feat: Add C bindings for Redis Big Segments store

libs/server-sdk-redis-source/include/launchdarkly/server_side/bindings/c/integrations/redis/redis_big_segment_store.h

@@ -0,0 +1,118 @@
+/** @file redis_big_segment_store.h
+ * @brief LaunchDarkly Server-side Redis Big Segments Store C Binding.
+ */
+// NOLINTBEGIN modernize-use-using
+#pragma once
+
+#include <launchdarkly/bindings/c/export.h>
+
+#ifdef __cplusplus
+extern "C" {
+// only need to export C interface if
+// used by C++ source code
+#endif
+
+/**
+ * @brief LDServerBigSegmentsRedisStore is a Big Segments persistent store for
+ * the Server-Side SDK backed by Redis. It is meant to be passed to the SDK
+ * via the Big Segments config builder.
+ *
+ * Call @ref LDServerBigSegmentsRedisStore_New to obtain a new instance. This
+ * instance is passed into the SDK's Big Segments configuration.
+ *
+ * Example:
+ * @code
+ *  // Stack allocate the result struct, which will hold the result pointer or
+ *  // an error message.
+ *  struct LDServerBigSegmentsRedisResult result;
+ *
+ *  // Create the Redis Big Segment store, passing in arguments for the URI,
+ *  // prefix, and pointer to the result.
+ *  if (!LDServerBigSegmentsRedisStore_New("redis://localhost:6379",
+ *                                         "testprefix", &result)) {
+ *      // On failure, you may print the error message (result.error_message),
+ *      // then exit or return.
+ *  }
+ *
+ *  // Create the Big Segments builder, taking ownership of the store pointer.
+ *  LDServerBigSegmentsBuilder bs_builder = LDServerBigSegmentsBuilder_New(
+ *      (LDServerBigSegmentStorePtr)result.store);
+ *
+ *  // Attach the Big Segments builder to the SDK config.
+ *  LDServerConfigBuilder cfg_builder = LDServerConfigBuilder_New("sdk-123");
+ *  LDServerConfigBuilder_BigSegments(cfg_builder, bs_builder);
+ * @endcode
+ *
+ * This implementation is backed by <a
+ * href="https://github.com/sewenew/redis-plus-plus">Redis++</a>, a C++ wrapper
+ * for the <a href="https://github.com/redis/hiredis">hiredis</a> library.
+ */
+typedef struct _LDServerBigSegmentsRedisStore* LDServerBigSegmentsRedisStore;
+
+/* Defines the size of the error message buffer in
+ * LDServerBigSegmentsRedisResult.
+ */
+#ifndef LDSERVER_BIGSEGMENTS_REDISSTORE_ERROR_MESSAGE_SIZE
+#define LDSERVER_BIGSEGMENTS_REDISSTORE_ERROR_MESSAGE_SIZE 256
+#endif
+
+/**
+ * @brief Stores the result of calling @ref LDServerBigSegmentsRedisStore_New.
+ *
+ * On successful creation, store will contain a pointer which may be passed
+ * into the LaunchDarkly SDK's Big Segments configuration.
+ *
+ * On failure, error_message contains a NULL-terminated string describing the
+ * error.
+ *
+ * The message may be truncated if it was originally longer than
+ * error_message's buffer size.
+ */
+struct LDServerBigSegmentsRedisResult {
+    LDServerBigSegmentsRedisStore store;
+    char error_message[LDSERVER_BIGSEGMENTS_REDISSTORE_ERROR_MESSAGE_SIZE];
+};
+
+/**
+ * @brief Creates a new Redis Big Segment store suitable for usage in the SDK's
+ * Big Segments configuration.
+ *
+ * In this system, the SDK will query Redis for Big Segments membership
+ * as required, with an in-memory cache to reduce the number of queries.
+ *
+ * Data is never written back to Redis by the SDK; the LaunchDarkly Relay
+ * Proxy populates the store.
+ *
+ * @param uri Redis URI string. Must not be NULL or empty string.
+ *
+ * @param prefix Prefix to use when reading SDK data from Redis. This allows
+ * multiple SDK environments to coexist in the same database, or for the SDK's
+ * data to coexist with other unrelated data. Must not be NULL.
+ *
+ * @param out_result Pointer to struct where the store pointer or an error
+ * message should be stored.
+ *
+ * @return True if the store was created successfully; out_result->store
+ * will contain the pointer. The caller must either free the pointer with
+ * @ref LDServerBigSegmentsRedisStore_Free, OR pass it into the SDK's Big
+ * Segments configuration which will take ownership (in which case do not
+ * call @ref LDServerBigSegmentsRedisStore_Free.)
+ */
+LD_EXPORT(bool)
+LDServerBigSegmentsRedisStore_New(
+    char const* uri,
+    char const* prefix,
+    struct LDServerBigSegmentsRedisResult* out_result);
+
+/**
+ * @brief Frees a Redis Big Segment store pointer. Only necessary to call if
+ * not passing ownership to the SDK's Big Segments configuration.
+ */
+LD_EXPORT(void)
+LDServerBigSegmentsRedisStore_Free(LDServerBigSegmentsRedisStore store);
+
+#ifdef __cplusplus
+}
+#endif
+
+// NOLINTEND modernize-use-using

