DNS dot-suffix: Adds TCP DNS dot-suffix for Direct mode to avoid Kubernetes ndots latency#5731
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…ency Adds opt-in DNS dot-suffix (FQDN trailing dot) for Direct/TCP connections to avoid Kubernetes ndots:5 search-domain expansion latency. - Add AZURE_COSMOS_DNS_DOT_SUFFIX_ENABLED environment variable - Add DnsDotSuffixHelper with ToFqdnHostName() and CreateDnsResolutionFunction() - Wire dnsResolutionFunction into StoreClientFactory via DocumentClient - Add unit tests for DnsDotSuffixHelper Fixes #5730 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Apr 3, 2026
- Rename AZURE_COSMOS_DNS_DOT_SUFFIX_ENABLED AZURE_COSMOS_TCP_DNS_DOT_SUFFIX_ENABLED - Rename DnsDotSuffixEnabled TcpDnsDotSuffixEnabled - Rename IsDnsDotSuffixEnabled() IsTcpDnsDotSuffixEnabled() - Restore original line endings in IsLengthAwareRangeComparatorEnabled() Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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## Release 3.59.0 ### Version Changes - ClientOfficialVersion: 3.58.0 → 3.59.0 - ClientPreviewVersion: 3.59.0 → 3.60.0 - ClientPreviewSuffixVersion: preview.0 → preview.0 ### Changelog (3.59.0 GA) #### Added - [5579](#5579) Change Feed Processor: Adds Lease container export support - [5709](#5709) Performance: Adds caching for URL-encoded AAD authorization signature - [5731](#5731) DNS dot-suffix: Adds TCP DNS dot-suffix for Direct mode to avoid Kubernetes ndots latency - [5755](#5755) Exceptionless: Adds enabling exception less 400 status code - [5756](#5756) Exceptionless: Adds enabling exception less 404/1002 status code - [5757](#5757) Exceptionless: Adds enabling exception less 403 - [5779](#5779) Direct: Adds Direct package version bump to 3.42.4 - [5786](#5786) Region Availability: Adds missing regions from Direct 3.42.4 - [5788](#5788) Socket Handler: Adds HTTP/2 PING keep-alive to detect broken connections in pool #### Fixed - [5553](#5553) NativeDLLs: Fixes Conditionally include win-x64 native DLLs based on RuntimeIdentifier - [5588](#5588) LINQ: Fixes memory leak from Expression.Compile() in all call sites - [5617](#5617) ChangeFeedProcessor: Fixes first-change skip during initial startup by anchoring StartTime - [5636](#5636) CosmosClientBuilder: Fixes self-referencing loop in GetSerializedConfiguration with STJ TypeInfoResolver - [5748](#5748) Routing: Fixes GetOverlappingRanges CPU overhead from repeated JSON deserialization - [5807](#5807) ChangeFeedProcessor: Fixes lease de-duplication for /partitionKey-partitioned lease containers ### Changelog (3.60.0-preview.0) #### Added - [5804](#5804) SemanticReranking: Adds Configurable Request Timeout #### Fixed - [5783](#5783) Container: Fixes SemanticRerankAsync TypeLoadException in derived classes ### API Contract Diff (GA) ```diff diff --git "a/Microsoft.Azure.Cosmos\\contracts\\API_3.58.0.txt" "b/Microsoft.Azure.Cosmos\\contracts\\API_3.59.0.txt" index 1b74a69..6fa9352 100644 --- "a/Microsoft.Azure.Cosmos\\contracts\\API_3.58.0.txt" +++ "b/Microsoft.Azure.Cosmos\\contracts\\API_3.59.0.txt" @@ -60,6 +60,7 @@ namespace Microsoft.Azure.Cosmos public ChangeFeedProcessor Build(); public ChangeFeedProcessorBuilder WithErrorNotification(Container.ChangeFeedMonitorErrorDelegate errorDelegate); public virtual ChangeFeedProcessorBuilder WithInMemoryLeaseContainer(); + public virtual ChangeFeedProcessorBuilder WithInMemoryLeaseContainer(MemoryStream leaseState); public