java - What is the difference between corePoolSize and maxPoolSize in the Spring ThreadPoolTaskExecutor

Question

I have to send out massEmails to all users of a website. I want to use a thread pool for each email that is sent out. Currently I have set the values to :

<property name="corePoolSize" value="500" />
<property name="maxPoolSize" value="1000" />

What is the difference between the two and will it scale. Currently I have approx. 10000 users.

Answer 1

Here are Sun’s rules for thread creation in simple terms:

1. If the number of threads is less than the corePoolSize, create a new Thread to run a new task.
2. If the number of threads is equal (or greater than) the corePoolSize, put the task into the queue.
3. If the queue is full, and the number of threads is less than the maxPoolSize, create a new thread to run tasks in.
4. If the queue is full, and the number of threads is greater than or equal to maxPoolSize, reject the task.

Full article

Origin answer