#!/usr/bin/env python3

# VMInstance.py - Class implementing a PVC virtual machine in pvcd
# Part of the Parallel Virtual Cluster (PVC) system
#
#    Copyright (C) 2018  Joshua M. Boniface <joshua@boniface.me>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <https://www.gnu.org/licenses/>.
#
###############################################################################

import os
import sys
import uuid
import socket
import time
import threading
import libvirt
import kazoo.client

import pvcd.log as log
import pvcd.zkhandler as zkhandler

import pvcd.VMConsoleWatcherInstance as VMConsoleWatcherInstance

class VMInstance(object):
    # Initialization function
    def __init__(self, domuuid, zk_conn, config, logger, this_node):
        # Passed-in variables on creation
        self.domuuid = domuuid
        self.zk_conn = zk_conn
        self.config = config
        self.logger = logger
        self.this_node = this_node

        # Get data from zookeeper
        self.domname = zkhandler.readdata(zk_conn, '/domains/{}'.format(domuuid))
        self.state = zkhandler.readdata(self.zk_conn, '/domains/{}/state'.format(self.domuuid))
        self.node = zkhandler.readdata(self.zk_conn, '/domains/{}/node'.format(self.domuuid))

        # These will all be set later
        self.instart = False
        self.inrestart = False
        self.inmigrate = False
        self.inreceive = False
        self.inshutdown = False
        self.instop = False

        # Libvirt domuuid
        self.dom = self.lookupByUUID(self.domuuid)

        # Log watcher instance
        self.console_log_instance = VMConsoleWatcherInstance.VMConsoleWatcherInstance(self.domuuid, self.domname, self.zk_conn, self.config, self.logger, self.this_node)

        # Watch for changes to the state field in Zookeeper
        @self.zk_conn.DataWatch('/domains/{}/state'.format(self.domuuid))
        def watch_state(data, stat, event=""):
            if event and event.type == 'DELETED':
                # The key has been deleted after existing before; terminate this watcher
                # because this class instance is about to be reaped in Daemon.py
                return False

            # If we get a delete state, just terminate outselves
            if data == None:
                return
            # Otherwise perform a management command
            else:
                self.manage_vm_state()


    # Get data functions
    def getstate(self):
        return self.state

    def getnode(self):
        return self.node

    def getdom(self):
        return self.dom

    def getmemory(self):
        try:
            memory = int(self.dom.info()[2] / 1024)
        except:
            memory = 0

        return memory

    def getvcpus(self):
        try:
            vcpus = int(self.dom.info()[3])
        except:
            vcpus = 0

        return vcpus

    # Manage local node domain_list
    def addDomainToList(self):
        if not self.domuuid in self.this_node.domain_list:
            try:
                # Add the domain to the domain_list array
                self.this_node.domain_list.append(self.domuuid)
                # Push the change up to Zookeeper
                zkhandler.writedata(self.zk_conn, { '/nodes/{}/runningdomains'.format(self.this_node.name): ' '.join(self.this_node.domain_list) })
            except Exception as e:
                self.logger.out('Error adding domain to list: {}'.format(e), state='c')

    def removeDomainFromList(self):
        if self.domuuid in self.this_node.domain_list:
            try:
                # Remove the domain from the domain_list array
                self.this_node.domain_list.remove(self.domuuid)
                # Push the change up to Zookeeper
                zkhandler.writedata(self.zk_conn, { '/nodes/{}/runningdomains'.format(self.this_node.name): ' '.join(self.this_node.domain_list) })
            except Exception as e:
                self.logger.out('Error removing domain from list: {}'.format(e), state='c')

    # Start up the VM
    def start_vm(self):
        # Start the log watcher
        self.console_log_instance.start()

        self.logger.out('Starting VM', state='i', prefix='Domain {}:'.format(self.domuuid))
        self.instart = True

        # Start up a new Libvirt connection
        libvirt_name = "qemu:///system"
        lv_conn = libvirt.open(libvirt_name)
        if lv_conn == None:
            self.logger.out('Failed to open local libvirt connection', state='e', prefix='Domain {}:'.format(self.domuuid))
            self.instart = False
            return

