From 5c69422a1d6d0858d6a199efa43c2d3ab7d729f0 Mon Sep 17 00:00:00 2001
From: Alexander Zeitler <alexander.zeitler@pdmlab.com>
Date: Tue, 4 Jun 2024 01:31:43 +0200
Subject: [PATCH] docs: sample how to wait for non-stale projections from IHost

---
 docs/events/projections/async-daemon.md       | 31 +++++++
 .../event_projections_end_to_end_ihost.cs     | 88 +++++++++++++++++++
 2 files changed, 119 insertions(+)
 create mode 100644 src/DaemonTests/event_projections_end_to_end_ihost.cs

diff --git a/docs/events/projections/async-daemon.md b/docs/events/projections/async-daemon.md
index 40773d8f72..fe37a3781c 100644
--- a/docs/events/projections/async-daemon.md
+++ b/docs/events/projections/async-daemon.md
@@ -237,6 +237,37 @@ The basic idea in your tests is to:
 There is also another overload to wait for just one tenant database in the case of using a database per tenant. The default
 overload **will wait for the daemon of all known databases to catch up to the latest sequence.**
 
+### Accessing the daemon from IHost:
+
+If you're integration testing with the `IHost` (e.g. using Alba) object, you can access the daemon and wait for non stale data like this:
+
+<!-- snippet: sample_accessing_daemon_from_ihost -->
+<a id='snippet-sample_accessing_daemon_from_ihost'></a>
+```cs
+[Fact]
+public async Task run_simultaneously()
+{
+    var host = await StartDaemonInHotColdMode();
+
+    StoreOptions(x => x.Projections.Add(new DistanceProjection(), ProjectionLifecycle.Async));
+
+    NumberOfStreams = 10;
+
+    var agent = await StartDaemon();
+
+    // This method publishes a random number of events
+    await PublishSingleThreaded();
+
+    // Wait for all projections to reach the highest event sequence point
+    // as of the time this method is called
+    await host.WaitForNonStaleProjectionDataAsync(15.Seconds());
+
+    await CheckExpectedResults();
+}
+```
+<sup><a href='https://github.com/JasperFx/marten/blob/master/src/DaemonTests/event_projections_end_to_end_ihost.cs#L22-L45' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_accessing_daemon_from_ihost' title='Start of snippet'>anchor</a></sup>
+<!-- endSnippet -->
+
 ## Diagnostics
 
 The following code shows the diagnostics support for the async daemon as it is today:
diff --git a/src/DaemonTests/event_projections_end_to_end_ihost.cs b/src/DaemonTests/event_projections_end_to_end_ihost.cs
new file mode 100644
index 0000000000..d72a4ed8a2
--- /dev/null
+++ b/src/DaemonTests/event_projections_end_to_end_ihost.cs
@@ -0,0 +1,88 @@
+using System.Linq;
+using System.Threading.Tasks;
+using DaemonTests.TestingSupport;
+using JasperFx.Core;
+using Marten;
+using Marten.Events;
+using Marten.Events.Projections;
+using Microsoft.Extensions.Logging;
+using Shouldly;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace DaemonTests;
+
+public class event_projections_end_to_end_ihost : DaemonContext
+{
+    public event_projections_end_to_end_ihost(ITestOutputHelper output) : base(output)
+    {
+        _output = output;
+    }
+
+    #region sample_accessing_daemon_from_ihost
+
+    [Fact]
+    public async Task run_simultaneously()
+    {
+        var host = await StartDaemonInHotColdMode();
+
+        StoreOptions(x => x.Projections.Add(new DistanceProjection(), ProjectionLifecycle.Async));
+
+        NumberOfStreams = 10;
+
+        var agent = await StartDaemon();
+
+        // This method publishes a random number of events
+        await PublishSingleThreaded();
+
+        // Wait for all projections to reach the highest event sequence point
+        // as of the time this method is called
+        await host.WaitForNonStaleProjectionDataAsync(15.Seconds());
+
+        await CheckExpectedResults();
+    }
+
+    #endregion
+
+    private Task CheckExpectedResults()
+    {
+        return CheckExpectedResults(theSession);
+    }
+
+    private async Task CheckExpectedResultsForTenants(params string[] tenants)
+    {
+        foreach (var tenantId in tenants)
+        {
+            await using (var session = theStore.LightweightSession(tenantId))
+            {
+                await CheckExpectedResults(session);
+            }
+        }
+    }
+
+
+
+    private async Task CheckExpectedResults(IDocumentSession session)
+    {
+        var distances = await session.Query<Distance>().ToListAsync();
+
+        var events = (await session.Events.QueryAllRawEvents().ToListAsync());
+        var travels = events.OfType<Event<Travel>>().ToDictionary(x => x.Id);
+
+        distances.Count.ShouldBe(travels.Count);
+        foreach (var distance in distances)
+        {
+            if (travels.TryGetValue(distance.Id, out var travel))
+            {
+                distance.Day.ShouldBe(travel.Data.Day);
+                distance.Total.ShouldBe(travel.Data.TotalDistance());
+            }
+            else
+            {
+                travel.ShouldNotBeNull();
+            }
+
+            Logger.LogDebug("Compared distance " + distance);
+        }
+    }
+}