#251 Health check circuit breaker

Signed-off-by: Richard Pringle <richardpringle@gmail.com>

Author: EtherZa

build/tasks.ps1

@@ -43,6 +43,8 @@ $projects = @(
 	"SlimMessageBus.Host.Outbox.Sql",
 	"SlimMessageBus.Host.Outbox.Sql.DbContext",
 
+	"SlimMessageBus.Host.CircuitBreaker.HealthCheck",
+
 	"SlimMessageBus.Host.AsyncApi"
 )
 

docs/intro.md

@@ -7,6 +7,7 @@
     - [Set message headers](#set-message-headers)
   - [Consumer](#consumer)
     - [Start or Stop message consumption](#start-or-stop-message-consumption)
+        - [Health check circuit breaker](#health-check-circuit-breaker)
     - [Consumer context (additional message information)](#consumer-context-additional-message-information)
     - [Per-message DI container scope](#per-message-di-container-scope)
     - [Hybrid bus and message scope reuse](#hybrid-bus-and-message-scope-reuse)
@@ -291,6 +292,32 @@ await consumerControl.Stop();
 
 > Since version 1.15.5
 
+#### Health check circuit breaker
+
+Consumers can be linked to [.NET app health checks](https://learn.microsoft.com/en-us/dotnet/core/diagnostics/diagnostic-health-checks) [tags](https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/health-checks#register-health-check-services), enabling or disabling the consumer based on the health check status reported by the [Health Check Publisher](https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/health-checks#health-check-publisher). A consumer associated with one or more tags will only be active if all health checks linked to the tags are passing.
+
+```cs
+    // add health checks with tags
+    builder.Services
+        .AddHealthChecks()
+        .AddCheck<StorageHealthCheck>("Storage", tags: ["Storage"]);
+        .AddCheck<SqlServerHealthCheck>("SqlServer", tags: ["Sql"]);
+
+    builder.Services
+        .AddSlimMessageBus(mbb => {
+            ...
+
+            mbb.Consume<Message>(cfg => {
+                ...
+
+                // configure consumer to monitor tag/state
+                cfg.PauseOnUnhealthyCheck("Storage");
+                cfg.PauseOnDegradedHealthCheck("Sql");
+            })
+        })
+```
+*Requires: SlimMessageBus.Host.CircuitBreaker.HealthCheck*
+
 #### Consumer context (additional message information)
 
 The consumer can access the [`IConsumerContext`](../src/SlimMessageBus/IConsumerContext.cs) object which:

docs/intro.t.md

@@ -7,6 +7,7 @@
     - [Set message headers](#set-message-headers)
   - [Consumer](#consumer)
     - [Start or Stop message consumption](#start-or-stop-message-consumption)
+        - [Health check circuit breaker](#health-check-circuit-breaker)
     - [Consumer context (additional message information)](#consumer-context-additional-message-information)
     - [Per-message DI container scope](#per-message-di-container-scope)
     - [Hybrid bus and message scope reuse](#hybrid-bus-and-message-scope-reuse)
@@ -291,6 +292,32 @@ await consumerControl.Stop();
 
 > Since version 1.15.5
 
+#### Health check circuit breaker
+
+Consumers can be linked to [.NET app health checks](https://learn.microsoft.com/en-us/dotnet/core/diagnostics/diagnostic-health-checks) [tags](https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/health-checks#register-health-check-services), enabling or disabling the consumer based on the health check status reported by the [Health Check Publisher](https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/health-checks#health-check-publisher). A consumer associated with one or more tags will only be active if all health checks linked to the tags are passing.
+
+```cs
+    // add health checks with tags
+    builder.Services
+        .AddHealthChecks()
+        .AddCheck<StorageHealthCheck>("Storage", tags: ["Storage"]);
+        .AddCheck<SqlServerHealthCheck>("SqlServer", tags: ["Sql"]);
+
+    builder.Services
+        .AddSlimMessageBus(mbb => {
+            ...
+
+            mbb.Consume<Message>(cfg => {
+                ...
+
+                // configure consumer to monitor tag/state
+                cfg.PauseOnUnhealthyCheck("Storage");
+                cfg.PauseOnDegradedHealthCheck("Sql");
+            })
+        })
+```
+*Requires: SlimMessageBus.Host.CircuitBreaker.HealthCheck*
+
 #### Consumer context (additional message information)
 