ChangeFeedProcessorBuilder WithInstanceName(string instanceName); public ChangeFeedProcessorBuilder WithLeaseAcquireNotification(Container.ChangeFeedMonitorLeaseAcquireDelegate acquireDelegate); public ChangeFeedProcessorBuilder WithLeaseConfiguration(Nullable<TimeSpan> acquireInterval=default(Nullable<TimeSpan>), Nullable<TimeSpan> expirationInterval=default(Nullable<TimeSpan>), Nullable<TimeSpan> renewInterval=default(Nullable<TimeSpan>)); @@ -956,6 +957,7 @@ namespace Microsoft.Azure.Cosmos public const string NorwayWest = "Norway West"; public const string PolandCentral = "Poland Central"; public const string QatarCentral = "Qatar Central"; + public const string SaudiArabiaEast = "Saudi Arabia East"; public const string SingaporeCentral = "Singapore Central"; public const string SingaporeNorth = "Singapore North"; public const string SouthAfricaNorth = "South Africa North"; @@ -963,6 +965,7 @@ namespace Microsoft.Azure.Cosmos public const string SouthCentralUS = "South Central US"; public const string SouthCentralUS2 = "South Central US 2"; public const string SoutheastAsia = "Southeast Asia"; + public const string SoutheastAsia3 = "Southeast Asia 3"; public const string SoutheastUS = "Southeast US"; public const string SoutheastUS3 = "Southeast US 3"; public const string SoutheastUS5 = "Southeast US 5"; @@ -990,6 +993,7 @@ namespace Microsoft.Azure.Cosmos public const string USSecWest = "USSec West"; public const string USSecWestCentral = "USSec West Central"; public const string WestCentralUS = "West Central US"; + public const string WestCentralUSFRE = "West Central US FRE"; public const string WestEurope = "West Europe"; public const string WestIndia = "West India"; public const string WestUS = "West US"; ``` ### API Contract Diff (Preview) ```diff diff --git "a/Microsoft.Azure.Cosmos\\contracts\\API_3.59.0-preview.0.txt" "b/Microsoft.Azure.Cosmos\\contracts\\API_3.60.0-preview.0.txt" index 1ae52c0..58df10f 100644 --- "a/Microsoft.Azure.Cosmos\\contracts\\API_3.59.0-preview.0.txt" +++ "b/Microsoft.Azure.Cosmos\\contracts\\API_3.60.0-preview.0.txt" @@ -91,6 +91,7 @@ namespace Microsoft.Azure.Cosmos public ChangeFeedProcessor Build(); public ChangeFeedProcessorBuilder WithErrorNotification(Container.ChangeFeedMonitorErrorDelegate errorDelegate); public virtual ChangeFeedProcessorBuilder WithInMemoryLeaseContainer(); + public virtual ChangeFeedProcessorBuilder WithInMemoryLeaseContainer(MemoryStream leaseState); public ChangeFeedProcessorBuilder WithInstanceName(string instanceName); public ChangeFeedProcessorBuilder WithLeaseAcquireNotification(Container.ChangeFeedMonitorLeaseAcquireDelegate acquireDelegate); public ChangeFeedProcessorBuilder WithLeaseConfiguration(Nullable<TimeSpan> acquireInterval=default(Nullable<TimeSpan>), Nullable<TimeSpan> expirationInterval=default(Nullable<TimeSpan>), Nullable<TimeSpan> renewInterval=default(Nullable<TimeSpan>)); @@ -302,7 +303,7 @@ namespace Microsoft.Azure.Cosmos public abstract Task<ResponseMessage> ReplaceItemStreamAsync(Stream streamPayload, string id, PartitionKey partitionKey, ItemRequestOptions requestOptions=null, CancellationToken cancellationToken=default(CancellationToken)); public abstract Task<ThroughputResponse> ReplaceThroughputAsync(ThroughputProperties throughputProperties, RequestOptions requestOptions=null, CancellationToken cancellationToken=default(CancellationToken)); public abstract Task<ThroughputResponse> ReplaceThroughputAsync(int