        # Try to get the current state in case it's already running
        try:
            self.dom = self.lookupByUUID(self.domuuid)
            curstate = self.dom.state()[0]
        except:
            curstate = 'notstart'

        if curstate == libvirt.VIR_DOMAIN_RUNNING:
            # If it is running just update the model
            self.addDomainToList()
            zkhandler.writedata(self.zk_conn, { '/domains/{}/failedreason'.format(self.domuuid): '' })
        else:
            # Or try to create it
            try:
                # Grab the domain information from Zookeeper
                xmlconfig = zkhandler.readdata(self.zk_conn, '/domains/{}/xml'.format(self.domuuid))
                dom = lv_conn.createXML(xmlconfig, 0)
                self.addDomainToList()
                self.logger.out('Successfully started VM', state='o', prefix='Domain {}:'.format(self.domuuid))
                self.dom = dom
                zkhandler.writedata(self.zk_conn, { '/domains/{}/failedreason'.format(self.domuuid): '' })
            except libvirt.libvirtError as e:
                self.logger.out('Failed to create VM', state='e', prefix='Domain {}:'.format(self.domuuid))
                zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'failed' })
                zkhandler.writedata(self.zk_conn, { '/domains/{}/failedreason'.format(self.domuuid): str(e) })
                self.dom = None

        lv_conn.close()

        self.instart = False

    # Restart the VM
    def restart_vm(self):
        self.logger.out('Restarting VM', state='i', prefix='Domain {}:'.format(self.domuuid))
        self.inrestart = True

        # Start up a new Libvirt connection
        libvirt_name = "qemu:///system"
        lv_conn = libvirt.open(libvirt_name)
        if lv_conn == None:
            self.logger.out('Failed to open local libvirt connection', state='e', prefix='Domain {}:'.format(self.domuuid))
            self.inrestart = False
            return

        self.shutdown_vm()
        time.sleep(0.2)
        self.start_vm()
        self.addDomainToList()

        zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'start' })
        lv_conn.close()
        self.inrestart = False

    # Stop the VM forcibly without updating state
    def terminate_vm(self):
        self.logger.out('Terminating VM', state='i', prefix='Domain {}:'.format(self.domuuid))
        self.instop = True
        try:
            self.dom.destroy()
        except AttributeError:
            self.logger.out('Failed to terminate VM', state='e', prefix='Domain {}:'.format(self.domuuid))
        self.removeDomainFromList()
        self.logger.out('Successfully terminated VM', state='o', prefix='Domain {}:'.format(self.domuuid))
        self.dom = None
        self.instop = False

        # Stop the log watcher
        self.console_log_instance.stop()

    # Stop the VM forcibly
    def stop_vm(self):
        self.logger.out('Forcibly stopping VM', state='i', prefix='Domain {}:'.format(self.domuuid))
        self.instop = True
        try:
            self.dom.destroy()
        except AttributeError:
            self.logger.out('Failed to stop VM', state='e', prefix='Domain {}:'.format(self.domuuid))
        self.removeDomainFromList()

        if self.inrestart == False:
            zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'stop' })

        self.logger.out('Successfully stopped VM', state='o', prefix='Domain {}:'.format(self.domuuid))
        self.dom = None
        self.instop = False

        # Stop the log watcher
        self.console_log_instance.stop()

    # Shutdown the VM gracefully
    def shutdown_vm(self):
        self.logger.out('Gracefully stopping VM', state='i', prefix='Domain {}:'.format(self.domuuid))
        self.inshutdown = True
        self.dom.shutdown()
        tick = 0
        while True:
            tick += 1
            time.sleep(1)

            try:
                lvdomstate = self.dom.state()[0]
            except:
                lvdomstate = None

            if lvdomstate != libvirt.VIR_DOMAIN_RUNNING:
                self.removeDomainFromList()
                zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'stop' })
                self.logger.out('Successfully shutdown VM', state='o', prefix='Domain {}:'.format(self.domuuid))
                self.dom = None
                # Stop the log watcher
                self.console_log_instance.stop()
                break

            # HARDCODE: 90s is a reasonable amount of time for any operating system to shut down cleanly
            if tick >= 90:
                self.logger.out('Shutdown timeout expired', state='e', prefix='Domain {}:'.format(self.domuuid))
                zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'stop' })
                break

        self.inshutdown = False

        if self.inrestart:
            # Wait to prevent race conditions
            time.sleep(1)
            zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'start' })

    def live_migrate_vm(self):
        dest_lv = 'qemu+tcp://{}.{}/system'.format(self.node, self.config['cluster_domain'])
        dest_tcp = 'tcp://{}.{}'.format(self.node, self.config['cluster_domain'])
        try:
            # Open a connection to the destination
            dest_lv_conn = libvirt.open(dest_lv)
            if not dest_lv_conn:
                raise
        except:
            self.logger.out('Failed to open connection to {}; aborting live migration.'.format(dest_lv), state='e', prefix='Domain {}:'.format(self.domuuid))
            return False

