private String getLocalHost(RpcContext rpcContext) {
        // Pinpoint finds caller - callee relation by matching caller's end point and callee's acceptor host.
        // https://github.com/naver/pinpoint/issues/1395
        return rpcContext.getLocalAddressString();
    }
clear {@link com.alibaba.dubbo.rpc.RpcContext#getAttachments()} trace header.
you should to know,since dubbo 2.6.2 version.
{@link com.alibaba.dubbo.rpc.protocol.AbstractInvoker#invoke(com.alibaba.dubbo.rpc.Invocation)}
will force put {@link com.alibaba.dubbo.rpc.RpcContext#getAttachments()} to current Invocation
replace origin invocation.addAttachmentsIfAbsent(context) method;
to imagine if application(B) methodB called by application(A), application(B) is dubbo provider, methodB call next dubbo application(C).
when application(C) received trace header is overwrite by application(B) received trace header.

@param rpcContext
agent-module/plugins/dubbo/src/main/java/com/navercorp/pinpoint/plugin/dubbo/interceptor/DubboProviderInterceptor.java