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server_job.py
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server_job.py
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# Copyright 2016 Google, Inc.
#
# 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 random
from server import Server
# ServerJob mimicks a Borg job with a number of tasks. It creates
# the required number of Server (task) instances and provides
# access to them. It also implements some methods that affect
# the entire job, such as triggering a master election.
class ServerJob(object):
all_server_jobs_list = list()
def __init__(self, job_name, level, size, downstream_job=None):
self.size = size
self.tasks = dict()
self.master = None
self.job_name = job_name
for i in range(0, size):
s = Server(self, job_name, level, downstream_job)
self.tasks[s.get_server_id()] = s
self.trigger_master_election()
ServerJob.all_server_jobs_list.append(self)
# Iterator over all server jobs. Used for gathering reporting stats.
@classmethod
def all_server_jobs(self):
for job in self.all_server_jobs_list:
yield job
# Returns a random job.
@classmethod
def get_random_server_job(self):
return self.all_server_jobs_list[random.randint(
0,
len(
self.all_server_jobs_list) -
1)]
def get_job_name(self):
return self.job_name
# Returns the current master in the job.
def get_master(self):
return self.master
# Returns a task by name.
def get_task_by_name(self, name):
return self.tasks[name]
# Returns a random task. Used by a client to find a server to
# send the Discovery RPC to. Mimicks a Stubby BNS channel.
def get_random_task(self):
return self.tasks.values()[random.randint(0, self.size - 1)]
# Instructs the job to lose the current master. No new master
# will be elected. Used to simulate an event where the master
# goes away and electing a new master takes some time.
def lose_master(self):
self.master.lose_mastership()
self.master = None
# Triggers a master election. A new master is randomly selected
# from the tasks in the job.
# Note: The old master might stay the master.
def trigger_master_election(self):
old_master = self.master
self.master = self.get_random_task()
# Nothing to be done. The intended master is already the master.
if old_master is self.master:
assert self.master.is_master()
return
if old_master:
old_master.lose_mastership()
self.master.become_master()