add additional readme for testing

Author: Pythonista7

src/test/kotlin/assets/img.png

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+# Doorman Simulations
+
+The Simulation test is a simple test that sends a large number of requests to the server from different client instances trying to concurrently access the same resource, but configured with a different rate limit. 
+The goal of this test is to ensure the rate limit and dynamic rate limit changes are working as expected based of additions/removals of clients.
+
+## Setup
+This is more of an end-to-end test, so you will need to have a few things setup before you can run the test and measure the results.
+
+### I. Setting up doorman. 
+   1. Clone this fork [doorman](https://github.com/Pythonista7/doorman) repository. I've tried to keep the changes minimal and only added changes with the intentions of being able to run the project by satisfying the modern go requirements to build & run.
+   2. `cd go/cmd/doorman` and run `go build` to build the binary after which you should see a `doorman` binary in the same directory.
+   3. Run the binary with the following command , 
+   ```shell
+   ./doorman -logtostderr -config=path-to-config.yml -port=15000 -debug_port=15050 -etcd_endpoints=http://localhost:2379 -master_election_lock=/doorman.master -master_delay=300s -hostname=localhost
+   ```
+     > *Note*: 
+     > * You will need to have etcd running on your machine `brew install etcd` and run `etcd` on a new sh to start the etcd server.
+     > * Also, you will need to have a config file, you can use the one in the `doc/simplecluster/config.yaml` directory or create your own.
+   4. You should see the doorman server running on `localhost:15000` and the debug server running on `localhost:15050`.
+   5. For the purposes of the test add the following to the `config.yaml` file which defines the resources which we will be testing against. (you will need to restart the doorman server for the changes to take effect)
+   ```yaml
+       - identifier_glob: tf
+         capacity: 100
+         safe_capacity: 10
+         description: fair share example
+         algorithm:
+         kind: FAIR_SHARE
+         lease_length: 60
+         refresh_interval: 30
+   ```
+   6. You can try a basic sanity check by building and running the cli client in the `go/cmd/doorman_shell` directory. 
+```shell
+ go build
+./doorman_shell --server=localhost:15000
+> get cli1 tf 100
+> get cli2 tf 100
+> get cli3 tf 30
+> show
+client: "cli1"
+resource: "tf"
+capacity: 0
+
+client: "cli2"
+resource: "tf"
+capacity: 0
+
+client: "cli3"
+resource: "tf"
+capacity: 0
+
+# After the  "refresh_interval" which should be 30 seconds as per the above config , if you try `show` again you should see this which indicates we are all good.
+> show
+client: "cli1"
+resource: "tf"
+capacity: 35
+
+client: "cli2"
+resource: "tf"
+capacity: 35
+
+client: "cli3"
+resource: "tf"
+capacity: 30
+
+# Release the resources
+> release cli1 tf
+> release cli2 tf
+> release cli3 tf
+> show
+> 
+# (should not return anything indicating resources are released from the cli-client, but the resources are still being held by the server until the lease expires i.e: 60sec in this config.)
+```
+
+### II. Set up a target server to test against.
+Clone [this sitting-duck server](https://github.com/Pythonista7/Ktor-Sitting-Duck) and follow the simple instructions in the readme to get the server and some grafana running on http://localhost:3000
+
+
+### III. Running this project
+   1. Clone this repository and gradle sync and build.
+   2. Run the test `simulationOne()` from the `src/test/kotlin/client/Simulation.kt` file.
+
+### IV. Observing the results
+1. You can observe the results in the grafana dashboard that you should have running on `http://localhost:3000` with the default credentials.
+2. You can also try to create additional clients from the `doorman_shell` cli client , try to access the same `tf` resource and observe the changes in the dashboard as the clients are added/removed and how that affects the actual through put of the other clients showcasing dynamic the rate limiting.
+
+# Results
+![img.png](../assets/img.png)
+
+*Note* : I sometimes find that only one client is actively sending requests or only the other 2 clients are sending requests, I'm not sure why this is happening but I suspect it has to do with the way the simulation test coroutines are being launched/scheduled. I will need to investigate this further. 
+But the individual tests for the rate limiter [RateLimiterTest.kt](RateLimiterTest.kt) seem to be working as expected and should ideally be the same for the simulation test as well.