        try:
            # Send the live migration; force the destination URI to ensure we transit over the cluster network
            target_dom = self.dom.migrate(dest_lv_conn, libvirt.VIR_MIGRATE_LIVE, None, dest_tcp, 0)
            if not target_dom:
                raise
        except Exception as e:
            self.logger.out('Failed to send VM to {} - aborting live migration; error: {}'.format(dest_lv, e), state='e', prefix='Domain {}:'.format(self.domuuid))
            dest_lv_conn.close()
            return False

        self.logger.out('Successfully migrated VM', state='o', prefix='Domain {}:'.format(self.domuuid))
        dest_lv_conn.close()
        return True

    # Migrate the VM to a target host
    def migrate_vm(self):
        self.inmigrate = True
        self.logger.out('Migrating VM to node "{}"'.format(self.node), state='i', prefix='Domain {}:'.format(self.domuuid))

        migrate_ret = self.live_migrate_vm()
        if not migrate_ret:
            self.logger.out('Could not live migrate VM; shutting down to migrate instead', state='e', prefix='Domain {}:'.format(self.domuuid))
            zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'shutdown' })
        else:
            self.removeDomainFromList()
            # Stop the log watcher
            self.console_log_instance.stop()

        self.inmigrate = False

    # Receive the migration from another host (wait until VM is running)
    def receive_migrate(self):
        self.inreceive = True
        live_receive = True
        tick = 0
        self.logger.out('Receiving migration', state='i', prefix='Domain {}:'.format(self.domuuid))
        while True:
            # Wait 1 second and increment the tick
            time.sleep(1)
            tick += 1

            # Get zookeeper state and look for the VM in the local libvirt database
            self.state = zkhandler.readdata(self.zk_conn, '/domains/{}/state'.format(self.domuuid))
            self.dom = self.lookupByUUID(self.domuuid)

            # If the dom is found
            if self.dom:
                lvdomstate = self.dom.state()[0]
                if lvdomstate == libvirt.VIR_DOMAIN_RUNNING:
                    # VM has been received and started
                    self.addDomainToList()
                    zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'start' })
                    self.logger.out('Successfully received migrated VM', state='o', prefix='Domain {}:'.format(self.domuuid))
                    break
                else:
                    # If the state is no longer migrate
                    if self.state != 'migrate':
                        # The receive was aborted before it timed out or was completed
                        self.logger.out('Receive aborted via state change', state='w', prefix='Domain {}:'.format(self.domuuid))
                        break
            # If the dom is not found
            else:
                # If the state is changed to shutdown or stop
                if self.state == 'shutdown' or self.state == 'stop':
                    # The receive failed on the remote end, and VM is being shut down instead
                    live_receive = False
                    self.logger.out('Send failed on remote end', state='w', prefix='Domain {}:'.format(self.domuuid))
                    break

            # If we've already been waiting 90s for a receive
            # HARDCODE: 90s should be plenty of time for even extremely large VMs on reasonable networks
            if tick > 90:
                # The receive timed out
                zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'failed' })
                self.logger.out('Receive timed out without state change', state='e', prefix='Domain {}:'.format(self.domuuid))
                break

        # We are waiting on a shutdown
        if not live_receive:
            tick = 0
            self.logger.out('Waiting for VM to shut down on remote end', state='i', prefix='Domain {}:'.format(self.domuuid))
            while True:
                # Wait 1 second and increment the tick
                time.sleep(1)
                tick += 1

                # Get zookeeper state and look for the VM in the local libvirt database
                self.state = zkhandler.readdata(self.zk_conn, '/domains/{}/state'.format(self.domuuid))

                # If the VM has stopped
                if self.state == 'stop':
                    # Wait one more second to avoid race conditions
                    time.sleep(1)
                    # Start the VM up
                    zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'start' })
                    break

