foreverVM implementation (Run ID: tripathi456_gvisor-based-python-repl_issue_15_326d48a9)

basic_impl/run_with_session_snapshots.sh

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+# docker run --runtime=runsc --rm -it \
+#   -v "$(pwd)/forevervm_minimal:/app" \
+#   -v "$(pwd)/snapshots:/var/forevervm/snapshots" \
+#   -p 8000:8000 \
+#   python:3.9.21-alpine3.21 \
+#   sh -c "cd /app && python main.py"
+
+docker run --runtime=runsc --rm -it \
+  -v "$(pwd)/forevervm_minimal:/app/forevervm_minimal" \
+  -v "$(pwd)/snapshots:/var/forevervm/snapshots" \
+  -p 8000:8000 \
+  python:3.9.21-alpine3.21 \
+  sh -c "cd /app/forevervm_minimal && pip install flask && python main.py"

basic_impl/scratchpad.md

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+# Scratchpad
+
+## Current Task
+Debugging and fixing the TCP client test script for the Python REPL server, creating a concurrent clients test, and enhancing the output with Rich library.
+
+## Progress
+[X] Identified the issue: The client was not properly receiving the initial greeting using the length-prefixed protocol
+[X] Fixed the client code by adding a `receive_response` function that follows the same protocol as the server
+[X] Successfully tested the client against the server
+[X] Created a new test script to simulate concurrent clients with different sessions
+[X] Improved the concurrent clients test to clearly demonstrate session isolation
+[X] Enhanced the test script with Rich library for better console output
+[X] Added a common variable name test to verify that both clients can set independent values to the same variable name
+
+## Lessons
+- The server uses a length-prefixed protocol for all communication (both sending and receiving)
+- Each message is prefixed with a 4-byte integer (big-endian) indicating the length of the following JSON message
+- All messages are JSON-encoded and UTF-8 encoded
+- The initial greeting from the server follows the same protocol as all other messages
+- When working with custom TCP protocols, it's important to ensure both client and server follow the same message format for all communications
+- The server maintains isolated session environments for different clients, ensuring that variables defined in one session are not accessible from another
+- When testing session isolation, it's important to use distinct variable names to clearly demonstrate that variables from one session cannot be accessed from another
+- The Rich library provides excellent tools for creating visually appealing and more readable console output in Python applications
+- Variables with the same name can have different values in different sessions, demonstrating complete session isolation
+
+## Technical Details
+- The server implements a Python REPL that maintains separate session environments
+- Each session is identified by a UUID
+- The server accepts JSON requests with the following fields:
+  - `code`: Python code to execute
+  - `session_id` (optional): ID of an existing session
+- The server responds with JSON containing:
+  - `status`: "ok" or "error"
+  - `output` or `error`: The output of the code execution or error message
+  - `session_id`: The ID of the session used
+
+## Concurrent Clients Test
+I created a new test script `test_concurrent_clients.py` that simulates two clients connecting to the server concurrently, each with their own session. The test does the following:
+
+1. Creates two client threads (Client A and Client B) that connect to the server simultaneously
+2. Each client:
+   - Creates a new session
+   - Defines a function in its session
+   - Creates a unique variable with a client-specific name (e.g., `unique_value_A` for Client A)
+   - Creates a variable with the same name (`common_variable`) but different values in each session
+   - Verifies the variables are still correct after a delay
+3. After both client threads complete, a third connection:
+   - Attempts to access Client A's variable from Client B's session (should fail)
+   - Verifies that `common_variable` in Client B's session has Client B's value
+   - Verifies that `common_variable` in Client A's session has Client A's value
+   - Attempts to access Client B's variable from Client B's session (should succeed)
+4. The test verifies that session isolation is maintained by confirming that:
+   - Client B cannot access Client A's variables (NameError is raised)
+   - Client B can access its own variables
+   - The `common_variable` in each session has a different value, specific to that session
+
+This test helps verify:
+- The server can handle multiple concurrent clients
+- Each client maintains its own isolated session state
+- Variables defined in one session are not accessible from another session
+- Variables with the same name can have different values in different sessions
+- The server correctly manages session IDs and their associated environments
+
+## Rich Library Enhancements
+I enhanced the test script with the Rich library to provide a more visually appealing and readable console output. The enhancements include:
+
+1. Progress tracking with spinners for each client thread
+2. Colorful panels to separate different sections of the test
+3. Tables to display test results in a structured format
+4. Color-coded status messages and results
+5. Clear visual indication of test success/failure
+
+These enhancements make it easier to:
+- Monitor the progress of concurrent client threads
+- Understand the relationships between sessions and variables
+- Quickly identify whether session isolation is properly maintained
+- View the test results in a well-organized format
+
+To run the test:
+```bash
+python test_concurrent_clients.py
+```
+
+
+https://claude.ai/chat/ad32c8cf-d589-4844-a85f-1084139269ea