libs/server-sdk-redis-source/src/CMakeLists.txt

@@ -16,6 +16,7 @@ target_sources(${LIBNAME}
         redis_source.cpp
         redis_big_segment_store.cpp
         bindings/redis/redis_source.cpp
+        bindings/redis/redis_big_segment_store.cpp
 )
 
 

libs/server-sdk-redis-source/src/bindings/redis/redis_big_segment_store.cpp

@@ -0,0 +1,51 @@
+#include <launchdarkly/server_side/bindings/c/integrations/redis/redis_big_segment_store.h>
+
+#include <launchdarkly/server_side/integrations/redis/redis_big_segment_store.hpp>
+
+#include <launchdarkly/detail/c_binding_helpers.hpp>
+
+#include <cstring>
+
+using namespace launchdarkly::server_side::integrations;
+
+LD_EXPORT(bool)
+LDServerBigSegmentsRedisStore_New(char const* uri,
+                                  char const* prefix,
+                                  LDServerBigSegmentsRedisResult* out_result) {
+    LD_ASSERT_NOT_NULL(uri);
+    LD_ASSERT_NOT_NULL(prefix);
+    LD_ASSERT_NOT_NULL(out_result);
+
+    // Explicitely zero out the exception_msg buffer in case the exception is
+    // shorter than the buffer.
+    memset(out_result->error_message, 0,
+           sizeof(LDServerBigSegmentsRedisResult::error_message));
+
+    // Ensure the store pointer isn't garbage.
+    out_result->store = nullptr;
+
+    auto maybe_store = RedisBigSegmentStore::Create(uri, prefix);
+    if (!maybe_store) {
+        // Avoid heap allocating another string to pass back to the caller;
+        // instead, we copy into the buffer and ensure a terminator is present.
+        // This does mean the message may be truncated.
+
+        std::size_t const len = maybe_store.error().copy(
+            out_result->error_message, sizeof(out_result->error_message) - 1);
+        out_result->error_message[len] = '\0';
+
+        return false;
+    }
+
+    // The pointer is no longer managed and must either be freed by the caller,
+    // or passed into the SDK which will take ownership.
+    out_result->store =
+        reinterpret_cast<LDServerBigSegmentsRedisStore>(maybe_store->release());
+
+    return true;
+}
+
+LD_EXPORT(void)
+LDServerBigSegmentsRedisStore_Free(LDServerBigSegmentsRedisStore store) {
+    delete reinterpret_cast<RedisBigSegmentStore*>(store);
+}

libs/server-sdk-redis-source/tests/c_bindings_test.cpp

@@ -1,5 +1,6 @@
 #include <gtest/gtest.h>
 
+#include <launchdarkly/server_side/bindings/c/integrations/redis/redis_big_segment_store.h>
 #include <launchdarkly/server_side/bindings/c/integrations/redis/redis_source.h>
 
 #include <launchdarkly/bindings/c/context_builder.h>
@@ -10,6 +11,10 @@
 
 #include "prefixed_redis_client.hpp"
 
+#include <chrono>
+#include <condition_variable>
+#include <mutex>
+
 using namespace launchdarkly::data_model;
 
 TEST(RedisBindings, SourcePointerIsStoredOnSuccessfulCreation) {
@@ -91,8 +96,8 @@ TEST(RedisBindings, CanUseInSDKLazyLoadDataSource) {
 
