feat: foundation of an event processor (#16)

* Add various Event definitions (feature events, debug, identify, etc.)

* Add IEventProcessor and an implementation based on boost::asio (AsioEventProcessor)

* add config builders for events

* add tag_invoke for EvaluationReason

* fix compilation due to unknown header in backoff.hpp

* add missing <functional> header to backoff.hpp

Author: cwaldren-ld

libs/common/include/config/client.hpp

@@ -12,6 +12,7 @@ using SDK = config::detail::ClientSDK;
 using ApplicationInfo = config::detail::ApplicationInfo;
 using Endpoints = config::detail::EndpointsBuilder<SDK>;
 using ConfigBuilder = config::detail::ConfigBuilder<SDK>;
+using EventsBuilder = config::detail::EventsBuilder<SDK>;
 using Config = config::detail::Config<SDK>;
 
 }  // namespace launchdarkly::client

libs/common/include/config/detail/config.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "config/detail/endpoints_builder.hpp"
+#include "config/detail/events_builder.hpp"
 
 namespace launchdarkly::config::detail {
 
@@ -15,9 +16,11 @@ struct Config {
     bool offline;
     detail::EndpointsBuilder<SDK> service_endpoints_builder;
     std::optional<std::string> application_tag;
+    detail::EventsBuilder<SDK> events_builder;
     Config(std::string sdk_key,
            bool offline,
            detail::EndpointsBuilder<SDK> service_endpoints_builder,
+           detail::EventsBuilder<SDK> events_builder,
            std::optional<std::string> application_tag);
 };
 

libs/common/include/config/detail/config_builder.hpp

@@ -5,6 +5,7 @@
 #include "config/detail/application_info.hpp"
 #include "config/detail/config.hpp"
 #include "config/detail/endpoints_builder.hpp"
+#include "config/detail/events_builder.hpp"
 #include "logger.hpp"
 
 namespace launchdarkly::config::detail {
@@ -18,6 +19,7 @@ template <typename SDK>
 class ConfigBuilder {
    public:
     using EndpointsBuilder = detail::EndpointsBuilder<SDK>;
+    using EventsBuilder = detail::EventsBuilder<SDK>;
     using ConfigType = detail::Config<SDK>;
     /**
      * A minimal configuration consists of a LaunchDarkly SDK Key.
@@ -31,7 +33,7 @@ class ConfigBuilder {
      * @param builder An EndpointsBuilder.
      * @return Reference to this builder.
      */
-    ConfigBuilder& service_endpoints(detail::EndpointsBuilder<SDK> builder);
+    ConfigBuilder& service_endpoints(EndpointsBuilder builder);
 
     /**
      * To include metadata about the application that is utilizing the SDK,
@@ -49,6 +51,14 @@ class ConfigBuilder {
      */
     ConfigBuilder& offline(bool offline);
 
+    /**
+     * To tune settings related to event generation and delivery, pass an
+     * EventsBuilder.
+     * @param builder An EventsBuilder.
+     * @return Reference to this builder.
+     */
+    ConfigBuilder& events(EventsBuilder builder);
+
     /**
      * Builds a Configuration, suitable for passing into an instance of Client.
      * @return
@@ -60,6 +70,7 @@ class ConfigBuilder {
     std::optional<bool> offline_;
     std::optional<EndpointsBuilder> service_endpoints_builder_;
     std::optional<ApplicationInfo> application_info_builder_;
+    std::optional<EventsBuilder> events_builder_;
 };
 
 }  // namespace launchdarkly::config::detail

libs/common/include/config/detail/defaults.hpp

@@ -1,8 +1,9 @@
 #pragma once
 
+#include "config/detail/events.hpp"
 #include "config/detail/http_properties.hpp"
 #include "config/detail/sdks.hpp"
-#include "service_endpoints.hpp"
+#include "config/detail/service_endpoints.hpp"
 
 namespace launchdarkly::config::detail {
 
@@ -30,6 +31,11 @@ struct Defaults<ClientSDK> {
                 "https://mobile.launchdarkly.com"};
     }
 
+    static Events events() {
+        return {100, std::chrono::seconds(30), "/mobile", false,
+                AttributeReference::SetType()};
+    }
+
     static HttpProperties http_properties() {
         return {std::chrono::milliseconds{10000},
                 std::chrono::milliseconds{10000},
@@ -48,6 +54,11 @@ struct Defaults<ServerSDK> {
                 "https://events.launchdarkly.com"};
     }
 
