摘要：我的客户代码通过将消息发布到发布/订阅主题来触发861后台Google Cloud Function。每个Cloud Function都执行一个任务，将结果上传到Google Storage，然后将消息发布到客户端代码正在监听的另一个Pub / Sub主题。尽管执行了所有Cloud Functions（通过Google Storage中的结果数验证），客户端代码不会接收所有消息。
服务器端：我有一个后台Google Cloud Function，每次将消息发布到TRIGGER Pub / Sub主题时都会触发。消息数据的自定义属性根据功能执行特定任务的方式充当功能参数。然后将结果上传到Google Storage中的存储桶，并将一条消息（带有taskID和执行时间详细信息）发布到RESULTS Pub / Sub主题（与用于触发此功能的消息不同）。
客户端：我需要执行861个不同的任务，这需要使用861个稍微不同的输入来调用Cloud Function。这些任务是相似的，云功能执行它们需要20秒钟至2分钟（中位数约为1分钟）。我为此创建了一个python脚本，该脚本是从Google Cloud Shell（或本地计算机Shell）运行的。客户端python脚本向TRIGGER Pub / Sub主题发布861条消息，该消息同时触发了多个Cloud Functions，每个函数都在[0，860]中传递了唯一的taskID。然后，客户端python脚本以“同步提取”方式轮询RESULTS Pub / Sub主题，以查找任何消息。执行任务后，Cloud Function将使用唯一的taskID和计时详细信息将消息发布到RESULTS Pub / Sub主题。客户端使用此唯一的taskID来标识消息来自哪个任务。它还有助于识别被丢弃的重复消息。
基本步骤：
问题：当客户端从RESULTS Pub / Sub主题轮询消息时，我没有收到所有taskID的消息。我确定Cloud Function已被调用并正确执行（我在Google存储桶中有861个结果）。我重复了几次，每次都发生。奇怪的是，每次运行时丢失的taskID的数量都会更改，并且不同的taskID也会丢失。我还跟踪收到的重复taskID的数量。表格中给出了5次独立运行所接收，丢失和重复的唯一taskID的数量。
SN # of Tasks Received Missing Repeated
1 861 860 1 25
2 861 840 21 3
3 861 851 10 1
4 861 837 24 3
5 861 856 5 1
我不确定此问题可能来自何处。考虑到数字的随机性以及缺少的taskID，我怀疑Pub / Sub至少一次传递逻辑中存在一些错误。如果在Cloud Function中，我睡了几秒钟而不是执行任务（例如使用time.sleep（5）），则一切正常（我在客户端收到了所有861 taskID）。
重现此问题的代码。
在下面，main.py与requirements.txt一起作为client.py客户端代码部署为Google Cloud Function 。用100个并发任务运行客户端，python client.py 100该任务重复5次。每次都会丢失不同数量的taskID。
requirements.txt
google-cloud-pubsub
main.py
"""
This file is deployed as Google Cloud Function. This function starts,
sleeps for some seconds and pulishes back the taskID.
Deloyment:
gcloud functions deploy gcf_run --runtime python37 --trigger-topic <TRIGGER_TOPIC> --memory=128MB --timeout=300s
"""
import time
from random import randint
from google.cloud import pubsub_v1
# Global variables
project_id = "<Your Google Cloud Project ID>" # Your Google Cloud Project ID
topic_name = "<RESULTS_TOPIC>" # Your Pub/Sub topic name
def gcf_run(data, context):
"""Background Cloud Function to be triggered by Pub/Sub.
Args:
data (dict): The dictionary with data specific to this type of event.
context (google.cloud.functions.Context): The Cloud Functions event
metadata.
"""
# Message should contain taskID (in addition to the data)
if 'attributes' in data:
attributes = data['attributes']
if 'taskID' in attributes:
taskID = attributes['taskID']
else:
print('taskID missing!')
return
else:
print('attributes missing!')
return
# Sleep for a random time beteen 30 seconds to 1.5 minutes
print("Start execution for {}".format(taskID))
sleep_time = randint(30, 90) # sleep for this many seconds
time.sleep(sleep_time) # sleep for few seconds
# Marks this task complete by publishing a message to Pub/Sub.
data = u'Message number {}'.format(taskID)
data = data.encode('utf-8') # Data must be a bytestring
publisher = pubsub_v1.PublisherClient()
topic_path = publisher.topic_path(project_id, topic_name)
publisher.publish(topic_path, data=data, taskID=taskID)
return
client.py
"""
The client code creates the given number of tasks and publishes to Pub/Sub,
which in turn calls the Google Cloud Functions concurrently.
Run:
python client.py 100
"""
from __future__ import print_function
import sys
import time
from google.cloud import pubsub_v1
# Global variables
project_id = "<Google Cloud Project ID>" # Google Cloud Project ID
topic_name = "<TRIGGER_TOPIC>" # Pub/Sub topic name to publish
subscription_name = "<subscriber to RESULTS_TOPIC>" # Pub/Sub subscription name
num_experiments = 5 # number of times to repeat the experiment
time_between_exp = 120.0 # number of seconds between experiments
# Initialize the Publisher (to send commands that invoke Cloud Functions)
# as well as Subscriber (to receive results written by the Cloud Functions)
# Configure the batch to publish as soon as there is one kilobyte
# of data or one second has passed.
batch_settings = pubsub_v1.types.BatchSettings(
max_bytes=1024, # One kilobyte
max_latency=1, # One second
)
publisher = pubsub_v1.PublisherClient(batch_settings)
topic_path = publisher.topic_path(project_id, topic_name)
subscriber = pubsub_v1.SubscriberClient()
subscription_path = subscriber.subscription_path(
project_id, subscription_name)
class Task:
"""
A task which will execute the Cloud Function once.
