final code changes to comply initial task description better

Author: kolomenkin

BackgroundWorker.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <condition_variable>
 #include <mutex>
 #include <string>
 

CMakeLists.txt

@@ -1,3 +1,6 @@
+cmake_minimum_required(VERSION 3.15) # 3.2 for Hunter; 3.15 for MSVC_RUNTIME_LIBRARY
+set(CMAKE_POLICY_DEFAULT_CMP0126 OLD) # for Hunter # New in version 3.21
+
 # ====================================
 
 set(CMAKE_MESSAGE_LOG_LEVEL         "VERBOSE"          CACHE STRING "Log verbosity (STATUS | VERBOSE | DEBUG | TRACE)")
@@ -9,9 +12,6 @@ set(DEPS_REQUIRED_RAPIDJSON_VERSION "1.1.0-b557259-p0" CACHE STRING "Required pa
 # Setup Hunter package manager
 # ====================================
 
-cmake_minimum_required(VERSION 3.2) # for Hunter
-set(CMAKE_POLICY_DEFAULT_CMP0126 OLD) # for Hunter # New in version 3.21
-
 option(HUNTER_NO_TOOLCHAIN_ID_RECALCULATION "No Toolchain-ID recalculation" OFF)
 
 include("cmake/HunterGate.cmake")
@@ -106,4 +106,7 @@ target_include_directories(WebServer PRIVATE ${RAPIDJSON_INCLUDE_DIRS})
 
 target_link_libraries(WebServer PRIVATE Crow)
 
+# Link to CRT statically in MSVC:
+set_property(TARGET WebServer PROPERTY MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
+
 # ====================================

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2022 Sergey Kolomenkin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -3,7 +3,11 @@
 An HTTP web server with a REST API for persistent key-value storage.
 Collects read-write statistics for the entire storage and for each key.
 
-## Test Task for a C++ Programmer
+**Language**: `C++20`  
+**Dependencies**: `Boost v1.78.0`, `RapidJSON v1.1.0-b557259-p0`, `CrowCpp v1.0+2`  
+**Software requirements**: `CMake 3.2+`, C++20 compatible compiler, `Python 3.7+`
+
+## Test Task Description
 
 You need to write two applications, a client and a server, that communicate with each other.
 
@@ -172,7 +176,7 @@ Reply body example:
 CPU Intel Core i5 (8th gen), mobile version, 8 logical cores.  
 Visual Studio 2019 (v16.11.13), Release build  
 Windows 10 Version 21H1 (Build 19043.1645)  
-Number of HTTP server threads: 8
+Number of HTTP server threads: 8  
 Logging of every request is disabled for both server and client side.
 
 ### Results

client.py

@@ -23,11 +23,11 @@
 ]
 
 COUNT_OF_OPERATIONS_PER_PROCESS = 10_000
-COUNT_OF_PROCESSES = multiprocessing.cpu_count()
+COUNT_OF_PROCESSES = 1  # multiprocessing.cpu_count()
 
 PERCENT_OF_WRITES = 1
 
-LOG_EVERY_REQUEST = False
+LOG_EVERY_REQUEST = True
 
 # =======================================
 
@@ -47,27 +47,37 @@ def one_request(conn: http.client.HTTPConnection) -> None:
         'Accept': 'application/json',
     }
 
-    if writing:
-        new_value = f'val_{random.randint(1000, 1000_000_000)}'
+    while True:  # retry connection loop
+        try:
+            if writing:
+                new_value = f'val_{random.randint(1000, 1000_000_000)}'
 
-        data = {"value": new_value}
+                data = {"value": new_value}
 
-        if LOG_EVERY_REQUEST:
-            print('====================================================')
-            print(f'POST {url}: {data}')
+                if LOG_EVERY_REQUEST:
+                    print('====================================================')
+                    print(f'POST {url}: {data}')
 
-        request_body_bytes = json.dumps(data, indent=2, sort_keys=True).encode(encoding='utf8')
-        conn.request(method='POST', url=url, body=request_body_bytes, headers=headers_post)
-    else:
-        if LOG_EVERY_REQUEST:
-            print(f'GET {url}')
-        conn.request(method='GET', url=url, headers=headers_get)
+                request_body_bytes = json.dumps(data, indent=2, sort_keys=True).encode(encoding='utf8')
+                conn.request(method='POST', url=url, body=request_body_bytes, headers=headers_post)
+            else:
+                if LOG_EVERY_REQUEST:
+                    print(f'GET {url}')
+                conn.request(method='GET', url=url, headers=headers_get)
 
-    response = conn.getresponse()
-    if LOG_EVERY_REQUEST:
-        print(f'REPLY: {response.status} {response.reason}')
+            response = conn.getresponse()
+            if LOG_EVERY_REQUEST:
+                print(f'REPLY: {response.status} {response.reason}')
 
-    body_bytes = response.read()
+            body_bytes = response.read()
+
+            break  # exit infinite retry connection loop
+        except ConnectionError as error:
+            print('Failed making HTTP request: ', repr(error))
+            conn.close()
+            sleep_duration_sec = 5.0
+            print(f'Retry after sleeping {sleep_duration_sec} seconds...')
+            time.sleep(sleep_duration_sec)
 
     if response.status not in (200, 404):
         print(f'RAW_REPLY_BODY: {body_bytes}')
@@ -113,10 +123,10 @@ def main() -> None:
     print('main: end')
 
 
-def main_owner() -> None:
-    print(f'main_owner: start {COUNT_OF_PROCESSES} child processes')
+def spawn_processes(process_count) -> None:
+    print(f'spawn_processes: start {process_count} child processes')
 
-    pool = [multiprocessing.Process(target=main, args=()) for _ in range(COUNT_OF_PROCESSES)]
+    pool = [multiprocessing.Process(target=main, args=()) for _ in range(process_count)]
 
     begin = time.perf_counter()
 
@@ -125,17 +135,20 @@ def main_owner() -> None:
 
     for process in pool:
         process.join()
-        print('Child process finished')
+        print('spawn_processes: Child process finished')
 
     end = time.perf_counter()
     elapsed = max(end - begin, 0.001)
-    operation_count = COUNT_OF_OPERATIONS_PER_PROCESS * COUNT_OF_PROCESSES
+    operation_count = COUNT_OF_OPERATIONS_PER_PROCESS * process_count
     ops_per_sec = int(operation_count / elapsed)
 
-    print(f'main_owner: It took {elapsed:.3f} seconds to execute {operation_count} requests; {ops_per_sec} requests per second')
+    print(f'spawn_processes: It took {elapsed:.3f} seconds to execute {operation_count} requests; {ops_per_sec} requests per second')
 
-    print('main_owner: end')
+    print('spawn_processes: end')
 
 
 if __name__ == '__main__':
-    main_owner()
+    if COUNT_OF_PROCESSES == 1:
+        main()
+    else:
+        spawn_processes(COUNT_OF_PROCESSES)

main.cpp

@@ -22,7 +22,7 @@ int main(void)
     const std::string   listenHost = "127.0.0.1";
     const std::uint16_t listenPort = 8000;
     const std::string databaseFilename = "database.json";
-    const bool logEachRequest = false;
+    const bool logEachRequest = true;
 
     // =========================================================