 The consumer can access the [`IConsumerContext`](../src/SlimMessageBus/IConsumerContext.cs) object which:

src/.editorconfig

@@ -178,11 +178,14 @@ dotnet_style_allow_multiple_blank_lines_experimental = true:silent
 dotnet_style_allow_statement_immediately_after_block_experimental = true:silent
 dotnet_style_prefer_collection_expression = when_types_loosely_match:suggestion
 dotnet_diagnostic.CA1859.severity = silent
+
 dotnet_style_qualification_for_field = false:suggestion
 dotnet_style_qualification_for_property = false:suggestion
 dotnet_style_qualification_for_method = false:suggestion
 dotnet_style_qualification_for_event = false:suggestion
 dotnet_diagnostic.VSTHRD200.severity = none
+# not supported by .netstandard2.0
+dotnet_diagnostic.CA1510.severity = none
 
 [*.{csproj,xml}]
 indent_style = space

src/Samples/Sample.CircuitBreaker.HealthCheck/Consumers/AddConsumer.cs

@@ -0,0 +1,17 @@
+namespace Sample.CircuitBreaker.HealthCheck.Consumers;
+
+public class AddConsumer : IConsumer<Add>
+{
+    private readonly ILogger<AddConsumer> _logger;
+
+    public AddConsumer(ILogger<AddConsumer> logger)
+    {
+        _logger = logger;
+    }
+
+    public Task OnHandle(Add message, CancellationToken cancellationToken)
+    {
+        _logger.LogInformation("{A} + {B} = {C}", message.a, message.b, message.a + message.b);
+        return Task.CompletedTask;
+    }
+}

src/Samples/Sample.CircuitBreaker.HealthCheck/Consumers/SubtractConsumer.cs

@@ -0,0 +1,17 @@
+namespace Sample.CircuitBreaker.HealthCheck.Consumers;
+
+public class SubtractConsumer : IConsumer<Subtract>
+{
+    private readonly ILogger<SubtractConsumer> _logger;
+
+    public SubtractConsumer(ILogger<SubtractConsumer> logger)
+    {
+        _logger = logger;
+    }
+
+    public Task OnHandle(Subtract message, CancellationToken cancellationToken)
+    {
+        _logger.LogInformation("{A} - {B} = {C}", message.a, message.b, message.a - message.b);
+        return Task.CompletedTask;
+    }
+}

src/Samples/Sample.CircuitBreaker.HealthCheck/GlobalUsings.cs

@@ -0,0 +1,17 @@
+global using System.Net.Mime;
+global using System.Reflection;
+
+global using Microsoft.Extensions.Configuration;
+global using Microsoft.Extensions.DependencyInjection;
+global using Microsoft.Extensions.Hosting;
+global using Microsoft.Extensions.Logging;
+
+global using Sample.CircuitBreaker.HealthCheck.Consumers;
+global using Sample.CircuitBreaker.HealthCheck.Models;
+
+global using SecretStore;
+
+global using SlimMessageBus;
+global using SlimMessageBus.Host;
+global using SlimMessageBus.Host.RabbitMQ;
+global using SlimMessageBus.Host.Serialization.SystemTextJson;

src/Samples/Sample.CircuitBreaker.HealthCheck/HealthChecks/AddRandomHealthCheck.cs

@@ -0,0 +1,11 @@
+namespace Sample.CircuitBreaker.HealthCheck.HealthChecks;
+
+using Microsoft.Extensions.Logging;
+
+public class AddRandomHealthCheck : RandomHealthCheck
+{
+    public AddRandomHealthCheck(ILogger<AddRandomHealthCheck> logger) 
+        : base(logger)
+    {
+    }
+}

src/Samples/Sample.CircuitBreaker.HealthCheck/HealthChecks/RandomHealthCheck.cs

@@ -0,0 +1,20 @@
+namespace Sample.CircuitBreaker.HealthCheck.HealthChecks;
+
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+public abstract class RandomHealthCheck : IHealthCheck
+{
+    private readonly ILogger _logger;
+
+    protected RandomHealthCheck(ILogger logger)
+    {
+        _logger = logger;
+    }
+
+    public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
+    {
+        var value = (HealthStatus)Random.Shared.Next(3);
+        _logger.LogInformation("{HealthCheck} evaluated as {HealthStatus}", this.GetType(), value);
+        return Task.FromResult(new HealthCheckResult(value, value.ToString()));
+    }
+}

src/Samples/Sample.CircuitBreaker.HealthCheck/HealthChecks/SubtractRandomHealthCheck.cs

@@ -0,0 +1,11 @@
+namespace Sample.CircuitBreaker.HealthCheck.HealthChecks;
+
+using Microsoft.Extensions.Logging;
+
+public class SubtractRandomHealthCheck : RandomHealthCheck
+{
+    public SubtractRandomHealthCheck(ILogger<SubtractRandomHealthCheck> logger) 
+        : base(logger)
+    {
+    }
+}