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TomPallisterTomPallister
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Merge branch 'DavidLievrouw-CustomLoadBalancers'
2 parents d58f314 + 7408060 commit 59af924

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‎docs/features/loadbalancer.rst‎

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@@ -108,3 +108,112 @@ subsequent requests. This means the sessions will be stuck across ReRoutes.
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Please note that if you give more than one DownstreamHostAndPort or you are using a Service Discovery provider such as Consul
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and this returns more than one service then CookieStickySessions uses round robin to select the next server. This is hard coded at the
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moment but could be changed.
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Custom Load Balancers
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^^^^^^^^^^^^^^^^^^^^
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`DavidLievrouw <https://github.com/DavidLievrouw`_ implemented a way to provide Ocelot with custom load balancer in `PR 1155 <https://github.com/ThreeMammals/Ocelot/pull/1155`_.
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In order to create and use a custom load balancer you can do the following. Below we setup a basic load balancing config and not the Type is CustomLoadBalancer this is the name of a class we will
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setup to do load balancing.
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.. code-block:: json
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{
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"DownstreamPathTemplate": "/api/posts/{postId}",
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"DownstreamScheme": "https",
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"DownstreamHostAndPorts": [
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{
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"Host": "10.0.1.10",
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"Port": 5000,
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},
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{
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"Host": "10.0.1.11",
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"Port": 5000,
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}
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],
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"UpstreamPathTemplate": "/posts/{postId}",
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"LoadBalancerOptions": {
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"Type": "CustomLoadBalancer"
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},
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"UpstreamHttpMethod": [ "Put", "Delete" ]
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}
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Then you need to create a class that implements the ILoadBalancer interface. Below is a simple round robin example.
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.. code-block:: csharp
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private class CustomLoadBalancer : ILoadBalancer
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{
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private readonly Func<Task<List<Service>>> _services;
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private readonly object _lock = new object();
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private int _last;
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public CustomLoadBalancer(Func<Task<List<Service>>> services)
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{
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_services = services;
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}
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public async Task<Response<ServiceHostAndPort>> Lease(DownstreamContext downstreamContext)
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{
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var services = await _services();
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lock (_lock)
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{
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if (_last >= services.Count)
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{
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_last = 0;
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}
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var next = services[_last];
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_last++;
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return new OkResponse<ServiceHostAndPort>(next.HostAndPort);
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}
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}
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public void Release(ServiceHostAndPort hostAndPort)
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{
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}
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}
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Finally you need to register this class with Ocelot. I have used the most complex example below to show all of the data / types that can be passed into the factory that creates load balancers.
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.. code-block:: csharp
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Func<IServiceProvider, DownstreamReRoute, IServiceDiscoveryProvider, CustomLoadBalancer> loadBalancerFactoryFunc = (serviceProvider, reRoute, serviceDiscoveryProvider) => new CustomLoadBalancer(serviceDiscoveryProvider.Get);
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s.AddOcelot()
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.AddCustomLoadBalancer(loadBalancerFactoryFunc);
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However there is a much simpler example that will work the same.
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.. code-block:: csharp
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s.AddOcelot()
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.AddCustomLoadBalancer<CustomLoadBalancer>();
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There are numerous extension methods to add a custom load balancer and the interface is as follows.
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.. code-block:: csharp
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IOcelotBuilder AddCustomLoadBalancer<T>()
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where T : ILoadBalancer, new();
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IOcelotBuilder AddCustomLoadBalancer<T>(Func<T> loadBalancerFactoryFunc)
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where T : ILoadBalancer;
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IOcelotBuilder AddCustomLoadBalancer<T>(Func<IServiceProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer;
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IOcelotBuilder AddCustomLoadBalancer<T>(
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Func<DownstreamReRoute, IServiceDiscoveryProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer;
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IOcelotBuilder AddCustomLoadBalancer<T>(
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Func<IServiceProvider, DownstreamReRoute, IServiceDiscoveryProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer;
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When you enable custom load balancers Ocelot looks up your load balancer by its class name when it decides if it should do load balancing. If it finds a match it will use your load balaner to load balance. If Ocelot cannot match the load balancer type in your configuration with the name of registered load balancer class then you will receive a HTTP 500 internal server error. If your load balancer factory throw an exception when Ocelot calls it you will receive a HTTP 500 internal server error.
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Remember if you specify no load balancer in your config Ocelot will not try and load balance.