+    static Events events() {
+        return {10000, std::chrono::seconds(5), "/bulk", false,
+                AttributeReference::SetType()};
+    }
+
     static HttpProperties http_properties() {
         return {std::chrono::milliseconds{2000},
                 std::chrono::milliseconds{10000},

libs/common/include/config/detail/endpoints_builder.hpp

@@ -63,8 +63,8 @@ class EndpointsBuilder {
 
     /**
      * Builds a ServiceEndpoints if the configuration is valid. If not,
-     * returns nullptr.
-     * @return Unique pointer to ServiceEndpoints, or nullptr.
+     * returns an error.
+     * @return Unique pointer to ServiceEndpoints, or error.
      */
     [[nodiscard]] tl::expected<ServiceEndpoints, Error> build();
 

libs/common/include/config/detail/events.hpp

@@ -0,0 +1,70 @@
+#pragma once
+
+#include <chrono>
+#include <cstddef>
+#include <string>
+#include <unordered_map>
+#include "attribute_reference.hpp"
+namespace launchdarkly::config::detail {
+
+struct Events {
+   public:
+    template <typename SDK>
+    friend class EventsBuilder;
+    /**
+     * Constructs configuration for the event subsystem.
+     * @param capacity How many events can queue in memory before new events
+     * are dropped.
+     * @param flush_interval How often events are automatically flushed to
+     * LaunchDarkly.
+     * @param path The path component of the LaunchDarkly event delivery
+     * endpoint.
+     * @param all_attributes_private Whether all attributes should be treated as
+     * private or not.
+     * @param private_attrs Which attributes should be treated as private, if
+     * all_attributes_private is false.
+     * @param security Whether a plaintext or encrypted client should be used
+     * for event delivery.
+     */
+    Events(std::size_t capacity,
+           std::chrono::milliseconds flush_interval,
+           std::string path,
+           bool all_attributes_private,
+           AttributeReference::SetType private_attrs);
+
+    /**
+     * Capacity of the event processor.
+     */
+    [[nodiscard]] std::size_t capacity() const;
+
+    /**
+     * Flush interval of the event processor, in milliseconds.
+     */
+    [[nodiscard]] std::chrono::milliseconds flush_interval() const;
+
+    /**
+     * Path component of the LaunchDarkly event delivery endpoint.
+     */
+    [[nodiscard]] std::string const& path() const;
+
+    /**
+     * Whether all attributes should be considered private or not.
+     */
+    [[nodiscard]] bool all_attributes_private() const;
+
+    /**
+     * Set of individual attributes that should be considered private.
+     */
+    [[nodiscard]] AttributeReference::SetType const& private_attributes() const;
+
+   private:
+    std::size_t capacity_;
+    std::chrono::milliseconds flush_interval_;
+    std::string path_;
+    bool all_attributes_private_;
+    AttributeReference::SetType private_attributes_;
+};
+
+bool operator==(Events const& lhs, Events const& rhs);
+
+}  // namespace launchdarkly::config::detail

libs/common/include/config/detail/events_builder.hpp

@@ -0,0 +1,97 @@
+#pragma once
+
+#include <tl/expected.hpp>
+#include "attribute_reference.hpp"
+#include "config/detail/events.hpp"
+#include "error.hpp"
+
+#include <memory>
+#include <optional>
+#include <string>
+#include <unordered_map>
+
+namespace launchdarkly::config::detail {
+
+template <typename SDK>
+class EventsBuilder;
+
+template <typename SDK>
+bool operator==(EventsBuilder<SDK> const& lhs, EventsBuilder<SDK> const& rhs);
+
+/**
+ * EventsBuilder allows for specification of parameters related to the
+ * SDK's event processor.
+ *
+ * @tparam SDK Type of SDK, such as ClientSDK or ServerSDK.
+ */
+template <typename SDK>
+class EventsBuilder {
+   public:
+    friend bool operator==
+        <SDK>(EventsBuilder<SDK> const& lhs, EventsBuilder<SDK> const& rhs);
+    /**
+     * Constructs an EventsBuilder.
+     */
+    EventsBuilder();
+
+    /**
+     * Sets the capacity of the event processor. When more events are generated
+     * within the processor's flush interval than this value, events will be
+     * dropped.
+     * @param capacity Event queue capacity.
+     * @return Reference to this builder.
+     */
+    EventsBuilder& capacity(std::size_t capacity);
+
+    /**
+     * Sets the flush interval of the event processor. The processor queues
+     * outgoing events based on the capacity parameter; these events are then
+     * delivered based on the flush interval.
+     * @param interval Interval between automatic flushes.
+     * @return Reference to this builder.
+     */
+    EventsBuilder& flush_interval(std::chrono::milliseconds interval);
+
+    /**
+     * Attribute privacy indicates whether or not attributes should be
+     * retained by LaunchDarkly after being sent upon initialization,
+     * and if attributes should later be sent in events.
+     *
+     * Attribute privacy may be specified in 3 ways:
+     *
+     * (1) To specify that all attributes should be considered private - not
+     * just those designated private on a per-context basis - call this method
+     * with true as the parameter.
+     *
+     * (2) To specify that a specific set of attributes should be considered
+     * private - in addition to those designated private on a per-context basis
+     * - call @ref private_attributes.
+     *
+     * (3) To specify private attributes on a per-context basis, it is not
+     * necessary to call either of these methods, as the default behavior is to
+     * treat all attributes as non-private unless otherwise specified.
+     *
+     * @param value True for behavior of (1), false for default behavior of (2)
+     * or (3).
+     * @return Reference to this builder.
+     */
+    EventsBuilder& all_attributes_private(bool);
+
+    /**
+     * Specify that a set of attributes are private.
+     * @return Reference to this builder.
+     */
+    EventsBuilder& private_attributes(
+        AttributeReference::SetType private_attrs);
+
+    /**
+     * Builds Events configuration, if the configuration is valid.
+     * @return Events config, or error.
+     */
+    [[nodiscard]] tl::expected<Events, Error> build();
+
+   private:
+    Events config_;
+};
+
+}  // namespace launchdarkly::config::detail

