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According to this link, the properties server.tomcat.max-connections and server.tomcat.max-threads determine the max number of connections and max number of threads in the application.
I have two questions:
What happens if at a given moment number of connections exceed number of threads? What will happen to the connections that did not get a thread?
What happens if the server has to serve more requests that server.tomcat.max-connections? Will it just ignore the requests that arrived after number of threads connections has reached its maximum value?
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By default, Tomcat sets maxThreads to 200, which represents the maximum number of threads allowed to run at any given time. You can also specify values for the following parameters: minSpareThreads : the minimum number of threads that should be running at all times.
The default installation of Tomcat sets the maximum number of HTTP servicing threads at 200. Effectively, this means that the system can handle a maximum of 200 simultaneous HTTP requests.
The Apache Tomcat's threadpool (is it called the connector Threadpool? ) has a number of threads ( 200 by default ). Now this means that at a particular time, 200 people can communicate with my web application. Now, taking a scenario when a particular connects with my application.
Tomcat will invoke your code (i.e. your servlets) from multiple threads, and if that code is not thread-safe, you'll have problems. Tomcat's threads are no different to any threads you create yourself.
The number of threads in the pool depends on the parameters you’ve set for the connector in your conf/server.xml file. By default, Tomcat sets maxThreads to 200, which represents the maximum number of threads allowed to run at any given time.
This being said, the 200 maximum connections as a default is merely an arbitrary number, so you’ll need to assess this in relation to the hardware you are running on. The bigger the server hardware you’re running on, the higher the number of maximum connections on Apache Tomcat your server will be able to handle.
Each incoming request is processed by a thread in Tomcat. The maxThreads attribute of a connector defines the maximum number of simultaneous threads that can be executing for a connector. The number of simultaneous threads executing depends on the hardware and the number of CPUs it has.
Each Tomcat connector manages its workload with a pool of worker threads and one or more acceptor threads. When a connector receives a request from a client, the acceptor thread assigns the connection to an available worker thread from the pool and then goes back to listening for new connections.
What happens if at a given moment number of connections exceed number of threads? What will happen to the connections that did not get a thread?
They will wait for a worker thread to become available.
Tomcat uses an "accept queue" to hold connections between accepting them and passing them off to a worker thread. The Tomcat config parameter that controls this is:
acceptCount: The maximum queue length for incoming connection requests when all possible request processing threads are in use. Any requests received when the queue is full will be refused. The default value is 100.
(Source https://tomcat.apache.org/tomcat-8.0-doc/config/http.html)
What happens if the server has to serve more requests than
server.tomcat.max-connections? Will it just ignore the requests that arrived after number of threads connections has reached its maximum value?
According to the above, the connections will be accepted up to the queue limit, and then refused. I take it to mean that the client will get a TCP/IP level "Connection Refused".
(It is not entirely clear what happens to a queued request if the client times it out and closes the TCP/IP connection from the client end.)
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