basic_impl/test_timeouts.py

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+#!/usr/bin/env python3
+import socket
+import json
+import sys
+import threading
+import time
+import uuid
+from rich.console import Console
+from rich.panel import Panel
+from rich.table import Table
+from rich import box
+from rich.progress import Progress, SpinnerColumn, TextColumn, TimeElapsedColumn
+
+console = Console()
+
+def send_receive(sock, request_dict):
+    """Send a request to the server and receive the response (length-prefixed JSON)."""
+    request_json = json.dumps(request_dict)
+    request_bytes = request_json.encode('utf-8')
+
+    # Send the length first (4 bytes, big-endian)
+    length = len(request_bytes)
+    sock.sendall(length.to_bytes(4, 'big'))
+    # Then send the actual data
+    sock.sendall(request_bytes)
+
+    # Read response length
+    length_bytes = sock.recv(4)
+    if not length_bytes:
+        return {}
+    response_length = int.from_bytes(length_bytes, 'big')
+
+    # Read response data
+    chunks = []
+    bytes_received = 0
+    while bytes_received < response_length:
+        chunk = sock.recv(min(4096, response_length - bytes_received))
+        if not chunk:
+            break
+        chunks.append(chunk)
+        bytes_received += len(chunk)
+
+    response_str = b''.join(chunks).decode('utf-8')
+    return json.loads(response_str)
+
+def receive_greeting(sock):
+    """Receive a single greeting message from the server (length-prefixed JSON)."""
+    length_bytes = sock.recv(4)
+    if not length_bytes:
+        return None
+    message_length = int.from_bytes(length_bytes, 'big')
+    chunks = []
+    bytes_received = 0
+    while bytes_received < message_length:
+        chunk = sock.recv(min(4096, message_length - bytes_received))
+        if not chunk:
+            break
+        chunks.append(chunk)
+        bytes_received += len(chunk)
+    data = b''.join(chunks).decode('utf-8')
+    return json.loads(data)
+
+def client_thread(name, results, progress):
+    """
+    Each client:
+      1. Connects to the server, receives greeting.
+      2. Creates a session by sending code with no session_id (server should create new).
+      3. Defines a variable, prints it.
+      4. Sleeps long enough to trigger session timeout (6s).
+      5. Executes code again to see if the session was snapshotted+restored.
+    """
+    host = "localhost"
+    port = 8000
+
+    task_id = progress.add_task(f"[green]{name} Starting", total=5)
+
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    session_id = None
+    try:
+        sock.connect((host, port))
+        progress.update(task_id, description=f"[green]{name}: Connected", advance=1)
+
+        # 1) Receive initial greeting
+        greeting = receive_greeting(sock)
+        results[name]["greeting"] = greeting
+
+        # 2) Create a new session by sending some code (omitting session_id => server should create it)
+        progress.update(task_id, description=f"[green]{name}: Creating session", advance=1)
+        resp_create = send_receive(sock, {
+            "code": f"client_name = '{name}'\nprint('Hello from {name}!')"
+        })
+        # The server should respond with something like: {"session_id": "...", "output": "..."}
+        session_id = resp_create.get("session_id")
+        results[name]["session_id"] = session_id
+        results[name]["outputs"].append(resp_create.get("output", ""))
+
+        # 3) Define a variable and print it
+        progress.update(task_id, description=f"[green]{name}: Defining variable", advance=1)
+        myvar = f"value_{uuid.uuid4().hex[:6]}"
+        code_str = f"""myvar_{name} = '{myvar}'\nprint('Set myvar_{name} = ' + myvar_{name})"""
+        resp_define = send_receive(sock, {
+            "session_id": session_id,
+            "code": code_str
+        })
+        results[name]["outputs"].append(resp_define.get("output", ""))
+
+        # 4) Sleep 7s to exceed the 6s inactivity timeout
+        progress.update(task_id, description=f"[yellow]{name}: Sleeping 7s (timeout test)", advance=1)
+        time.sleep(7)
+
+        # 5) Execute new code => triggers restore if session was snapshotted
+        progress.update(task_id, description=f"[green]{name}: Checking session restore", advance=1)
+        resp_after_sleep = send_receive(sock, {
+            "session_id": session_id,
+            "code": f"print('After timeout, myvar_{name} is ' + myvar_{name})"
+        })
+        results[name]["outputs"].append(resp_after_sleep.get("output", ""))
+
+        progress.update(task_id, description=f"[green]{name}: Finished", completed=True)
+
+    except Exception as e:
+        results[name]["error"] = str(e)
+    finally:
+        sock.close()
+
+def main():
+    console.clear()
+    console.print(Panel.fit("[bold cyan]Timeout & Concurrency Test (6s Inactivity)[/bold cyan]", border_style="cyan"))
+
+    # We'll track results from multiple clients
+    # For demonstration, let's spin up two concurrent clients
+    results = {
+        "ClientA": {"session_id": None, "greeting": None, "outputs": [], "error": None},
+        "ClientB": {"session_id": None, "greeting": None, "outputs": [], "error": None}
+    }
+
+    with Progress(
+        SpinnerColumn(),
+        TextColumn("[progress.description]{task.description}"),
+        TimeElapsedColumn(),
+        console=console
+    ) as progress:
+        console.print("[bold]Starting two client threads...[/bold]\n")
+
+        tA = threading.Thread(target=client_thread, args=("ClientA", results, progress))
+        tB = threading.Thread(target=client_thread, args=("ClientB", results, progress))
+
+        tA.start()
+        tB.start()
+
+        tA.join()
+        tB.join()
+
+    console.print("\n[bold green]All client threads completed![/bold green]\n")
+
+    # Present a brief results summary table
+    table = Table(title="Results Summary", box=box.ROUNDED, show_header=True, header_style="bold magenta")
+    table.add_column("Client")
+    table.add_column("Session ID")
+    table.add_column("Error")
+    table.add_column("Outputs")
+
+    for client_name, data in results.items():
+        session_id = data["session_id"] or "[None]"
+        error = data["error"] or "[None]"
+        outputs_joined = "\n---\n".join(data["outputs"]) if data["outputs"] else "[No outputs]"
+        table.add_row(client_name, session_id, error, outputs_joined)
+
+    console.print(table)
+
+    console.print(Panel.fit(
+        "[bold green]✓ Test completed. Check the logs above or your server logs to confirm sessions got snapshotted/restored after 6s of inactivity.[/bold green]",
+        border_style="green"
+    ))
+
+if __name__ == "__main__":
+    main()

forevervm_minimal/.gitignore

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+__pycache__/
+
+.venv/
+data_dir/

forevervm_minimal/.python-version

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+3.13