Add simple Hello World lambda example using API Gateway (awslabs#97)

Author: Bradley Bottomlee

examples/api-gateway/CMakeLists.txt

@@ -0,0 +1,12 @@
+cmake_minimum_required(VERSION 3.5)
+set(CMAKE_CXX_STANDARD 11)
+
+project(api LANGUAGES CXX)
+
+find_package(aws-lambda-runtime REQUIRED)
+find_package(AWSSDK COMPONENTS core)
+
+add_executable(${PROJECT_NAME} "main.cpp")
+target_link_libraries(${PROJECT_NAME} PUBLIC AWS::aws-lambda-runtime ${AWSSDK_LINK_LIBRARIES})
+
+aws_lambda_package_target(${PROJECT_NAME})

examples/api-gateway/README.md

@@ -0,0 +1,81 @@
+# Example using the AWS C++ Lambda runtime and Amazon API Gateway
+
+In this example, we'll build a simple "Hello, World" lambda function that can be invoked using an api endpoint created using Amazon API gateway. This example can be viewed as the C++ counterpart to the NodeJS "Hello, World" API example as viewed [here](https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-create-api-as-simple-proxy-for-lambda.html). At the end of this example, you should be able to invoke your lambda via an api endpoint and receive a raw JSON response. This example employs the use of the AWS C++ SDK to parse the request and write the necessary response. 
+ 
+## Build the AWS C++ SDK
+Start by building the SDK from source.
+
+```bash
+$ mkdir ~/install
+$ git clone https://github.com/aws/aws-sdk-cpp.git
+$ cd aws-sdk-cpp
+$ mkdir build
+$ cd build
+$ cmake .. -DBUILD_ONLY="core" \
+  -DCMAKE_BUILD_TYPE=Release \
+  -DBUILD_SHARED_LIBS=OFF \
+  -DENABLE_UNITY_BUILD=ON \
+  -DCUSTOM_MEMORY_MANAGEMENT=OFF \
+  -DCMAKE_INSTALL_PREFIX=~/install \
+  -DENABLE_UNITY_BUILD=ON
+$ make
+$ make install
+```
+
+## Build the Runtime
+We need to build the C++ Lambda runtime as outlined in the other examples.
+
+```bash
+$ git clone https://github.com/awslabs/aws-lambda-cpp-runtime.git
+$ cd aws-lambda-cpp-runtime
+$ mkdir build
+$ cd build
+$ cmake .. -DCMAKE_BUILD_TYPE=Release \
+  -DBUILD_SHARED_LIBS=OFF \
+  -DCMAKE_INSTALL_PREFIX=~/install \
+$ make
+$ make install
+```
+
+## Build the application
+The next step is to build the Lambda function in `main.cpp` and run the packaging command as follows:
+
+```bash
+$ mkdir build
+$ cd build
+$ cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_PREFIX_PATH=~/install
+$ make
+$ make aws-lambda-package-api
+```
+
+You should now have a zip file called `api.zip`. Follow the instructions in the main README to upload it and return here once complete.
+
+## Using Amazon API Gateway 
+For the rest of this example, we will use the AWS Management Console to create the API endpoint using Amazon API Gateway.
+
+1. Navigate to AWS Lambda within the console [here](https://console.aws.amazon.com/lambda/home)   
+1. Select the newly created function. Within the specific function, the "Designer" window should appear.   
+1. Simply click "Add trigger" -> "API Gateway" -> "Create an API". Please view the settings below.
+   * API Type: HTTP API
+   * Security: Open
+   * API name: Hello-World-API (or desired name)
+   * Deployment stage: default
+1. Once you have added the API gateway, locate the newly created endpoint. View how to test the endpoint below.
+
+## Test the endpoint
+Feel free to test the endpoint any way you desire. Below is a way to test using cURL: 
+
+```
+curl -v -X POST \
+  '<YOUR-API-ENDPOINT>?name=Bradley&city=Chicago' \
+  -H 'content-type: application/json' \
+  -H 'day: Sunday' \
+  -d '{ "time": "evening" }'
+```
+
+With the expected response being: 
+```
+{
+  "message": "Good evening, Bradley of Chicago. Happy Sunday!"
+}
+```

examples/api-gateway/main.cpp

@@ -0,0 +1,61 @@
+#include <aws/lambda-runtime/runtime.h>
+#include <aws/core/utils/json/JsonSerializer.h>
+#include <aws/core/utils/memory/stl/SimpleStringStream.h>
+
+using namespace aws::lambda_runtime;
+
+invocation_response my_handler(invocation_request const& request)
+{
+
+    using namespace Aws::Utils::Json;
+
+    JsonValue json(request.payload);
+    if (!json.WasParseSuccessful()) {
+        return invocation_response::failure("Failed to parse input JSON", "InvalidJSON");
+    }
+
+    auto v = json.View();
+    Aws::SimpleStringStream ss;
+    ss << "Good ";
+
+    if (v.ValueExists("body") && v.GetObject("body").IsString()) {
+        auto body = v.GetString("body");
+        JsonValue body_json(body);
+
+        if (body_json.WasParseSuccessful()) {
+            auto body_v = body_json.View();
+            ss << (body_v.ValueExists("time") && body_v.GetObject("time").IsString() ? body_v.GetString("time") : "");
+        }
+    }
+    ss << ", ";
+
+    if (v.ValueExists("queryStringParameters")) {
+        auto query_params = v.GetObject("queryStringParameters");
+        ss << (query_params.ValueExists("name") && query_params.GetObject("name").IsString()
+                   ? query_params.GetString("name")
+                   : "")
+           << " of ";
+        ss << (query_params.ValueExists("city") && query_params.GetObject("city").IsString()
+                   ? query_params.GetString("city")
+                   : "")
+           << ". ";
+    }
+
+    if (v.ValueExists("headers")) {
+        auto headers = v.GetObject("headers");
+        ss << "Happy "
+           << (headers.ValueExists("day") && headers.GetObject("day").IsString() ? headers.GetString("day") : "")
+           << "!";
+    }
+
+    JsonValue resp;
+    resp.WithString("message", ss.str());
+
+    return invocation_response::success(resp.View().WriteCompact(), "application/json");
+}
+
+int main()
+{
+    run_handler(my_handler);
+    return 0;
+}