# EventFlow
```
$ dotnet add package EventFlow
```
EventFlow is a basic CQRS+ES framework designed to be easy to use.
Have a look at our [getting started guide](https://geteventflow.net/getting-started/),
the [do’s and don’ts](https://geteventflow.net/additional/dos-and-donts/) and the
[FAQ](https://geteventflow.net/additional/faq/).
Alternatively, join our [Discord](https://discord.gg/QfgNPs5WxR) server to engage with the community. Its hopefully getting a reboot to kickstart the upcoming release of v1.
## Features
* **Easy to use**: Designed with sensible defaults and implementations that make it
easy to create an example application
* **Highly configurable and extendable**: EventFlow uses interfaces for every part of
its core, making it easy to replace or extend existing features with custom
implementation
* **No use of threads or background workers**
* **MIT licensed** Easy to understand and use license for enterprise
## Versions
Development of version 1.0 has started and is mainly braking changes regarding changes
related to replacing EventFlow types with that of Microsoft extension abstractions,
mainly `IServiceProvider` and `ILogger<>`.
The following list key characteristics of each version as well as its related branches
(not properly configured yet).
* `1.x`
Represents the next iteration of EventFlow that aligns EventFlow with the standard
packages for .NET. Releases here will only support .NET Standard, .NET Core
and .NET versions 6+ going forward.
- Released
- Still development
- Not all projects migrated yet
Read the [migration guide](https://geteventflow.net/migrations/v0-to-v1/) to view the full list of breaking
changes as well as recommendations on how to migrate.
### Documentation
Version 1.x documentation has been pulled into this repository in order to have
the code and documentation closer together and have the documentation
updated in the same pull-requests as any code changes. The compiled version of the
documentation is available at https://geteventflow.net/.
### NuGet package status
- 🟢 ported
- 💚 newly added to 1.0
- 🟠 not yet ported to 1.0
- 💀 for packages that are removed as part of 1.0 (see the [migration guide](https://geteventflow.net/migrations/v0-to-v1/) for details)
Projects
- 🟢 `EventFlow`
- 🟠 `EventFlow.AspNetCore`
- 💀 `EventFlow.Autofac`
- 💀 `EventFlow.DependencyInjection`
- 🟠 `EventFlow.Elasticsearch`
- 🟢 `EventFlow.EntityFramework`
- 🟠 `EventFlow.EventStores.EventStore`
- 🟢 `EventFlow.Hangfire`
- 🟢 `EventFlow.MongoDB`
- 🟢 `EventFlow.MsSql`
- 💀 `EventFlow.Owin`
- 🟢 `EventFlow.PostgreSql`
- 🟠 `EventFlow.Redis`
- 🟢 `EventFlow.RabbitMQ`
- 🟢 `EventFlow.Sql`
- 🟢 `EventFlow.SQLite`
- 🟢 `EventFlow.TestHelpers`
### Branches
- `develop-v1`: Development branch, pull requests should be done here
- `release-v1`: Release branch, merge commits are done to this branch from
`develop-v1` to create releases. Typically each commit represents a release
* `0.x` (legacy)
The current stable version of EventFlow and has been the version of EventFlow
for almost six years. 0.x versions have .NET Framework support and limited
support to the Microsoft extension packages through extra NuGet packages.
Feature and bug fix releases will still be done while there's interest in
the community.
### Branches
- `develop-v0`: Development branch, pull requests should be done here
- `release-v0`: Release branch, merge commits are done to this branch from
`develop-v0` to create releases. Typically each commit represents a release
### Documentation
Version 0.x documentation is (although a bit outdated) is live at
https://docs.geteventflow.net/.
Alternatively, join our Discord server to engage with the community. Its hopefully getting a reboot to kickstart the upcoming release of v1.
Features
Easy to use: Designed with sensible defaults and implementations that make it
easy to create an example application
Highly configurable and extendable: EventFlow uses interfaces for every part of
its core, making it easy to replace or extend existing features with custom
implementation
No use of threads or background workers
MIT licensed Easy to understand and use license for enterprise
Versions
Development of version 1.0 has started and is mainly braking changes regarding changes
related to replacing EventFlow types with that of Microsoft extension abstractions,
mainly IServiceProvider and ILogger<>.
The following list key characteristics of each version as well as its related branches
(not properly configured yet).
1.x
Represents the next iteration of EventFlow that aligns EventFlow with the standard
packages for .NET. Releases here will only support .NET Standard, .NET Core
and .NET versions 6+ going forward.
Released
Still development
Not all projects migrated yet
Read the migration guide to view the full list of breaking
changes as well as recommendations on how to migrate.
Documentation
Version 1.x documentation has been pulled into this repository in order to have
the code and documentation closer together and have the documentation
updated in the same pull-requests as any code changes. The compiled version of the
documentation is available at https://geteventflow.net/.
