CHANGELOG.md

Change log

All notable changes to the LaunchDarkly .NET Server-Side SDK will be documented in this file. This project adheres to Semantic Versioning.

[8.3.0] - 2024-04-03

Added:

• This release introduces a Hooks API. Hooks are collections of user-defined callbacks that are executed by the SDK at various points of interest. You can use them to augment the SDK with metrics or tracing.

Changed:

• Dropped explicit support for .NET Core 3.1.

[8.2.0] - 2024-03-14

Changed:

• Redact anonymous attributes within feature events
• Always inline contexts for feature events

[8.1.0] - 2024-03-06

Added:

• Added the ability to set wrapper information independent of HTTP configuration. This change is intended primarily for use by LaunchDarkly in the development of wrapper SDKs.

[8.0.0] - 2023-10-16

The latest version of this SDK supports the ability to manage migrations or modernizations, using migration flags. You might use this functionality if you are optimizing queries, upgrading to new tech stacks, migrating from one database to another, or other similar technology changes. Migration flags are part of LaunchDarkly's Early Access Program. This feature is available to all LaunchDarkly customers but may undergo additional changes before it is finalized.

For detailed information about this version, refer to the list below. For information on how to upgrade from the previous version, read the migration guide.

Added:

• A new Migration type which provides an out-of-the-box configurable migration framework.
• For more advanced use cases, added new MigrationVariation and TrackMigration methods on LdClient.
• ApplicationInfo, for configuration of application metadata that may be used in LaunchDarkly analytics or other product features. This does not affect feature flag evaluations.
• Added IsOffline method to ILdClient. This was previously only available on the concrete LdClient implementation.

Removed:

• Remove support for User in LdClient methods. The Context.FromUser method can be used to convert a User to a Context. In a future version it may be removed.

Changed:

• Upgraded LaunchDarkly.EventSource to 5.1.0. This will change the minimum LaunchDarkly.Logging version to 2.0.0 for all dependencies.

[7.0.3] - 2023-04-21

Changed:

• Updated LaunchDarkly.InternalSdk to 3.1.2.

[7.0.2] - 2023-04-04

Fixed:

• Fixed an issue with generating the FullyQualifiedKey. The key generation was not sorted by the kind, so the key was not stable depending on the order of the context construction. This also affected the generation of the secure mode hash for mulit-contexts.

[7.0.1] - 2023-03-08

Changed:

• Update to LaunchDarkly.InternalSdk 3.1.1

Fixed:

• (From LaunchDarkly.InternalSdk) Fixed an issue where calling FlushAndWait with TimeSpan.Zero would never complete if there were no events to flush.

[7.0.0] - 2022-12-07

The latest version of this SDK supports LaunchDarkly's new custom contexts feature. Contexts are an evolution of a previously-existing concept, "users." Contexts let you create targeting rules for feature flags based on a variety of different information, including attributes pertaining to users, organizations, devices, and more. You can even combine contexts to create "multi-contexts."

For detailed information about this version, please refer to the list below. For information on how to upgrade from the previous version, please read the migration guide.

Added:

• In LaunchDarkly.Sdk, the types Context and ContextKind define the new context model.
• For all SDK methods that took a User parameter, there is now a corresponding method that takes a Context. These are defined as extension methods. The SDK still supports User for now, but Context is the preferred model and User may be removed in a future version.
• The TestData flag builder methods have been extended to support now context-related options, such as matching a key for a specific context type other than "user".
• LdClient.FlushAndWait() is a synchronous version of Flush().

Changed (breaking changes from 6.x):

• It was previously allowable to set a user key to an empty string. In the new context model, the key is not allowed to be empty. Trying to use an empty key will cause evaluations to fail and return the default value.
• There is no longer such a thing as a Secondary meta-attribute that affects percentage rollouts. If you set an attribute with that name in a Context, it will simply be a custom attribute like any other.
• The Anonymous attribute in LDUser is now a simple boolean, with no distinction between a false state and a null state.
• Types such as IDataStore, which define the low-level interfaces of LaunchDarkly SDK components and allow implementation of custom components, have been moved out of the Interfaces namespace into a new Subsystems namespace. Some types have been removed by using generics: for instance, the interface type IDataSourceFactory has been replaced by IComponentConfigurer<IDataSource>. Application code normally does not refer to these types except possibly to hold a value for a configuration property such as ConfigurationBuilder.DataStore, so this change is likely to only affect configuration-related logic.

Changed (requirements/dependencies/build):

• .NET Core 2.1, .NET Framework 4.5.2, .NET Framework 4.6.1, and .NET 5.0 are now unsupported. The minimum platform versions are now .NET Core 3.1, .NET Framework 4.6.2, .NET 6.0, and .NET Standard 2.0.
• Applications that use the database integrations for Redis, DynamoDB, or Consul must update to the latest major versions of the corresponding packages (LaunchDarkly.ServerSdk.Redis, etc.).
• There is no longer a dependency on LaunchDarkly.JsonStream. This package existed because some platforms did not support the System.Text.Json API, but that is no longer the case and the SDK now uses System.Text.Json directly for all of its JSON operations.
• If you are using the package LaunchDarkly.CommonSdk.JsonNet for interoperability with the Json.NET library, you must update this to the latest major version.

Changed (behavioral changes):

• The SDK can now evaluate segments that have rules referencing other segments.
• Analytics event data now uses a new JSON schema due to differences between the context model and the old user model.

Removed:

• Removed all types, fields, and methods that were deprecated as of the most recent 6.x release.
• Removed the Secondary meta-attribute in User and UserBuilder.
• The Alias method no longer exists because alias events are not needed in the new context model.
• The InlineUsersInEvents option no longer exists because it is not relevant in the new context model.
• LaunchDarkly.Sdk.Json.JsonException: this type is no longer necessary because the SDK now always uses System.Text.Json, so any error when deserializing an object from JSON will throw a System.Text.Json.JsonException.

