public static void premain()

in apm-sniffer/apm-agent/src/main/java/org/apache/skywalking/apm/agent/SkyWalkingAgent.java [71:147]
64 lines of code
8 McCabe index (conditional complexity)

    public static void premain(String agentArgs, Instrumentation instrumentation) throws PluginException {
        final PluginFinder pluginFinder;
        try {
            SnifferConfigInitializer.initializeCoreConfig(agentArgs);
        } catch (Exception e) {
            // try to resolve a new logger, and use the new logger to write the error log here
            LogManager.getLogger(SkyWalkingAgent.class)
                    .error(e, "SkyWalking agent initialized failure. Shutting down.");
            return;
        } finally {
            // refresh logger again after initialization finishes
            LOGGER = LogManager.getLogger(SkyWalkingAgent.class);
        }

        if (!Config.Agent.ENABLE) {
            LOGGER.warn("SkyWalking agent is disabled.");
            return;
        }

        try {
            pluginFinder = new PluginFinder(new PluginBootstrap().loadPlugins());
        } catch (AgentPackageNotFoundException ape) {
            LOGGER.error(ape, "Locate agent.jar failure. Shutting down.");
            return;
        } catch (Exception e) {
            LOGGER.error(e, "SkyWalking agent initialized failure. Shutting down.");
            return;
        }

        LOGGER.info("Skywalking agent begin to install transformer ...");

        AgentBuilder agentBuilder = newAgentBuilder().ignore(
            nameStartsWith("net.bytebuddy.")
                .or(nameStartsWith("org.slf4j."))
                .or(nameStartsWith("org.groovy."))
                .or(nameContains("javassist"))
                .or(nameContains(".asm."))
                .or(nameContains(".reflectasm."))
                .or(nameStartsWith("sun.reflect"))
                .or(allSkyWalkingAgentExcludeToolkit())
                .or(ElementMatchers.isSynthetic()));

        JDK9ModuleExporter.EdgeClasses edgeClasses = new JDK9ModuleExporter.EdgeClasses();
        try {
            agentBuilder = BootstrapInstrumentBoost.inject(pluginFinder, instrumentation, agentBuilder, edgeClasses);
        } catch (Exception e) {
            LOGGER.error(e, "SkyWalking agent inject bootstrap instrumentation failure. Shutting down.");
            return;
        }

        try {
            agentBuilder = JDK9ModuleExporter.openReadEdge(instrumentation, agentBuilder, edgeClasses);
        } catch (Exception e) {
            LOGGER.error(e, "SkyWalking agent open read edge in JDK 9+ failure. Shutting down.");
            return;
        }

        agentBuilder.type(pluginFinder.buildMatch())
                    .transform(new Transformer(pluginFinder))
                    .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
                    .with(new RedefinitionListener())
                    .with(new Listener())
                    .installOn(instrumentation);

        PluginFinder.pluginInitCompleted();

        LOGGER.info("Skywalking agent transformer has installed.");

        try {
            ServiceManager.INSTANCE.boot();
        } catch (Exception e) {
            LOGGER.error(e, "Skywalking agent boot failure.");
        }

        Runtime.getRuntime()
               .addShutdownHook(new Thread(ServiceManager.INSTANCE::shutdown, "skywalking service shutdown thread"));
    }