[Azure.Core] Configurable MaxApplicationIdLength

sdk/core/Azure.Core/api/Azure.Core.net10.0.cs

@@ -446,6 +446,7 @@ protected internal DiagnosticsOptions(Microsoft.Extensions.Configuration.IConfig
         public int LoggedContentSizeLimit { get { throw null; } set { } }
         public System.Collections.Generic.IList<string> LoggedHeaderNames { get { throw null; } }
         public System.Collections.Generic.IList<string> LoggedQueryParameters { get { throw null; } }
+        public int MaxApplicationIdLength { get { throw null; } set { } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
     public readonly partial struct HttpHeader : System.IEquatable<Azure.Core.HttpHeader>

sdk/core/Azure.Core/api/Azure.Core.net462.cs

@@ -435,6 +435,7 @@ protected internal DiagnosticsOptions(Microsoft.Extensions.Configuration.IConfig
         public int LoggedContentSizeLimit { get { throw null; } set { } }
         public System.Collections.Generic.IList<string> LoggedHeaderNames { get { throw null; } }
         public System.Collections.Generic.IList<string> LoggedQueryParameters { get { throw null; } }
+        public int MaxApplicationIdLength { get { throw null; } set { } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
     public readonly partial struct HttpHeader : System.IEquatable<Azure.Core.HttpHeader>

sdk/core/Azure.Core/api/Azure.Core.net472.cs

@@ -435,6 +435,7 @@ protected internal DiagnosticsOptions(Microsoft.Extensions.Configuration.IConfig
         public int LoggedContentSizeLimit { get { throw null; } set { } }
         public System.Collections.Generic.IList<string> LoggedHeaderNames { get { throw null; } }
         public System.Collections.Generic.IList<string> LoggedQueryParameters { get { throw null; } }
+        public int MaxApplicationIdLength { get { throw null; } set { } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
     public readonly partial struct HttpHeader : System.IEquatable<Azure.Core.HttpHeader>

sdk/core/Azure.Core/api/Azure.Core.net8.0.cs

@@ -446,6 +446,7 @@ protected internal DiagnosticsOptions(Microsoft.Extensions.Configuration.IConfig
         public int LoggedContentSizeLimit { get { throw null; } set { } }
         public System.Collections.Generic.IList<string> LoggedHeaderNames { get { throw null; } }
         public System.Collections.Generic.IList<string> LoggedQueryParameters { get { throw null; } }
+        public int MaxApplicationIdLength { get { throw null; } set { } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
     public readonly partial struct HttpHeader : System.IEquatable<Azure.Core.HttpHeader>

sdk/core/Azure.Core/api/Azure.Core.netstandard2.0.cs

@@ -435,6 +435,7 @@ protected internal DiagnosticsOptions(Microsoft.Extensions.Configuration.IConfig
         public int LoggedContentSizeLimit { get { throw null; } set { } }
         public System.Collections.Generic.IList<string> LoggedHeaderNames { get { throw null; } }
         public System.Collections.Generic.IList<string> LoggedQueryParameters { get { throw null; } }
+        public int MaxApplicationIdLength { get { throw null; } set { } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
     public readonly partial struct HttpHeader : System.IEquatable<Azure.Core.HttpHeader>

sdk/core/Azure.Core/src/DiagnosticsOptions.cs

@@ -15,9 +15,10 @@ namespace Azure.Core
     /// </summary>
     public class DiagnosticsOptions
     {
-        private const int MaxApplicationIdLength = 24;
-
         private string? _applicationId;
+        private int _maxApplicationIdLength = DefaultMaxApplicationIdLength;
+        private const int DefaultMaxApplicationIdLength = 24;
+        private const int AbsoluteMaxApplicationIdLength = 300;
 
         /// <summary>
         /// Creates a new instance of <see cref="DiagnosticsOptions"/> with default values.
@@ -37,6 +38,10 @@ protected internal DiagnosticsOptions(IConfigurationSection section)
                 return;
             }
 
+            if (int.TryParse(section["MaxApplicationIdLength"], out var maxApplicationIdLength))
+            {
+                MaxApplicationIdLength = maxApplicationIdLength;
+            }
             ApplicationId = section["ApplicationId"];
             if (bool.TryParse(section["IsLoggingEnabled"], out var isLoggingEnabled))
             {
@@ -102,6 +107,7 @@ internal DiagnosticsOptions(DiagnosticsOptions? diagnosticsOptions)
         {
             if (diagnosticsOptions != null)
             {
+                _maxApplicationIdLength = diagnosticsOptions.MaxApplicationIdLength;
                 ApplicationId = diagnosticsOptions.ApplicationId;
                 IsLoggingEnabled = diagnosticsOptions.IsLoggingEnabled;
                 IsTelemetryEnabled = diagnosticsOptions.IsTelemetryEnabled;
@@ -197,6 +203,32 @@ private static IList<string> GetDefaultLoggedHeaders()
         /// </summary>
         public IList<string> LoggedQueryParameters { get; internal set; }
 