     std::unordered_map<std::string, launchdarkly::Value> values;
     LDValue_ObjectIter iter;
-    for (iter = LDValue_ObjectIter_New(all);
-         !LDValue_ObjectIter_End(iter); LDValue_ObjectIter_Next(iter)) {
+    for (iter = LDValue_ObjectIter_New(all); !LDValue_ObjectIter_End(iter);
+         LDValue_ObjectIter_Next(iter)) {
         char const* key = LDValue_ObjectIter_Key(iter);
         // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
         auto value_ref = reinterpret_cast<launchdarkly::Value const* const>(
@@ -112,3 +117,100 @@ TEST(RedisBindings, CanUseInSDKLazyLoadDataSource) {
     LDContext_Free(context);
     LDServerSDK_Free(sdk);
 }
+
+TEST(RedisBindings, BigSegmentsStorePointerIsStoredOnSuccessfulCreation) {
+    LDServerBigSegmentsRedisResult result;
+    ASSERT_TRUE(LDServerBigSegmentsRedisStore_New("tcp://localhost:1234", "foo",
+                                                  &result));
+    ASSERT_NE(result.store, nullptr);
+    LDServerBigSegmentsRedisStore_Free(result.store);
+}
+
+TEST(RedisBindings, BigSegmentsErrorMessageIsPropagatedOnFailure) {
+    LDServerBigSegmentsRedisResult result;
+    ASSERT_FALSE(
+        LDServerBigSegmentsRedisStore_New("totally not a URI", "foo", &result));
+    ASSERT_STRNE(result.error_message, "");
+}
+
+TEST(RedisBindings, BigSegmentsStorePointerIsNullptrOnFailure) {
+    LDServerBigSegmentsRedisResult result;
+    ASSERT_FALSE(
+        LDServerBigSegmentsRedisStore_New("totally not a URI", "foo", &result));
+    ASSERT_EQ(result.store, nullptr);
+}
+
+// This is an end-to-end test that uses an actual Redis instance with
+// provisioned Big Segments metadata. The store is passed into the SDK's Big
+// Segments configuration, and the SDK's Big Segment store status listener is
+// used to verify that the store is reachable and reports available.
+TEST(RedisBindings, CanUseInSDKBigSegmentsConfig) {
+    sw::redis::Redis redis("tcp://localhost:6379");
+    redis.flushdb();
+
+    // Set the store's sync timestamp so the poll reports available.
+    auto const now_ms = std::chrono::duration_cast<std::chrono::milliseconds>(
+                            std::chrono::system_clock::now().time_since_epoch())
+                            .count();
+    redis.set("testprefix:big_segments_synchronized_on",
+              std::to_string(now_ms));
+
+    LDServerBigSegmentsRedisResult result;
+    ASSERT_TRUE(LDServerBigSegmentsRedisStore_New("tcp://localhost:6379",
+                                                  "testprefix", &result));
+
+    LDServerBigSegmentsBuilder bs_builder = LDServerBigSegmentsBuilder_New(
+        reinterpret_cast<LDServerBigSegmentStorePtr>(result.store));
+    LDServerBigSegmentsBuilder_StatusPollIntervalMs(bs_builder, 50);
+
+    LDServerConfigBuilder cfg_builder = LDServerConfigBuilder_New("sdk-123");
+    LDServerConfigBuilder_BigSegments(cfg_builder, bs_builder);
+    LDServerConfigBuilder_Offline(cfg_builder, true);
+
+    LDServerConfig config;
+    LDStatus status = LDServerConfigBuilder_Build(cfg_builder, &config);
+    ASSERT_TRUE(LDStatus_Ok(status));
+
+    LDServerSDK sdk = LDServerSDK_New(config);
+
+    std::mutex mu;
+    std::condition_variable cv;
+    bool available = false;
+
+    struct ListenerCtx {
+        std::mutex* mu;
+        std::condition_variable* cv;
+        bool* available;
+    };
+    ListenerCtx ctx{&mu, &cv, &available};
+
+    struct LDServerBigSegmentStoreStatusListener listener{};
+    LDServerBigSegmentStoreStatusListener_Init(&listener);
+    listener.UserData = &ctx;
+    listener.StatusChanged =
+        +[](LDServerBigSegmentStoreStatus s, void* user_data) {
+            auto* c = static_cast<ListenerCtx*>(user_data);
+            {
+                std::lock_guard<std::mutex> lk(*c->mu);
+                *c->available = LDServerBigSegmentStoreStatus_Available(s);
+            }
+            c->cv->notify_all();
+        };
+
+    LDListenerConnection connection =
+        LDServerSDK_BigSegmentStoreStatus_OnStatusChange(sdk, listener);
+    ASSERT_NE(connection, nullptr);
+
+    LDServerSDK_Start(sdk, LD_NONBLOCKING, nullptr);
+
+    {
+        std::unique_lock<std::mutex> lk(mu);
+        cv.wait_for(lk, std::chrono::seconds(3), [&] { return available; });
+    }
+
+    EXPECT_TRUE(available);
+
+    LDListenerConnection_Disconnect(connection);
+    LDListenerConnection_Free(connection);
+    LDServerSDK_Free(sdk);
+}