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  13.         Week 4 - Remote Procedure Call - HackMD

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  37.     <div id="doc" class="markdown-body container-fluid comment-inner comment-enabled" data-hard-breaks="true"><h1 id="Week-4---Remote-Procedure-Call" data-id="Week-4---Remote-Procedure-Call"><a class="anchor hidden-xs" href="#Week-4---Remote-Procedure-Call" title="Week-4---Remote-Procedure-Call"><span class="octicon octicon-link"></span></a><span>Week 4 - Remote Procedure Call</span></h1><blockquote>

  38. <p><span>Distributed Systems and Network Programming - Spring 2023</span></p>

  39. </blockquote><h2 id="Overview" data-id="Overview"><a class="anchor hidden-xs" href="#Overview" title="Overview"><span class="octicon octicon-link"></span></a><span>Overview</span></h2><p><span>Your task for this lab is to use </span><a href="https://grpc.io/docs/what-is-grpc/core-concepts/" target="_blank" rel="noopener"><span>gRPC</span></a><span> to remotely call functions defined on a server.</span></p><ul>

  40. <li><span>The client calls stub functions to do some CRUD operations against a SQLite database.</span></li>

  41. <li><span>The server executes the corresponding implementations to modify the database content.</span></li>

  42. <li><span>Communication happens over the network, with </span><a href="https://protobuf.dev/overview/" target="_blank" rel="noopener"><span>Protocol Buffers</span></a><span> as the data serialization format.</span></li>

  43. </ul><h2 id="Remote-Functions" data-id="Remote-Functions"><a class="anchor hidden-xs" href="#Remote-Functions" title="Remote-Functions"><span class="octicon octicon-link"></span></a><span>Remote Functions</span></h2><p><span>The server should expose the following functions for RPC, the logic for each function is explained below:</span></p><ul>

  44. <li>

  45. <p><code>PutUser(user_id: int, user_name: str)</code></p>

  46. <ul>

  47. <li><span>Update the entry for the user with </span><code>user_id</code><span> to have the specified </span><code>user_name</code></li>

  48. <li><span>If such user does not exist, create one and insert it into the database</span></li>

  49. <li><span>Return </span><code>True</code><span> on success and </span><code>False</code><span> on failure</span></li>

  50. </ul>

  51. </li>

  52. <li>

  53. <p><code>DeleteUser(user_id: int)</code></p>

  54. <ul>

  55. <li><span>Delete the entry for the user with the supplied </span><code>user_id</code></li>

  56. <li><span>Return </span><code>True</code><span> on success and </span><code>False</code><span> on failure</span></li>

  57. </ul>

  58. </li>

  59. <li>

  60. <p><code>GetUsers()</code></p>

  61. <ul>

  62. <li><span>Return a list of user objects (all users in the database).</span></li>

  63. <li><span>Each object should have two accessible properties named </span><code>user_id</code><span> and </span><code>user_name</code></li>

  64. </ul>

  65. </li>

  66. </ul><h2 id="Task" data-id="Task"><a class="anchor hidden-xs" href="#Task" title="Task"><span class="octicon octicon-link"></span></a><span>Task</span></h2><ol>

  67. <li>

  68. <p><span>Create a Python virtual environment and install the required external dependencies</span></p>

  69. <pre><code class="bash hljs">python3 -m venv venv

  70. <span class="hljs-built_in">source</span> venv/bin/activate

  71. pip3 install grpcio grpcio-tools

  72. </code></pre>

  73. </li>

  74. <li>

  75. <p><span>Create </span><code>schema.proto</code><span> which defines the following:</span></p>

  76. <ul>

  77. <li><span>The database </span><code>service</code><span> with remote functions that can be called through </span><code>rpc</code><span>.</span></li>

  78. <li><span>Request/response </span><code>message</code><span> format for the client/server communication.</span></li>

  79. </ul>

  80. </li>

  81. <li>

  82. <p><span>Compile the schema file to generate the stub and service source files (</span><code>schema_pb2_grpc.py</code><span> and </span><code>schema_pb2.py</code><span>) using the following command:</span></p>

  83. <pre><code class="bash hljs">python3 -m grpc_tools.protoc --proto_path=. --python_out=. --grpc_python_out=. schema.proto

