snapshot of https://github.com/ThreeDotsLabs/watermill.git (master, 2026-09-15; blobs > 131072B omitted)

_examples/basic/1-your-first-app/README.md

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+# Your first Watermill app
+
+This example project shows a basic setup of Watermill. The application runs in a loop, consuming events from a Kafka
+topic, modifying them and publishing to another topic.
+
+There's a docker-compose file included, so you can run the example and see it in action.
+
+To understand the background and internals, see [getting started guide](https://watermill.io/learn/getting-started/).
+
+## Files
+
+- [main.go](main.go) - example source code, the **most interesting file for you**
+- [docker-compose.yml](docker-compose.yml) - local environment Docker Compose configuration, contains Golang, Kafka and Zookeeper
+- [go.mod](go.mod) - Go modules dependencies, you can find more information at [Go wiki](https://github.com/golang/go/wiki/Modules)
+- [go.sum](go.sum) - Go modules checksums
+
+## Requirements
+
+To run this example you will need Docker and docker-compose installed. See the [installation guide](https://docs.docker.com/compose/install/).
+
+## Running
+
+```bash
+> docker-compose up
+[some initial logs]
+server_1     | 2019/08/29 19:41:23 received event {ID:0}
+server_1     | 2019/08/29 19:41:23 received event {ID:1}
+server_1     | 2019/08/29 19:41:23 received event {ID:2}
+server_1     | 2019/08/29 19:41:23 received event {ID:3}
+server_1     | 2019/08/29 19:41:24 received event {ID:4}
+server_1     | 2019/08/29 19:41:25 received event {ID:5}
+server_1     | 2019/08/29 19:41:26 received event {ID:6}
+server_1     | 2019/08/29 19:41:27 received event {ID:7}
+server_1     | 2019/08/29 19:41:28 received event {ID:8}
+server_1     | 2019/08/29 19:41:29 received event {ID:9}
+```
+
+Open another terminal and take a look at Kafka topics to see that all messages are there. The initial events should be present on the `events` topic:
+
+```bash
+> docker-compose exec server mill kafka consume -b kafka:9092 --topic events
+
+{"id":12}
+{"id":13}
+{"id":14}
+{"id":15}
+{"id":16}
+{"id":17}
+```
+
+And the processed messages will be stored in the `events-processed` topic:
+
+```bash
+> docker-compose exec server mill kafka consume -b kafka:9092 -t events-processed 
+
+{"processed_id":21,"time":"2019-08-29T19:42:31.4464598Z"}
+{"processed_id":22,"time":"2019-08-29T19:42:32.4501767Z"}
+{"processed_id":23,"time":"2019-08-29T19:42:33.4530692Z"}
+{"processed_id":24,"time":"2019-08-29T19:42:34.4561694Z"}
+{"processed_id":25,"time":"2019-08-29T19:42:35.4608918Z"}
+```