[6.3.3] - 2022-10-24

Fixed:

• Fixed a bug in the parsing of string values in feature flags and user attributes when they were referenced with date/time operators in a targeting rule. As described in LaunchDarkly documentation, such values must use the RFC3339 date/time format; the SDK was also accepting strings in other formats (for instance, ones that did not have a time or a time zone), which would cause undefined behavior inconsistent with evaluations done by other LaunchDarkly services. This fix ensures that all targeting rules that reference an invalid date/time value are a non-match, and does not affect how the SDK treats values that are in the correct format.

[6.3.2] - 2022-02-04

Fixed:

• When using AllFlagsState to produce bootstrap data for the JavaScript SDK, the .NET SDK was not returning the correct metadata for evaluations that involved an experiment. As a result, the analytics events produced by the JavaScript SDK did not correctly reflect experimentation results.
• Improved efficiency of the logic for processing flag/segment changes, which could cause high CPU usage if there were large numbers of flags. (Thanks, JeffAshton!)
• JSON data produced by AllFlagsState was sometimes larger than necessary due to the inclusion of null properties.
• Network errors on polling requests were being logged at Error level, inconsistent with other equivalent kinds of errors. They now use Warn level.
• If flag updates were unable to be stored due to a database error, the data store status is supposed to reflect this with the error value StoreError. That was not happening.
• The type LaunchDarkly.Sdk.UnixMillisecondTime now serializes and deserializes correctly with System.Text.Json.
• In analytics event data, index events were including an unnecessary contextKind property for anonymous users; this was not in the schema for that type of event and was ignored by LaunchDarkly.

[6.3.1] - 2021-10-28

Fixed:

• The HttpConfigurationBuilder methods Proxy and ConnectTimeout were not working correctly: they were being applied to polling requests and analytics event posts, but not streaming requests. Now they apply to all requests. (#148)

[6.3.0] - 2021-10-25

Added:

• ConfigurationBuilder.ServiceEndpoints provides a simpler way of setting custom service base URIs, if you are connecting to a LaunchDarkly Relay Proxy instance, a private LaunchDarkly instance, or a test fixture. Previously, this required setting a BaseURI property for each individual service (streaming, events, etc.). If using the Relay Proxy, simply remove any BaseURI calls in your SDK configuration and call ServiceEndpoints(Components.ServiceEndpoints().RelayProxy(myRelayProxyUri)) on the IConfigurationBuilder.
• Convenience methods for working with JSON object and array values: LdValue.Dictionary, LdValue.List, LdValue.ObjectBuilder.Set, LdValue.ObjectBuilder.Remove, and LdValue.ObjectBuilder.Copy.

Fixed:

• When using the adapter that allows SDK types to be deserialized with the System.Text.Json API, temporary JsonDocument instances are now disposed of immediately rather than leaving them to be garbage-collected. (Thanks, JeffAshton!)

Deprecated:

• StreamingDataSourceBuilder.BaseURI, PollingDataSourceBuilder.BaseURI, and EventProcessorBuilder.BaseURI. The preferred way to set these is now with ConfigurationBuilder.ServiceEndpoints.

[6.2.2] - 2021-10-06

There are no functional changes in the SDK in this release; its only purpose is to address the version conflict issue mentioned below.

Fixed:

• Fixed conflicting dependency versions that existed in several LaunchDarkly packages. In .NET Core these would be resolved automatically, but in .NET Framework they could result in runtime assembly loading errors for LaunchDarkly.CommonSdk, LaunchDarkly.Logging, or System.Collections.Immutable, unless binding redirects were used. Note that it may still be necessary to use a binding redirect if your application (or one of its dependencies) relies on an assembly that is also used by the SDK with a different version.

[6.2.1] - 2021-09-28

Changed:

• When event handlers are called for events such as IFlagTracker.FlagChanged, the sender parameter will be the LdClient instance that generated the event. Previously, sender was being set to one of several internal components that were not useful to application code.

Fixed:

• When using IFlagTracker, flag change events would not fire if the data source was FileData and there was a change in the test data file(s). Now, any change to the test data will cause a flag change event to fire for every flag. (#144)
• A race condition could cause IDataSourceStatusProvider.WaitFor to wait indefinitely or time out even if the desired status was found.

[6.2.0] - 2021-07-22

Added:

• The SDK now supports evaluation of Big Segments. An Early Access Program for creating and syncing Big Segments from customer data platforms is available to enterprise customers.

[6.1.0] - 2021-06-22

Added:

• The SDK now supports the ability to control the proportion of traffic allocation to an experiment. This works in conjunction with a new platform feature now available to early access customers.

[6.0.0] - 2021-06-09

This is a major rewrite that introduces a cleaner API design, adds new features, and makes the SDK code easier to maintain and extend. See the .NET 5.x to 6.0 migration guide for an in-depth look at the changes in 6.0.0; the following is a summary.

Added:

