Embedded Tomcat container binds port before application is completely started

[nebhale]

Currently, when an application is starting up, the embedded Tomcat container binds to its port before the application has finished starting. To see this in action, attempt to start a controller that sleeps in a static block. Something like the following:

Controller
class Example {

    static {
        Thread.sleep(30*1000)
    }

    @RequestMapping("/")
    @ResponseBody
    public String controller(HttpEntity<String> requestEntity) {
        return "Hello World!"
    }
}

When you run spring run app.groovy, you'll see the console stall before the application has stated completely. However, if you attempt to curl http://localhost:8080, curl will also stall because the port is bound and while no response has been returned, a socket connection can be completed. An alternative test is to telnet localhost 8080 and see if a connection can be made.

This is problematic in Cloud Foundry as the HealthManager determines when an application has started by attempted a socket connection to it's provided port. Whether the application is running behind the scenes isn't actually checked, so a false-positive started can be returned.

The intended behavior should be that when the console is stalled as described above, curl should return curl: (7) couldn't connect to host indicating that the port hasn't even been bound to yet. This is typically set in the Tomcat configuration using bindOnInit. I believe that there is a programmatic equivalent to this configuration parameter.

[dsyer]

I don't see a way to get a hold of an AbstractEndpoint to call that setter. Going to have to ask a friend...

[dsyer]

OK, Mark T showed me how to set the property (connector.setProperty("bindOnInit", "false")), but it doesn't seem to solve the problem - curl hangs connecting to localhost while the Controller above is initializing. Any other ideas?

[dsyer]

I think I may have cracked it - we have to explicitly stop the connector after it has started (e.g. in TomcatEmbeddedServletContainer.initialize()), to set the endpoint into the UNBOUND state. Testing...