Leader Election

class LeaderElection:
    def __init__(self, election_config: Config):
        """
        Initialize leader election with configuration.
        
        Parameters:
        - election_config: Election configuration including lock, timings, and callbacks
        """
    
    def run(self) -> None:
        """
        Start the leader election process.
        Blocks until leadership is lost or process terminates.
        """
    
    def acquire(self) -> bool:
        """
        Attempt to acquire leadership.
        
        Returns:
        - bool: True if leadership acquired, False otherwise
        """
    
    def renew_loop(self) -> None:
        """
        Continuously renew leadership lease while leader.
        Called automatically after acquiring leadership.
        """

class Config:
    def __init__(
        self,
        lock,
        lease_duration: int,
        renew_deadline: int,
        retry_period: int,
        onstarted_leading: callable,
        onstopped_leading: callable = None
    ):
        """
        Configure leader election parameters.
        
        Parameters:
        - lock: Resource lock implementation (ConfigMapLock, etc.)
        - lease_duration: Duration of leadership lease in seconds
        - renew_deadline: Deadline for lease renewal in seconds
        - retry_period: Retry interval in seconds
        - onstarted_leading: Callback when becoming leader
        - onstopped_leading: Callback when losing leadership
        
        Constraints:
        - lease_duration > renew_deadline
        - renew_deadline > jitter_factor * retry_period
        - All timing values must be >= 1
        """

class LeaderElectionRecord:
    def __init__(
        self,
        holder_identity: str,
        lease_duration: int,
        acquire_time: str,
        renew_time: str
    ):
        """
        Leader election record data.
        
        Parameters:
        - holder_identity: Unique identifier of current leader
        - lease_duration: Duration of leadership lease
        - acquire_time: When leadership was acquired (ISO format)
        - renew_time: When lease was last renewed (ISO format)
        """

class ConfigMapLock:
    def __init__(self, name: str, namespace: str, identity: str):
        """
        ConfigMap-based resource lock for leader election.
        
        Parameters:
        - name: Name of the ConfigMap to use as lock
        - namespace: Namespace containing the ConfigMap
        - identity: Unique identifier for this candidate
        """
    
    def get(self, name: str, namespace: str) -> tuple:
        """
        Get current election record from ConfigMap.
        
        Returns:
        - tuple: (success: bool, record: LeaderElectionRecord or exception)
        """
    
    def create(self, name: str, namespace: str, election_record: LeaderElectionRecord) -> bool:
        """
        Create new election record in ConfigMap.
        
        Returns:
        - bool: True if created successfully
        """
    
    def update(self, election_record: LeaderElectionRecord) -> bool:
        """
        Update existing election record.
        
        Returns:
        - bool: True if updated successfully
        """

from kubernetes import client, config
from kubernetes.leaderelection import LeaderElection
from kubernetes.leaderelection.electionconfig import Config
from kubernetes.leaderelection.resourcelock.configmaplock import ConfigMapLock

# Load Kubernetes configuration
config.load_kube_config()

def on_started_leading():
    """Called when this instance becomes the leader."""
    print("Started leading - performing leader tasks")
    # Implement leader-specific logic here
    while True:
        # Leader work loop
        time.sleep(30)

def on_stopped_leading():
    """Called when this instance loses leadership."""
    print("Stopped leading - cleaning up")
    # Cleanup leader-specific resources

# Create resource lock using ConfigMap
lock = ConfigMapLock(
    name="my-app-lock",
    namespace="default", 
    identity="instance-1"
)

# Configure election parameters
election_config = Config(
    lock=lock,
    lease_duration=30,        # Leadership lease duration (seconds)
    renew_deadline=20,        # Lease renewal deadline (seconds)
    retry_period=5,           # Retry interval (seconds)
    onstarted_leading=on_started_leading,
    onstopped_leading=on_stopped_leading
)

# Start leader election
election = LeaderElection(election_config)
election.run()  # Blocks until process terminates

import time
import threading
from kubernetes.leaderelection import LeaderElection
from kubernetes.leaderelection.electionconfig import Config
from kubernetes.leaderelection.resourcelock.configmaplock import ConfigMapLock

class HighAvailabilityService:
    def __init__(self, service_name, namespace, instance_id):
        self.service_name = service_name
        self.running = False
        
        # Create resource lock
        self.lock = ConfigMapLock(
            name=f"{service_name}-leader-election",
            namespace=namespace,
            identity=instance_id
        )
        
        # Configure election
        self.config = Config(
            lock=self.lock,
            lease_duration=60,
            renew_deadline=40, 
            retry_period=10,
            onstarted_leading=self.become_leader,
            onstopped_leading=self.stop_leading
        )
    
    def become_leader(self):
        """Start service operations as leader."""
        print(f"{self.service_name}: Became leader, starting operations")
        self.running = True
        
        # Start background service operations
        while self.running:
            self.perform_leader_tasks()
            time.sleep(10)
    
    def stop_leading(self):
        """Stop service operations when losing leadership."""
        print(f"{self.service_name}: Lost leadership, stopping operations")
        self.running = False
    
    def perform_leader_tasks(self):
        """Core service logic that should only run on leader."""
        print("Performing leader-only tasks...")
        # Implement your service logic here
    
    def start(self):
        """Start participating in leader election."""
        election = LeaderElection(self.config)
        election.run()

# Usage
service = HighAvailabilityService(
    service_name="data-processor",
    namespace="production",
    instance_id="pod-12345"
)
service.start()

from kubernetes import leaderelection
from kubernetes.leaderelection import LeaderElection
from kubernetes.leaderelection.electionconfig import Config
from kubernetes.leaderelection.leaderelectionrecord import LeaderElectionRecord
from kubernetes.leaderelection.resourcelock.configmaplock import ConfigMapLock