• You can tell the SDK to notify you whenever a feature flag's configuration has changed (either in general, or in terms of its result for a specific user), using LdClient.FlagTracker.
• You can monitor the status of the SDK's data source (which normally means the streaming connection to the LaunchDarkly service) with LdClient.DataSourceStatusProvider. This allows you to check the current connection status, and to be notified if this status changes.
• You can monitor the status of a persistent data store with LdClient.DataStoreStatusProvider. This allows you to check whether database updates are succeeding, or to be notified if this status changes.
• The TestData class in LaunchDarkly.Sdk.Server.Integrations is a new way to inject feature flag data programmatically into the SDK for testing—either with fixed values for each flag, or with targets and/or rules that can return different values for different users. Unlike FileData, this mechanism does not use any external resources, only the data that your test code has provided.
• HttpConfigurationBuilder.Proxy allows you to specify an HTTP/HTTPS proxy server programmatically, rather than using .NET's HTTPS_PROXY environment variable. That was already possibly to do by specifying an HttpClientHandler that had a proxy; this is a shortcut for the same thing.
• HttpConfigurationBuilder.CustomHeader allows you to specify custom HTTP headers that should be added to every HTTP/HTTPS request made by the SDK.
• HttpConfigurationBuilder.ResponseStartTimeout sets the timeout interval for "start of request until beginning of server response", which .NET represents as System.Net.HttpClient.Timeout. The SDK previously referred to this as ConnectTimeout, but it was not a real connection timeout in the sense that most TCP/IP frameworks use the term, so the new name more clearly defines the behavior.
• There is now a DoubleVariation method for getting a numeric flag value as the double type (as opposed to FloatVariation which returns a float).
• The Alias method of LdClient can be used to associate two user objects for analytics purposes with an alias event.
• ConfigurationBuilder.Logging is a new configuration category for options related to logging. This includes a new mechanism for specifying where log output should be sent, instead of using the Common.Logging framework to configure this.
• LoggingConfigurationBuilder.LogDataSourceOutageAsErrorAfter controls the new connection failure logging behavior described below under "behavioral changes".
• The LaunchDarkly.Sdk.Json namespace provides methods for converting types like User and FeatureFlagsState to and from JSON.
• The LaunchDarkly.Sdk.UserAttribute type provides a less error-prone way to refer to user attribute names in configuration, and can also be used to get an arbitrary attribute from a user.
• The LaunchDarkly.Sdk.UnixMillisecondTime type provides convenience methods for converting to and from the Unix epoch millisecond time format that LaunchDarkly uses for all timestamp values.

Changed (requirements/dependencies/build):

• The SDK's build targets are now .NET Standard 2.0, .NET Core 2.1, .NET Framework 4.5.2, .NET Framework 4.7.1, and .NET 5.0. This means it can be used in applications that run on .NET Core 2.1 and above, .NET Framework 4.5.2 and above, .NET 5.0 and above, or in a portable library that is targeted to .NET Standard 2.0 and above.
• The SDK no longer has a dependency on Common.Logging. Instead, it uses a similar but simpler logging facade, the LaunchDarkly.Logging package, which has adapters for various logging destinations (including one for Common.Logging, if you want to keep an existing configuration that uses that framework).
• The SDK no longer has a dependency on Newtonsoft.Json. It uses the System.Text.Json API internally on platforms where that is available; on others, such as .NET Framework 4.5.x, it uses a lightweight custom implementation. This removes the potential for dependency version conflicts in applications that use Newtonsoft.Json for their own purposes. Converting data types like User and LdValue to and from JSON with System.Text.Json will always work; converting them with Newtonsoft.Json requires an extra package, LaunchDarkly.CommonSdk.JsonNet.
• The SDK's dependencies for its own implementation details are now LaunchDarkly.CommonSdk, LaunchDarkly.EventSource, LaunchDarkly.InternalSdk, and LaunchDarkly.JsonStream. You should not need to reference these assemblies directly, as they are loaded automatically when you install the main NuGet package LaunchDarkly.ServerSdk. Previously there was also a variant called LaunchDarkly.CommonSdk.StrongName that was used by the release build of the SDK, but that has been removed.

Changed (API changes):

• The base namespace has changed: types that were previously in LaunchDarkly.Client are now in either LaunchDarkly.Sdk or LaunchDarkly.Sdk.Server. The LaunchDarkly.Sdk namespace contains types that are not specific to the server-side .NET SDK (that is, they will also be used by the Xamarin SDK): EvaluationDetail, LdValue, User, and UserBuilder. Types that are specific to the server-side .NET SDK, such as Configuration and LdClient, are in LaunchDarkly.Sdk.Server.
• Many properties have been moved out of ConfigurationBuilder, into sub-builders that are specific to one area of functionality (such as streaming, or analytics events). See ConfigurationBuilder and Components.
• User and Configuration objects are now immutable. To specify properties for these classes, you must now use User.Builder and Configuration.Builder.
• The following things now use the type LdValue instead of JToken: custom attribute values in User.Custom; JSON flag variations returned by JsonVariation, JsonVariationDetail, and AllFlags; the optional data parameter of LdClient.Track.
• EvaluationReason is now a single struct type rather than a base class.
• LaunchDarkly.Client.Files.FileComponents has been moved to LaunchDarkly.Sdk.Server.Integrations.FileData.
• LdClient.Initialized is now a read-only property rather than a method.
• Interfaces for creating custom components, such as IFeatureStore, now have a new namespace (LaunchDarkly.Sdk.Server.Interfaces), new names, and somewhat different semantics due to changes in the SDK's internal architecture. Any existing custom component implementations will need to be revised to work with .NET SDK 5.x.
• The ILdClient interface is now in LaunchDarkly.Sdk.Server.Interfaces instead of the main namespace.
• The IConfigurationBuilder interface has been replaced by the concrete class ConfigurationBuilder.

Changed (behavioral changes):

• In streaming mode, the SDK will now drop and restart the stream connection if either 1. it receives malformed data (indicating that some data may have been lost before reaching the application) or 2. you are using a database integration (a persistent data store) and a database error happens while trying to store the received data. In both cases, the intention is to make sure updates from LaunchDarkly are not lost; restarting the connection causes LaunchDarkly to re-send the entire flag data set. This makes the .NET SDK's behavior consistent with other LaunchDarkly server-side SDKs.
• However, if you have set the caching behavior to "cache forever" (see PersistentDataStoreConfiguration), the stream will not restart after a database error; instead, all updates will still be accumulated in the cache, and will be written to the database automatically if the database becomes available again.
• Logging now uses a simpler, more stable set of logger names instead of using the names of specific implementation classes that are subject to change. General messages are logged under LaunchDarkly.Sdk.Server.LdClient, while messages about specific areas of functionality are logged under that name plus .DataSource (streaming, polling, file data, etc.), .DataStore (database integrations), .Evaluation (unexpected errors during flag evaluations), or .Events (analytics event processing).
• Network failures and server errors for streaming or polling requests were previously logged at Error level in most cases but sometimes at Warn level. They are now all at Warn level, but with a new behavior: if connection failures continue without a successful retry for a certain amount of time, the SDK will log a special Error-level message to warn you that this is not just a brief outage. The amount of time is one minute by default, but can be changed with the new LogDataSourceOutageAsErrorAfter option in LoggingConfigurationBuilder.
• Many internal methods have been rewritten to reduce the number of heap allocations in general.
• Evaluation of rules involving regex matches, date/time values, and semantic versions, has been sped up by pre-parsing the values in the rules.
• Evaluation of rules involving an equality match to multiple values (such as "name is one of X, Y, Z") has been sped up by converting the list of values to a set.
• If analytics events are disabled with Components.NoEvents, the SDK now avoids generating any analytics event objects internally. Previously they were created and then discarded, causing unnecessary heap churn.
• When accessing a floating-point flag value with IntVariation, it will now truncate (round toward zero) rather than rounding to the nearest integer. This is consistent with normal C# behavior and with most other LaunchDarkly SDKs.
• HttpConfigurationBuilder.ConnectTimeout now sets the timeout for making a network connection, so it is consistent with what is called a connection timeout in other LaunchDarkly SDKs and in most networking libraries. It only has an effect in .NET Core 2.1+ and .NET 5.0+; other .NET platforms do not support this kind of timeout.

