refactored lockfile implementation, address PR comments

source/config/Config.cpp

@@ -251,6 +251,12 @@ bool PlainConfig::LoadFromEnvironment()
         }
     }
 
+    const char *lockFilePathStr = std::getenv("LOCK_FILE_PATH");
+    if (lockFilePathStr)
+    {
+        lockFilePath = lockFilePathStr;
+    }
+
     return logConfig.LoadFromEnvironment() && jobs.LoadFromEnvironment() && tunneling.LoadFromEnvironment() &&
            deviceDefender.LoadFromEnvironment() && fleetProvisioning.LoadFromEnvironment() &&
            fleetProvisioningRuntimeConfig.LoadFromEnvironment() && pubSub.LoadFromEnvironment() &&

source/config/Config.h

@@ -93,6 +93,7 @@ namespace Aws
                 Aws::Crt::Optional<std::string> thingName;
 
                 aws_mem_trace_level memTraceLevel{AWS_MEMTRACE_NONE};
+                std::string lockFilePath;
 
                 struct LogConfig : public LoadableFromJsonAndCliAndEnvironment
                 {

source/main.cpp

@@ -7,7 +7,7 @@
 #include "Version.h"
 #include "config/Config.h"
 #include "util/EnvUtils.h"
-#include "util/LockFileUtils.h"
+#include "util/LockFile.h"
 #include "util/Retry.h"
 
 #if !defined(EXCLUDE_DD)
@@ -87,10 +87,34 @@ const char *TAG = "Main.cpp";
 
 vector<Feature *> features;
 shared_ptr<SharedCrtResourceManager> resourceManager;
+unique_ptr<LockFile> lockFile;
 mutex featuresReadWriteLock;
 bool attemptingShutdown{false};
 Config config;
 
+/**
+ * TODO: For future expandability of main
+ * Currently creates a lockfile to prevent the creation of multiple Device Client processes.
+ * @return true if no exception is caught, false otherwise
+ */
+bool init()
+{
+    try
+    {
+        string filename = config.config.lockFilePath;
+        if (!filename.empty())
+        {
+            lockFile = unique_ptr<LockFile>(new LockFile{filename});
+        }
+    }
+    catch (std::runtime_error &e)
+    {
+        std::cout << e.what() << std::endl;
+        return false;
+    }
+    return true;
+}
+
 /**
  * Attempts to perform a graceful shutdown of each running feature. If this function is
  * executed more than once, it will terminate immediately.
@@ -121,7 +145,6 @@ void shutdown()
         resourceManager.get()->disconnect();
 #endif
         LoggerFactory::getLoggerInstance().get()->shutdown();
-        LockFileUtils::ProcessUnlock();
         exit(0);
     }
 }
@@ -166,7 +189,8 @@ void handle_feature_stopped(Feature *feature)
 void attemptConnection()
 {
     Retry::ExponentialRetryConfig retryConfig = {10 * 1000, 900 * 1000, -1, nullptr};
-    auto publishLambda = []() -> bool {
+    auto publishLambda = []() -> bool
+    {
         int connectionStatus = resourceManager.get()->establishConnection(config.config);
         if (SharedCrtResourceManager::ABORT == connectionStatus)
         {
@@ -189,8 +213,8 @@ void attemptConnection()
             return false;
         }
     };
-    std::thread attemptConnectionThread(
-        [retryConfig, publishLambda] { Retry::exponentialBackoff(retryConfig, publishLambda); });
+    std::thread attemptConnectionThread([retryConfig, publishLambda]
+                                        { Retry::exponentialBackoff(retryConfig, publishLambda); });
     attemptConnectionThread.join();
 }
 
@@ -272,7 +296,6 @@ namespace Aws
 
 int main(int argc, char *argv[])
 {
-    LockFileUtils::ProcessLock();
     CliArgs cliArgs;
     if (!Config::ParseCliArgs(argc, argv, cliArgs) || !config.init(cliArgs))
     {
@@ -297,6 +320,11 @@ int main(int argc, char *argv[])
         LOG_WARN(TAG, "Unable to append current working directory to PATH environment variable.");
     }
 
+    if (!init())
+    {
+        return -1;
+    }
+
     LOGM_INFO(TAG, "Now running AWS IoT Device Client version %s", DEVICE_CLIENT_VERSION_FULL);
 
     // Register for listening to interrupt signals
@@ -469,6 +497,5 @@ int main(int argc, char *argv[])
                 break;
         }
     }
-
     return 0;
 }

source/util/LockFile.cpp

@@ -1,18 +1,17 @@
 // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-#include <stdexcept>
 #include "LockFile.h"
+#include <stdexcept>
 
+using namespace std;
 using namespace Aws::Iot::DeviceClient::Util;
 
-LockFile::LockFile(const std::string& filename)
-    : filename(filename)
-      , file(fopen(filename.c_str(), "wx"))
+LockFile::LockFile(const std::string &filename) : filename(filename), file(fopen(filename.c_str(), "wx"))
 {
     if (!file)
     {
-        throw std::runtime_error{"unable to open lockfile"};
+        throw std::runtime_error{"Unable to open lockfile... please check permissions and if device client is already running."};
     }
     flockfile(file);
 }

source/util/LockFile.h

@@ -22,7 +22,7 @@ namespace Aws
                     FILE *file{nullptr};
 
                   public:
-                    LockFile(const std::string& filename);
+                    LockFile(const std::string &filename);
                     ~LockFile();
 
                     // Non-copyable.