagation · 2026-09-29
• Monitoring distributed systems · 2026-09-29
• Effective troubleshooting · 2026-09-29
• Java diagnostic tools · 2026-09-29
• Garbage collection tuning introduction · 2026-09-29
• Troubleshooting memory leaks · 2026-09-29
• Connection manager configuration · 2026-09-29
• SSL configuration · 2026-09-29
• OpenSSL client diagnostics · 2026-09-29
• Consumer acknowledgements and publisher confirms · 2026-09-29
• Reliability guide · 2026-09-29
• Consumers · 2026-09-29
• Canarying releases · 2026-09-29
• Handling overload · 2026-09-29
• Making retries safe with idempotent APIs · 2026-09-29
• Histograms and summaries · 2026-09-29
• Metric and label naming · 2026-09-29
• Addressing cascading failures · 2026-09-29
• Native Memory Tracking · 2026-10-01
• The jcmd command · 2026-10-01
• Diagnostic tools and Flight Recorder · 2026-10-01
• Java dump · 2026-10-01
• Resource management for Pods and containers · 2026-10-01
• Garbage collector implementation · 2026-10-01
• HikariCP configuration reference · 2026-10-01
• Connection Manager · 2026-10-01
• The cumulative statistics system · 2026-10-01
• Explicit locking · 2026-10-01
• JDBC Connection API · 2026-10-01
• Consumer acknowledgements and publisher confirms · 2026-10-01
• Consumer prefetch · 2026-10-01
• Dead letter exchanges · 2026-10-01
• Quorum queues · 2026-10-01
• Consumers · 2026-10-01
• ConfigMaps · 2026-10-01
• Pod lifecycle and termination · 2026-10-01
• Liveness,readiness,and startup probes · 2026-10-01
• OpenSSL certificate inspection · 2026-10-01
• Controlling nginx · 2026-10-01