                # If we've already been waiting 120s for a shutdown
                # HARDCODE: The remote timeout is 90s, so an extra 30s of buffer
                if tick > 120:
                    # The shutdown timed out; something is very amiss, so switch state to failed and abort
                    zkhandler.writedata(self.zk_conn, {
                       '/domains/{}/state'.format(self.domuuid): 'failed',
                       '/domains/{}/failedreason'.format(self.domuuid): 'Timeout waiting for migrate or shutdown'
                    })
                    self.logger.out('Shutdown timed out without state change', state='e', prefix='Domain {}:'.format(self.domuuid))
                    break

        self.inreceive = False

    #
    # Main function to manage a VM (taking only self)
    #
    def manage_vm_state(self):
        # Update the current values from zookeeper
        self.state = zkhandler.readdata(self.zk_conn, '/domains/{}/state'.format(self.domuuid))
        self.node = zkhandler.readdata(self.zk_conn, '/domains/{}/node'.format(self.domuuid))

        # Check the current state of the VM
        try:
            if self.dom != None:
                running, reason = self.dom.state()
            else:
                raise
        except:
            running = libvirt.VIR_DOMAIN_NOSTATE

        self.logger.out('VM state change for "{}": {} {}'.format(self.domuuid, self.state, self.node), state='i')

        #######################
        # Handle state changes
        #######################
        # Valid states are:
        #   start
        #   migrate
        #   restart
        #   shutdown
        #   stop

        # Conditional pass one - Are we already performing an action
        if self.instart == False \
        and self.inrestart == False \
        and self.inmigrate == False \
        and self.inreceive == False \
        and self.inshutdown == False \
        and self.instop == False:
            # Conditional pass two - Is this VM configured to run on this node
            if self.node == self.this_node.name:
                # Conditional pass three - Is this VM currently running on this node
                if running == libvirt.VIR_DOMAIN_RUNNING:
                    # VM is already running and should be
                    if self.state == "start":
                        # Start the log watcher
                        self.console_log_instance.start()
                        # Add domain to running list
                        self.addDomainToList()
                    # VM is already running and should be but stuck in migrate state
                    elif self.state == "migrate":
                        # Start the log watcher
                        self.console_log_instance.start()
                        zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'start' })
                        # Add domain to running list
                        self.addDomainToList()
                    # VM should be restarted
                    elif self.state == "restart":
                        self.restart_vm()
                    # VM should be shut down
                    elif self.state == "shutdown":
                        self.shutdown_vm()
                    # VM should be stopped
                    elif self.state == "stop":
                        self.stop_vm()
                else:
                    # VM should be started
                    if self.state == "start":
                        # Start the domain
                        self.start_vm()
                    # VM should be migrated to this node
                    elif self.state == "migrate":
                        # Receive the migration
                        self.receive_migrate()
                    # VM should be restarted (i.e. started since it isn't running)
                    if self.state == "restart":
                        zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'start' })
                    # VM should be shut down; ensure it's gone from this node's domain_list
                    elif self.state == "shutdown":
                        self.removeDomainFromList()
                        # Stop the log watcher
                        self.console_log_instance.stop()
                    # VM should be stoped; ensure it's gone from this node's domain_list
                    elif self.state == "stop":
                        self.removeDomainFromList()
                        # Stop the log watcher
                        self.console_log_instance.stop()

            else:
                # Conditional pass three - Is this VM currently running on this node
                if running == libvirt.VIR_DOMAIN_RUNNING:
                    # VM should be migrated away from this node
                    if self.state == "migrate":
                        self.migrate_vm()
                    # VM should be shutdown gracefully
                    elif self.state == 'shutdown':
                        self.shutdown_vm()
                    # VM should be forcibly terminated
                    else:
                        self.terminate_vm()


    # This function is a wrapper for libvirt.lookupByUUID which fixes some problems
    # 1. Takes a text UUID and handles converting it to bytes
    # 2. Try's it and returns a sensible value if not
    def lookupByUUID(self, tuuid):
        # Don't do anything if the VM shouldn't live on this node
        if self.node != self.this_node.name:
            return None

        lv_conn = None
        libvirt_name = "qemu:///system"

        # Convert the text UUID to bytes
        buuid = uuid.UUID(tuuid).bytes

        # Try
        try:
            # Open a libvirt connection
            lv_conn = libvirt.open(libvirt_name)
            if lv_conn == None:
                self.logger.out('Failed to open local libvirt connection', state='e', prefix='Domain {}:'.format(self.domuuid))
                return None

            # Lookup the UUID
            dom = lv_conn.lookupByUUID(buuid)

        # Fail
        except:
            dom = None

        # After everything
        finally:
            # Close the libvirt connection
            if lv_conn != None:
                lv_conn.close()

        # Return the dom object (or None)
        return dom