1. 前端用戶發起http連接請求。
2. jboss監聽響應請求。
2.1 如果thread pool有可用線程，則分配可用線程處理用戶請求。顯示如下，一般表示有空閒的線程。
2.2 如果thread pool沒有有可用線程，則拒絕連接，如前端client(瀏覽器,調用方）有重試次數，則繼續重試，否則返回失敗。
3. 如果該請求需要連接數據庫處理，則線程向數據連接池申請
3.1 如果數據連接池沒有可用連接，則jboss線程就按連接池配置的timeout時間進行等待。 這時用jstack dump出來看到線程狀態是TIMED_WAIT。
3.2 如果數據連接池有可用連接，則jboss線程線程獲取db連接，提交sql
4. 提交sql到數據庫處理，在數據庫處理期間，jstack dump出來看到線程狀態爲Runnable
5. 處理完返回結果
備註：
And TIMED_WAITING? Explained Through Real-Life Examples
BLOCKED, WAITING, and TIMED_WAITING are important thread states, but often confusing to many of us. One must have a proper understanding of both in order to analyze thread dumps. Using real-life examples, this article breaks down each state into simpler terms.
BLOCKED
Java doc formally defines BLOCKED state as: “A thread that is blocked waiting for a monitor lock is in this state.”
Real-life example: Today you are going for a job interview. This is your dream job, which you have been targeting for last few years. You woke up early in the morning, got ready, put on your best outfit, looking sharp in front of the mirror. Now you step out to your garage and realize that your wife has already taken the car. In this scenario, you only have one car, so what will happen? In real life, a fight may happen :-). Here you are BLOCKED because your wife has already taken the car. You won't be able to go to the interview.
This is the BLOCKED state. Explaining it in technical terms, you are the thread T1 and your wife is the thread T2 and lock is the car. T1 is BLOCKED on the lock (i.e. the car), because T2 has already acquired this lock.
Titbit: A Thread will enter in to BLOCKED state when it’s waiting for a monitor lock to enter a synchronized block/method or reenter a synchronized block/method after calling Object#wait() method.
WAITING
Java doc formally defines WAITING state as: “A thread that is waiting indefinitely for another thread to perform a particular action is in this state.”
Real-life example: Let’s say few minutes later your wife comes back home with the car. Now you realize that the interview time is approaching, and there is a long distance to drive to get there. So, you put all the power on the gas pedal in the car. You drive at 100 mph when the allowed speed limit is only 60 mph. Your luck, a traffic cop sees you driving over the speed limit, and he pulls you over to the curb. Now you are entering into the WAITING state, my friend. You stop driving the car and sit idly in the car until the cop investigates you, and then lets you go. Basically, until he lets you go, you are stuck in the WAITING state.
Explaining it in technical terms, you are thread T1 and the cop is thread T2. You released your lock (i.e. you stopped driving the car), and went into the WAITING state. Until the cop (i.e. T2) lets you go, you will be stuck in this WAITING state.
Titbit: A Thread will enter in to WAITING state when it’s calling one of the following methods:
- Object#wait() with no timeout
- Thread#join() with no timeout
- LockSupport#park()
Thread that has called Object.wait() on an object is in WAITING state until another thread to call Object.notify() or Object.notifyAll() on that object. A thread that has called Thread.join() is in WAITINGstate for a specified thread to terminate.
TIMED_WAITING
Java doc formally defines TIMED_WAITING state as: “A thread that is waiting for another thread to perform an action for up to a specified waiting time is in this state.”
Real-life example: Despite all the drama, you did extremely well in the interview, impressed everyone and got this high paying job. (Congratulations!) You come back home and tell to your neighbor about this new job and how excited you are about it. Your friend says that he is also working in the same office building. He suggests that the two of you should drive together. You think it’s a great idea. So on the first day of work, you go to his house. You stop your car in front of his house. You wait for 10 minutes, but your neighbor still doesn’t come out. You go ahead and start driving to work, as you don’t want to be delayed on your first day. Now this is TIMED_WAITING.
Explaining it in technical terms, you are thread T1 and your neighbor is thread T2. You release lock (i.e. stop driving the car) and wait up to 10 minutes. If your neighbor, T2, doesn’t come out in 10 minutes, you start driving the car again.
Titbit: A Thread will enter in to TIMED_WAITING state when it’s calling one of the following methods:
- Thread#sleep()
- Object#wait() with timeout
- Thread#join() with timeout
- LockSupport#parkNanos()
- LockSupport#parkUntil()
Conclusion
When someone is analyzing thread dumps, understanding these different thread states are critical. How many threads are in RUNNABLE, BLOCKED, WAITING, and TIMED_WATING states? Which threads are blocked? Who is blocking them? What object used for locking? These are some of the important metrics to be analyzed in thread dumps. These kinds of detailed thread dump analyses can easily be done through an online tool such as: http://fastthread.io/