Issue 1:
I have searched the issues of this repository and believe that this is not a duplicate.

I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

Dubbo version: 2.6.6

Operating System version: centos

Java version: 1.8

Steps to reproduce this issue

服务出现线程池打满的情况打印了Dubbo的堆栈

2.但是出现的线程都是等待任务

3.配置了dubbo的业务线程是1000，qps大概是1500+

Expected Result

不应该是线程池满了，但是并发量比较高

Actual Result

打印的dubbo线程的状态都是这种，我查到是说现在这个状态都是空闲状态

"DubboServerHandler-xxx-thread-234" Id=322 WAITING on java.util.concurrent.SynchronousQueue$TransferStack@53452753
at sun.misc.Unsafe.park(Native Method)
- waiting on java.util.concurrent.SynchronousQueue$TransferStack@53452753
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.SynchronousQueue$TransferStack.awaitFulfill(SynchronousQueue.java:458)
at java.util.concurrent.SynchronousQueue$TransferStack.transfer(SynchronousQueue.java:362)
at java.util.concurrent.SynchronousQueue.take(SynchronousQueue.java:924)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

我需要调整线程数吗，还是有什么其他的优化的方法，谢谢

Issue 2:
I have searched the issues of this repository and believe that this is not a duplicate.

I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

Dubbo version: 2.7.0

Operating System version: Ubuntu18.04

Java version: jdk8

dubbo-ops with dubbo 2.7.0 and other appication use old version.

Copy MonitorService from old version to dubbo-ops.

Other application send url call com.alibaba.dubbo.monitor.MonitorService#collect(URL statistics).

result:

WARN dubbo.DecodeableRpcInvocation - [DUBBO] Decode argument failed: 'com.alibaba.dubbo.common.URL' could not be instantiated, dubbo version: 2.7.0-SNAPSHOT, current host: 10.236.105.240

com.alibaba.com.caucho.hessian.io.HessianProtocolException: 'com.alibaba.dubbo.common.URL' could not be instantiated

https://github.com/ebourg/hessian/blob/git-svn/src/com/caucho/hessian/io/JavaDeserializer.java

`for (int i = 0; i < constructors.length; i++) {

Class<?> []param = constructors[i].getParameterTypes();

long cost = 0;

for (int j = 0; j < param.length; j++) {
cost = 4 * cost;

if (Object.class.equals(param[j]))
cost += 1;
else if (String.class.equals(param[j]))
cost += 2;
else if (int.class.equals(param[j]))
cost += 3;
else if (long.class.equals(param[j]))
cost += 4;
else if (param[j].isPrimitive())
cost += 5;
else
cost += 6;
}

if (cost < 0 || cost > (1 << 48))
cost = 1 << 48;

cost += (long) param.length << 48;

if (cost < bestCost) {
_constructor = constructors[i];
bestCost = cost;
}
}
if (_constructor != null) {
_constructor.setAccessible(true);
Class<?> []params = _constructor.getParameterTypes();
_constructorArgs = new Object[params.length];
for (int i = 0; i < params.length; i++) {
_constructorArgs[i] = getParamArg(params[i]);
}
}`

https://github.com/apache/incubator-dubbo/blob/master/dubbo-compatible/src/main/java/com/alibaba/dubbo/common/URL.java

the bestcost constructor is this one;

public URL(org.apache.dubbo.common.URL url) { super(url.getProtocol(), url.getUsername(), url.getPassword(), url.getHost(), url.getPort(), url.getPath(), url.getParameters()); }

and _constructorArgs[0] is null

when run at _constructor.newInstance(_constructorArgs) application throw NullPointerException

Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.alibaba.com.caucho.hessian.io.JavaDeserializer.instantiate(JavaDeserializer.java:312)
... 32 more
Caused by: java.lang.NullPointerException
at com.alibaba.dubbo.common.URL.<init>(URL.java:30)