throughput, RequestOptions requestOptions=null, CancellationToken cancellationToken=default(CancellationToken)); - public abstract Task<SemanticRerankResult> SemanticRerankAsync(string rerankContext, IEnumerable<string> documents, IDictionary<string, object> options=null, CancellationToken cancellationToken=default(CancellationToken)); + public virtual Task<SemanticRerankResult> SemanticRerankAsync(string rerankContext, IEnumerable<string> documents, IDictionary<string, object> options=null, CancellationToken cancellationToken=default(CancellationToken)); public abstract Task<ItemResponse<T>> UpsertItemAsync<T>(T item, Nullable<PartitionKey> partitionKey=default(Nullable<PartitionKey>), ItemRequestOptions requestOptions=null, CancellationToken cancellationToken=default(CancellationToken)); public abstract Task<ResponseMessage> UpsertItemStreamAsync(Stream streamPayload, PartitionKey partitionKey, ItemRequestOptions requestOptions=null, CancellationToken cancellationToken=default(CancellationToken)); public delegate Task ChangeFeedHandlerWithManualCheckpoint<T>(ChangeFeedProcessorContext context, IReadOnlyCollection<T> changes, Func<Task> checkpointAsync, CancellationToken cancellationToken); @@ -407,6 +408,7 @@ namespace Microsoft.Azure.Cosmos public int GatewayModeMaxConnectionLimit { get; set; } public Func<HttpClient> HttpClientFactory { get; set; } public Nullable<TimeSpan> IdleTcpConnectionTimeout { get; set; } + public TimeSpan InferenceRequestTimeout { get; set; } public bool LimitToEndpoint { get; set; } public Nullable<int> MaxRequestsPerTcpConnection { get; set; } public Nullable<int> MaxRetryAttemptsOnRateLimitedRequests { get; set; } @@ -1092,6 +1094,7 @@ namespace Microsoft.Azure.Cosmos public const string NorwayWest = "Norway West"; public const string PolandCentral = "Poland Central"; public const string QatarCentral = "Qatar Central"; + public const string SaudiArabiaEast = "Saudi Arabia East"; public const string SingaporeCentral = "Singapore Central"; public const string SingaporeNorth = "Singapore North"; public const string SouthAfricaNorth = "South Africa North"; @@ -1099,6 +1102,7 @@ namespace Microsoft.Azure.Cosmos public const string SouthCentralUS = "South Central US"; public const string SouthCentralUS2 = "South Central US 2"; public const string SoutheastAsia = "Southeast Asia"; + public const string SoutheastAsia3 = "Southeast Asia 3"; public const string SoutheastUS = "Southeast US"; public const string SoutheastUS3 = "Southeast US 3"; public const string SoutheastUS5 = "Southeast US 5"; @@ -1126,6 +1130,7 @@ namespace Microsoft.Azure.Cosmos public const string USSecWest = "USSec West"; public const string USSecWestCentral = "USSec West Central"; public const string WestCentralUS = "West Central US"; + public const string WestCentralUSFRE = "West Central US FRE"; public const string WestEurope = "West Europe"; public const string WestIndia = "West India"; public const string WestUS = "West US"; @@ -1504,6 +1509,7 @@ namespace Microsoft.Azure.Cosmos.Fluent public CosmosClientBuilder WithEnableRemoteRegionPreferredForSessionRetry(bool enableRemoteRegionPreferredForSessionRetry); public CosmosClientBuilder WithFaultInjection(IFaultInjector faultInjector); public CosmosClientBuilder WithHttpClientFactory(Func<HttpClient> httpClientFactory); + public CosmosClientBuilder WithInferenceRequestTimeout(TimeSpan inferenceRequestTimeout); public CosmosClientBuilder WithLimitToEndpoint(bool limitToEndpoint); public