‎src/Ocelot/DependencyInjection/IOcelotBuilder.cs‎

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using Ocelot.Middleware.Multiplexer;
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using System;
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using System.Net.Http;
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using Ocelot.Configuration;
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using Ocelot.LoadBalancer.LoadBalancers;
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using Ocelot.ServiceDiscovery.Providers;
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namespace Ocelot.DependencyInjection
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{
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IOcelotBuilder AddTransientDefinedAggregator<T>()
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where T : class, IDefinedAggregator;
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IOcelotBuilder AddCustomLoadBalancer<T>()
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where T : ILoadBalancer, new();
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IOcelotBuilder AddCustomLoadBalancer<T>(Func<T> loadBalancerFactoryFunc)
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where T : ILoadBalancer;
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IOcelotBuilder AddCustomLoadBalancer<T>(Func<IServiceProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer;
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IOcelotBuilder AddCustomLoadBalancer<T>(
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Func<DownstreamReRoute, IServiceDiscoveryProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer;
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IOcelotBuilder AddCustomLoadBalancer<T>(
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Func<IServiceProvider, DownstreamReRoute, IServiceDiscoveryProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer;
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IOcelotBuilder AddConfigPlaceholders();
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}
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}

‎src/Ocelot/DependencyInjection/OcelotBuilder.cs‎

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using Ocelot.ServiceDiscovery.Providers;
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using Ocelot.Configuration.ChangeTracking;
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namespace Ocelot.DependencyInjection
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Services.TryAddSingleton<IFileConfigurationRepository, DiskFileConfigurationRepository>();
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Services.TryAddSingleton<IFileConfigurationSetter, FileAndInternalConfigurationSetter>();
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Services.TryAddSingleton<IServiceDiscoveryProviderFactory, ServiceDiscoveryProviderFactory>();
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Services.AddSingleton<ILoadBalancerCreator, NoLoadBalancerCreator>();
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Services.AddSingleton<ILoadBalancerCreator, RoundRobinCreator>();
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Services.AddSingleton<ILoadBalancerCreator, CookieStickySessionsCreator>();
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Services.AddSingleton<ILoadBalancerCreator, LeastConnectionCreator>();
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Services.TryAddSingleton<ILoadBalancerFactory, LoadBalancerFactory>();
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Services.TryAddSingleton<ILoadBalancerHouse, LoadBalancerHouse>();
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Services.TryAddSingleton<IOcelotLoggerFactory, AspDotNetLoggerFactory>();
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return this;
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}
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public IOcelotBuilder AddCustomLoadBalancer<T>()
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where T : ILoadBalancer, new()
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{
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AddCustomLoadBalancer((provider, reRoute, serviceDiscoveryProvider) => new T());
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return this;
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}
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public IOcelotBuilder AddCustomLoadBalancer<T>(Func<T> loadBalancerFactoryFunc)
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where T : ILoadBalancer
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{
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AddCustomLoadBalancer((provider, reRoute, serviceDiscoveryProvider) =>
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loadBalancerFactoryFunc());
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return this;
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}
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public IOcelotBuilder AddCustomLoadBalancer<T>(Func<IServiceProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer
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{
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AddCustomLoadBalancer((provider, reRoute, serviceDiscoveryProvider) =>
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loadBalancerFactoryFunc(provider));
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return this;
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}
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public IOcelotBuilder AddCustomLoadBalancer<T>(Func<DownstreamReRoute, IServiceDiscoveryProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer
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{
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AddCustomLoadBalancer((provider, reRoute, serviceDiscoveryProvider) =>
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loadBalancerFactoryFunc(reRoute, serviceDiscoveryProvider));
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return this;
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}
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public IOcelotBuilder AddCustomLoadBalancer<T>(Func<IServiceProvider, DownstreamReRoute, IServiceDiscoveryProvider, T> loadBalancerFactoryFunc)
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where T : ILoadBalancer
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{
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Services.AddSingleton<ILoadBalancerCreator>(provider =>
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new DelegateInvokingLoadBalancerCreator<T>(
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(reRoute, serviceDiscoveryProvider) =>
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loadBalancerFactoryFunc(provider, reRoute, serviceDiscoveryProvider)));
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return this;
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}
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private void AddSecurity()
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{
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Services.TryAddSingleton<ISecurityOptionsCreator, SecurityOptionsCreator>();

