Netflix/Hystrix · error · RuntimeException

Failed trying to wrap method [" + method.getName() + "] of c

Error message

Failed trying to wrap method [" + method.getName() + "] of class: " + className

What it means

Thrown by the hystrix-network-auditor javaagent when Javassist fails to inject the network-auditing hook into a matched method of a class being loaded. The agent iterates declared methods of transformed classes and calls method.insertBefore(...); any Exception (usually a Javassist CompileError from bad source insertion or an incompatible class) is rethrown as a RuntimeException naming the method and class.

Source

Thrown at hystrix-contrib/hystrix-network-auditor-agent/src/main/java/com/netflix/hystrix/contrib/networkauditor/NetworkClassTransform.java:109

                try {
                    constructor.insertBefore("{ com.netflix.hystrix.contrib.networkauditor.HystrixNetworkAuditorAgent.notifyOfNetworkEvent(); }");
                } catch (Exception e) {
                    throw new RuntimeException("Failed trying to wrap constructor of class: " + className, e);
                }

            }
        }
        // methods
        CtMethod[] methods = ctClazz.getDeclaredMethods();
        for (CtMethod method : methods) {
            try {
                for (String methodName : methodNames) {
                    if (method.getName().equals(methodName)) {
                        method.insertBefore("{ com.netflix.hystrix.contrib.networkauditor.HystrixNetworkAuditorAgent.handleNetworkEvent(); }");
                    }
                }
            } catch (Exception e) {
                throw new RuntimeException("Failed trying to wrap method [" + method.getName() + "] of class: " + className, e);
            }
        }
        return ctClazz.toBytecode();
    }

}

View on GitHub (pinned to 5ce3bc58c3)

Solutions

  1. Check the wrapped cause in the stack trace (getCause()) — it names the exact Javassist failure (e.g. CompileError) and method
  2. Upgrade/align the hystrix-network-auditor-agent version with the Hystrix and Javassist versions on the classpath
  3. Exclude the offending class/method from instrumentation via the agent's configured method/class filters
  4. If the agent is not essential, remove the -javaagent JVM flag to let the app start uninstrumented

Example fix

# before
java -javaagent:hystrix-network-auditor-agent-1.5.x.jar -jar app.jar
# after
# pin matching versions and exclude the failing class
java -javaagent:hystrix-network-auditor-agent-1.5.x.jar=excludedClasses=com.example.ProblemClass -jar app.jar
Defensive patterns

Strategy: try-catch

Validate before calling

null

Type guard

null

Try / catch

catch (RuntimeException e) where e.getMessage() starts with "Failed trying to wrap method" — log e.getCause() (the Javassist error) and the transform class name; decide between aborting startup (fail fast in test envs) or excluding the class and continuing.

Prevention

When it happens

Trigger: Running the JVM with -javaagent:hystrix-network-auditor-agent and loading a class whose method matches the agent's method-name filter but whose bytecode/signature cannot accept the inserted snippet (abstract/native methods, or a Javassist compile error on the inserted '{ ... }' block).

Common situations: Version skew between the agent (built against an old Javassist) and the target JVM/app classes; instrumenting native or abstract methods; a corrupted or obfuscated class hitting the ClassFileTransformer; agent jar missing a dependency at runtime.

Related errors

AI-assisted analysis of Netflix/Hystrix@5ce3bc58c3 (2026-08-14). Data as JSON: /api/errors/be9890dc28a75915. Report an issue: GitHub.