elastic.py

# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import time
import socket
import os
import six
import logging
import signal
import random

logging.basicConfig(level=os.environ.get('LOGLEVEL', 'INFO').upper())
logger = logging.getLogger("ELASTIC")

ELASTIC_EXIT_CODE = 101


class ElasticStatus:
    COMPLETED = "completed"
    ERROR = "error"
    HOLD = "hold"
    RESTART = "restart"
    EXIT = "exit"


class LauncherInterface(object):
    def __init__(self, args):
        self.args = args
        self.procs = []

    def _terminate_procs(self):
        # try to terminate process by group, this happend in multiprocess senario in user process
        if os.name != 'nt':
            for p in self.procs:
                if p.proc.poll() is None:
                    os.killpg(os.getpgid(p.proc.pid), signal.SIGTERM)
                    if p.log_fn:
                        p.log_fn.close()
                    logger.info("terminate process group gid:{}".format(
                        p.proc.pid))

            time.sleep(1)
        for p in self.procs:
            if p.proc.poll() is None:
                p.proc.terminate()
                if p.log_fn:
                    p.log_fn.close()
                logger.info("terminate process id:{}".format(p.proc.pid))

        for step in range(0, 50):
            alive = False
            for p in self.procs:
                if p.proc.poll() is None:  # not termniate
                    os.kill(p.proc.pid, signal.SIGKILL)
                    alive = True

            if not alive:
                logger.info("terminated all the procs")
                return True

            time.sleep(1)
        return False

    def _check_procs(self):
        alive = False
        result = None
        for p in self.procs:
            ret = p.proc.poll()
            if ret is None:
                alive = True
            elif ret != 0:
                logger.error("ERROR rank {} error with code {}".format(p.rank,
                                                                       ret))
                result = ret
        if not alive and result is None:
            return 0
        else:
            return result

    def launch(self):
        raise NotImplementedError

    def stop(self):
        raise NotImplementedError

    def watch(self):
        raise NotImplementedError


class ElasticManager(object):
    def __init__(self, args):

        self.args = args
        server = args.elastic_server or os.getenv('PADDLE_ELASTIC_SERVER')
        name = args.job_id or os.getenv('PADDLE_ELASTIC_JOB_ID')
        np = args.np or int(os.getenv('PADDLE_ELASTIC_NP', 0))
        host = args.host or os.getenv('POD_IP')
        scale = args.scale or int(os.getenv('PADDLE_ELASTIC_SCALE', 0))
        force = args.force or os.getenv('PADDLE_ELASTIC_FORCE')

        self.endpoints = os.getenv('DISTRIBUTED_TRAINER_ENDPOINTS', '')
        self.trainers = os.getenv('PADDLE_TRAINERS', '')

        self.elastic_level = int(
            os.getenv('PADDLE_ELASTIC_FAULT_TOLERANC_LEVEL', 1))

        # compatible with kuberntes service discovery
        if not server and os.getenv(
                'PADDLE_ELASTIC_ETCD_SERVICE_HOST') and os.getenv(
                    'PADDLE_ELASTIC_ETCD_SERVICE_PORT'):
            server = '{}:{}'.format(
                os.getenv('PADDLE_ELASTIC_ETCD_SERVICE_HOST'),
                os.getenv('PADDLE_ELASTIC_ETCD_SERVICE_PORT'))

        #elastic_timeout = os.getenv('PADDLE_ELASTIC_TIMEOUT',1)

        logger.debug('init with server {} host {}'.format(server, host))

        self.hosts = []
        self.stopped = False

        self.sigint = 0

        if not server or ':' not in server or not name or not np:
            logger.info(
                'Elastic is not enabled with server {} name {} and np {}'.
                format(server, name, np))
            self.enable = False
            return
        else:
            self.enable = True

        import etcd3

        srv, port = server.split(':')
        self.etcd = etcd3.client(host=srv, port=port)
        self.host = host if host else self._get_host()

        # etcd data
        self.prefix = "/paddle/" + name
        self.node_prefix = self.prefix + '/nodes'
        self.np_path = self.prefix + '/np'
        self.endpoints_path = self.prefix + '/endpoints'

        node_tag = ''.join(
            random.choice('abcdefghijklmnopqrstuvwxyz') for _ in range(6))
        self.host_path = '{}/{}{}'.format(self.node_prefix, node_tag,
                                          time.time())

        self.np = np + scale
        '''
        0 group mode, be aware of healthy status of other workers
        1 decouple mode, check own status only
        '''
        self.etcd.put(self.prefix, b'0')

        # host
        # register self host to etcd
        # register watch to reset host after host been deleted
        self.etcd.delete_prefix(self.node_prefix)

        def host_call_back(event):
            if self.etcd.get(self.host_path)[0] == None:
                logger.info('register host again {}'.format(self.host))

                self.etcd.put(self.host_path, six.b(self.host))

        host_watch = self.etcd.add_watch_callback(self.host_path,
                                                  host_call_back)
        self.etcd.put(self.host_path, six.b(self.host))

