Eric: On 12/29/2021 1:04 PM, Eric Robinson wrote:
We want to run a large number of tomcat instances on the same server without virtualization or containerization. Each instance is executed from its own folder tree and listens on its own unique TCP port. Each instance will run code that connects to a backend database server to send queries that are triggered by JSP calls from users. We've done this successfully with up to 120 instances of tomcat running on the same server while avoiding the overhead of virtualization and the complexity of containers. Based on our experience over the past decade, we know that we could potentially host 500 or more separate tomcat instances on the same server without running into performance problems. So now we want to make it 500 parallel instances.Here's the problem. When tomcat initiates an outbound connection (for example, with Connector/J to query a backend database) it establishes a socket, and the socket has a client port. With thousands of users making requests that require the tomcat services to query back end databases, the OS can easily run out of available client ports to allocate to sockets. To avoid that problem, we can assign multiple IPs to the server and use the localSocketAddress property of Connector/J to group tomcats such that only a subset of them each use the same source IP. Then each group will have its own range of 64,000-ish client ports. I've tested this and it works. My question is, is there a better way?
Are you using database connection pooling? If you are, wouldn't the outbound connections to the database from a particular Tomcat be limited to the maxTotal in your context.xml (maxActive in Tomcat 7).
So unless you're using a huge pool, wouldn't the required number of outbound ports be fairly small?
. . . just my two cents /mde/
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