Fixed:

• The default value for ConfigurationBuilder.StartWaitTime was documented as being 5 seconds, but the actual value was 10 seconds. It is now really 5 seconds, consistent with other LaunchDarkly server-side SDKs.
• If an unexpected exception occurred while evaluating one clause in a flag rule, the SDK was simply ignoring the clause. For consistency with the other SDKs, it now treats this as a failed evaluation.

Removed:

• All types and methods that were deprecated as of the last .NET SDK 5.x release have been removed. This includes many ConfigurationBuilder methods, which have been replaced by the modular configuration syntax that was already added in the 5.14.0 release. See the migration guide for details on how to update your configuration code if you were using the older syntax.

[5.14.2] - 2021-03-24

Fixed:

• Setting a custom base URI to use instead of the regular LaunchDarkly service endpoints did not work correctly if the base URI included a path prefix, as it might if for instance you were using a reverse proxy that would forward requests from http://my-proxy/launchdarkly-stream/some-endpoint-path to https://stream.launchdarkly.com/some-endpoint-path. In this example, the /launchdarkly-stream part was being dropped from the request URL, preventing this type of proxy configuration from working. Now the base path will always be preserved.

[5.14.1] - 2021-03-03

Fixed:

• The long-running task that the SDK uses to process analytics events was being created in a way that could unnecessarily reduce availability of the managed thread pool, potentially causing unexpected delays in asynchronous task scheduling elsewhere in an application.

[5.14.0] - 2021-01-26

The purpose of this release is to introduce newer APIs for configuring the SDK, corresponding to how configuration will work in the upcoming 6.0 release. These are very similar to the configuration APIs in the recent 5.x releases of the LaunchDarkly server-side Java and Go SDKs.

The corresponding older APIs are now deprecated. If you update to this release, you will see deprecation warnings where you have used them, but they will still work. This should make it easier to migrate your code to the newer APIs, in order to be ready to update to the 6.0 release in the future without drastic changes. For details, see below, and also see the API documentation for IConfigurationBuilder.

Other than the configuration methods, there are no changes to SDK functionality in this release.

Added:

• Previously, most configuration options were set by setter methods in IConfigurationBuilder. These are being superseded by builders that are specific to one area of functionality: for instance, Components.StreamingDataSource() and Components.PollingDataSource() provide builders/factories that have options specific to streaming or polling, the SDK's many options related to analytics events are now in a builder returned by Components.SendEvents(), and HTTP-related options such as ConnectTimeout are now in a builder returned by Components.HttpConfiguration(). Using this newer API makes it clearer which options are for what, and makes it impossible to write contradictory configurations like .IsStreamingEnabled(false).StreamUri(someUri).
• There is a new API for specifying a persistent data store (usually a database integration). This is now done using the new method Components.PersistentDataStore and one of the new integration factories in the namespace Launchdarkly.Client.Integrations. The next releases of the integration packages for Redis, Consul, and DynamoDB will use these semantics.

Changed:

• The components "feature store" and "update processor" are being renamed to "data store" and "data source". The interfaces for these are still called IFeatureStore and IUpdateProcessor for backward compatibility, but the newer configuration methods use the new names. The interfaces will be renamed in the next major version.
• In the newer API, the mode formerly named "LDD" (LaunchDarkly daemon), where the SDK reads feature flags from a database that is populated by the LaunchDarkly Relay Proxy or some other process, has been renamed to ExternalUpdatesOnly. It is now an option for the DataSource configuration method.

Deprecated:

• In IConfigurationBuilder: all methods for setting individual properties related to streaming, polling, events, and HTTP configuration; also, the UseLdd option (see above).
• In Components: DefaultEventProcessor, DefaultUpdateProcessor, InMemoryFeatureStore, NullEventProcessor, NullUpdateProcessor. Replacements for these are described in the API documentation.

[5.13.1] - 2020-11-05

Changed:

• Updated the LaunchDarkly.EventSource dependency to a version that has a specific target for .NET Standard 2.0. Previously, that package targeted only .NET Standard 1.4 and .NET Framework 4.5. There is no functional difference between these targets, but .NET Core application developers may wish to avoid linking to any .NET Standard 1.x assemblies on general principle.

[5.13.0] - 2020-02-10

Note: if you are using the LaunchDarkly Relay Proxy to forward events, update the Relay to version 5.10.0 or later before updating to this .NET SDK version.

Added:

• The SDK now periodically sends diagnostic data to LaunchDarkly, describing the version and configuration of the SDK, the architecture and version of the runtime platform, and performance statistics. No credentials, hostnames, or other identifiable values are included. This behavior can be disabled with IConfigurationBuilder.DiagnosticOptOut or configured with IConfigurationBuilder.DiagnosticRecordingInterval.
• With the file data source, it is now possible to customize the logic for reading a file in case there are special OS considerations. (Thanks, JeffAshton!)

