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Refactor exceptions handling in etcd.py and ha.py

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update_leader can throw EtcdError exception
unused HealthiestMemberError exception is removed
This commit is contained in:
Alexander Kukushkin
2015-05-24 15:40:36 +02:00
parent 188741de5a
commit 8dd99170bf
5 changed files with 75 additions and 30 deletions
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helpers/errors.py
-4
View File
@@ -9,7 +9,3 @@ class EtcdError(Exception):
class CurrentLeaderError(EtcdError):
pass
class HealthiestMemberError(EtcdError):
pass
helpers/etcd.py
+34 -18
View File
@@ -2,12 +2,12 @@ import logging
import requests
import time
from requests.exceptions import RequestException
from collections import namedtuple
from helpers.errors import CurrentLeaderError, EtcdError
logger = logging.getLogger(__name__)
Member = namedtuple('Member', 'hostname,address,ttl')
@@ -35,7 +35,7 @@ class Etcd:
response = requests.get(self.client_url(path))
if response.status_code == 200:
break
except Exception as e:
except RequestException as e:
logger.exception('get_client_path')
ex = e
@@ -54,15 +54,15 @@ class Etcd:
try:
response = requests.put(self.client_url(path), data=data)
return response.status_code in [200, 201, 202, 204]
except:
except RequestException:
logger.exception('PUT %s data=%s', path, data)
return False
raise EtcdError('Etcd is not responding properly')
def delete_client_path(self, path):
try:
response = requests.delete(self.client_url(path))
return response.status_code in [200, 202, 204]
except:
except RequestException:
logger.exception('DELETE %s', path)
return False
@@ -108,7 +108,7 @@ class Etcd:
leader = m
break
if not leader:
leader = Member(leader['value'], None, None)
leader = Member(node['value'], None, None)
return Cluster(leader, last_leader_operation, members)
elif status_code == 404:
@@ -122,27 +122,43 @@ class Etcd:
try:
cluster = self.get_cluster()
return None if cluster.is_unlocked() else cluster.leader
except:
raise CurrentLeaderError("Etcd is not responding properly")
except EtcdError:
raise CurrentLeaderError('Etcd is not responding properly')
def touch_member(self, member, connection_string):
return self.put_client_path('/members/' + member, value=connection_string, ttl=self.member_ttl)
def touch_member(self, member, connection_string, ttl=None):
try:
return self.put_client_path('/members/' + member, value=connection_string, ttl=ttl or self.member_ttl)
except EtcdError:
return False
def take_leader(self, value):
return self.put_client_path('/leader', value=value, ttl=self.ttl)
try:
return self.put_client_path('/leader', value=value, ttl=self.ttl)
except EtcdError:
return False
def attempt_to_acquire_leader(self, value):
ret = self.put_client_path('/leader', value=value, ttl=self.ttl, prevExist=False)
ret or logger.info('Could not take out TTL lock')
return ret
try:
ret = self.put_client_path('/leader', value=value, ttl=self.ttl, prevExist=False)
ret or logger.info('Could not take out TTL lock')
return ret
except EtcdError:
return False
def update_leader(self, state_handler):
ret = self.put_client_path('/leader', value=state_handler.name, ttl=self.ttl, prevValue=state_handler.name)
ret and self.put_client_path('/optime/leader', value=state_handler.last_operation())
return ret
if self.put_client_path('/leader', value=state_handler.name, ttl=self.ttl, prevValue=state_handler.name):
try:
self.put_client_path('/optime/leader', value=state_handler.last_operation())
except EtcdError:
pass
return True
return False
def race(self, path, value):
return self.put_client_path(path, value=value, prevExist=False)
try:
return self.put_client_path(path, value=value, prevExist=False)
except EtcdError:
return False
def delete_member(self, member):
return self.delete_client_path('/members/' + member)
helpers/ha.py
+1 -3
View File
@@ -1,6 +1,6 @@
import logging
from helpers.errors import EtcdError, HealthiestMemberError
from helpers.errors import EtcdError
from psycopg2 import InterfaceError, OperationalError
logger = logging.getLogger(__name__)
@@ -94,5 +94,3 @@ class Ha:
return 'demoted self because etcd is not accessible and i was a leader'
except (InterfaceError, OperationalError):
logger.error('Error communicating with Postgresql. Will try again')
except HealthiestMemberError:
logger.error('failed to determine healthiest member fromt etcd')
tests/test_etcd.py
+39 -5
View File
@@ -17,28 +17,39 @@ class MockResponse:
return json.loads(self.content)
class MockPostgresql:
name = ''
def last_operation(self):
return 0
def requests_get(url, **kwargs):
