Asynchronous initialization causing concurrently problem in DashboardApplication

[jasonjoo2010]

Issue Description

Some racing problem occurred like ConcurrentModification on System.properties

Describe what happened (or what feature you want)

How to reproduce it (as minimally and precisely as possible)

Calling setProperty putting new keys into property set while InitExecutor.doInit is executed asynchronously.

Discussion

Asynchronism Supporting

We should declare whether asynchronism should be supported here.
We take the answer YES till someone submitted different opinions.

Direct Cause of the Issue

The main method is shown below used by Dashboard booting up.

public class DashboardApplication {

    public static void main(String[] args) {
        triggerSentinelInit();
        SpringApplication.run(DashboardApplication.class, args);
    }

    private static void triggerSentinelInit() {
        new Thread(() -> InitExecutor.doInit()).start();
    }
}

The InitExecutor.doInit() is called in another thread when spring boot is starting.
It may add new keys calling System.setProperty when booting. And we have the code below to load config from properties in SentinelConfig.loadProps:

        // JVM parameter override file config.
        for (Map.Entry<Object, Object> entry : System.getProperties().entrySet()) {
            String configKey = entry.getKey().toString();
            String configValue = entry.getValue().toString();
            String configValueOld = getConfig(configKey);
            SentinelConfig.setConfig(configKey, configValue);
            if (configValueOld != null) {
                RecordLog.info("[SentinelConfig] JVM parameter overrides {0}: {1} -> {2}", configKey, configValueOld, configValue);
            }
        }

Which we may use CopyOnWriteArraySet instead to walk through the values safely.

Is there any opinions, folks?

[sczyh30]

Yes, it's necessary to make it thread-safe.

[sczyh30]

Fixed in #706