Fixed:

• The SDK now specifies a uniquely identifiable request header when sending events to LaunchDarkly to ensure that events are only processed once, even if the SDK sends them two times due to a failed initial attempt.

[5.12.0] - 2020-01-06

Added:

• IUserBuilder.Secondary is a new name for SecondaryKey (for consistency with other SDKs), and allows you to make the secondary attribute private.
• User.Secondary (same as SecondaryKey).
• FeatureFlagsState now has a Builder method for constructing a new instance (useful in testing). (#125)

Deprecated:

• IUserBuilder.SecondaryKey, User.SecondaryKey.

[5.11.0] - 2019-12-13

Added:

• With FileDataSourceFactory, it is now possible to specify that duplicate flag keys in data files should be ignored rather than causing an error; in this mode, it will use only the first occurrence of each flag key. This allows, for instance, implementing rolling updates of flag data by putting the newest data in a file that is specified first in your file list. (Thanks, JeffAshton!)

Fixed:

• In rare circumstances (depending on the exact data in the flag configuration, the flag's salt value, and the user properties), a percentage rollout could fail and return a default value, logging the error "Data inconsistency in feature flag ... variation/rollout object with no variation or rollout". This would happen if the user's hashed value fell exactly at the end of the last "bucket" (the last variation defined in the rollout). This has been fixed so that the user will get the last variation.

[5.10.0] - 2019-11-12

Added:

• Added ILdClient extension methods EnumVariation and EnumVariationDetail, which convert strings to enums.
• Added LaunchDarkly.Logging.ConsoleAdapter as a convenience for quickly enabling console logging; this is equivalent to Common.Logging.Simple.ConsoleOutLoggerFactoryAdapter, but the latter is not available on some platforms.
• LdValue helpers for dealing with array/object values, without having to use an intermediate List or Dictionary: BuildArray, BuildObject, Count, Get.
• LdValue.Parse(). It is also possible to use Newtonsoft.Json.JsonConvert to parse or serialize LdValue, but since the implementation may change in the future, using the type's own methods is preferable.

Changed:

• EvaluationReason properties all exist on the base class now, so for instance you do not need to cast to RuleMatch to get the RuleId property. This is in preparation for a future API change in which EvaluationReason will become a struct instead of a base class.

Fixed:

• Improved memory usage and performance when processing analytics events: the SDK now encodes event data to JSON directly, instead of creating intermediate objects and serializing them via reflection.
• LdValue.Equals() incorrectly returned true for object (dictionary) values that were not equal.

Deprecated:

• EvaluationReason subclasses. Use only the base class properties and methods to ensure compatibility with future versions.

[5.9.0] - 2019-10-07

Added:

• IUserBuilder.AnonymousOptional allows setting the Anonymous property to null (necessary for consistency with other SDKs). See note about this under Fixed.
• FileDataSourceBuilder.WithSkipMissingPaths allows suppressing file-not-found errors in FileDataSource, if you have a test setup that may add or remove data files dynamically. (Thanks, JeffAshton!)

Changed:

• It is now possible to specify an infinite cache TTL for persistent feature stores by setting the TTL to a negative number, in which case the persistent store will never be read unless the application restarts. Use this mode with caution as described in the comment for FeatureStoreCacheConfig.Ttl.
• Improved the performance of InMemoryFeatureStore by using an ImmutableDictionary that is replaced under a lock whenever there is an update, so reads do not need a lock. (Thanks, JeffAshton!)
• The SDK now has a dependency on System.Collections.Immutable. It refers to version 1.2.0 because the SDK does not use any APIs that were added or changed after that point, but if you want to use that package yourself it is best to declare your own dependency rather than relying on this transitive dependency, since there may have been fixes or improvements in other APIs.

Fixed:

• IUserBuilder was incorrectly setting the user's Anonymous property to null even if it had been explicitly set to false. Null and false behave the same in terms of LaunchDarkly's user indexing behavior, but currently it is possible to create a feature flag rule that treats them differently. So IUserBuilder.Anonymous(false) now correctly sets it to false, just as the deprecated method UserExtensions.WithAnonymous(false) would.
• LdValue.Convert.Long was mistakenly converting to an int rather than a long. (CommonSdk #32)
• FileDataSource could fail to read a file if it noticed the file being modified by another process before the other process had finished writing it. This fix only affects Windows, since in Windows it is not possible to replace a file's contents atomically; in a Unix-like OS, the preferred approach is to create a temporary file and rename it to replace the original file. (Thanks, JeffAshton!)

[5.8.0] - 2019-10-01

Added:

• Added support for upcoming LaunchDarkly experimentation features. See ILdClient.Track(string, User, LdValue, double).

Fixed:

• Fixed a bug due to incorrect use of a lock that could cause a read from InMemoryFeatureStore to fail if done at the same time as an update. (Thanks, JeffAshton!)

[5.7.1] - 2019-09-13

(The changes below were originally released in 5.7.0, but that release was broken; 5.7.1 is its replacement.)

This release includes new types and deprecations that correspond to upcoming changes in version 6.0.0. Developers are encouraged to start adopting these changes in their code now so that migrating to 6.0.0 in the future will be easier. Most of these changes are related to the use of mutable types, which are undesirable in a concurrent environment. User and Configuration are currently mutable types; they will be made immutable in the future, so there are now builders for them. Arbitrary JSON values are currently represented with the Newtonsoft.Json type JToken, which is mutable (if it contains an array or a JSON object); the new type LdValue is safer, and will eventually completely replace JToken in the public API.

Also, generated HTML documentation for all of the SDK's public types, properties, and methods is now available online at https://launchdarkly.github.io/dotnet-server-sdk/. Currently this will only show the latest released version.