if url.startswith('http://local'):
raise Exception()
raise requests.exceptions.RequestException()
response = MockResponse()
if url.startswith('http://remote'):
response.content = '{"action":"get","node":{"key":"/service/batman5","dir":true,"nodes":[{"key":"/service/batman5/initialize","value":"postgresql0","modifiedIndex":1582,"createdIndex":1582},{"key":"/service/batman5/leader","value":"postgresql1","expiration":"2015-05-15T09:11:00.037397538Z","ttl":21,"modifiedIndex":20728,"createdIndex":20434},{"key":"/service/batman5/optime","dir":true,"nodes":[{"key":"/service/batman5/optime/leader","value":"2164261704","modifiedIndex":20729,"createdIndex":20729}],"modifiedIndex":20437,"createdIndex":20437},{"key":"/service/batman5/members","dir":true,"nodes":[{"key":"/service/batman5/members/postgresql1","value":"postgres://replicator:[email protected]:5434/postgres","expiration":"2015-05-15T09:10:59.949384522Z","ttl":21,"modifiedIndex":20727,"createdIndex":20727},{"key":"/service/batman5/members/postgresql0","value":"postgres://replicator:[email protected]:5433/postgres","expiration":"2015-05-15T09:11:09.611860899Z","ttl":30,"modifiedIndex":20730,"createdIndex":20730}],"modifiedIndex":1581,"createdIndex":1581}],"modifiedIndex":1581,"createdIndex":1581}}'
elif url.startswith('http://other'):
response.status_code = 404
elif url.startswith('http://noleader'):
response.content = '{"action":"get","node":{"key":"/service/batman5","dir":true,"nodes":[{"key":"/service/batman5/initialize","value":"postgresql0","modifiedIndex":1582,"createdIndex":1582},{"key":"/service/batman5/leader","value":"postgresql1","expiration":"2015-05-15T09:11:00.037397538Z","ttl":21,"modifiedIndex":20728,"createdIndex":20434},{"key":"/service/batman5/optime","dir":true,"nodes":[{"key":"/service/batman5/optime/leader","value":"2164261704","modifiedIndex":20729,"createdIndex":20729}],"modifiedIndex":20437,"createdIndex":20437},{"key":"/service/batman5/members","dir":true,"nodes":[{"key":"/service/batman5/members/postgresql0","value":"postgres://replicator:[email protected]:5433/postgres","expiration":"2015-05-15T09:11:09.611860899Z","ttl":30,"modifiedIndex":20730,"createdIndex":20730}],"modifiedIndex":1581,"createdIndex":1581}],"modifiedIndex":1581,"createdIndex":1581}}'
return response
def requests_put(url, **kwargs):
if url.startswith('http://local'):
raise Exception()
if url.startswith('http://local') or '/optime/leader' in url:
raise requests.exceptions.RequestException()
response = MockResponse()
response.status_code = 201
if url.startswith('http://other'):
response.status_code = 404
return response
def requests_delete(url):
if url.startswith('http://local'):
raise Exception()
raise requests.exceptions.RequestException()
response = MockResponse()
response.status_code = 204
return response
@@ -65,7 +76,7 @@ class TestEtcd(unittest.TestCase):
self.assertRaises(Exception, self.etcd.get_client_path, '', 2)
def test_put_client_path(self):
self.assertFalse(self.etcd.put_client_path(''))
self.assertRaises(EtcdError, self.etcd.put_client_path, '')
def test_delete_client_path(self):
self.assertFalse(self.etcd.delete_client_path(''))
@@ -77,6 +88,29 @@ class TestEtcd(unittest.TestCase):
self.assertIsInstance(cluster, Cluster)
self.etcd.base_client_url = self.etcd.base_client_url.replace('remote', 'other')
self.etcd.get_cluster()
self.etcd.base_client_url = self.etcd.base_client_url.replace('other', 'noleader')
self.etcd.get_cluster()
def test_current_leader(self):
self.assertRaises(CurrentLeaderError, self.etcd.current_leader)
def test_touch_member(self):
self.assertFalse(self.etcd.touch_member('', ''))
def test_take_leader(self):
self.assertFalse(self.etcd.take_leader(''))
def test_attempt_to_acquire_leader(self):
self.assertFalse(self.etcd.attempt_to_acquire_leader(''))
def test_update_leader(self):
self.etcd.base_client_url = self.etcd.base_client_url.replace('local', 'remote')
self.assertTrue(self.etcd.update_leader(MockPostgresql()))
self.etcd.base_client_url = self.etcd.base_client_url.replace('remote', 'other')
self.assertFalse(self.etcd.update_leader(MockPostgresql()))
def test_race(self):
self.assertFalse(self.etcd.race('', ''))
def test_delete_member(self):
self.assertFalse(self.etcd.delete_member(''))
tests/test_ha.py
+1
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@@ -72,6 +72,7 @@ class TestHa(unittest.TestCase):
self.p = MockPostgresql()
self.e = Etcd({'ttl': 30, 'host': 'remotehost', 'scope': 'test'})
self.ha = Ha(self.p, self.e)
self.ha.load_cluster_from_etcd()
self.ha.cluster = Cluster(None, None, [])
self.ha.load_cluster_from_etcd = nop