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Use caching header for stale checks #42

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ee91424
Use caching header for stale checks
dylanlerch Mar 18, 2026
70be197
Fix ETags
dylanlerch Mar 18, 2026
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38 changes: 14 additions & 24 deletions src/Octopus.OpenFeature.Provider.Tests/OctopusFeatureContextProviderTests.cs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
using System.Net.Http.Headers;
using FluentAssertions;
using FluentAssertions.Execution;
using Microsoft.Extensions.Logging;
Expand All @@ -17,12 +18,7 @@ class MockOctopusFeatureClient(FeatureToggles? featureToggles) : IOctopusFeature
{
FeatureToggles? featureToggles = featureToggles;

public Task<bool> HaveFeaturesChanged(byte[] contentHash, CancellationToken cancellationToken)
{
return Task.FromResult(true);
}

public Task<FeatureToggles?> GetFeatureToggleEvaluationManifest(CancellationToken cancellationToken)
public Task<FeatureToggles?> GetLatestManifest(EntityTagHeaderValue? eTag, CancellationToken cancellationToken)
{
return Task.FromResult(featureToggles);
}
Expand All @@ -42,36 +38,33 @@ public void WhenInstantiated_ProvidesAnEmptyEvaluationContext()

using var scope = new AssertionScope();
context.Should().NotBeNull();
context.ContentHash.Length.Should().Be(0);
context.ETag.Should().BeNull();
}

[Fact]
public async Task WhenInitialized_ProvidesRetrievedEvaluationContext()
{
byte[] contentHash = [0x01, 0x02, 0x03, 0x04];

var client = new MockOctopusFeatureClient(new FeatureToggles(
[new FeatureToggleEvaluation("Test Feature", "test-feature", true, [])],
contentHash));
new("\"01-02-03-04\"")));

var provider = new OctopusFeatureContextProvider(configuration, client, NullLogger.Instance);
await provider.Initialize();
var context = provider.GetEvaluationContext();

using var scope = new AssertionScope();
context.Should().NotBeNull();
context.ContentHash.Should().BeEquivalentTo(contentHash);
context.ETag.Should().NotBeNull();
context.ETag!.Tag.Should().Be("\"01-02-03-04\"");
context.Evaluate("test-feature", false, context: null).Value.Should().BeTrue();
}

[Fact]
public async Task WhenInitialized_RefreshesCacheAfterCacheDurationExpires()
{
byte[] contentHash = [0x01, 0x02, 0x03, 0x04];

var client = new MockOctopusFeatureClient(new FeatureToggles(
[new FeatureToggleEvaluation("Test Feature", "test-feature", true, [])],
contentHash));
new("\"01-02-03-04\"")));

// Initialize the provider
var provider = new OctopusFeatureContextProvider(configuration, client, NullLogger.Instance);
Expand All @@ -80,31 +73,28 @@ [new FeatureToggleEvaluation("Test Feature", "test-feature", true, [])],
// Validate the initial state
using var scope = new AssertionScope();
var context = provider.GetEvaluationContext();
context.ContentHash.Should().BeEquivalentTo(contentHash);
context.ETag.Should().NotBeNull();
context.ETag!.Tag.Should().Be("\"01-02-03-04\"");
context.Evaluate("test-feature", false, context: null).Value.Should().BeTrue();

// Simulate a change in the available feature toggles
client.ChangeToggles(new FeatureToggles(
[new FeatureToggleEvaluation("Test Feature", "test-feature", false, [])],
[0x01, 0x02, 0x03, 0x05]));
new("\"01-02-03-05\"")));

// Wait for the cache to expire
await Task.Delay(TimeSpan.FromSeconds(5));

// Validate the updated toggles are available
context = provider.GetEvaluationContext();
context.ContentHash.Should().BeEquivalentTo(new byte[] { 0x01, 0x02, 0x03, 0x05 });
context.ETag.Should().NotBeNull();
context.ETag!.Tag.Should().Be("\"01-02-03-05\"");
context.Evaluate("test-feature", false, context: null).Value.Should().BeFalse();
}

class AlwaysFailsFeatureClient : IOctopusFeatureClient
{
public Task<bool> HaveFeaturesChanged(byte[] contentHash, CancellationToken cancellationToken)
{
return Task.FromResult(true);
}

public Task<FeatureToggles?> GetFeatureToggleEvaluationManifest(CancellationToken cancellationToken)
public Task<FeatureToggles?> GetLatestManifest(EntityTagHeaderValue? eTag, CancellationToken cancellationToken)
{
throw new Exception("Oops!");
}
Expand All @@ -120,7 +110,7 @@ public async Task WhenFeatureEvaluationRetrievalFails_LogsError()
await provider.Initialize();

using var scope = new AssertionScope();
provider.GetEvaluationContext().ContentHash.Length.Should().Be(0);
provider.GetEvaluationContext().ETag.Should().BeNull();
logger.LatestRecord.Level.Should().Be(LogLevel.Error);
logger.LatestRecord.Message.Should().StartWith("Failed to retrieve feature manifest");