Added:

• Configuration.Builder provides a fluent builder pattern for constructing Configuration objects. This is now the preferred method for building a user, rather than using ConfigurationExtension methods like WithStartWaitTime() that modify the existing configuration object.
• Configuration.EventCapacity and Configuration.EventFlushInterval (new names for EventQueueCapacity and EventQueueFrequency, for consistency with other LaunchDarkly SDKs).
• User.Builder provides a fluent builder pattern for constructing User objects. This is now the preferred method for building a user, rather than setting User properties directly or using UserExtension methods like AndName() that modify the existing user object.
• User.IPAddress is equivalent to User.IpAddress, but has the standard .NET capitalization for two-letter acronyms.
• The new LdValue type is a better alternative to using JToken, JValue, JArray, etc. for arbitrary JSON values (such as the return value of JsonVariation, or a custom attribute for a user).
• There is now more debug-level logging for stream connection state changes.
• XML documentation comments are now included in the package for all target frameworks. Previously they were only included for .NET Standard 1.4.

Changed:

• Calls to flag evaluation methods such as BoolVariation are now somewhat more efficient because they no longer convert the default value to a JToken internally; also, user attributes no longer need to be converted to JToken internally when evaluating flag rules. If flag evaluations are very frequent, this reduces the number of ephemeral objects created on the heap.

Fixed:

• Due to the default parsing behavior of Newtonsoft.Json, strings in the date/time format "1970-01-01T00:00:01Z" or "1970-01-01T00:00:01.001Z" would not be considered equal to an identical string in a flag rule.

Deprecated:

• All ConfigurationExtension methods are now deprecated.
• Configuration.SamplingInterval. The intended use case for the SamplingInterval feature was to reduce analytics event network usage in high-traffic applications. This feature is being deprecated in favor of summary counters, which are meant to track all events.
• Configuration.EventQueueCapacity and Configuration.EventQueueFrequency (see new names above).
• User constructors (use User.WithKey or User.Builder).
• User.IpAddress (use IPAddress).
• All UserExtension methods are now deprecated. The setters for all User properties should also be considered deprecated, although C# does not allow these to be marked with [Obsolete].
• IBaseConfiguration and ICommonLdClient interfaces.
• The InMemoryFeatureStore constructor. Use Components.InMemoryFeatureStore.

[5.6.5] - 2019-05-30

Fixed:

• If streaming is disabled, polling requests could stop working if the client ever received an HTTP error from LaunchDarkly. This bug was introduced in the 5.6.3 release.

[5.6.4] - 2019-05-10

Changed:

• The NuGet package name and assembly name have changed: they are now LaunchDarkly.ServerSdk instead of LaunchDarkly.Client. There are no other changes in this release; the namespace used in .NET code is still LaunchDarkly.Client. Substituting LaunchDarkly.Client version 5.6.3 with LaunchDarkly.ServerSdk version 5.6.4 will not affect functionality.

[5.6.3] - 2019-05-10

Fixed:

• If Track or Identify is called without a user, the SDK now will not send an analytics event to LaunchDarkly (since it would not be processed without a user).

Note on future releases

The LaunchDarkly SDK repositories are being renamed for consistency. This repository is now dotnet-server-sdk rather than dotnet-client.

The NuGet package name and assembly name will also change. In the 5.6.3 release, it is still LaunchDarkly.Client; in all releases after 5.6.3, it will be LaunchDarkly.ServerSdk. No further updates to the LaunchDarkly.Client package will be published after this release.

[5.6.2] - 2019-03-26

Changed:

• The default value for the configuration property capacity (maximum number of events that can be stored at once) is now 10000, consistent with the other SDKs, rather than 500.

Fixed:

• Under some circumstances, a CancellationTokenSource might not be disposed of after making an HTTP request, which could cause a timer object to be leaked. (#100)
• In polling mode, if the client received an HTTP error it would retry the same request one second later. This was inconsistent with the other SDKs; the correct behavior is for it to wait until the next scheduled poll.
• The HttpClientTimeout configuration property was being ignored when making HTTP requests to send analytics events.

[5.6.1] - 2019-01-14

Fixed:

• The assemblies in this package now have Authenticode signatures.

[5.6.0] - 2019-01-09

Added:

• There are now helper classes that make it much simpler to write a custom IFeatureStore implementation. See the LaunchDarkly.Client.Utils namespace.
• The new FeatureStoreCaching class will be used by database feature store integrations in the future. It is not used by the SDK client itself.

Changed:

• Some support code has been moved into a separate assembly, LaunchDarkly.Cache.
• The published assemblies are now built in Release configuration and no longer contain debug information.
• If you are building a copy of the SDK yourself, the Debug configuration no longer does any signing, so does not require a key file.

[5.5.0] - 2018-10-30

Added:

• It is now possible to inject feature flags into the client from local JSON or YAML files, replacing the normal LaunchDarkly connection. This would typically be for testing purposes. See LaunchDarkly.Client.Files.FileComponents.

• The AllFlagsState method now accepts a new option, FlagsStateOption.DetailsOnlyForTrackedFlags, which reduces the size of the JSON representation of the flag state by omitting some metadata. Specifically, it omits any data that is normally used for generating detailed evaluation events if a flag does not have event tracking or debugging turned on.

• The non-strong-named version of this library (LaunchDarkly.Common) can now be used with a non-strong-named version of LaunchDarkly.Client, which does not normally exist but could be built as part of a fork of the SDK.

Changed:

• Previously, the delay before stream reconnect attempts would increase exponentially only if the previous connection could not be made at all or returned an HTTP error; if it received an HTTP 200 status, the delay would be reset to the minimum even if the connection then immediately failed. Now, if the stream connection fails after it has been up for less than a minute, the reconnect delay will continue to increase.

Fixed:

• Fixed an unobserved exception that could occur following a stream timeout, which could cause a crash in .NET 4.0.

• Fixed a NullReferenceException that could sometimes appear in the log if a stream connection failed.

• Fixed the documentation for Configuration.StartWaitTime to indicate that the default is 10 seconds, not 5 seconds. (Thanks, KimboTodd!)

• JSON data from AllFlagsState is now slightly smaller even if you do not use the new option described above, because it completely omits the flag property for event tracking unless that property is true.