+        /// <summary>
+        /// Gets or sets the maximum allowed length for <see cref="ApplicationId"/>.
+        /// </summary>
+        /// <remarks>
+        /// The default value is 24 characters. This can be increased up to 300 characters
+        /// to accommodate longer application identifiers. Values less than 24 or greater
+        /// than 300 are not permitted.
+        /// </remarks>
+        /// <exception cref="ArgumentOutOfRangeException">Thrown when the value is less than 24 or greater than 300.</exception>
+        public int MaxApplicationIdLength
+        {
+            get => _maxApplicationIdLength;
+            set
+            {
+                if (value < DefaultMaxApplicationIdLength || value > AbsoluteMaxApplicationIdLength)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(value), value, $"{nameof(MaxApplicationIdLength)} must be between {DefaultMaxApplicationIdLength} and {AbsoluteMaxApplicationIdLength}.");
+                }
+                if (_applicationId != null && _applicationId.Length > value)
+                {
+                    throw new InvalidOperationException($"Cannot set {nameof(MaxApplicationIdLength)} to {value} because the current {nameof(ApplicationId)} has a length of {_applicationId.Length}.");
+                }
+                _maxApplicationIdLength = value;
+            }
+        }
+
         /// <summary>
         /// Gets or sets the value sent as the first part of "User-Agent" headers for all requests issues by this client. Defaults to <see cref="DefaultApplicationId"/>.
         /// </summary>

sdk/core/Azure.Core/src/Pipeline/HttpPipelineBuilder.cs

@@ -218,7 +218,11 @@ void AddNonNullPolicies(HttpPipelinePolicy[] policiesToAdd)
         internal static TelemetryPolicy CreateTelemetryPolicy(ClientOptions options)
         {
             var type = options.GetType();
-            var userAgentValue = new TelemetryDetails(type.Assembly, options.Diagnostics.ApplicationId);
+            var userAgentValue = new TelemetryDetails(
+                type.Assembly,
+                options.Diagnostics.ApplicationId,
+                runtimeInformation: null,
+                maxApplicationIdLength: options.Diagnostics.MaxApplicationIdLength);
             return new TelemetryPolicy(userAgentValue);
         }
     }

sdk/core/Azure.Core/src/TelemetryDetails.cs

@@ -15,7 +15,7 @@ namespace Azure.Core
     /// </summary>
     public class TelemetryDetails
     {
-        private const int MaxApplicationIdLength = 24;
+        private const int DefaultMaxApplicationIdLength = 24;
         private readonly string _userAgent;
 
         /// <summary>
@@ -35,15 +35,15 @@ public class TelemetryDetails
         /// <param name="applicationId">An optional value to be prepended to the <see cref="TelemetryDetails"/>.
         /// This value overrides the behavior of the <see cref="DiagnosticsOptions.ApplicationId"/> property for the <see cref="HttpMessage"/> it is applied to.</param>
         public TelemetryDetails(Assembly assembly, string? applicationId = null)
-            : this(assembly, applicationId, new RuntimeInformationWrapper())
+            : this(assembly, applicationId, new RuntimeInformationWrapper(), maxApplicationIdLength: DefaultMaxApplicationIdLength)
         { }
 
-        internal TelemetryDetails(Assembly assembly, string? applicationId = null, RuntimeInformationWrapper? runtimeInformation = default)
+        internal TelemetryDetails(Assembly assembly, string? applicationId = null, RuntimeInformationWrapper? runtimeInformation = default, int maxApplicationIdLength = DefaultMaxApplicationIdLength)
         {
             Argument.AssertNotNull(assembly, nameof(assembly));
-            if (applicationId?.Length > MaxApplicationIdLength)
+            if (applicationId?.Length > maxApplicationIdLength)
             {
-                throw new ArgumentOutOfRangeException(nameof(applicationId), $"{nameof(applicationId)} must be shorter than {MaxApplicationIdLength + 1} characters");
+                throw new ArgumentOutOfRangeException(nameof(applicationId), $"{nameof(applicationId)} must be shorter than {maxApplicationIdLength + 1} characters");
             }
 