libs/common/include/config/server.hpp

@@ -12,6 +12,7 @@ using SDK = config::detail::ServerSDK;
 using ApplicationInfo = config::detail::ApplicationInfo;
 using Endpoints = config::detail::EndpointsBuilder<SDK>;
 using ConfigBuilder = config::detail::ConfigBuilder<SDK>;
+using EventsBuilder = config::detail::EventsBuilder<SDK>;
 using Config = config::detail::Config<SDK>;
 
 }  // namespace launchdarkly::server

libs/common/include/context.hpp

@@ -76,8 +76,8 @@ class Context final {
      *
      * @return Returns a map of kinds to keys.
      */
-    [[nodiscard]] std::map<std::string, std::string> const&
-    keys_and_kinds() const;
+    [[nodiscard]] std::map<std::string, std::string> const& kinds_to_keys()
+        const;
 
     /**
      * Get a string containing errors the context encountered during
@@ -114,7 +114,6 @@ class Context final {
     Context& operator=(Context const&) = default;
     Context& operator=(Context&&) = default;
 
-
    private:
     /**
      * Create an invalid context with the given error message.
@@ -129,7 +128,7 @@ class Context final {
 
     std::map<std::string, Attributes> attributes_;
     std::vector<std::string> kinds_;
-    std::map<std::string, std::string> keys_and_kinds_;
+    std::map<std::string, std::string> kinds_to_keys_;
     bool valid_ = false;
     std::string errors_;
     std::string canonical_key_;

libs/common/include/data/evaluation_result.hpp

@@ -36,7 +36,7 @@ class EvaluationResult {
 
     /**
      * A timestamp, which if the current time is before, a client SDK
-     * should send debug events for the flag.
+     * should AsyncSend debug events for the flag.
      * @return
      */
     [[nodiscard]] std::optional<

libs/common/include/error.hpp

@@ -18,6 +18,8 @@ enum class Error : std::uint32_t {
     kConfig_ApplicationInfo_InvalidKeyCharacters = 202,
     kConfig_ApplicationInfo_InvalidValueCharacters = 203,
 
+    kConfig_Events_ZeroCapacity = 300,
+
     /* Client-side errors: 10000-19999 */
     /* Server-side errors: 20000-29999 */
 

libs/common/include/events/client_events.hpp

@@ -0,0 +1,42 @@
+#pragma once
+
+#include "events/common_events.hpp"
+
+namespace launchdarkly::events::client {
+
+struct IdentifyEventParams {
+    Date creation_date;
+    Context context;
+};
+
+struct IdentifyEvent {
+    Date creation_date;
+    EventContext context;
+};
+
+struct FeatureEventParams {
+    Date creation_date;
+    std::string key;
+    Context context;
+    EvaluationResult eval_result;
+};
+
+struct FeatureEventBase {
+    Date creation_date;
+    std::string key;
+    Version version;
+    std::optional<VariationIndex> variation;
+    Value value;
+    std::optional<Reason> reason;
+    Value default_;
+};
+
+struct FeatureEvent : public FeatureEventBase {
+    ContextKeys context_keys;
+};
+
+struct DebugEvent : public FeatureEventBase {
+    EventContext context;
+};
+
+}  // namespace launchdarkly::events::client