[5.4.0] - 2018-08-30

Added:

• The new LDClient methods BoolVariationDetail, IntVariationDetail, DoubleVariationDetail, StringVariationDetail, and JsonVariationDetail allow you to evaluate a feature flag (using the same parameters as you would for BoolVariation, etc.) and receive more information about how the value was calculated. This information is returned in an EvaluationDetail object, which contains both the result value and an EvaluationReason which will tell you, for instance, if the user was individually targeted for the flag or was matched by one of the flag's rules, or if the flag returned the default value due to an error.

Fixed:

• When evaluating a prerequisite feature flag, the analytics event for the evaluation did not include the result value if the prerequisite flag was off.

[5.3.1] - 2018-08-30

Fixed:

• Fixed a bug in streaming mode that prevented the client from reconnecting to the stream if it received an HTTP error status from the server (as opposed to simply losing the connection). (#88)
• Numeric flag values can now be queried with either IntVariation or FloatVariation and the result will be coerced to the requested type, as long as it is numeric. Previously, if the type of value that came from LaunchDarkly in JSON (or, more specifically, the type that Newtonsoft.Json decided to decode the value as) was different, it was considered an error and the default value would be returned. This change makes the .NET SDK consistent with the Go and Java SDKs.

[5.3.0] - 2018-08-27

Added:

• The new ILdClient method AllFlagsState() should be used instead of AllFlags() if you are passing flag data to the front end for use with the JavaScript SDK. It preserves some flag metadata that the front end requires in order to send analytics events correctly. Versions 2.5.0 and above of the JavaScript SDK are able to use this metadata, but the output of AllFlagsState() will still work with older versions.
• The AllFlagsState() method also allows you to select only client-side-enabled flags to pass to the front end, by using the option FlagsStateOption.ClientSideOnly.

Deprecated:

• ILdClient.AllFlags()

[5.2.2] - 2018-08-02

• In streaming mode, if the stream connection fails, there should be an increasing backoff interval before each reconnect attempt. Previously, it would log a message about waiting some number of milliseconds, but then not actually wait.
• The required package LaunchDarkly.EventSource no longer has PackageReferences to System assemblies.

[5.2.1] - 2018-08-01

Fixed:

• The internal classes representing feature flag and segment data were not JSON-serializable. This did not affect the SDK itself, but prevented any IFeatureStore implementation based on Json.Net serialization from working.
• The event processor did not post to the correct URI if the base events URI was set to a custom value with a non-root path. This did not affect normal usage, but would be a problem if events were being redirected to some other service.

[5.2.0] - 2018-07-27

Added:

• New configuration property UseLdd allows the client to use the "LaunchDarkly Daemon", i.e. getting feature flag data from a store that is updated by an ld-relay instance. However, this will not be usable until the Redis feature store integration is released (soon).

Changed:

• If you attempt to evaluate a flag before the client has established a connection, but you are using a feature store that has already been populated, the client will now use the last known values from the store instead of returning default values.
• The LaunchDarkly.Common package, which is used by LaunchDarkly.Client, has been renamed to LaunchDarkly.Common.StrongName. Note that you should not have to explicitly install this package; it will be imported automatically.

Fixed:

• The SDK was referencing several system assemblies via <PackageReference>, which could cause dependency conflicts. These have been changed to framework <Reference>s. A redundant reference to System.Runtime was removed. (#83)
• The client was logging (at debug level) a lengthy exception stacktrace whenever a string comparison operator was applied to a user property that was null. It no longer does this.

[5.1.1] - 2018-07-02

Changed:

• When targeting the .NET 4.5 framework, the dependency on Newtonsoft's JSON.Net framework has been changed: the minimum version is now 6.0.1 rather than 9.0.1. This was changed in order to support customer code that uses older versions of JSON.Net. For most applications, this change should have no effect since it is only a minimum version, which can be overridden by any higher version specified in your own dependencies. Note that when targeting .NET Standard, the minimum JSON.Net version is still 9.0.1 because earlier versions were not compatible with .NET Standard.
• The Identify method has been moved back into ILdClient rather than being in ILdCommonClient.

[5.1.0] - 2018-06-26

Added:

• A new overload of LDClient.Track allows you to pass any kind of JSON value for the custom event data, not just a string.
• The User class now implements Equals and GetHashCode, and has a copy constructor.

Changed:

• Some classes and interfaces have been moved into a separate assembly, LaunchDarkly.Common (source code here), because they will also be used by the LaunchDarkly Xamarin SDK. The names and namespaces have not changed, so you do not need to make any code changes. LaunchDarkly.Common will be installed automatically when you upgrade LaunchDarkly.Client; all other dependencies are unchanged.
• The client now treats most HTTP 4xx errors as unrecoverable: that is, after receiving such an error, it will not make any more HTTP requests for the lifetime of the client instance, in effect taking the client offline. This is because such errors indicate either a configuration problem (invalid SDK key) or a bug, which is not likely to resolve without a restart or an upgrade. This does not apply if the error is 400, 408, 429, or any 5xx error.
• During initialization, if the client receives any of the unrecoverable errors described above, the client constructor will return immediately; previously it would continue waiting until a timeout. The Initialized() method will return false in this case.

Fixed:

• Ensured that all HttpClient instances managed by the client are disposed of immediately if you call Dispose on the client.
• Passing null for user when calling Identify or Track no longer causes a NullReferenceException. Instead, the appropriate event will be sent with no user.

[5.0.0] - 2018-05-10

Changed:

• To reduce the network bandwidth used for analytics events, feature request events are now sent as counters rather than individual events, and user details are now sent only at intervals rather than in each event. These behaviors can be modified through the LaunchDarkly UI and with the new configuration option InlineUsersInEvents.
• The IStoreEvents interface has been renamed to IEventProcessor, has slightly different methods, and includes IDisposable. Also, the properties of the Event classes have changed. This will only affect developers who created their own implementation of IStoreEvents.

Added:

• New extension methods on Configuration (WithUpdateProcessorFactory, WithFeatureStoreFactory, WithEventProcessorFactory) allow you to specify different implementations of each of the main client subcomponents (receiving feature state, storing feature state, and sending analytics events) for testing or for any other purpose. The Components class provides factories for all built-in implementations of these.

