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Author: Rimkomatic

.gitignore

@@ -0,0 +1,3 @@
+.idea
+app/test.py
+__pycache__

README.md

@@ -1,8 +1,8 @@
-
-# Python Redis Server
+# Redis Clone
 
 This is a simple implementation of a Redis clone written in Python.
 It is not meant to be a fully-featured Redis server, but rather a demonstration of how the Redis protocol works.
+I developed it following the challenge on the wonderful website [CodeCrafters](https://codecrafters.io/).
 
 ## Features
 
@@ -39,27 +39,4 @@ This Redis clone has several limitations compared to a real Redis server:
 
 - Only a limited set of commands are implemented.
 - The database is not persisted to disk, so all data is lost when the server is stopped.
-- There is no support for multiple databases or authentication.
-
-## Common Bug
-
-When running your server locally, you might see an error like this:
-
-```
-Traceback (most recent call last):
-  File "/.../python3.7/runpy.py", line 193, in _run_module_as_main
-    "__main__", mod_spec)
-  File "/.../python3.7/runpy.py", line 85, in _run_code
-    exec(code, run_globals)
-  File "/app/app/main.py", line 11, in <module>
-    main()
-  File "/app/app/main.py", line 6, in main
-    s = socket.create_server(("localhost", 6379), reuse_port=True)
-AttributeError: module 'socket' has no attribute 'create_server'
-```
-
-This is because `socket.create_server` was introduced in Python 3.8, and you
-might be running an older version.
-
-You can fix this by installing Python 3.8 locally and using that.
-
+- There is no support for multiple databases or authentication.

app/main.py

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+import socket
+import threading
+import time
+
+from .resp_decoder import RESPDecoder
+
+database = {}
+
+
+def handle_ping(client_connection):
+    client_connection.send(b"+PONG\r\n")
+
+
+def handle_echo(client_connection, args):
+    client_connection.send(b"$%d\r\n%b\r\n" % (len(args[0]), args[0]))
+
+
+def handle_set(client_connection, args):
+    expiry = None
+    # Check for "px" argument and extract expiry value
+    if b"px" in args:
+        expiry_index = args.index(b"px") + 1
+        expiry = int(args[expiry_index])
+        expiry = int(time.time() * 1000) + expiry
+        args = args[: expiry_index - 1] + args[expiry_index + 1 :]
+
+    database[args[0]] = (args[1], expiry)
+    client_connection.send(b"+OK\r\n")
+
+
+def handle_get(client_connection, args):
+    key = args[0]
+    entry = database.get(key)
+
+    if entry is None:
+        client_connection.send(b"$-1\r\n")
+        return
+
+    value, expiry = entry
+    if expiry is not None and expiry <= int(time.time() * 1000):
+        del database[key]
+        client_connection.send(b"$-1\r\n")
+    else:
+        client_connection.send(b"$%d\r\n%b\r\n" % (len(value), value))
+
+
+def handle_connection(client_connection):
+    while True:
+        try:
+            command, *args = RESPDecoder(client_connection).decode()
+            command = command.decode("ascii").lower()
+            if command == "ping":
+                handle_ping(client_connection)
+            elif command == "echo":
+                handle_echo(client_connection, args)
+            elif command == "set":
+                handle_set(client_connection, args)
+            elif command == "get":
+                handle_get(client_connection, args)
+            else:
+                client_connection.send(b"-ERR unknown command\r\n")
+        except ConnectionError:
+            break  # Stop serving if the client connection is closed
+
+
+def main():
+    server_socket = socket.create_server(("localhost", 6379), reuse_port=True)
+
+    while True:
+        client_connection, _ = server_socket.accept()  # wait for client
+        threading.Thread(target=handle_connection, args=(client_connection,)).start()
+
+
+if __name__ == "__main__":
+    main()

app/resp_decoder.py

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+# ConnectionBuffer wraps socket.Socket and adds support for reading until a delimiter.
+class ConnectionBuffer:
+    def __init__(self, connection):
+        self.connection = connection
+        self.buffer = b''
+
+    def read_until_delimiter(self, delimiter):
+        while delimiter not in self.buffer:
+            data = self.connection.recv(1024)
+
+            if not data:  # socket closed
+                return None
+
+            self.buffer += data
+
+        data_before_delimiter, delimiter, self.buffer = self.buffer.partition(delimiter)
+        return data_before_delimiter
+
+    def read(self, bufsize):
+        if len(self.buffer) < bufsize:
+            data = self.connection.recv(1024)
+
+            if not data:  # socket closed
+                return None
+
+            self.buffer += data
+
+        data, self.buffer = self.buffer[:bufsize], self.buffer[bufsize:]
+        return data
+
+
+class RESPDecoder:
+    def __init__(self, connection):
+        self.connection = ConnectionBuffer(connection)
+
+    def decode(self):
+        data_type_byte = self.connection.read(1)
+
+        if data_type_byte == b"+":
+            return self.decode_simple_string()
+        elif data_type_byte == b"$":
+            return self.decode_bulk_string()
+        elif data_type_byte == b"*":
+            return self.decode_array()
+        else:
+            raise Exception(f"Unknown data type byte: {data_type_byte}")
+
+    def decode_simple_string(self):
+        return self.connection.read_until_delimiter(b"\r\n")
+
+    def decode_bulk_string(self):
+        bulk_string_length = int(self.connection.read_until_delimiter(b"\r\n"))
+        data = self.connection.read(bulk_string_length)
+        assert self.connection.read_until_delimiter(b"\r\n") == b""  # delimiter should be immediately after string
+        return data
+
+    def decode_array(self):
+        result = []
+        array_length = int(self.connection.read_until_delimiter(b"\r\n"))
+
+        for _ in range(array_length):
+            result.append(self.decode())
+
+        return result

redis-clone

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+#!/bin/sh
+#
+# DON'T EDIT THIS!
+#
+# CodeCrafters uses this file to test your code. Don't make any changes here!
+#
+# DON'T EDIT THIS!
+exec python3 -m app.main