CosmosClientBuilder WithPriorityLevel(PriorityLevel priorityLevel); public CosmosClientBuilder WithReadConsistencyStrategy(ReadConsistencyStrategy readConsistencyStrategy); ``` ### Checklist - [ ] Changelog entries reviewed by team - [ ] API contract diff reviewed by Kiran and Kirill - [ ] Preview APIs reviewed (email sent to azurecosmossdkdotnet@microsoft.com) - [ ] Kiran sign-off obtained Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Feature: Enable DNS dot-suffix for Direct mode to avoid Kubernetes ndots latency
Description
Fixes #5730
On Kubernetes with
ndots:5, Cosmos DB endpoints likemyaccount.documents.azure.com(only 3 dots) trigger multiple failed DNS search-domain expansions before the absolute lookup succeeds. This adds 50-200ms latency per DNS resolution in Direct mode (TCP/RNTBD).This fix leverages the existing
dnsResolutionFunctioninjection point onStoreClientFactoryto append a trailing dot (.) to hostnames at DNS resolution time, making them fully qualified (FQDN). This signals the DNS resolver to skip search-domain expansion entirely.Issue Summary
Root Cause Analysis
Code Path
Root Cause
Connection.ResolveHostAsync()callsDns.GetHostAddressesAsync(hostName)with bare hostnames (e.g.,myaccount.documents.azure.com). On Kubernetes withndots:5, hostnames with fewer than 5 dots trigger search-domain expansion: the resolver first triesmyaccount.documents.azure.com.default.svc.cluster.local, then.svc.cluster.local, etc — all failing — before the absolute lookup. This is not a regression; it has always worked this way, but the latency only manifests in Kubernetes environments.Changes Made
Files Modified
ConfigurationManager.csAZURE_COSMOS_DNS_DOT_SUFFIX_ENABLEDenv var constant +IsDnsDotSuffixEnabled()accessorDnsDotSuffixHelper.cs(new)ToFqdnHostName()appends trailing dot (skips IPs/nulls/already-dotted).CreateDnsResolutionFunction()factory for the StoreClientFactory lambdaDocumentClient.csdnsResolutionFunction:intoStoreClientFactoryconstructor, conditionally enabled via env varDnsDotSuffixHelperTests.cs(new)Code Changes
ToFqdnHostName()usesIPAddress.TryParseto skip IPs, checksEndsWith(".")for idempotency.CreateDnsResolutionFunction()wrapsDns.GetHostAddressesAsyncwith dot-suffix logic.dnsResolutionFunction:in existingStoreClientFactoryconstructor call. Passesnullwhen disabled (preserving default behavior).Generated Output (Before/After)
Before (bare hostname — triggers ndots expansion):
After (FQDN with trailing dot — single query):
Testing
Test Results
New Tests Added
DnsDotSuffixHelperTests.ToFqdnHostName_AppendsTrailingDot- Standard Cosmos DB endpointDnsDotSuffixHelperTests.ToFqdnHostName_IdempotentWhenAlreadyDotSuffixed- Already FQDNDnsDotSuffixHelperTests.ToFqdnHostName_SkipsIPv4Address- IPv4 passthroughDnsDotSuffixHelperTests.ToFqdnHostName_SkipsIPv6Address- IPv6 loopbackDnsDotSuffixHelperTests.ToFqdnHostName_SkipsIPv6FullAddress- Full IPv6DnsDotSuffixHelperTests.ToFqdnHostName_ReturnsNullForNull- Null guardDnsDotSuffixHelperTests.ToFqdnHostName_ReturnsEmptyForEmpty- Empty guardDnsDotSuffixHelperTests.ToFqdnHostName_AppendsTrailingDotToLocalhost- Single-label hostDnsDotSuffixHelperTests.ToFqdnHostName_AppendsTrailingDotToSingleLabel- Short hostnameDnsDotSuffixHelperTests.CreateDnsResolutionFunction_ReturnsNonNullFunction- Factory sanityBreaking Changes
None. Opt-in via environment variable. Default behavior unchanged.
External References
Checklist
Generated by GitHub Copilot CLI Agent