Troubleshooting Java: Read, debug, and optimize JVM applications

Troubleshooting Java....1 contents....5 preface....9 acknowledgments....11 about this book....13 Who should read this book....13 How this book is organized: A roadmap....14 About the code....15 liveBook discussion forum....15 Author online....15 about the author....16 about the cover illustration....17 Part 1: The basics of investigating a codebase....19 Chapter 1: Revealing an app’s obscurities....21 1.1 How to more easily understand your app....22 1.2 Typical scenarios for using investigation techniques....25 1.2.1 Demystifying the unexpected output....26 1.2.2 Learning certain technologies....31 1.2.3 Clarifying slowness....31 1.2.4 Understanding app crashes....33 1.3 What you will learn in this book....35 Chapter 2: Understanding your app’s logic through debugging techniques....37 2.1 When analyzing code is not enough....39 2.2 Investigating code with a debugger....42 2.2.1 What is the execution stack trace, and how do I use it?....47 2.2.2 Navigating code with the debugger....52 2.3 When using the debugger might not be enough....58 Chapter 3: Finding problem root causes using advanced debugging techniques....61 3.1 Minimizing investigation time with conditional breakpoints....62 3.2 Using breakpoints that don’t pause the execution....66 3.3 Dynamically altering the investigation scenario....69 3.4 Rewinding the investigation case....72 Chapter 4: Debugging apps remotely....79 4.1 What is remote debugging?....81 4.2 Investigating in remote environments....83 4.2.1 The scenario....84 4.2.2 Finding issues in remote environments....85 Chapter 5: Making the most of logs: Auditing an app’s behavior....97 5.1 Investigating issues with logs....101 5.1.1 Using logs to identify exceptions....102 5.1.2 Using exception stack traces to identify what calls a method....103 5.1.3 Measuring time spent to execute a given instruction....104 5.1.4 Investigating issues in multithreaded architectures....105 5.2 Implementing logging....107 5.2.1 Persisting logs....107 5.2.2 Defining logging levels and using logging frameworks....108 5.2.3 Problems caused by logging and how to avoid them....115 5.3 Logs vs. remote debugging....119 Part 2: Deep analysis of an app’s execution....123 Chapter 6: Identifying resource consumption problems using profiling techniques....125 6.1 Where would a profiler be useful?....126 6.1.1 Identifying abnormal usage of resources....126 6.1.2 Finding out what code executes....127 6.1.3 Identifying slowness in an app’s execution....128 6.2 Using a profiler....128 6.2.1 Installing and configuring VisualVM....128 6.2.2 Observing the CPU and memory usage....131 6.2.3 Identifying memory leaks....141 Chapter 7: Finding hidden issues using profiling techniques....147 7.1 Sampling to observe executing code....148 7.2 Profiling to learn how many times a method executed....157 7.3 Using a profiler to identify SQL queries an app executes....159 7.3.1 Using a profiler to retrieve SQL queries not generated by a framework....159 7.3.2 Using the profiler to get the SQL queries generated by a framework....164 7.3.3 Using the profiler to get programmatically generated SQL queries....167 Chapter 8: Using advanced visualization tools for profiled data....172 8.1 Detecting problems with JDBC connections....173 8.2 Understanding the app’s code design using call graphs....187 8.3 Using flame graphs to spot performance problems....189 8.4 Analyzing queries on NoSQL databases....193 Chapter 9: Investigating locks in multithreaded architectures....196 9.1 Monitoring threads for locks....197 9.2 Analyzing thread locks....202 9.3 Analyzing waiting threads....211 Chapter 10: Investigating deadlocks with thread dumps....220 10.1 Getting a thread dump....221 10.1.1 Getting a thread dump using a profiler....223 10.1.2 Generating a thread dump from the command line....225 10.2 Reading thread dumps....228 10.2.1 Reading plain-text thread dumps....228 10.2.2 Using tools to better grasp thread dumps....234 Chapter 11: Finding memory- related issues in an app’s execution....239 11.1 Sampling and profiling for memory issues....240 11.2 Using heap dumps to find memory leaks....247 11.2.1 Obtaining a heap dump....248 11.2.2 Reading a heap dump....252 11.2.3 Using the OQL console to query a heap dump....257 Part 3: Finding problems in large systems....265 Chapter 12: Investigating apps’ behaviors in large systems....267 12.1 Investigating communication between services....268 12.1.1 Using HTTP server probes to observe HTTP requests....269 12.1.2 Using HTTP client probes to observe HTTP requests the app sends....272 12.1.3 Investigating low-level events on sockets....273 12.2 The relevance of integrated log monitoring....276 12.3 Using deployment tools in investigations....282 12.3.1 Using fault injection to mimic hard-to-replicate issues....284 12.3.2 Using mirroring to facilitate testing and error detection....285 appendix A: Tools you’ll need....289 appendix B: Opening a project....290 appendix C: Recommended further reading....293 appendix D: Understanding Java threads....295 D.1 What is a thread?....296 D.2 A thread’s life cycle....298 D.3 Synchronizing threads....300 D.3.1 Synchronized blocks....300 D.3.2 Using wait(), notify(), and notifyAll()....302 D.3.3 Joining threads....304 D.3.4 Blocking threads for a defined time....305 D.3.5 Synchronizing threads with blocking objects....306 D.4 Common issues in multithreaded architectures....306 D.4.1 Race conditions....307 D.4.2 Deadlocks....307 D.4.3 Livelocks....309 D.4.4 Starvation....310 D.5 Further reading....310 appendix E: Memory management in Java apps....311 E.1 How the JVM organizes an app’s memory....312 E.2 The stack used by threads to store local data....314 E.3 The heap the app uses to store object instances....320 E.4 The metaspace memory location for storing data types....322 index....323 A....323 B....323 C....323 D....324 E....324 F....324 G....324 H....324 I....324 J....324 L....325 M....325 N....325 O....325 P....326 Q....326 R....326 S....326 T....327 U....327 V....327 W....327 X....327 Z....327