Expand Down
18 changes: 9 additions & 9 deletions src/Octopus.OpenFeature.Provider.Tests/OctopusFeatureContextTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ public void EvaluatesToTrue_IfFeatureIsContainedWithinTheSet_AndFeatureIsEnabled
{
var featureToggles = new FeatureToggles([
new FeatureToggleEvaluation("testfeature", "test-feature", true, [])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand All @@ -27,7 +27,7 @@ public void WhenEvaluatedWithCasingDifferences_EvaluationIsInsensitiveToCase()
{
var featureToggles = new FeatureToggles([
new FeatureToggleEvaluation("testfeature", "test-feature", true, [])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand All @@ -41,7 +41,7 @@ public void EvaluatesToFalse_IfFeatureIsContainedWithinTheSet_AndFeatureIsNotEna
{
var featureToggles = new FeatureToggles([
new FeatureToggleEvaluation("testfeature", "test-feature", false, [])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand All @@ -55,7 +55,7 @@ public void GivenAFlagKeyThatIsNotASlug_ReturnsFlagNotFound_AndEvaluatesToDefaul
{
var featureToggles = new FeatureToggles([
new FeatureToggleEvaluation("This is clearly not a slug!", "this-is-clearly-not-a-slug", true, [])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand All @@ -70,7 +70,7 @@ public void EvaluatesToDefaultValue_IfFeatureIsNotContainedWithinSet()
{
var featureToggles = new FeatureToggles([
new FeatureToggleEvaluation("testfeature", "testfeature", true, [])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand All @@ -97,7 +97,7 @@ public void
{
var featureToggles = new FeatureToggles([
new FeatureToggleEvaluation("testfeature", "testfeature", true, [new("license", "trial")])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand All @@ -113,7 +113,7 @@ public void
{
var featureToggles = new FeatureToggles([
new FeatureToggleEvaluation("testfeature", "testfeature", true, [])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand All @@ -131,7 +131,7 @@ public void WhenAFeatureIsToggledOnForMultipleSegments_EvaluatesCorrectly()
new("region", "au"),
new("region", "us"),
])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand Down Expand Up @@ -170,7 +170,7 @@ public void
{
var featureToggles = new FeatureToggles([
new FeatureToggleEvaluation("testfeature", "testfeature", true, [new("license", "trial")])
], []);
], null);

var context = new OctopusFeatureContext(featureToggles, NullLoggerFactory.Instance);

Expand Down
104 changes: 17 additions & 87 deletions src/Octopus.OpenFeature.Provider/OctopusFeatureClient.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,11 +5,11 @@

namespace Octopus.OpenFeature.Provider;

public class FeatureToggles(FeatureToggleEvaluation[] evaluations, byte[] contentHash)
class FeatureToggles(FeatureToggleEvaluation[] evaluations, EntityTagHeaderValue? eTag)
{
public FeatureToggleEvaluation[] Evaluations { get; } = evaluations;
internal FeatureToggleEvaluation[] Evaluations { get; } = evaluations;

public byte[] ContentHash { get; } = contentHash;
internal EntityTagHeaderValue? ETag { get; } = eTag;
}

public class FeatureToggleEvaluation(string name, string slug, bool isEnabled, KeyValuePair<string, string>[] segments)
Expand All @@ -25,64 +25,22 @@ public class FeatureToggleEvaluation(string name, string slug, bool isEnabled, K

interface IOctopusFeatureClient
{
Task<bool> HaveFeaturesChanged(byte[] contentHash, CancellationToken cancellationToken);
Task<FeatureToggles?> GetFeatureToggleEvaluationManifest(CancellationToken cancellationToken);
Task<FeatureToggles?> GetLatestManifest(EntityTagHeaderValue? eTag, CancellationToken cancellationToken);
}

/// <summary>
/// Responsible for retrieving feature toggles from OctoToggle and determining if they have changed.
/// </summary>
class OctopusFeatureClient(OctopusFeatureConfiguration configuration, ILogger logger) : IOctopusFeatureClient
{
public async Task<bool> HaveFeaturesChanged(byte[] contentHash, CancellationToken cancellationToken)
{
if (contentHash.Length == 0)
{
return true;
}

var client = new HttpClient
{
BaseAddress = configuration.ServerUri
};
client.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue(configuration.ProductMetadata.ProductHeaderValue));

FeatureCheck? hash = null;
client.DefaultRequestHeaders.Add("Authorization", $"Bearer {configuration.ClientIdentifier}");

var result = await ExecuteWithRetry(async ct => await client.GetAsync("api/featuretoggles/check/v3/", ct), cancellationToken);

if (result is not null && result.IsSuccessStatusCode)
{
var rawResult = await result.Content.ReadAsStringAsync();

hash = JsonSerializer.Deserialize<FeatureCheck>(rawResult, JsonSerializerOptions.Web);
}

if (hash is null)
{
logger.LogWarning("Failed to retrieve feature toggles after 3 retries. Previously retrieved feature toggle values will continue to be used.");
return false;
}

var haveFeaturesChanged = !hash.ContentHash.SequenceEqual(contentHash);

return haveFeaturesChanged;
}

class FeatureCheck(byte[] contentHash)
{
public byte[] ContentHash { get; } = contentHash;
}