Attributes:
taskID (int) : A unique number given to a task (starting from 0).
complete (boolean) : Flag to indicate if this task has completed.
"""
def __init__(self, taskID):
self.taskID = taskID
self.complete = False
def start(self):
"""
Start the execution of Cloud Function by publishing a message with
taskID to the Pub/Sub topic.
"""
data = u'Message number {}'.format(self.taskID)
data = data.encode('utf-8') # Data must be a bytestring
publisher.publish(topic_path, data=data, taskID=str(self.taskID))
def end(self):
"""
Mark the end of this task.
Returns (boolean):
True if normal, False if task was already marked before.
"""
# If this task was not complete, mark it as completed
if not self.complete:
self.complete = True
return True
return False
# [END of Task Class]
def createTasks(num_tasks):
"""
Create a list of tasks and return it.
Args:
num_tasks (int) : Number of tasks (Cloud Function calls)
Returns (list):
A list of tasks.
"""
all_tasks = list()
for taskID in range(0, num_tasks):
all_tasks.append(Task(taskID=taskID))
return all_tasks
def receiveResults(all_tasks):
"""
Receives messages from the Pub/Sub subscription. I am using a blocking
Synchronous Pull instead of the usual asynchronous pull with a callback
funtion as I rely on a polling pattern to retrieve messages.
See: https://cloud.google.com/pubsub/docs/pull
Args:
all_tasks (list) : List of all tasks.
"""
num_tasks = len(all_tasks)
total_msg_received = 0 # track the number of messages received
NUM_MESSAGES = 10 # maximum number of messages to pull synchronously
TIMEOUT = 600.0 # number of seconds to wait for response (10 minutes)
# Keep track of elapsed time and exit if > TIMEOUT
__MyFuncStartTime = time.time()
__MyFuncElapsedTime = 0.0
print('Listening for messages on {}'.format(subscription_path))
while (total_msg_received < num_tasks) and (__MyFuncElapsedTime < TIMEOUT):
# The subscriber pulls a specific number of messages.
response = subscriber.pull(subscription_path,
max_messages=NUM_MESSAGES, timeout=TIMEOUT, retry=None)
ack_ids = []
# Keep track of all received messages
for received_message in response.received_messages:
if received_message.message.attributes:
attributes = received_message.message.attributes
taskID = int(attributes['taskID'])
if all_tasks[taskID].end():
# increment count only if task completes the first time
# if False, we received a duplicate message
total_msg_received += 1
# print("Received taskID = {} ({} of {})".format(
# taskID, total_msg_received, num_tasks))
# else:
# print('REPEATED: taskID {} was already marked'.format(taskID))
else:
print('attributes missing!')
ack_ids.append(received_message.ack_id)
# Acknowledges the received messages so they will not be sent again.
if ack_ids:
subscriber.acknowledge(subscription_path, ack_ids)
time.sleep(0.2) # Wait 200 ms before polling again
__MyFuncElapsedTime = time.time() - __MyFuncStartTime
# print("{} s elapsed. Listening again.".format(__MyFuncElapsedTime))
# if total_msg_received != num_tasks, function exit due to timeout
if total_msg_received != num_tasks:
print("WARNING: *** Receiver timed out! ***")
print("Received {} messages out of {}. Done.".format(
total_msg_received, num_tasks))
def main(num_tasks):
"""
Main execution point of the program
"""
for experiment_num in range(1, num_experiments + 1):
print("Starting experiment {} of {} with {} tasks".format(
experiment_num, num_experiments, num_tasks))
# Create all tasks and start them
all_tasks = createTasks(num_tasks)
for task in all_tasks: # Start all tasks
task.start()
print("Published {} taskIDs".format(num_tasks))
receiveResults(all_tasks) # Receive message from Pub/Sub subscription
print("Waiting {} seconds\n\n".format(time_between_exp))
time.sleep(time_between_exp) # sleep between experiments
if __name__ == "__main__":
if(len(sys.argv) != 2):
print("usage: python client.py <num_tasks>")
print(" num_tasks: Number of concurrent Cloud Function calls")
sys.exit()
num_tasks = int(sys.argv[1])
main(num_tasks)
在您的云功能中，此行：
Publisher.publish（topic_path，data = data，taskID = taskID）
您不是在等待Publisher.publish返回的未来。这意味着您无法保证当您离开该gcf_run函数的结尾时，实际上已经在该主题上进行了发布，但是无论如何，TRIGGER主题云函数订阅上的消息还是会被确认。
相反，要等到发布发生云功能终止时，这应该是：
publisher.publish(topic_path, data=data, taskID=taskID).result()
您还应该避免在每次函数调用时启动和关闭发布者客户端，而应将客户端作为全局变量。
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