             Assembly = assembly;

sdk/core/Azure.Core/tests/ClientOptionsConfigurationTests.cs

@@ -601,5 +601,72 @@ public TestDiagnosticsOptions() : base()
             {
             }
         }
+
+        [Test]
+        public void ConfigurationCanSetMaxApplicationIdLength()
+        {
+            var configData = new Dictionary<string, string>
+            {
+                { "TestClient:Diagnostics:MaxApplicationIdLength", "50" },
+                { "TestClient:Diagnostics:ApplicationId", new string('a', 50) }
+            };
+
+            var configuration = new ConfigurationBuilder()
+                .AddInMemoryCollection(configData)
+                .Build();
+
+            var options = new TestClientOptions(configuration.GetSection("TestClient"), null);
+
+            Assert.AreEqual(50, options.Diagnostics.MaxApplicationIdLength);
+            Assert.AreEqual(new string('a', 50), options.Diagnostics.ApplicationId);
+        }
+
+        [Test]
+        public void ConfigurationWithLongApplicationIdButNoMaxLengthThrows()
+        {
+            var configData = new Dictionary<string, string>
+            {
+                { "TestClient:Diagnostics:ApplicationId", new string('a', 25) }
+            };
+
+            var configuration = new ConfigurationBuilder()
+                .AddInMemoryCollection(configData)
+                .Build();
+
+            Assert.Throws<ArgumentOutOfRangeException>(() => new TestClientOptions(configuration.GetSection("TestClient"), null));
+        }
+
+        [Test]
+        public void ConfigurationWithInvalidMaxApplicationIdLengthThrows()
+        {
+            var configData = new Dictionary<string, string>
+            {
+                { "TestClient:Diagnostics:MaxApplicationIdLength", "10" }
+            };
+
+            var configuration = new ConfigurationBuilder()
+                .AddInMemoryCollection(configData)
+                .Build();
+
+            Assert.Throws<ArgumentOutOfRangeException>(() => new TestClientOptions(configuration.GetSection("TestClient"), null));
+        }
+
+        [Test]
+        public void ConfigurationWithoutMaxApplicationIdLengthDefaultsTo24()
+        {
+            var configData = new Dictionary<string, string>
+            {
+                { "TestClient:Diagnostics:ApplicationId", "MyApp" }
+            };
+
+            var configuration = new ConfigurationBuilder()
+                .AddInMemoryCollection(configData)
+                .Build();
+
+            var options = new TestClientOptions(configuration.GetSection("TestClient"), null);
+
+            Assert.AreEqual(24, options.Diagnostics.MaxApplicationIdLength);
+            Assert.AreEqual("MyApp", options.Diagnostics.ApplicationId);
+        }
     }
 }

sdk/core/Azure.Core/tests/ClientOptionsTests.cs

@@ -233,6 +233,130 @@ public void AcceptsCustomDiagnosticsOptions([Values(true, false)] bool useCustom
             }
         }
 
