Resilient Functions is a .NET framework realizing the saga-pattern for .NET funcs / actions.
By registering a function with the framework, it will ensure that the function invocation completes despite: failures, restarts, deployments, data migrations etc.
The framework also supports failing invocations for manually handling and facilitates data migrations.
It requires a minimal amount of setup to get started and seamlessly scales with multiple running instances.
Providing a simple way to ensure your code gets run - until you say it is done!
Resilient Functions is a simple and intuitive .NET framework for managing the execution of functions which must complete in their entirety despite: failures, restarts, deployments, versioning etc.
It automatically retries a function invocation until it completes potentially across process restarts and physical nodes.
The framework also supports postponing/suspending invocations or failing invocations for manually handling. Furthermore, versioning is natively supported.
It requires a minimal amount of setup to get started and seamlessly scales with multiple running instances.
Crucially, all this allows the saga pattern / process manager pattern to be implemented in a simple yet powerful way.
Out-of-the-box you also get:
synchronized invocation across multiple process instances
cloud independence & support for multiple databases
simple debuggability & testability
easy versioning of functions
native support for rpc and message-based communication
graceful-shutdown
What it is not?
Unlike other saga frameworks Resilient Functions does not require a message-broker to operate. It is a fully self-contained solution - which operates on top of a database of choice or in-memory when testing.
Getting Started
Only three steps needs to be performed to get started.
Firstly, install the relevant nuget package (using either Postgres, SqlServer, MariaDB or Azure Blob-storage as persistence layer). I.e.
var store = new PostgreSqlFunctionStore(ConnStr);
await store.Initialize();
var functionsRegistry = new FunctionsRegistry(
store,
new Settings(
unhandledExceptionHandler: e => Console.WriteLine($"Unhandled framework exception occured: '{e}'"),
leaseLength: TimeSpan.FromSeconds(5)
)
);
Finally, register and invoke a function using the framework:
Congrats, any non-completed Order flows are now automatically restarted by the framework.
Message-based solution:
It is also possible to implement message-based flows using the framework.
I.e. awaiting 2 external messages before completing an invocation can be accomplished as follows:
In the following chapter several stand-alone examples are presented.
Hello-World
Firstly, the compulsory, ‘hello world’-example can be realized as follows:
var store = new InMemoryFunctionStore();
var functions = new FunctionsRegistry(store, unhandledExceptionHandler: Console.WriteLine);
var rFunc = functions.RegisterFunc(
flowType: "HelloWorld",
inner: (string param) => param.ToUpper()
).Invoke;
var returned = await rFunc(flowInstance: "", param: "hello world");
Console.WriteLine($"Returned: '{returned}'");
Allright, not useful, here are a couple of simple, but common, use-cases.
Invoking a HTTP-endpoint and storing the response in a database table:
public static async Task RegisterAndInvoke(IDbConnection connection, IFunctionStore store)
{
var functions = new FunctionsRegistry(store, new Settings(UnhandledExceptionHandler: Console.WriteLine));
var httpClient = new HttpClient();
var rAction = functions.RegisterAction(
flowType: "HttpAndDatabaseSaga",
inner: async (Guid id) =>
{
var response = await httpClient.PostAsync(URL, new StringContent(id.ToString()));
response.EnsureSuccessStatusCode();
var content = await response.Content.ReadAsStringAsync();
await connection.ExecuteAsync(
"UPDATE Entity SET State=@State WHERE Id=@Id",
new {State = content, Id = id}
);
}).Invoke;
var id = Guid.NewGuid();
await rAction(flowInstance: id.ToString(), param: id);
}
Consider a travel agency which wants to send a promotional email to its customers:
public static class EmailSenderSaga
{
public static async Task Start(MailAndRecipients mailAndRecipients, Workflow workflow)
{
var state = workflow.States.CreateOrGet<State>();
var (recipients, subject, content) = mailAndRecipients;
using var client = new SmtpClient();
await client.ConnectAsync("mail.smtpbucket.com", 8025);
for (var atRecipient = state.AtRecipient; atRecipient < mailAndRecipients.Recipients.Count; atRecipient++)
{
var recipient = recipients[atRecipient];
var message = new MimeMessage();
message.To.Add(new MailboxAddress(recipient.Name, recipient.Address));
message.From.Add(new MailboxAddress("The Travel Agency", "offers@thetravelagency.co.uk"));
message.Subject = subject;
message.Body = new TextPart(TextFormat.Html) { Text = content };
await client.SendAsync(message);
state.AtRecipient = atRecipient;
await state.Save();
}
}
public class State : FlowState
{
public int AtRecipient { get; set; }
}
}
