How can I remove messages from an ActiveMQ queue using Python? - activemq

Question

I have an ActiveMQ queue which has several messages that were sent using persistent set to true. When I create a subscriber in Python to read the queue, I get all of the messages in the queue. The next time I open the subscriber, I get all of the same messages. I adjusted the code that writes to the queue to set persistent to false, but the message remains in the queue. Have I neglected to send an acknowledgement?
The code is written using Python 2.7 because that's what our customer is using. I'd love to upgrade them, but I don't have the time.
Here's the script that reads the queue:
import socket
import threading
import xml.etree.ElementTree as etree
from xml.dom import minidom # for pretty printing
# import SampleXML
import sys
import os
import math
import time
from time import monotonic
import string
import stomp # for queue support
import platform
class ConnectionListener(stomp.ConnectionListener):
def __init__(self, connection):
self.connection = connection
print ("Listener created")
def on_message(self, message):
print ("Received message with body ") + message.body
class Reader:
def __init__(self):
pass
def ConnectToQueue(self):
#For Production
user = os.getenv("ACTIVEMQ_USER") or "worthington"
#user = os.getenv("ACTIVEMQ_USER") or "worthington_test"
password = os.getenv("ACTIVEMQ_PASSWORD") or "level3"
host = os.getenv("ACTIVEMQ_HOST") or "localhost"
port = os.getenv("ACTIVEMQ_PORT") or 61613
# destination = sys.argv[1:2] or ["/topic/event"]
# destination = destination[0]
dest = "from_entec_test"
#For Production
# dest = "from_entec"
try:
conn = stomp.Connection10(host_and_ports = [(host, port)])
conn.set_listener('message', ConnectionListener(conn))
# conn.start()
# subscribe_id = '-'.join(map(str, (platform.node(), os.getppid(), os.getpid())))
conn.connect(login=user,passcode=password)
subscribe_id = "Queue Test Listener"
conn.subscribe(destination=dest, id=subscribe_id, ack='client-individual')
conn.unsubscribe(id=subscribe_id)
conn.disconnect()
except Exception as error:
reason = str(error)
print("Exception when readig data from queue: " + str(error))
pass
if __name__ == "__main__" :
try:
UploadData = Reader()
UploadData.ConnectToQueue()
print ("Reader finished.")
except Exception as Value:
reason = str(Value)
pass
And here's the code that writes to it:
import socket
import threading
import xml.etree.ElementTree as etree
from xml.dom import minidom # for pretty printing
# import SampleXML
import sys
import os
import math
import time
from time import monotonic
import string
import stomp # for queue support
import platform
class ConnectionListener(stomp.ConnectionListener):
def __init__(self, connection):
self.connection = connection
print "Listener created"
def on_message(self, message):
print "Received message with body " + message.body
class UploadData:
def __init__(self):
pass
def ConnectToQueue(self):
#For Production
user = os.getenv("ACTIVEMQ_USER") or "worthington"
#user = os.getenv("ACTIVEMQ_USER") or "worthington_test"
password = os.getenv("ACTIVEMQ_PASSWORD") or "level3"
host = os.getenv("ACTIVEMQ_HOST") or "localhost"
port = os.getenv("ACTIVEMQ_PORT") or 61613
# destination = sys.argv[1:2] or ["/topic/event"]
# destination = destination[0]
dest = "from_entec_test"
#For Production
# dest = "from_entec"
try:
conn = stomp.Connection10(host_and_ports = [(host, port)])
# conn.start()
# subscribe_id = '-'.join(map(str, (platform.node(), os.getppid(), os.getpid())))
subscribe_id = "Queue Test Listener"
conn.connect(login=user,passcode=password)
message = "This is a test message."
conn.send(dest, message, persistent='true')
print "Sent message containing: " + message
conn.disconnect()
except Exception, error:
reason = str(error)
print "Exception when writing data to queue: " + str(error)
pass
if __name__ == "__main__" :
try:
UploadData = UploadData()
UploadData.ConnectToQueue()
except Exception, Value:
reason = str(Value)
print "Main routine exception: " + str(Value)
pass

Answer 1

I'm not very familiar with Python STOMP clients but from the code you appear to be subscribing using the 'client-individual' mode of STOMP which means that each message you receive requires you to send an ACK frame back with the message Id value so that the remote can mark it as consumed. Since you are not doing that the messages will not be removed from the Queue.
As an alternative you can use the 'auto' acknowledgement mode which marks the message as consumed as soon as the broker dispatches them. To understand the STOMP subscription model please refer to the STOMP specification.