/// <summary>
/// Retrieves the evaluated feature set from OctoToggle for a given installation and project.
/// This method will return null if:
/// - Toggles are not found for the installation and id
/// - We don't receive a ContentHash header
/// - We cannot deserialize the content response into a OctoToggleFeatureManifest
/// - The toggles have not changed since the last request.
/// - Toggles are not found for the installation and id.
/// - We cannot deserialize the content response into a OctoToggleFeatureManifest.
/// </summary>
public async Task<FeatureToggles?> GetFeatureToggleEvaluationManifest(CancellationToken cancellationToken)
public async Task<FeatureToggles?> GetLatestManifest(EntityTagHeaderValue? eTag, CancellationToken cancellationToken)
{
var client = new HttpClient
{
Expand All @@ -97,31 +55,25 @@ class FeatureCheck(byte[] contentHash)

client.DefaultRequestHeaders.Add("Authorization", $"Bearer {configuration.ClientIdentifier}");

var response = await ExecuteWithRetry(async ct => await client.GetAsync("api/featuretoggles/v3/", ct), cancellationToken);
if (eTag is not null)
{
client.DefaultRequestHeaders.IfNoneMatch.Add(eTag);
}

var response = await client.GetAsync("api/featuretoggles/v3/", cancellationToken);

if (response is null or { StatusCode: HttpStatusCode.NotFound })
{
logger.LogWarning("Failed to retrieve feature toggles for client identifier {ClientIdentifier} from {OctoToggleUrl}", configuration.ClientIdentifier, configuration.ServerUri);
return null;
}

if (!response.Headers.TryGetValues("ContentHash", out IEnumerable<string> values))
if (response.StatusCode == HttpStatusCode.NotModified)
{
logger.LogWarning("Feature toggle response from {OctoToggleUrl} did not contain expected ContentHash header", configuration.ServerUri);
return null;
}
var headerValues = values.ToArray();
if (!headerValues.Any())
{
logger.LogWarning("Feature toggle response from {OctoToggleUrl} returned an empty ContentHash header", configuration.ServerUri);
return null;
}
var rawContentHash = headerValues.First();

// WARNING: v2 and v3 endpoints have identical response contracts.
// If for any reason the v3 endpoint response contract starts to diverge from the v2 contract,
// This code will need to update accordingly
var result = await response.Content.ReadAsStringAsync();
var result = await response.Content.ReadAsStreamAsync();

var evaluations = JsonSerializer.Deserialize<FeatureToggleEvaluation[]>(result, JsonSerializerOptions.Web);

Expand All @@ -131,28 +83,6 @@ class FeatureCheck(byte[] contentHash)
return null;
}

var toggles = new FeatureToggles(evaluations, Convert.FromBase64String(rawContentHash));

return toggles;
}

async Task<T?> ExecuteWithRetry<T>(Func<CancellationToken, Task<T>> callback, CancellationToken cancellationToken)
{
var attempts = 0;
while (attempts < 3)
{
try
{
return await callback(cancellationToken);
}
catch (Exception e)
{
attempts++;
await Task.Delay(TimeSpan.FromSeconds(Math.Pow(2, attempts)), cancellationToken);
logger.LogTrace(e, "Error occurred retrieving feature toggles from {OctoToggleUrl}. Retrying (attempt {attempt} out of 3).", configuration.ServerUri, attempts);
}
}

return default;
return new FeatureToggles(evaluations, response.Headers.ETag);
}
}
7 changes: 4 additions & 3 deletions src/Octopus.OpenFeature.Provider/OctopusFeatureContext.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
using System.Text.RegularExpressions;
using System.Net.Http.Headers;
using System.Text.RegularExpressions;
using Microsoft.Extensions.Logging;
using OpenFeature.Constant;
using OpenFeature.Model;
Expand All @@ -7,13 +8,13 @@ namespace Octopus.OpenFeature.Provider;

partial class OctopusFeatureContext(FeatureToggles toggles, ILoggerFactory loggerFactory)
{
public byte[] ContentHash => toggles.ContentHash;
public EntityTagHeaderValue? ETag => toggles.ETag;
readonly Regex expression = new("^([a-z0-9]+(-[a-z0-9]+)*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
readonly ILogger logger = loggerFactory.CreateLogger<OctopusFeatureContext>();

public static OctopusFeatureContext Empty(ILoggerFactory loggerFactory)
{
return new OctopusFeatureContext(new FeatureToggles([], []), loggerFactory);
return new OctopusFeatureContext(new FeatureToggles([], null), loggerFactory);
}

public ResolutionDetails<bool> Evaluate(string slug, bool defaultValue, EvaluationContext? context)
Expand Down
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