        # np describes the exact number of nodes to run the job
        inp = int(self.etcd.get(self.np_path)[0] or 0)
        if scale == 0 and not force:
            assert inp == np or inp == 0, "np {} is not consistent with np in etcd {}".format(
                np, inp)
        else:
            assert inp == np or inp == self.np, "np {} scale to {} by {} is not allowed".format(
                inp, self.np, scale)

        self.etcd.put(self.np_path, six.b("%d" % (self.np)))

        def np_call_back(event):
            gnp = int(self.etcd.get(self.np_path)[0])
            if gnp != self.np:
                logger.info("scale np {} to {} ".format(self.np, gnp))
                self.np = gnp

        np_watch = self.etcd.add_watch_callback(self.np_path, np_call_back)

        # endpoints handle DISTRIBUTED_TRAINER_ENDPOINTS and PADDLE_TRAINERS
        self.etcd.put(self.endpoints_path,
                      six.b('{}|{}'.format(self.endpoints, self.trainers)))

        def endpoints_call_back(event):
            if not self.endpoints:
                return
            edps = six.ensure_str(self.etcd.get(self.endpoints_path)[0] or '')
            self.endpoints, self.trainers = edps.split('|')
            logger.info("set DISTRIBUTED_TRAINER_ENDPOINTS {} ".format(
                self.endpoints))
            logger.info("set PADDLE_TRAINERS {} ".format(self.trainers))

        endpoints_watch = self.etcd.add_watch_callback(self.endpoints_path,
                                                       endpoints_call_back)

        self.watches = [host_watch, np_watch, endpoints_watch]

        self.launcher = None

    def exit(self, completed=False):
        logger.info('manager exist completed {}'.format(completed))

        if self.launcher:
            self.launcher.stop()

        if not self.enable:
            return

        if completed:
            self.etcd.put(self.prefix, b'1')

        for watch in self.watches:
            self.etcd.cancel_watch(watch)
        self.etcd.delete(self.host_path)

        hosts = [i for i in self.etcd.get_prefix(self.node_prefix)]
        if len(hosts) == 0:
            self.etcd.delete_prefix(self.prefix)

    def _get_host(self):
        try:
            return socket.gethostbyname(socket.getfqdn(socket.gethostname()))
        except:
            return '127.0.0.1'

    def _completed(self):
        if not self.enable:
            return True

        return int(self.etcd.get(self.prefix)[0]) == 1

    def _match(self):
        self.hosts = [
            six.ensure_str(i[0]) for i in self.etcd.get_prefix(self.node_prefix)
        ]
        if len(self.hosts) == self.np:
            return True
        else:
            return False

    def _update_hosts(self):
        assert len(self.hosts) != 0, 'hosts empty'

        if self.host in self.endpoints:
            os.environ['DISTRIBUTED_TRAINER_ENDPOINTS'] = self.endpoints
            os.environ['PADDLE_TRAINERS'] = self.trainers
            logger.info("update env DISTRIBUTED_TRAINER_ENDPOINTS {} ".format(
                self.endpoints))
            logger.info("update env PADDLE_TRAINERS {} ".format(self.trainers))
            return

        rank = int(os.getenv('PADDLE_TRAINER_ID', -1))
        idx = self.hosts.index(self.host)

        # swap if self.host not in the right position
        if rank >= 0:
            self.hosts[idx] = self.hosts[rank]
            self.hosts[rank] = self.host
        else:
            os.environ['PADDLE_TRAINER_ID'] = '{}'.format(idx)

        hosts = ','.join(self.hosts)
        self.args.ips = hosts
        os.environ['PADDLE_TRAINERS'] = hosts

    def wait(self):
        if not self.enable:
            return

        idx = 1
        while not self.stopped:
            if self._match():
                logger.info('ready with hosts {}'.format(self.hosts))
                self._update_hosts()
                return
            logger.info('not ready for np {} with hosts {}'.format(self.np,
                                                                   self.hosts))

            # reset hosts every 30s to prevent fake deadlock
            if idx % 10 == 0:
                self.etcd.delete_prefix(self.node_prefix)
                logger.info('reset np {} with hosts {}'.format(self.np,
                                                               self.hosts))

            idx += 1
            time.sleep(3)
        return

    def run(self, launcher):
        if self.stopped:
            return

        self.launcher = launcher(self.args)
        self.launcher.launch()

    def watch(self):

        while not self.stopped:
            ret = self.launcher.watch()

            if ret is not None:  # self terminated
                logger.info('job exit with code {}'.format(ret))
                # process is completed if ret >= 0 or error else
                completed = True if ret == 0 else False
                self.exit(completed=completed)
                if completed:
                    return ElasticStatus.COMPLETED
                if self.elastic_level == 1:
                    return ElasticStatus.RESTART
                else:
                    return ElasticStatus.ERROR

            if not self._completed() and not self._match():
                self.launcher.stop()
                return ElasticStatus.HOLD

            time.sleep(2)

        if self.launcher:
            self.launcher.stop()
        return ElasticStatus.EXIT

    def signal_handler(self, sigint, frame):
        if self.enable:
            self.exit()
        self.sigint = sigint
        self.stopped = True