‎src/Ocelot/Errors/OcelotErrorCode.cs‎

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QuotaExceededError = 36,
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RequestCanceled = 37,
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ConnectionToDownstreamServiceError = 38,
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CouldNotFindLoadBalancerCreator = 39,
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ErrorInvokingLoadBalancerCreator = 40,
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}
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}

‎src/Ocelot/LoadBalancer/LoadBalancers/CookieStickySessionsCreator.cs‎

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namespace Ocelot.LoadBalancer.LoadBalancers
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{
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using System.Threading.Tasks;
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using Ocelot.Configuration;
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using Ocelot.Infrastructure;
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using Ocelot.ServiceDiscovery.Providers;
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using Ocelot.Responses;
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public class CookieStickySessionsCreator : ILoadBalancerCreator
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{
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public Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
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{
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var loadBalancer = new RoundRobin(async () => await serviceProvider.Get());
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var bus = new InMemoryBus<StickySession>();
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return new OkResponse<ILoadBalancer>(new CookieStickySessions(loadBalancer, reRoute.LoadBalancerOptions.Key,
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reRoute.LoadBalancerOptions.ExpiryInMs, bus));
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}
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public string Type => nameof(CookieStickySessions);
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}
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}

‎src/Ocelot/LoadBalancer/LoadBalancers/CouldNotFindLoadBalancerCreator.cs‎

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namespace Ocelot.LoadBalancer.LoadBalancers
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{
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using Errors;
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public class CouldNotFindLoadBalancerCreator : Error
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{
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public CouldNotFindLoadBalancerCreator(string message)
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: base(message, OcelotErrorCode.CouldNotFindLoadBalancerCreator)
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{
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}
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}
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}

‎src/Ocelot/LoadBalancer/LoadBalancers/DelegateInvokingLoadBalancerCreator.cs‎

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namespace Ocelot.LoadBalancer.LoadBalancers
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{
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using System;
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using Ocelot.Configuration;
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using Ocelot.ServiceDiscovery.Providers;
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using Ocelot.Responses;
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public class DelegateInvokingLoadBalancerCreator<T> : ILoadBalancerCreator
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where T : ILoadBalancer
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{
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private readonly Func<DownstreamReRoute, IServiceDiscoveryProvider, ILoadBalancer> _creatorFunc;
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public DelegateInvokingLoadBalancerCreator(
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Func<DownstreamReRoute, IServiceDiscoveryProvider, ILoadBalancer> creatorFunc)
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{
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_creatorFunc = creatorFunc;
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}
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public Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider)
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{
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try
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{
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return new OkResponse<ILoadBalancer>(_creatorFunc(reRoute, serviceProvider));
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}
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catch (Exception e)
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{
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return new ErrorResponse<ILoadBalancer>(new ErrorInvokingLoadBalancerCreator(e));
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}
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}
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public string Type => typeof(T).Name;
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}
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}

‎src/Ocelot/LoadBalancer/LoadBalancers/ErrorInvokingLoadBalancerCreator.cs‎

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namespace Ocelot.LoadBalancer.LoadBalancers
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{
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using System;
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using Errors;
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public class ErrorInvokingLoadBalancerCreator : Error
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{
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public ErrorInvokingLoadBalancerCreator(Exception e) : base($"Error when invoking user provided load balancer creator function, Message: {e.Message}, StackTrace: {e.StackTrace}", OcelotErrorCode.ErrorInvokingLoadBalancerCreator)
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{
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}
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}
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}

‎src/Ocelot/LoadBalancer/LoadBalancers/ILoadBalancerCreator.cs‎

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namespace Ocelot.LoadBalancer.LoadBalancers
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{
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using Ocelot.Responses;
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using Ocelot.Configuration;
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using Ocelot.ServiceDiscovery.Providers;
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public interface ILoadBalancerCreator
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{
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Response<ILoadBalancer> Create(DownstreamReRoute reRoute, IServiceDiscoveryProvider serviceProvider);
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string Type { get; }
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}
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}

‎src/Ocelot/LoadBalancer/LoadBalancers/ILoadBalancerFactory.cs‎

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{
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using Ocelot.Configuration;
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using Ocelot.Responses;
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using System.Threading.Tasks;
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public interface ILoadBalancerFactory
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{
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Task<Response<ILoadBalancer>> Get(DownstreamReRoute reRoute, ServiceProviderConfiguration config);
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Response<ILoadBalancer> Get(DownstreamReRoute reRoute, ServiceProviderConfiguration config);
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}
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}

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