调试Kubernetes事件中的NATS消息

Question

我有一个简单的脚本，它监视Kubernetes事件，然后向NATS服务器发布消息：

#!/usr/bin/env python
import asyncio
import argparse
import json
import logging
import os
from kubernetes import client, config, watch
from nats.aio.client import Client as NATS
from nats.aio.errors import ErrConnectionClosed, ErrTimeout, ErrNoServers
# monkey patch
from kube import local_load_oid_token
config.kube_config.KubeConfigLoader._load_oid_token = local_load_oid_token
parser = argparse.ArgumentParser()
parser.add_argument('--in-cluster', help="use in cluster kubernetes config", action="store_true")
parser.add_argument('-a', '--nats-address', help="address of nats cluster", default=os.environ.get('NATS_ADDRESS', None))
parser.add_argument('-d', '--debug', help="enable debug logging", action="store_true")
parser.add_argument('-p', '--publish-events', help="publish events to NATS", action="store_true")
parser.add_argument('--output-events', help="output all events to stdout", action="store_true", dest='enable_output')
parser.add_argument('--connect-timeout', help="NATS connect timeout (s)", type=int, default=10, dest='conn_timeout')
parser.add_argument('--max-reconnect-attempts', help="number of times to attempt reconnect", type=int, default=1, dest='conn_attempts')
parser.add_argument('--reconnect-time-wait', help="how long to wait between reconnect attempts", type=int, default=10, dest='conn_wait')
args = parser.parse_args()
logger = logging.getLogger('script')
ch = logging.StreamHandler()
if args.debug:
logger.setLevel(logging.DEBUG)
ch.setLevel(logging.DEBUG)
else:
logger.setLevel(logging.INFO)
ch.setLevel(logging.INFO)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
ch.setFormatter(formatter)
logger.addHandler(ch)
if not args.nats_address:
logger.critical("No NATS cluster specified")
exit(parser.print_usage())
else:
logger.debug("Using nats address: %s", args.nats_address)
if args.in_cluster:
config.load_incluster_config()
else:
try:
config.load_kube_config()
except Exception as e:
logger.critical("Error creating Kubernetes configuration: %s", e)
exit(2)
v1 = client.CoreV1Api()

async def run(loop):
nc = NATS()
try:
await nc.connect(args.nats_address, loop=loop, connect_timeout=args.conn_timeout, max_reconnect_attempts=args.conn_attempts, reconnect_time_wait=args.conn_wait)
logger.info("Connected to NATS at %s..." % (nc.connected_url.netloc))
except Exception as e:
exit(e)
#print("Connected to NATS at {}...".format(nc.connected_url.netloc))
async def get_node_events():
w = watch.Watch()
for event in w.stream(v1.list_node):
accepted = ["DELETED"]
if event['type'] in accepted:
logger.info("Event: %s %s %s" % (event['type'], event['object'].kind, event['object'].metadata.name))
msg = {'type':event['type'],'object':event['raw_object']}
logger.debug("Raw Message: %s"  % msg)
await nc.publish("k8s_events", json.dumps(msg).encode('utf-8'))
if args.enable_output:
print(json.dumps(msg))
await get_node_events()
await nc.flush(timeout=3)
await nc.close()


if __name__ == '__main__':
loop = asyncio.get_event_loop()
loop.create_task(run(loop))
try:
loop.run_forever()
except KeyboardInterrupt:
logger.info('keyboard shutdown')
tasks = asyncio.gather(*asyncio.Task.all_tasks(loop=loop), loop=loop, return_exceptions=True)
tasks.add_done_callback(lambda t: loop.stop())
tasks.cancel()
# Keep the event loop running until it is either destroyed or all
# tasks have really terminated
while not tasks.done() and not loop.is_closed():
loop.run_forever()
finally:
logger.info('closing event loop')
loop.close()

在启用事件发布的情况下运行此程序时，我可以看到正在输出的事件JSON。

然而，由于某种原因，我的接收器实际上并没有收到删除事件的NATS消息。

• 如何调试将消息放到主题上？我可以添加什么来验证通过代码将消息放到主题上的消息吗
• 这里的异步逻辑正确吗
• 为什么删除事件不能以这种逻辑进入主题

Answer 1

您可以通过NATS服务器日志验证消息传递。在配置NATS服务器时，使用传递给NATS服务器的-DV标志或NATS配置文件中的临时启用调试/跟踪

debug=true
trace=true 

你应该看到这样的东西：

[31070] 2019/09/10 13:34:40.426198 [DBG] 127.0.0.1:53203 - cid:6 - Client connection created
[31070] 2019/09/10 13:34:40.426582 [TRC] 127.0.0.1:53203 - cid:6 - <<- [CONNECT {"verbose":false,"pedantic":false,"tls_required":false,"name":"NATS Sample Subscriber","lang":"go","version":"1.7.0","protocol":1,"echo":true}]
[31070] 2019/09/10 13:34:40.426614 [TRC] 127.0.0.1:53203 - cid:6 - <<- [PING]
[31070] 2019/09/10 13:34:40.426625 [TRC] 127.0.0.1:53203 - cid:6 - ->> [PONG]
[31070] 2019/09/10 13:34:40.426804 [TRC] 127.0.0.1:53203 - cid:6 - <<- [SUB k8s_events  1]
[31070] 2019/09/10 13:34:40.426821 [TRC] 127.0.0.1:53203 - cid:6 - <<- [PING]
[31070] 2019/09/10 13:34:40.426827 [TRC] 127.0.0.1:53203 - cid:6 - ->> [PONG]
[31070] 2019/09/10 13:34:44.167844 [DBG] ::1:53206 - cid:7 - Client connection created
[31070] 2019/09/10 13:34:44.168352 [TRC] ::1:53206 - cid:7 - <<- [CONNECT {"verbose":false,"pedantic":false,"tls_required":false,"name":"NATS Sample Publisher","lang":"go","version":"1.7.2","protocol":1,"echo":true}]
[31070] 2019/09/10 13:34:44.168383 [TRC] ::1:53206 - cid:7 - <<- [PING]
[31070] 2019/09/10 13:34:44.168390 [TRC] ::1:53206 - cid:7 - ->> [PONG]
[31070] 2019/09/10 13:34:44.168594 [TRC] ::1:53206 - cid:7 - <<- [PUB k8s_events 11]
[31070] 2019/09/10 13:34:44.168607 [TRC] ::1:53206 - cid:7 - <<- MSG_PAYLOAD: ["{json data}"]
[31070] 2019/09/10 13:34:44.168623 [TRC] 127.0.0.1:53203 - cid:6 - ->> [MSG k8s_events 1 11]
[31070] 2019/09/10 13:34:44.168648 [TRC] ::1:53206 - cid:7 - <<- [PING]
[31070] 2019/09/10 13:34:44.168653 [TRC] ::1:53206 - cid:7 - ->> [PONG]

使用连接ID，您可以看到连接ID 7将11个字节发布到k8s_events(协议消息PUB k8s_events 11及其后面的消息有效负载(，连接ID 6(订阅者(接收到消息(MSG k8s_events 1 11(。

这是一种检查客户端是否正在发布消息以及订阅者是否正在收听正确主题的方法。