Getting Started

Ocelot is designed to work with ASP.NET Core <https://learn.microsoft.com/en-us/aspnet/core/?view=aspnetcore-9.0>_ and is currently on .NET 8 <https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-core#lifecycle>_ LTS <https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-core#release-types>_ and .NET 9 <https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-core#lifecycle>_ STS <https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-core#release-types>_ frameworks.

Install

Install Ocelot and it's dependencies using NuGet <https://www.nuget.org/>. You will need to create a ASP.NET Core minimal API project <https://learn.microsoft.com/en-us/aspnet/core/tutorials/min-web-api> with "ASP.NET Core Empty" template but without app.Map* methods, and bring the package into it. Then follow the startup below and :doc:../features/configuration sections to get up and running.

.. code-block:: powershell

Install-Package Ocelot

All versions can be found in the NuGet Gallery | Ocelot <https://www.nuget.org/packages/Ocelot/>_.

.. _getstarted-configuration:

Configuration

The following is a very basic ocelot.json_. It won't do anything but should get Ocelot starting.

.. code-block:: json

{ "Aggregates": [], // optional "Routes": [], // required section "DynamicRoutes": [], // optional section "GlobalConfiguration": { // required "BaseUrl": "https://api.mybusiness.com" } }

If you want some example that actually does something use the following:

.. code-block:: json

{ "Routes": [ { "UpstreamHttpMethod": [ "Get" ], "UpstreamPathTemplate": "/ocelot/posts/{id}", "DownstreamPathTemplate": "/todos/{id}", "DownstreamScheme": "https", "DownstreamHostAndPorts": [ { "Host": "jsonplaceholder.typicode.com", "Port": 443 } ] } ], "GlobalConfiguration": { "BaseUrl": "https://api.mybusiness.com" } }

The most important thing to note here is BaseUrl property. Ocelot needs to know the URL it is running under in order to do Header :ref:ht-find-and-replace and for certain :doc:../features/administration configurations. When setting this URL it should be the external URL that clients will see Ocelot running on e.g. If you are running containers Ocelot might run on the URL http://123.12.1.2:6543 but has something like nginx <https://nginx.org/>_ in front of it responding on https://api.mybusiness.com. In this case the Ocelot BaseUrl should be https://api.mybusiness.com.

If you are using containers and require Ocelot to respond to clients on http://123.12.1.2:6543 then you can do this, however if you are deploying multiple Ocelot's you will probably want to pass this on the command line in some kind of script. Hopefully whatever scheduler you are using can pass the IP.

Program

Then in your Program.cs <https://github.com/ThreeMammals/Ocelot/blob/main/samples/Basic/Program.cs>_ (with top-level statements <https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/program-structure/top-level-statements>_) you will want to have the following.

.. code-block:: csharp :emphasize-lines: 9,11,21

using Ocelot.DependencyInjection;
using Ocelot.Middleware;

var builder = WebApplication.CreateBuilder(args);

// Ocelot Basic setup
builder.Configuration
    .SetBasePath(builder.Environment.ContentRootPath)
    .AddOcelot(); // single ocelot.json file in read-only mode
builder.Services
    .AddOcelot(builder.Configuration);

// Add your features
if (builder.Environment.IsDevelopment())
{
    builder.Logging.AddConsole();
}

// Add middlewares aka app.Use*()
var app = builder.Build();
await app.UseOcelot();
await app.RunAsync();

The main things to note are

• builder.Configuration.AddOcelot() adds single ocelot.json_ configuration file in read-only mode.
• builder.Services.AddOcelot(builder.Configuration) adds Ocelot required and default services [#f1]_
• app.UseOcelot() sets up all the Ocelot middlewares. Note, we have to await the threading result before calling app.RunAsync()
• Do not add endpoint mappings (minimal API methods) such as app.MapGet() because the Ocelot pipeline is not compatible with them!

.. _gettingstarted-samples:

Samples

Solution: Ocelot.Samples.sln_

For beginners, we have prepared basic samples <https://github.com/ThreeMammals/Ocelot/tree/main/samples>_ to help Ocelot newbies clone, compile, and get it running.

• Basic <https://github.com/ThreeMammals/Ocelot/tree/main/samples/Basic>_ sample: It has a single configuration file, ocelot.json_.
• Basic Configuration <https://github.com/ThreeMammals/Ocelot/tree/main/samples/Configuration>_ sample: It has multiple configuration files (ocelot.*.json) to be merged into ocelot.json and written back to disk.

After running in Visual Studio [#f2]_, you may use API.http files to send testing requests to the localhost Ocelot application instance.

""""

.. [#f1] The :ref:di-services-addocelot-method adds default ASP.NET services to the DI container. You can call another extended :ref:di-addocelotusingbuilder-method while configuring services to develop your own :ref:di-custom-builder. See more instructions in the ":ref:di-addocelotusingbuilder-method" section of the :doc:../features/dependencyinjection feature. .. [#f2] All :ref:gettingstarted-samples projects are organized as the Ocelot.Samples.sln_ file for Visual Studio 2022 IDE.

.. _ocelot.json: https://github.com/ThreeMammals/Ocelot/blob/main/samples/Basic/ocelot.json .. _Ocelot.Samples.sln: https://github.com/ThreeMammals/Ocelot/blob/main/samples/Ocelot.Samples.sln