Files
patroni/features/steps/patroni_api.py
T
Ants AasmaandOleksii Kliukin 7e53a604d4 Add synchronous replication support. (#314)
Adds a new configuration variable synchronous_mode. When enabled Patroni will manage synchronous_standby_names to enable synchronous replication whenever there are healthy standbys available. With synchronous mode enabled Patroni will automatically fail over only to a standby that was synchronously replicating at the time of master failure. This effectively means zero lost user visible transactions.

To enforce the synchronous failover guarantee Patroni stores current synchronous replication state in the DCS, using strict ordering, first enable synchronous replication, then publish the information. Standby can use this to verify that it was indeed a synchronous standby before master failed and is allowed to fail over.

We can't enable multiple standbys as synchronous, allowing PostreSQL to pick one because we can't know which one was actually set to be synchronous on the master when it failed. This means that on standby failure commits will be blocked on the master until next run_cycle iteration. TODO: figure out a way to poke Patroni to run sooner or allow for PostgreSQL to pick one without the possibility of lost transactions.

On graceful shutdown standbys will disable themselves by setting a nosync tag for themselves and waiting for the master to notice and pick another standby. This adds a new mechanism for Ha to publish dynamic tags to the DCS.

When the synchronous standby goes away or disconnects a new one is picked and Patroni switches master over to the new one. If no synchronous standby exists Patroni disables synchronous replication (synchronous_standby_names=''), but not synchronous_mode. In this case, only the node that was previously master is allowed to acquire the leader lock.

Added acceptance tests and documentation.

Implementation by @ants with extensive review by @CyberDem0n.
2016-10-19 16:12:51 +02:00

157 lines
5.8 KiB
Python

import json
import os
import parse
import pytz
import requests
import shlex
import subprocess
import time
import yaml
from behave import register_type, step, then
from datetime import datetime, timedelta
@parse.with_pattern(r'https?://(?:\w|\.|:|/)+')
def parse_url(text):
return text
register_type(url=parse_url)
# there is no way we can find out if the node has already
# started as a leader without checking the DCS. We cannot
# just rely on the database availability, since there is
# a short gap between the time PostgreSQL becomes available
# and Patroni assuming the leader role.
@step('{name:w} is a leader after {time_limit:d} seconds')
@then('{name:w} is a leader after {time_limit:d} seconds')
def is_a_leader(context, name, time_limit):
time_limit *= context.timeout_multiplier
max_time = time.time() + int(time_limit)
while (context.dcs_ctl.query("leader") != name):
time.sleep(1)
assert time.time() < max_time, "{0} is not a leader in dcs after {1} seconds".format(name, time_limit)
@step('I sleep for {value:d} seconds')
def sleep_for_n_seconds(context, value):
time.sleep(int(value))
def _set_response(context, response):
context.status_code = response.status_code
data = response.content.decode('utf-8')
ct = response.headers.get('content-type', '')
if ct.startswith('application/json') or\
ct.startswith('text/yaml') or\
ct.startswith('text/x-yaml') or\
ct.startswith('application/yaml') or\
ct.startswith('application/x-yaml'):
try:
context.response = yaml.safe_load(data)
except ValueError:
context.response = data
else:
context.response = data
@step('I issue a GET request to {url:url}')
def do_get(context, url):
try:
r = requests.get(url)
except requests.exceptions.RequestException:
context.status_code = None
context.response = None
else:
_set_response(context, r)
@step('I issue an empty POST request to {url:url}')
def do_post_empty(context, url):
do_request(context, 'POST', url, None)
@step('I issue a {request_method:w} request to {url:url} with {data}')
def do_request(context, request_method, url, data):
data = data and json.loads(data) or {}
try:
if request_method == 'PATCH':
r = requests.patch(url, json=data)
else:
r = requests.post(url, json=data)
except requests.exceptions.RequestException:
context.status_code = None
context.response = None
else:
_set_response(context, r)
@step('I run {cmd}')
def do_run(context, cmd):
cmd = ['coverage', 'run', '--source=patroni', '-p'] + shlex.split(cmd)
try:
# XXX: Dirty hack! We need to take name/passwd from the config!
env = os.environ.copy()
env.update({'PATRONI_RESTAPI_USERNAME': 'username', 'PATRONI_RESTAPI_PASSWORD': 'password'})
response = subprocess.check_output(cmd, stderr=subprocess.STDOUT, env=env)
context.status_code = 0
except subprocess.CalledProcessError as e:
response = e.output
context.status_code = e.returncode
context.response = response.decode('utf-8').strip()
@then('I receive a response {component:w} {data}')
def check_response(context, component, data):
if component == 'code':
assert context.status_code == int(data),\
"status code {0} != {1}, response: {2}".format(context.status_code, data, context.response)
elif component == 'returncode':
assert context.status_code == int(data), "return code {0} != {1}".format(context.status_code, data)
elif component == 'text':
assert context.response == data.strip('"'), "response {0} does not contain {1}".format(context.response, data)
elif component == 'output':
assert data.strip('"') in context.response, "response {0} does not contain {1}".format(context.response, data)
else:
assert component in context.response, "{0} is not part of the response".format(component)
assert str(context.response[component]) == str(data), "{0} does not contain {1}".format(component, data)
@step('I issue a scheduled failover from {from_host:w} to {to_host:w} in {in_seconds:d} seconds')
def scheduled_failover(context, from_host, to_host, in_seconds):
context.execute_steps(u"""
Given I run patronictl.py failover batman --master {0} --candidate {1} --scheduled "{2}" --force
""".format(from_host, to_host, datetime.now(pytz.utc) + timedelta(seconds=int(in_seconds))))
@step('I issue a scheduled restart at {url:url} in {in_seconds:d} seconds with {data}')
def scheduled_restart(context, url, in_seconds, data):
data = data and json.loads(data) or {}
data.update(schedule='{0}'.format((datetime.now(pytz.utc) + timedelta(seconds=int(in_seconds))).isoformat()))
context.execute_steps(u"""Given I issue a POST request to {0}/restart with {1}""".format(url, json.dumps(data)))
@step('I add tag {tag:w} {value:w} to {pg_name:w} config')
def add_tag_to_config(context, tag, value, pg_name):
context.pctl.add_tag_to_config(pg_name, tag, value)
@then('Response on GET {url} contains {value} after {timeout:d} seconds')
def check_http_response(context, url, value, timeout, negate=False):
timeout *= context.timeout_multiplier
for _ in range(int(timeout)):
r = requests.get(url)
if (value in r.content.decode('utf-8')) != negate:
break
time.sleep(1)
else:
assert False,\
"Value {0} is {1} present in response after {2} seconds".format(value, "not" if not negate else "", timeout)
@then('Response on GET {url} does not contain {value} after {timeout:d} seconds')
def check_not_in_http_response(context, url, value, timeout):
check_http_response(context, url, value, timeout, negate=True)