uncloud/scheduler/main.py

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# TODO
# 1. send an email to an email address defined by env['admin-email']
# if resources are finished
# 2. Introduce a status endpoint of the scheduler -
# maybe expose a prometheus compatible output
import logging
from ucloud_common.request import RequestEntry, RequestType
from config import etcd_client as client
from config import (host_pool, request_pool, vm_pool, request_prefix)
from helper import (get_suitable_host, dead_host_mitigation, dead_host_detection,
assign_host, NoSuitableHostFound)
def main():
pending_vms = []
for request_iterator in [
client.get_prefix(request_prefix, value_in_json=True),
client.watch_prefix(request_prefix, timeout=5, value_in_json=True),
]:
for request_event in request_iterator:
request_entry = RequestEntry(request_event)
logging.debug("%s, %s", request_entry.key, request_entry.value)
# Never Run time critical mechanism inside timeout
# mechanism because timeout mechanism only comes
# when no other event is happening. It means under
# heavy load there would not be a timeout event.
if request_entry.type == "TIMEOUT":
# Detect hosts that are dead and set their status
# to "DEAD", and their VMs' status to "KILLED"
logging.debug("TIMEOUT event occured")
dead_hosts = dead_host_detection()
logging.debug("Dead hosts: %s", dead_hosts)
dead_host_mitigation(dead_hosts)
# If there are VMs that weren't assigned a host
# because there wasn't a host available which
# meets requirement of that VM then we would
# create a new ScheduleVM request for that VM
# on our behalf.
while pending_vms:
pending_vm_entry = pending_vms.pop()
r = RequestEntry.from_scratch(type="ScheduleVM",
uuid=pending_vm_entry.uuid,
hostname=pending_vm_entry.hostname)
request_pool.put(r)
elif request_entry.type == RequestType.ScheduleVM:
vm_entry = vm_pool.get(request_entry.uuid)
client.client.delete(request_entry.key) # consume Request
# If the Request is about a VM which is labelled as "migration"
# and has a destination
if hasattr(request_entry, "migration") and request_entry.migration \
and hasattr(request_entry, "destination") and request_entry.destination:
try:
get_suitable_host(vm_specs=vm_entry.specs,
hosts=[host_pool.get(request_entry.destination)])
except NoSuitableHostFound:
logging.info("Requested destination host doesn't have enough capacity"
"to hold %s", vm_entry.uuid)
else:
r = RequestEntry.from_scratch(type=RequestType.InitVMMigration,
uuid=request_entry.uuid,
destination=request_entry.destination)
request_pool.put(r)
# If the Request is about a VM that just want to get started/created
else:
# assign_host only returns None when we couldn't be able to assign
# a host to a VM because of resource constraints
try:
assign_host(vm_entry)
except NoSuitableHostFound:
vm_entry.log.append("Can't schedule VM. No Resource Left.")
vm_pool.put(vm_entry)
pending_vms.append(vm_entry)
logging.info("No Resource Left. Emailing admin....")
logging.info("%s SESSION STARTED %s", '*' * 5, '*' * 5)
main()