Deprecated:

• The WithFeatureStore configuration method is deprecated, replaced by the new factory-based mechanism described above.
• The LdClient constructor overload that takes an IEventProcessor (formerly IStoreEvents) is deprecated, replaced by WithEventProcessorFactory.

[4.1.1] - 2018-03-23

Fixed

• Fixed a bug in the event sampling feature that was introduced in 4.1.0: sampling might not work correctly if events were generated from multiple threads.

[4.1.0] - 2018-03-05

Added

• Configuration now has an EventSamplingInterval property. If greater than zero, this causes a fraction of analytics events to be sent to LaunchDarkly: one per that number of events (pseudo-randomly). For instance, setting it to 5 would cause 20% of events to be sent on average.

Changed

• ConfigurationExtensions.WithPollingInterval will no longer throw an exception if the parameter is lower than the minimum. Instead, it will simply set the value to the minimum and log a warning.

[4.0.0] - 2018-02-21

Added

• Support for a new LaunchDarkly feature: reusable user segments.

Changed

• The client now uses Common.Logging.
• The FeatureStore interface has been changed to support user segment data as well as feature flags. Existing code that uses InMemoryFeatureStore or RedisFeatureStore should work as before, but custom feature store implementations will need to be updated.
• Some previously public classes that were not meant to be public are now internal.

Fixed

• All previously undocumented methods now have documentation comments.

Removed

• Obsolete/deprecated methods have been removed.
• Removed Configuration.WithLoggerFactory since the logging framework has changed. For more details on setting up logging, see here.

[3.6.1] - 2018-02-21

Fixed

• Improved performance of the semantic version operators by precompiling a regex.

[3.6.0] - 2018-02-19

Added

• New property LdClient.Version returns the client's current version number.
• Adds support for a future LaunchDarkly feature, coming soon: semantic version user attributes.
• Custom attributes can now have long integer values.

Changed

• It is now possible to compute rollouts based on an integer attribute of a user, not just a string attribute.

[3.5.0] - 2018-01-29

Added

• Support for specifying private user attributes in order to prevent user attributes from being sent in analytics events back to LaunchDarkly. See the AllAttributesPrivate and PrivateAttributeNames methods on Configuration as well as the AndPrivateX methods on User.

Changed

• The stream connection will now restart when a large feature flag update fails repeatedly to ensure that the client is using most recent flag values.
• Client no longer reconnects after detecting an invalidated SDK key.

[3.4.1] - 2018-01-19

Added

• Framework target for netstandard1.4 and netstandard2.0. Thanks @nolanblew and @ISkomorokh!
• Added the Apache 2.0 license to LaunchDarkly.Client.csproj

Changed

• Fixed a bug causing ASP.NET applications to be blocked during client initialization.
• Removed unused and transitive dependencies.
• Improved logging. Thanks @MorganVergara and @JeffAshton!

[3.4.0] - 2017-11-29

Added

• 🚀 Support for Streaming via Server-Sent Events as an alternative to Polling. HTTP-based streaming is favored over polling to reduce network traffic and propagate feature flag updates faster. 🚀
• New builder parameters to complement streaming functionality
  • WithIsStreamingEnabled: Set whether streaming mode should be enabled, true by default.
  • WithStreamUri: Set the base URL of the LaunchDarkly streaming server. May be used in conjunction with the LaunchDarkly Relay Proxy.
  • WithReadTimeout: The timeout when reading data from the streaming API. Defaults to 5 minutes
  • WithReconnectTime: The time to wait before attempting to reconnect to the streaming API. Defaults to 1 second
• Apache 2.0 License

Changed

• Streaming is now used to retrieve feature flag configurations by default.
• Minimum (and default) polling interval changed from 1 second to 30 seconds.
• PollingProcessor no longer retries failed feature flag polling attempts.

[3.3.2] - 2017-08-30

Changed

• Updated dependency versions. Thanks @ISkomorokh!
• Exceptions in FeatureRequestor are rethrown without replacing stack information

[3.3.1] - 2017-07-14

Fixed

• UserExtensions.AndName updates user.Name instead of user.LastName

[3.3.0] - 2017-06-16

Added

• Config option to use custom implementation of IFeatureStore
• Artifact is now signed

Changed

• Removed NETStandard.Library from dependencies so it isn't brought in by non-.NET core projects.
• Project files migrated to current *.csproj standard
• Fixed release that inadvertently removed the ability to set a custom HttpClientHandler

[3.2.0] - 2017-05-25

Added

• Config option to use custom implementation of IFeatureStore
• Artifact is now signed

Changed

• Removed NETStandard.Library from dependencies so it isn't brought in by non-.NET core projects.
• Project files migrated to current *.csproj standard

[3.1.1] - 2017-01-16

Changed

• Improved error handling when sending events

[3.1.0] - 2016-12-07

Added

• Configurable http request timeout

Changed

• Made http requests more resilient and logging more informative.

[3.0.0] - 2016-10-27

Changed

• Addresses Unnecesary Lock contention when polling: #18
• Logging framework: Now using Microsoft.Extensions.Logging
• No longer depending on ASP.NET: #8

Added

• Support for .NET core: #9
• Http client now has a request timeout: #27

Deprecated

• File-based configuration override option has been removed

[2.0.3] - 2016-10-10

Changed

• Code cleanup

[2.0.2] - 2016-10-06

Added

• Address #27
• Improve error logging- we're now logging messages from inner exceptions.

[2.0.1] - 2016-10-05

Changed

• Async http client code improvements.

[2.0.0] - 2016-08-10

Added

• Support for multivariate feature flags. New methods StringVariation, JsonVariation and IntVariation and FloatVariation for multivariates.
• New AllFlags method returns all flag values for a specified user.
• New SecureModeHash function computes a hash suitable for the new LaunchDarkly JavaScript client's secure mode feature.

Changed

• LdClient now implements a new interface: ILdClient

Deprecated

• The Toggle call has been deprecated in favor of BoolVariation.