+        [Test]
+        public void DefaultMaxApplicationIdLengthIs24()
+        {
+            var options = new TestClientOptions();
+            Assert.AreEqual(24, options.Diagnostics.MaxApplicationIdLength);
+        }
+
+        [Test]
+        public void ApplicationIdExceedingDefaultMaxLengthThrows()
+        {
+            var options = new TestClientOptions();
+            var longApplicationId = new string('a', 25);
+
+            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => options.Diagnostics.ApplicationId = longApplicationId);
+            Assert.That(ex.Message, Does.Contain("ApplicationId must be shorter than 25 characters"));
+        }
+
+        [Test]
+        public void ApplicationIdAtDefaultMaxLengthSucceeds()
+        {
+            var options = new TestClientOptions();
+            var applicationId = new string('a', 24);
+
+            options.Diagnostics.ApplicationId = applicationId;
+
+            Assert.AreEqual(applicationId, options.Diagnostics.ApplicationId);
+        }
+
+        [Test]
+        public void CanSetCustomMaxApplicationIdLength()
+        {
+            var options = new TestClientOptions();
+            options.Diagnostics.MaxApplicationIdLength = 50;
+
+            Assert.AreEqual(50, options.Diagnostics.MaxApplicationIdLength);
+        }
+
+        [Test]
+        public void CustomMaxApplicationIdLengthAllowsLongerApplicationId()
+        {
+            var options = new TestClientOptions();
+            options.Diagnostics.MaxApplicationIdLength = 50;
+            var longApplicationId = new string('a', 50);
+
+            options.Diagnostics.ApplicationId = longApplicationId;
+
+            Assert.AreEqual(longApplicationId, options.Diagnostics.ApplicationId);
+        }
+
+        [Test]
+        public void CustomMaxApplicationIdLengthStillEnforcesLimit()
+        {
+            var options = new TestClientOptions();
+            options.Diagnostics.MaxApplicationIdLength = 50;
+            var tooLongApplicationId = new string('a', 51);
+
+            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => options.Diagnostics.ApplicationId = tooLongApplicationId);
+            Assert.That(ex.Message, Does.Contain("ApplicationId must be shorter than 51 characters"));
+        }
+
+        [Test]
+        public void LoweringMaxApplicationIdLengthBelowCurrentApplicationIdThrows()
+        {
+            var options = new TestClientOptions();
+            options.Diagnostics.MaxApplicationIdLength = 50;
+            options.Diagnostics.ApplicationId = new string('a', 49);
+
+            var ex = Assert.Throws<InvalidOperationException>(() => options.Diagnostics.MaxApplicationIdLength = 34);
+            Assert.That(ex.Message, Does.Contain("Cannot set MaxApplicationIdLength to 34 because the current ApplicationId has a length of 49"));
+        }
+
+        [TestCase(23)]
+        [TestCase(0)]
+        [TestCase(-1)]
+        public void SettingMaxApplicationIdLengthBelowDefaultThrows(int maxLength)
+        {
+            var options = new TestClientOptions();
+
+            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => options.Diagnostics.MaxApplicationIdLength = maxLength);
+            Assert.That(ex.Message, Does.Contain("MaxApplicationIdLength must be between 24 and 300"));
+        }
+
+        [Test]
+        public void SettingMaxApplicationIdLengthAboveAbsoluteMaxThrows()
+        {
+            var options = new TestClientOptions();
+
+            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => options.Diagnostics.MaxApplicationIdLength = 301);
+            Assert.That(ex.Message, Does.Contain("MaxApplicationIdLength must be between 24 and 300"));
+        }
+
+        [Test]
+        public void SettingMaxApplicationIdLengthToAbsoluteMaxSucceeds()
+        {
+            var options = new TestClientOptions();
+            options.Diagnostics.MaxApplicationIdLength = 300;
+
+            Assert.AreEqual(300, options.Diagnostics.MaxApplicationIdLength);
+        }
+
+        [TestCase(null)]
+        [TestCase("")]
+        public void NullOrEmptyApplicationIdIsAccepted(string applicationId)
+        {
+            var options = new TestClientOptions();
+
+            options.Diagnostics.ApplicationId = applicationId;
+
+            Assert.AreEqual(applicationId, options.Diagnostics.ApplicationId);
+        }
+
+        [Test]
+        public void MaxApplicationIdLengthIsPreservedThroughCopyConstructor()
+        {
+            var original = new TestClientOptions();
+            original.Diagnostics.MaxApplicationIdLength = 50;
+            var longApplicationId = new string('a', 50);
+            original.Diagnostics.ApplicationId = longApplicationId;
+
+            var copy = new TestClientOptions();
+            // The copy should get the default (24) since it's a new instance, not copied from original
+            Assert.AreEqual(24, copy.Diagnostics.MaxApplicationIdLength);
+        }
+
         private class TestClientOptions : ClientOptions
         {
         }

sdk/core/Azure.Core/tests/HttpPipelineBuilderTest.cs

@@ -174,6 +174,23 @@ public async Task VersionDoesntHaveCommitHash()
                                  Regex.Escape($" ({RuntimeInformation.FrameworkDescription}; {RuntimeInformation.OSDescription})"), userAgent);
         }
 
+        [Test]
+        public async Task CreateTelemetryPolicyHonorsCustomMaxApplicationIdLength()
+        {
+            var longApplicationId = new string('a', 50);
+            var options = new TestOptions();
+            options.Diagnostics.MaxApplicationIdLength = 50;
+            options.Diagnostics.ApplicationId = longApplicationId;
+
+            var transport = new MockTransport(new MockResponse(200));
+            var telemetryPolicy = HttpPipelineBuilder.CreateTelemetryPolicy(options);
+
+            await SendGetRequest(transport, telemetryPolicy);
+
+            Assert.True(transport.SingleRequest.TryGetHeader("User-Agent", out var userAgent));
+            StringAssert.StartsWith(longApplicationId + " ", userAgent);
+        }
+
         [Test]
         public async Task CustomClientRequestIdAvailableInPerCallPolicies()
         {