NuGet package status
🟢 ported
💚 newly added to 1.0
🟠 not yet ported to 1.0
💀 for packages that are removed as part of 1.0 (see the migration guide for details)
Projects
🟢 EventFlow
🟠 EventFlow.AspNetCore
💀 EventFlow.Autofac
💀 EventFlow.DependencyInjection
🟠 EventFlow.Elasticsearch
🟢 EventFlow.EntityFramework
🟠 EventFlow.EventStores.EventStore
🟢 EventFlow.Hangfire
🟢 EventFlow.MongoDB
🟢 EventFlow.MsSql
💀 EventFlow.Owin
🟢 EventFlow.PostgreSql
🟠 EventFlow.Redis
🟠 EventFlow.RabbitMQ
🟢 EventFlow.Sql
🟢 EventFlow.SQLite
🟢 EventFlow.TestHelpers
Branches
develop-v1: Development branch, pull requests should be done here
release-v1: Release branch, merge commits are done to this branch from
develop-v1 to create releases. Typically each commit represents a release
0.x (legacy)
The current stable version of EventFlow and has been the version of EventFlow
for almost six years. 0.x versions have .NET Framework support and limited
support to the Microsoft extension packages through extra NuGet packages.
Feature and bug fix releases will still be done while there's interest in
the community.
Branches
develop-v0: Development branch, pull requests should be done here
release-v0: Release branch, merge commits are done to this branch from
develop-v0 to create releases. Typically each commit represents a release
Complete: Shows a complete example on how to use
EventFlow with in-memory event store and read models in a relatively few lines
of code
Shipping: To get a more complete example of how EventFlow could be used,
have a look at the shipping example found here in the code base. The example
is based on the shipping example from the book "Domain-Driven Design -
Tackling Complexity in the Heart of Software" by Eric Evans. Its
in-progress, but should provide inspiration on how to use EventFlow on a
larger scale. If you have ideas and/or comments, create a pull request or
an issue
External Examples
List of examples create by different community members. Note that many of these
examples will be using EventFlow 0.x.
Create a pull request to get your exampled linked from here.
Racetimes:
Shows some features of EventFlow that are not covered in the
complete example. It features entities, a read model for
an entity, delete on read models, specifications and snapshots.
.NET Core:
A Web API running .NET Core 2.2 using the event flow. It uses the pre-defined
command/entities/events from the complete example. There are endpoints to
create a new example event, getting a data model and to replay all data models.
ElasticSearch/.NET Core:
It is configured with EventFlow, ElasticSearch, EventStore, and RabbitMq. See "withRabbitMq" branch for #384.
Vehicle Tracking:
A Microservice on .NET Core 2.2 with docker based, you can up the service with docker-compose, this project using various
tools to up the services aka. Linux Docker based on .NET Core, RabbitMq, EntityFramework with SQL Server and using EventFlow following CQRS-ES architecture
and all microservice can access through ApiGateway which using Ocelot
RestAirline:
A classic DDD with CQRS-ES, Hypermedia API project based on EventFlow. It's targeted to ASP.NET Core 2.2 and can be deployed to docker and k8s.
Full Example:
A console application on .NET Core 2.2. You can up the services using docker-compose file. Docker-compose file include EventStore, RabbitMq, MongoDb, and PostgreSQL. It include following EventFlow concepts:
Subscribers:
Listeners that act on specific domain events. Useful if an specific action
needs to be triggered after a domain event has been committed.
Read models:
Denormalized representation of aggregate events optimized for reading fast.
Currently there is support for these read model storage types.
For the SQL storage types the queries are being generated automatically with quoted columns and table names.
Elasticsearch
In-memory - only for test
Microsoft SQL Server
Entity Framework Core
SQLite
PostgreSQL
Snapshots:
Instead of reading the entire event stream every single time, a snapshot can
be created every so often that contains the aggregate state. EventFlow
supports upgrading existing snapshots, which is useful for long-lived
aggregates. Snapshots in EventFlow are opt-in and EventFlow has support for
In-memory - only for test
Microsoft SQL Server
Entity Framework Core
SQLite
PostgreSQL
Sagas:
Also known as process managers, coordinates and routes messages between
bounded contexts and aggregates
Queries:
Value objects that represent a query without specifying how its executed,
that is let to a query handler
Jobs: Perform scheduled tasks at
a later time, e.g. publish a command. EventFlow provides support for these
job schedulers
Event upgrade:
As events committed to the event store is never changed, EventFlow uses the
concept of event upgraders to deprecate events and replace them with new
during aggregate load.
Event publishing: Sometimes you want other applications or services to
consume and act on domains. For this EventFlow supports event publishing.
RabbitMQ
Metadata:
Additional information for each aggregate event, e.g. the IP of
the user behind the event being emitted. EventFlow ships with
several providers ready to use used.
Value objects:
Data containing classes used to validate and hold domain data, e.g. a
username or e-mail.
