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June 20, 2019 16:55
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NATS Streaming Reconnect Example
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# Copyright 2016-2018 The NATS Authors | |
# 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 asyncio | |
from nats.aio.client import Client as NATS | |
from stan.aio.client import Client as STAN | |
class Component(): | |
def __init__(self, loop=None): | |
self.sc = None | |
self.nc = None | |
self._start_seq = 0 | |
async def conn_lost_cb(err): | |
print("Connection lost:", err) | |
for i in range(0, 100): | |
try: | |
print("Reconnecting...") | |
await self.connect() | |
except Exception as e: | |
print("Error", e, type(e)) | |
continue | |
break | |
self._stan_conn_lost_cb = conn_lost_cb | |
self._loop = loop | |
async def connect(self): | |
print("Connecting...") | |
self.nc = NATS() | |
await self.nc.connect(loop=self._loop) | |
self.sc = STAN() | |
await self.sc.connect("test-cluster", "client-123", | |
nats=self.nc, | |
ping_interval=1, | |
ping_max_out=5, | |
conn_lost_cb=self._stan_conn_lost_cb, | |
loop=self._loop, | |
) | |
async def cb(msg): | |
if msg.seq == self._start_seq: | |
print("Redelivery after reconnect, skipping... (seq={})".format(msg.seq)) | |
return | |
print("Received a message (seq={}): {}".format(msg.seq, msg.data)) | |
self._start_seq = msg.seq | |
await self.sc.subscribe("hi", | |
start_at='sequence', | |
cb=cb, | |
sequence=self._start_seq, | |
) | |
async def run(loop): | |
c = Component(loop=loop) | |
await c.connect() | |
for i in range(0, 10000): | |
try: | |
await c.sc.publish("hi", ('hello world: %d' % i).encode()) | |
except Exception as e: | |
print("Error during publishing:", e) | |
await asyncio.sleep(1, loop=loop) | |
await self.sc.close() | |
await self.nc.close() | |
if __name__ == '__main__': | |
loop = asyncio.get_event_loop() | |
loop.run_until_complete(run(loop)) | |
loop.run_forever() | |
loop.close() |
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Running NATS and NATS Streaming server as separate processes: