WebfluxSofaTracerFilter should not use thread local to keep SofaTracerSpan

[shengxiang205]

Describe the bug

when we using webflux with sofa tracer, we have controller code like this:

@RestController
public class SampleRestController {

    private static Logger logger = LoggerFactory.getLogger(SampleRestController.class);
    private static final String TEMPLATE = "Hello, %s!";

    private final AtomicLong counter  = new AtomicLong();

    /***
     * http://localhost:8080/springwebflux
     * @param name name
     * @return map
     */
    @RequestMapping("/springwebflux")
    public Mono<Map<String, Object>> springwebflux(@RequestParam(value = "name", defaultValue = "SOFATracer SpringWebFlux DEMO") String name) {
        Map<String, Object> resultMap = new HashMap<String, Object>();
        resultMap.put("success", true);
        resultMap.put("id", counter.incrementAndGet());
        resultMap.put("content", String.format(TEMPLATE, name));
        logger.info("result: {}", resultMap);
        return Mono.delay(Duration.ofSeconds(3)).map(i -> resultMap);
    }
}

application.properties:

# Application Name
spring.application.name=SOFATracerSpringWebFlux
# logging path
logging.path=./logs
com.alipay.sofa.tracer.samplerPercentage=100
com.alipay.sofa.tracer.samplerName=PercentageBasedSampler
com.alipay.sofa.tracer.zipkin.base-url=http://127.0.0.1:9411
com.alipay.sofa.tracer.zipkin.enabled=true

we visit http://localhost:8080/springwebflux in concurrent mode with env -Dreactor.netty.ioWorkerCount=1

Expected behavior

logs/tracelog/spring-mvc-digest.log should have output lines for every request

Actual behavior

logs/tracelog/spring-mvc-digest.log lost some logs

Steps to reproduce

Minimal yet complete reproducer code (or GitHub URL to code)

Environment

• SOFATracer version: 3.0.6
• JVM version (e.g. java -version):
• OS version (e.g. uname -a):
• Maven version:
• IDE version:

[shengxiang205]

code in WebfluxSofaTracrFilter.java using code:

SofaTracerSpan springMvcSpan = springMvcTracer.serverReceive(spanContext);

to create first SofaTracerSpan,

but serverReceive in AbstractTracer using

SofaTraceContext sofaTraceContext = SofaTraceContextHolder.getSofaTraceContext();
SofaTracerSpan serverSpan = sofaTraceContext.pop();

to keep SofaTracerSpan in ThreadLocal

as we known, in concurrent mode, multi reactor stream may share same thread,
it will lead to unknown bug with thread local variables