Complete example
Here's a complete example on how to use the default in-memory event store
along with an in-memory read model.
The example consists of the following classes, each shown below
ExampleAggregate: The aggregate root
ExampleId: Value object representing the identity of the aggregate root
ExampleEvent: Event emitted by the aggregate root
ExampleCommand: Value object defining a command that can be published to the
aggregate root
ExampleCommandHandler: Command handler which EventFlow resolves using its IoC
container and defines how the command specific is applied to the aggregate root
ExampleReadModel: In-memory read model providing easy access to the current
state
Note: This example is part of the EventFlow test suite, so checkout the
code and give it a go.
[Test]
public async Task Example()
{
// We wire up EventFlow with all of our classes. Instead of adding events,
// commands, etc. explicitly, we could have used the the simpler
// AddDefaults(Assembly) instead.
var serviceCollection = new ServiceCollection()
.AddLogging()
.AddEventFlow(o => o
.AddEvents(typeof(ExampleEvent))
.AddCommands(typeof(ExampleCommand))
.AddCommandHandlers(typeof(ExampleCommandHandler))
.UseInMemoryReadStoreFor<ExampleReadModel>());
using (var serviceProvider = serviceCollection.BuildServiceProvider())
{
// Create a new identity for our aggregate root
var exampleId = ExampleId.New;
// Resolve the command bus and use it to publish a command
var commandBus = serviceProvider.GetRequiredService<ICommandBus>();
await commandBus.PublishAsync(
new ExampleCommand(exampleId, 42), CancellationToken.None);
// Resolve the query handler and use the built-in query for fetching
// read models by identity to get our read model representing the
// state of our aggregate root
var queryProcessor = serviceProvider.GetRequiredService<IQueryProcessor>();
var exampleReadModel = await queryProcessor.ProcessAsync(
new ReadModelByIdQuery<ExampleReadModel>(exampleId), CancellationToken.None);
// Verify that the read model has the expected magic number
exampleReadModel.MagicNumber.Should().Be(42);
}
}
// The aggregate root
public class ExampleAggregate : AggregateRoot<ExampleAggregate, ExampleId>,
IEmit<ExampleEvent>
{
private int? _magicNumber;
public ExampleAggregate(ExampleId id) : base(id) { }
// Method invoked by our command
public void SetMagicNumber(int magicNumber)
{
if (_magicNumber.HasValue)
throw DomainError.With("Magic number already set");
Emit(new ExampleEvent(magicNumber));
}
// We apply the event as part of the event sourcing system. EventFlow
// provides several different methods for doing this, e.g. state objects,
// the Apply method is merely the simplest
public void Apply(ExampleEvent aggregateEvent)
{
_magicNumber = aggregateEvent.MagicNumber;
}
}
// Represents the aggregate identity (ID)
public class ExampleId : Identity<ExampleId>
{
public ExampleId(string value) : base(value) { }
}
// A basic event containing some information
public class ExampleEvent : AggregateEvent<ExampleAggregate, ExampleId>
{
public ExampleEvent(int magicNumber)
{
MagicNumber = magicNumber;
}
public int MagicNumber { get; }
}
// Command for update magic number
public class ExampleCommand : Command<ExampleAggregate, ExampleId>
{
public ExampleCommand(
ExampleId aggregateId,
int magicNumber)
: base(aggregateId)
{
MagicNumber = magicNumber;
}
public int MagicNumber { get; }
}
// Command handler for our command
public class ExampleCommandHandler
: CommandHandler<ExampleAggregate, ExampleId, ExampleCommand>
{
public override Task ExecuteAsync(
ExampleAggregate aggregate,
ExampleCommand command,
CancellationToken cancellationToken)
{
aggregate.SetMagicNumber(command.MagicNumber);
return Task.CompletedTask;;
}
}
// Read model for our aggregate
public class ExampleReadModel : IReadModel,
IAmReadModelFor<ExampleAggregate, ExampleId, ExampleEvent>
{
public int MagicNumber { get; private set; }
public Task ApplyAsync(
IReadModelContext context,
IDomainEvent<ExampleAggregate, ExampleId, ExampleEvent> domainEvent,
CancellationToken _cancellationToken
{
MagicNumber = domainEvent.AggregateEvent.MagicNumber;
return Task.CompletedTask;
}
}
State of EventFlow
EventFlow is still under development, especially the parts regarding
how read models are re-populated.
EventFlow is currently used in production environments and performs very well,
but it needs to mature before key APIs are stable.
EventFlow is greatly opinionated, but it's possible to create new implementations
for almost every part of EventFlow by registering a different implementation of
an interface.
Useful articles related to EventFlow and DDD
Many of the technical design decisions in EventFlow is based on articles. This
section lists some of them. If you have a link with a relevant article, please
share it by creating an issue with the link.
The MIT License (MIT)
Copyright (c) 2015-2025 Rasmus Mikkelsen
https://github.com/eventflow/EventFlow
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