  84. </code></pre>

  85. </li>

  86. <li>

  87. <p><span>Write the gRPC server code to do the following:</span></p>

  88. <ul>

  89. <li><span>Create or overwrite a local database file </span><code>db.sqlite</code><span> in the current directory.</span></li>

  90. <li><span>Initialize the database with an empty table </span><code>Users(id INTEGER, name STRING)</code></li>

  91. <li><span>Create a </span><code>grpc.server</code><span> that listens forever for client RPC requests and executes them.</span>

  92. <ul>

  93. <li><span>The server should terminate gracefully whenever a </span><code>KeyboardInterrupt</code><span> is received.</span></li>

  94. <li><span>Upon receiving a request from the client, the server should print the name of the function to be executed along with the supplied arguments.</span></li>

  95. </ul>

  96. </li>

  97. <li><span>Implement the functions for </span><code>PutUser</code><span>, </span><code>DeleteUser</code><span>, and </span><code>GetUsers</code><span> as explained above.</span></li>

  98. </ul>

  99. </li>

  100. <li>

  101. <p><span>Run your gRPC server, then run the given client (you are not supposed to modify the client).</span></p>

  102. </li>

  103. <li>

  104. <p><span>Verify that the database was populated by inspecting the file </span><code>db.sqlite</code><span> using your favorite SQLite viewer tool/extension.</span></p>

  105. </li>

  106. </ol><h2 id="Example-Run" data-id="Example-Run"><a class="anchor hidden-xs" href="#Example-Run" title="Example-Run"><span class="octicon octicon-link"></span></a><span>Example Run</span></h2><pre><code class="bash hljs">$ python3 server.py

  107. gRPC server is listening on 0.0.0.0:1234

  108. PutUser(1, <span class="hljs-string">'User1'</span>)

  109. PutUser(2, <span class="hljs-string">'User2'</span>)

  110. PutUser(3, <span class="hljs-string">'User3'</span>)

  111. PutUser(4, <span class="hljs-string">'User4'</span>)

  112. PutUser(2, <span class="hljs-string">'User2_updated'</span>)

  113. DeleteUser(3)

  114. GetUsers()

  115. </code></pre><pre><code class="bash hljs">$ python3 client.py

  116. PutUser(1, <span class="hljs-string">'User1'</span>) = True

  117. PutUser(2, <span class="hljs-string">'User2'</span>) = True

  118. PutUser(3, <span class="hljs-string">'User3'</span>) = True

  119. PutUser(4, <span class="hljs-string">'User4'</span>) = True

  120. PutUser(2, <span class="hljs-string">'User2_updated'</span>) = True

  121. DeleteUser(3) = True

  122. GetUsers() = {1: <span class="hljs-string">'User1'</span>, 2: <span class="hljs-string">'User2_updated'</span>, 4: <span class="hljs-string">'User4'</span>}

  123. </code></pre><h2 id="Checklist" data-id="Checklist"><a class="anchor hidden-xs" href="#Checklist" title="Checklist"><span class="octicon octicon-link"></span></a><span>Checklist</span></h2><ul class="contains-task-list">

  124. <li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> A single submitted file (</span><code>NameSurname.zip</code><span>) containing only </span><code>server.py</code><span> and </span><code>schema.proto</code></li>

  125. <li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> The code is formatted and does not use any external dependencies (apart from  </span><code>grpc</code><span>)</span></li>

  126. <li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> The </span><code>schema.proto</code><span> file correctly compiles without errors or warnings.</span></li>

  127. <li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> The server code executes successfully and prints the expected output.</span></li>

  128. <li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> The created database file </span><code>db.sqlite</code><span> contains the expected data after applying all queries.</span></li>

  129. <li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> The source code is the author’s original work. Both parties will be penalized for detected plagiarism</span></li>

  130. </ul></div>

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  138. <li class=""><a href="#Week-4---Remote-Procedure-Call" title="Week 4 - Remote Procedure Call">Week 4 - Remote Procedure Call</a><ul class="nav">

  139. <li class=""><a href="#Overview" title="Overview">Overview</a></li>

  140. <li class=""><a href="#Remote-Functions" title="Remote Functions">Remote Functions</a></li>

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