Async Service

A small proof-of-concept on preserving Thread Local Storage when making async calls from a java service.

NOTE: This is the sole creation of Thierry Duchastel, and it is solely a proof-of-concept. No support of any kind is implied or provided.

Compile It

Run ./gradlew.bat clean build on Windows, or equivalent on macOS.

This will produce a WAR file at build\libs

Run it

Stand-Alone Spring-Boot

To start the service as a stand-alone Spring-Boot service type java -jar .\build\libs\async-service-0.0.1-SNAPSHOT.war

Tomcat

To start the service in Tomcat do the following:

1. (Recommended) Rename your war file to something simple, such as async-service.war
2. Copy the war file to your Tomcat's \webapps directory.
3. Start Tomcat if it's not already running.

Sanity Check

Stand-Alone Spring-Boot

If you ran it as a stand-alone Spring-Boot service then open a web browser and navigate to http://localhost:8083/api/jersey/ping or http://localhost:8083/api/mvc/ping

NOTE: That is port 8083, not the usual port 8080.

You should get back a response that says "pong".

Tomcat

If you ran it as a stand-alone Spring-Boot service then open a web browser and navigate to http://localhost:8080/async-service/api/jersey/ping or http://localhost:8080/async-service/api/mvc/ping

You should get back a response that says "pong".

Try it Out

Let's show the benefits of using async in the outbound network calls from our service. First we'll show what it's like with synchronous calls.

If you're running it as a stand-alone Spring-Boot service then access http://localhost:8083/api/jersey/sync/tenant/{name} For example http://localhost:8083/api/jersey/sync/tenant/Customer1

If you're running it as a Tomcat-hosted service then access http://localhost:8080/async-service/api/jersey/sync/tenant/{name} For example http://localhost:8080/async-service/api/jersey/sync/tenant/Customer1

For Spring MVC it's similar but the path has 'mvc' instead of 'spring'. For example: http://localhost:8080/async-service/api/mvc/sync/tenant/Customer1

This will store the string "Customer1" in Thread Local Storage, make a synchronous outbound call, then return with whatever was stored in Thread Local Storage. That means that you should get the tenant's name, in this case Customer1.

Notes

When running it as a stand-alone SpringBoot the thread pool is set to 10 threads. You can see that by calling the 'ping' API repeatedly. You'll see something like this:

Handling request for 'ping' on thread http-nio-8083-exec-1
Handling request for 'ping' on thread http-nio-8083-exec-2
Handling request for 'ping' on thread http-nio-8083-exec-3
Handling request for 'ping' on thread http-nio-8083-exec-4
Handling request for 'ping' on thread http-nio-8083-exec-5
Handling request for 'ping' on thread http-nio-8083-exec-6
Handling request for 'ping' on thread http-nio-8083-exec-7
Handling request for 'ping' on thread http-nio-8083-exec-8
Handling request for 'ping' on thread http-nio-8083-exec-9
Handling request for 'ping' on thread http-nio-8083-exec-10
Handling request for 'ping' on thread http-nio-8083-exec-1
Handling request for 'ping' on thread http-nio-8083-exec-2

And so on.

If you run the war file in a Tomcat server then be sure to modify Tomcat's conf\server.xml so that it sets the maxThreads to 10. For example in server.xml:

    <Executor name="tomcatThreadPool" namePrefix="catalina-exec-" maxThreads="10" minSpareThreads="10"/>