Merge pull request #5 from DataDog/sarahchen6/update-readme-for-docke…

…r-usage

Update readme for Docker usage

README.md

@@ -2,22 +2,36 @@
 
 ## Quick start
 
+### Using Docker
+
+Run the following command to start a new Docker container with `catadog`.
+
+```
+docker run --rm -d --name catadog ghcr.io/datadog/catadog
+```
+
+### or Ruby Bundler
+
+Run the following commands to install and run `catadog` locally.
+
 ```
 git clone https://github.com/DataDog/catadog
 cd catadog
 bundle install
 bundle exec catadog
 ```
 
-Now start your agent and app!
+### Now start your agent and app!
 
-Remember to do either one of:
+Remember to do one of the following:
 
 - configure your app's agent connection to hit on the correct port
-- configure your agent to listen to another port, and have `catadog` listen on 8126 as the default and point to the new agent's port by using the settings below
+- configure your agent to listen to another port, have `catadog` listen on 8126 as the default, and point to the new agent's port by using the settings below
 
 ## Examples
 
+_**Note that if using Docker, replace `bundle exec catadog` with `docker run ghcr.io/datadog/catadog` in the examples below.**_
+
 Change listening host and port (defaults to 127.0.0.1:8128)
 
 ```
@@ -60,6 +74,12 @@ Bring your own mock! (you can use `--mock` multuiple times)
 bundle exec catadog --mock /path/to/mock.rb:MockMiddlewareClass --no-forward
 ```
 
+Run program as a background process
+
+```
+bundle exec catadog --daemon
+```
+
 Select specific areas:
 
 ```
@@ -135,6 +155,53 @@ Show the contents of the blocked ips list:
 bundle exec catadog | jq 'select(.kind=="rc") | .response.body.target_files | .[] | select(.path | test("ASM_DATA/blocked_ips"))'
 ```
 
+## Using Docker Compose
+
+By leveraging the `docker-compose.yaml` file, you can automatically connect your app to `catadog` and your datadog agent. 
+
+First, [instrument your app](https://docs.datadoghq.com/tracing/trace_collection/automatic_instrumentation/dd_libraries/ruby/#instrument-your-application) with the datadog gem.
+
+Then, include the following environment variables in a `.env` file.
+
+```
+DD_ENV=env-name.dev
+DD_HOSTNAME=host-name
+DD_API_KEY=<api_key>
+```
+
+Update your `docker-compose.yaml` such as below.
+
+```
+services:
+  app:
+    ...
+  catadog:
+    image: ghcr.io/datadog/catadog:latest
+    command: --agent-host agent
+    depends_on:
+      - agent
+    ports:
+      - "8126:8128"
+  agent:
+    image: datadog/agent
+    env_file:
+      - ".env"
+    environment: 
+      - DD_APM_ENABLED=true
+      - DD_BIND_HOST=0.0.0.0
+      - DD_APM_NON_LOCAL_TRAFFIC=true
+      - DD_REMOTE_CONFIGURATION_ENABLED=true
+```
+
+Run the following commands.
+
+```
+docker compose build
+docker compose up -d
+```
+
+Finally, see your app send traces to `catadog`!
+
 ## The big idea
 
 *dd-trace-cat*
@@ -158,28 +225,3 @@ TODO:
 - *traces*: GUI like dd-trace-cat
 - *all*: mock (static, dynamic)
 - *all*: record, replay
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