** Capital One built this project to help our engineers as well as users in the community. We are no longer able to fully support the project. We have archived the project as of Jul 9 2019 where it will be available in a read-only state. Feel free to fork the project and maintain your own version. **
CQRS Manager for Distributed Reactive Services
CQRS Manager for Distributed Reactive Services (herein abbreviated CMDR), is a reference implementation for the key component in a specific architecture for building distributed information services following a Log-centric REST+CQRS+ES design.
The role of the CMDR component is to handle incoming Commands by:
- Ensuring their conformity to Schemas (coming soon)
- Writing them down to the Log (Kafka in this implementation)
Additionally, CMDR indexes all Commands and Events from their respective Kafka topics in order to:
- Respond to read (GET) requests for information about Commands and Events
- Provide a Server Sent Events (SSE) interface to both Commands (
/commands/updates
) and Events (/events/updates
)
Status
IMPORTANT! This is alpha-quality software, meant mostly to demonstrate the Log-centric REST+CQRS+ES architecture described in the linked talks, and to facilitate learning and discussion.
As this implementation reaches maturity, and becomes suited for production-use, this note will be removed from the README.
Documentation
CMDR is the component in your system that handles all incoming actions/writes, but it's totally ignorant of your business logic and domain. You'll need to build microservices that implement your business logic, and read-only REST endpoints to expose the resulting data. You'll end up with a system architecture that looks like this, and has many benefits.
This README will help you get CMDR running, but doesn't tell you how to integrate with it or why you might want to. See the rationale for why you'd use CMDR, and the contract documentation for details about how to integrate with CMDR.
Running in development
CMDR is a Leiningen project, and behaves as you would expect in terms of running tests, launching REPLs, packaging uberjars, etc.
CMDR runs as two microservices
(com.capitalone.commander.indexer
and
com.capitalone.commander.rest
) that coordinate via
Apache Kafka and a JDBC-compliant database
like PostgreSQL. In order to run the
CMDR services, you'll first need to run a Kafka Cluster and a
database.
Supporting Services
There is a handy Makefile
for running and interacting with the
supporting services and/or the example application. This Makefile
uses docker
and docker-compose
under the hood to orchestrate the
various services.
Running the supporting services (Kafka, ZooKeeper, PostgreSQL) via the
Makefile
is the easiest way to get started. However, if you want to
run the supporting services manually, you can use a package manager to
install the services.
Makefile
The easiest way to get CMDR's supporting services up-and-running
quickly in development is via the Makefile
.
$ make services
$ make service-bootstrap # bootstraps database, etc.
Then run the CMDR services locally from the REPL or via lein run
as described below, and visit http://localhost:3000/ui/ to see
the Swagger/OpenAPI user interface to the CMDR service.
Or you can run an entire example system (including both CMDR services and an example business logic service):
$ make example
Then you can visit the CMDR service at http://localhost:3000/ui/, and the sample application's REST API at http://localhost:8080/customers.
Running Manually
The following instructions provide an example for those running on Mac OS X using the Homebrew package manager to install the supporting services.
Install
Kafka and ZooKeeper
Kafka uses Apache ZooKeeper to maintain runtime state and configuration consistently across the cluster. You'll need to install both Kafka and ZooKeeper.
$ brew update
$ brew install kafka
PostgresQL
To install postgres:
$ brew install postgresql
Running
Kafka and ZooKeeper
In one shell:
$ zookeeper-server-start /usr/local/etc/kafka/zookeeper.properties
In a second shell:
$ kafka-server-start /usr/local/etc/kafka/server.properties
PostgreSQL
In third shell:
$ postgres -D /usr/local/var/postgres
Then bootstrap the database in a fourth shell:
$ bin/run com.capitalone.commander.database 'jdbc:postgresql://localhost/postgres?user=postgres&password=postgres' commander commander commander
You'll want to use commander
as the password for the commander
user for
the dev environment to work.
Clojure REPL
In the third shell:
# build Protobufs classes (only necessary on first run, or when making changes to .proto files)
$ lein do javac, compile
# launch repl
$ lein repl
Connect an nrepl client -- perhaps in your favorite editor, or else type directly into the REPL session in your shell:
(go)
Workflow
This application follows the reloaded workflow using the component pattern, providing a clean system architecture and reloadable REPL development environment.
Running in development
At the Clojure REPL, you first need to run database migrations.
(migrate-database)
You can then run the system:
(go)
And then reload the entire app, refreshing all the code:
(reset)
You can also run the tests right from the REPL (in addition to running
via lein test
):
(test)
Running tests
To run tests:
$ lein test
or
$ lein auto test
to run tests automatically every time a file is saved.
Swagger/OpenAPI
When running the API, you can view the Swagger/OpenAPI UI.
Swagger/OpenAPI functionality provided by pedestal-api.
Build
Uberjar
You can build a self-contained JAR that includes all dependencies via:
$ lein do clean, uberjar
You then run the application:
$ java -jar target/uberjar/cmdr-standalone.jar -m com.capitalone.commander.indexer
$ # OR
$ java -jar target/uberjar/cmdr-standalone.jar -m com.capitalone.commander.rest
Docker
The Docker image is based on the Alpine Linux version of the official Clojure repository on Docker Hub
$ docker build -t my-cmdr-build .
You can then run either of the CMDR services via the built image:
$ docker run my-cmdr-build com.capitalone.commander.indexer
$ # OR
$ docker run my-cmdr-build com.capitalone.commander.rest
Contributors
We welcome your interest in Capital One’s Open Source Projects (the “Project”). Any Contributor to the project must accept and sign a CLA indicating agreement to the license terms. Except for the license granted in this CLA to Capital One and to recipients of software distributed by Capital One, you reserve all right, title, and interest in and to your contributions; this CLA does not impact your rights to use your own contributions for any other purpose.
This project adheres to the Open Source Code of Conduct. By participating, you are expected to honor this code.
License
Copyright 2016 Capital One Services, LLC
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.