Fix ContextManager.activeSpan() API usage error

[zhaoyuguang]

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• Bug fix

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  Fix ContextManager.activeSpan() API usage error #3055

[kezhenxu94]

Seems that there are more such usages, just to name a few:

skywalking/apm-sniffer/optional-plugins/optional-spring-plugins/optional-spring-cloud/gateway-2.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/spring/cloud/gateway/v2/FilteringWebHandlerInterceptor.java

Lines 45 to 49 in 98b495e

	AbstractSpan span = ContextManager.activeSpan();
	if (span != null) {
	span.tag("route", route.getId());
	}
	}

I'd suggest fixing them all to defend future "potential bug" @zhaoyuguang

[wu-sheng]

+1 for code scan. I also think, we should check all ContextManager#activeSpan in plugin, and decide whether we should @Deprecated or delete. Let's check that and talk.

[dmsolr]

As I know, ContextManager#activeSpan() is used for handleMethodException

[dmsolr]

I think it cannot be deleted. Because it is useful sometimes.

[wu-sheng]

From the current failures, I am thinking about, is this right using ContextManager#activeSpan() even for logging error? It could cause an NPE too, right?

[dmsolr]

Not NPE. It throws 'No active span.' exception when ContextManager#activeSpan() called.

[wu-sheng]

Not NPE. It throws 'No active span.' exception when ContextManager#activeSpan() called.

But the exception should not happen in agent, it costs too much.

[dmsolr]

I entirely agree with you. Maybe I have a mistake. I mean we need ContextManager#activeSpan() in other scenario.

[zhaoyuguang]

I scanned the code and found only the two places, which are obvious usage errors.