A workaround for redis sync exec (#1216)

nosql_lib/redis/inc/drogon/nosql/RedisClient.h

@@ -21,6 +21,7 @@
 #include <trantor/utils/Logger.h>
 #include <memory>
 #include <functional>
+#include <future>
 #ifdef __cpp_impl_coroutine
 #include <drogon/utils/coroutine.h>
 #endif
@@ -122,6 +123,62 @@ class DROGON_EXPORT RedisClient
                                   string_view command,
                                   ...) noexcept = 0;
 
+    /**
+     * @brief Execute a redis command synchronously
+     *
+     * @param processFunc Function to extract data from redis result.
+     * received successfully.
+     * @param command The command to be executed. the command string can contain
+     * some placeholders for parameters, such as '%s', '%d', etc.
+     * @param ... The command parameters.
+     * @return Returns the same value as process callback.
+     * For example:
+     * @code
+       try
+       {
+           std::string res = redisClientPtr->execCommandSync<std::string>(
+               [](const RedisResult &r){
+                   return r.asString();
+               },
+               "get %s",
+               key.data()
+           );
+       }
+       catch (const RedisException & err)
+       {
+       }
+       catch (const std::exception & err)
+       {
+       }
+       @endcode
+     */
+    template <typename T, typename... Args>
+    T execCommandSync(std::function<T(const RedisResult &)> &&processFunc,
+                      string_view command,
+                      Args &&...args)
+    {
+        std::shared_ptr<std::promise<T>> pro(new std::promise<T>);
+        std::future<T> f = pro->get_future();
+        execCommandAsync(
+            [process = std::move(processFunc), pro](const RedisResult &result) {
+                try
+                {
+                    pro->set_value(process(result));
+                }
+                catch (...)
+                {
+                    pro->set_exception(std::current_exception());
+                }
+            },
+            [pro](const RedisException &err) {
+                pro->set_exception(std::make_exception_ptr(err));
+            },
+            command,
+            std::forward<Args>(args)...);
+
+        return f.get();
+    }
+
     /**
      * @brief Create a redis transaction object.
      *

nosql_lib/redis/tests/redis_test.cc

@@ -41,7 +41,7 @@ DROGON_TEST(RedisTest)
             MANDATE(r.asArray().size() == 1UL);
         },
         [TEST_CTX](const std::exception &err) { MANDATE(err.what()); },
-        "keys *");
+        "keys id_*");
     // 5
     redisClient->execCommandAsync(
         [TEST_CTX](const drogon::nosql::RedisResult &r) {
@@ -80,6 +80,102 @@ DROGON_TEST(RedisTest)
     };
     drogon::sync_wait(coro_test());
 #endif
+
+    // 9. Test sync
+    try
+    {
+        auto res = redisClient->execCommandSync<std::string>(
+            [](const RedisResult &result) { return result.asString(); },
+            "set %s %s",
+            "sync_key",
+            "sync_value");
+        MANDATE(res == "OK");
+    }
+    catch (const RedisException &err)
+    {
+        MANDATE(err.what());
+    }
+
+    try
+    {
+        auto [isNull, str] =
+            redisClient->execCommandSync<std::pair<bool, std::string>>(
+                [](const RedisResult &result) -> std::pair<bool, std::string> {
+                    if (result.isNil())
+                    {
+                        return {true, ""};
+                    }
+                    return {false, result.asString()};
+                },
+                "get %s",
+                "sync_key");
+        MANDATE(isNull == false);
+        MANDATE(str == "sync_value");
+    }
+    catch (const RedisException &err)
+    {
+        MANDATE(err.what());
+    }
+
+    // 10. Test sync redis exception
+    try
+    {
+        auto [isNull, str] =
+            redisClient->execCommandSync<std::pair<bool, std::string>>(
+                [](const RedisResult &result) -> std::pair<bool, std::string> {
+                    if (result.isNil())
+                    {
+                        return {true, ""};
+                    }
+                    return {false, result.asString()};
+                },
+                "get %s %s",
+                "sync_key",
+                "sync_key");
+        MANDATE(false);
+    }
+    catch (const RedisException &err)
+    {
+        LOG_INFO << "Successfully catch sync error: " << err.what();
+        MANDATE(err.code() == RedisErrorCode::kRedisError);
+        SUCCESS();
+    }
+
+    // 11. Test sync process function exception
+    try
+    {
+        auto value = redisClient->execCommandSync<std::string>(
+            [](const RedisResult &result) {
+                if (result.isNil())
+                {
+                    throw std::runtime_error("Key not exists");
+                }
+                return result.asString();
+            },
+            "get %s",
+            "not_exists");
+        MANDATE(false);
+    }
+    catch (const RedisException &err)
+    {
+        MANDATE(false);
+    }
+    catch (const std::runtime_error &err)
+    {
+        MANDATE(std::string("Key not exists") == err.what());
+        SUCCESS();
+    }
+
+    try
+    {
+        redisClient->execCommandSync<int>([](const RedisResult &) { return 1; },
+                                          "del %s",
+                                          "sync_key");
+    }
+    catch (const RedisException &err)
+    {
+        MANDATE(err.what());
+    }
 }
 
 int main(int argc, char **argv)