I've implemented an async connection pool (ConnectionPool) and transport layer (Transport) in Python for managing persistent connections to a backend service. The goal is to handle multiple clients efficiently with sticky sessions, timeouts, and connection reuse. However, I'm unsure about:

TLS/SSL Integration:

Currently, the code doesn't implement TLS. How should I properly add TLS encryption to the Transport class (e.g., using asyncio.open_connection with SSL contexts)?

Are there security pitfalls (e.g., certificate verification, protocol versions) to avoid?

Connection Pool Optimization:

The pool uses a Semaphore for max connections and sticky sessions via sticky_map. Is this approach thread-safe and scalable for high concurrency?

How can I improve connection reuse (e.g., health checks, idle timeout)?

Dynamic Client Handling:

The current design assumes a single backend address. How can I extend it to support dynamic endpoints (e.g., load balancing across multiple hosts)?

Should I pre-warm connections or implement lazy initialization?

Error Handling:

Are there critical edge cases (e.g., partial writes, zombie connections) that aren’t handled robustly?

Code Reference: ConnectionPool: Manages connections with sticky sessions and semaphore-based limits.

Transport: Handles low-level socket communication with retries and timeouts. Connection_pool.py

import asyncio
import logging
from transport import Transport

logger = logging.getLogger(__name__)

class ConnectionPool:
    def __init__(self, address, max_connections=100, timeout=5):
        self.address = address
        self.max_connections = max_connections
        self.timeout = timeout
        self.connections = set()  # All active connections (alive or dead)
        self.available_connections = asyncio.Queue()  # Connections ready for reuse
        self.sticky_map = {}  # request_id -> Transport (lazily cleaned)
        self.semaphore = asyncio.Semaphore(max_connections)  # Limits concurrency

    async def _create_connection(self):
        """Create and return a new connection (internal)."""
        host, port = self.address.split(":")
        conn = Transport(host, int(port), self.timeout)
        try:
            if await conn.connect():
                self.connections.add(conn)
                return conn
        except Exception as e:
            logger.error(f"Connection failed: {e}")
        return None

    async def get_connection(self, request_id=None, sticky=False):
        """Get a connection, reusing sticky/available ones or creating new."""
        # Fast path: Reuse sticky connection if valid
        if sticky and request_id:
            async with asyncio.Lock():
                if request_id in self.sticky_map:
                    conn = self.sticky_map[request_id]
                    if conn.is_alive():
                        return conn
                    del self.sticky_map[request_id]  # Cleanup dead sticky

        # Reuse available connections
        while not self.available_connections.empty():
            conn = await self.available_connections.get()
            if conn.is_alive():
                if sticky and request_id:
                    async with asyncio.Lock():
                        self.sticky_map[request_id] = conn
                return conn
            else:
                async with asyncio.Lock():
                    self.connections.discard(conn)  # Remove dead

        # Create a new connection if under limit
        async with self.semaphore:
            conn = await self._create_connection()
            if conn and sticky and request_id:
                async with asyncio.Lock():
                    self.sticky_map[request_id] = conn
            return conn

    async def release_connection(self, conn, request_id=None):
        """Release a connection back to the pool."""
        if request_id:
            async with asyncio.Lock():
                self.sticky_map.pop(request_id, None)  # Unstick if needed

        if conn.is_alive():
            await self.available_connections.put(conn)  # Reuse alive connections
        else:
            async with asyncio.Lock():
                self.connections.discard(conn)  # Remove dead
        self.semaphore.release()  # Important: Release after cleanup!

    async def send_request(self, request, sticky=False):
        """Send a request using the pool (handles timeouts and errors)."""
        await self.semaphore.acquire()
        conn = None
        try:
            conn = await self.get_connection(request.id, sticky)
            if not conn:
                return {"error": "No connection available."}

            response = await asyncio.wait_for(
                conn.send_request(request),
                timeout=self.timeout
            )
            return response
        except asyncio.TimeoutError:
            logger.error("Request timed out.")
            return {"error": "Timeout"}
        except Exception as e:
            logger.error(f"Request failed: {e}")
            return {"error": str(e)}
        finally:
            if conn:
                await self.release_connection(conn, request.id if sticky else None)

    async def close_all(self):
        """Close all connections and reset the pool."""
        async with asyncio.Lock():
            for conn in self.connections:
                await conn.close()
            self.connections.clear()
            self.sticky_map.clear()
            while not self.available_connections.empty():
                self.available_connections.get_nowait()

Transport.py

import asyncio
import struct
import logging
import response_pb2 as pb2_response

logger = logging.getLogger(__name__)

class Transport:
    def __init__(self, host, port, timeout=5):
        self.host = host
        self.port = port
        self.timeout = timeout
        self.reader = None
        self.writer = None
        self.lock = asyncio.Lock()  # Per-connection lock
        self.connected = False

    async def connect(self):
        """Establish a connection with retries and exponential backoff."""
        retry_delay = 1
        for _ in range(3):
            try:
                self.reader, self.writer = await asyncio.wait_for(
                    asyncio.open_connection(self.host, self.port),
                    timeout=self.timeout
                )
                self.connected = True
                logger.info(f"Connected to {self.host}:{self.port}")
                return True
            except (asyncio.TimeoutError, ConnectionRefusedError) as e:
                logger.error(f"Connection failed: {e}")
                break
            except Exception as e:
                logger.warning(f"Retrying connection: {e}")
                await asyncio.sleep(retry_delay)
                retry_delay *= 2

        self.connected = False
        return False

    def is_alive(self):
        """Check if the connection is active."""
        return (
            self.connected 
            and self.writer 
            and not self.writer.is_closing()
        )

    async def send_request(self, request):
        """Thread-safe request sending with timeout."""
        if not self.is_alive() and not await self.connect():
            return {"error": "Connection failed."}

        async with self.lock:  # Ensure only one coroutine uses this connection
            try:
                # Serialize and send request
                req_data = request.SerializeToString()
                req_len = struct.pack(">I", len(req_data))
                self.writer.write(req_len + req_data)
                await self.writer.drain()
                
                # Await response
                return await asyncio.wait_for(
                    self.receive_response(),
                    timeout=self.timeout
                )
            except Exception as e:
                logger.error(f"Request failed: {e}")
                self.connected = False
                return {"error": str(e)}

    async def receive_response(self):
        """Receive and parse a protobuf response."""
        try:
            len_buf = await self.reader.readexactly(4)
            resp_len = struct.unpack(">I", len_buf)[0]
            response_data = await self.reader.readexactly(resp_len)
            response = pb2_response.Response()
            response.ParseFromString(response_data)
            return response
        except Exception as e:
            self.connected = False
            return {"error": f"Receiver error: {e}"}

    async def close(self):
        """Gracefully close the connection."""
        if self.writer:
            self.writer.close()
            await self.writer.wait_closed()
        self.connected = False

Observe the codes, implement the changes and give me the updated code files