[ironic] [oslo] ironic overloading notifications for internal messaging
Hi,
I’ve been chasing a bug in ironic’s neutron agent for the last few days and I think its time to ask for some advice.
Specifically, I was asked to debug why a set of controllers was using so much RAM, and the answer was that rabbitmq had a queue called ironic-neutron-agent-heartbeat.info with 800,000 messages enqueued. This notification queue is used by ironic’s neutron agent to calculate the hash ring. I have been able to duplicate this issue in a stock kolla-ansible install with ironic turned on but no bare metal nodes enrolled in ironic. About 0.6 messages are queued per second.
I added some debugging code (hence the thread yesterday about mangling the code kolla deploys), and I can see that the messages in the queue are being read by the ironic neutron agent and acked correctly. However, they are not removed from the queue.
You can see your queue size while using kolla with this command:
docker exec rabbitmq rabbitmqctl list_queues messages name messages_ready consumers | sort -n | tail -1
My stock install that’s been running for about 12 hours currently has 8,244 messages in that queue.
Where I’m a bit stumped is I had assumed that the messages weren’t being acked correctly, which is not the case. Is there something obvious about notification queues like them being persistent that I’ve missed in my general ignorance of the underlying implementation of notifications?
Thanks, Michael
On Tue, 2019-02-05 at 09:54 +1100, Michael Still wrote:
Hi,
I’ve been chasing a bug in ironic’s neutron agent for the last few days and I think its time to ask for some advice.
I'm working on the same issue. (In fact there are two issues.)
Specifically, I was asked to debug why a set of controllers was using so much RAM, and the answer was that rabbitmq had a queue called ironic-neutron-agent-heartbeat.info with 800,000 messages enqueued. This notification queue is used by ironic’s neutron agent to calculate the hash ring. I have been able to duplicate this issue in a stock kolla-ansible install with ironic turned on but no bare metal nodes enrolled in ironic. About 0.6 messages are queued per second.
I added some debugging code (hence the thread yesterday about mangling the code kolla deploys), and I can see that the messages in the queue are being read by the ironic neutron agent and acked correctly. However, they are not removed from the queue.
You can see your queue size while using kolla with this command:
docker exec rabbitmq rabbitmqctl list_queues messages name messages_ready consumers | sort -n | tail -1
My stock install that’s been running for about 12 hours currently has 8,244 messages in that queue.
Where I’m a bit stumped is I had assumed that the messages weren’t being acked correctly, which is not the case. Is there something obvious about notification queues like them being persistent that I’ve missed in my general ignorance of the underlying implementation of notifications?
I opened a oslo.messaging bug[1] yesterday. When using notifications and all consumers use one or more pools. The ironic-neutron-agent does use pools for all listeners in it's hash-ring member manager. And the result is that notifications are published to the 'ironic-neutron- agent-heartbeat.info' queue and they are never consumed.
The second issue, each instance of the agent uses it's own pool to ensure all agents are notified about the existance of peer-agents. The pools use a uuid that is generated at startup (and re-generated on restart, stop/start etc). In the case where `[oslo_messaging_rabbit]/amqp_auto_delete = false` in neutron config these uuid queues are not automatically removed. So after a restart of the ironic-neutron-agent the queue with the old UUID is left in the message broker without no consumers, growing ...
I intend to push patches to fix both issues. As a workaround (or the permanent solution) will create another listener consuming the notifications without a pool. This should fix the first issue.
Second change will set amqp_auto_delete for these specific queues to 'true' no matter. What I'm currently stuck on here is that I need to change the control_exchange for the transport. According to oslo.messaging documentation it should be possible to override the control_exchange in the transport_url[3]. The idea is to set amqp_auto_delete and a ironic-neutron-agent specific exchange on the url when setting up the transport for notifications, but so far I belive the doc string on the control_exchange option is wrong.
NOTE: The second issue can be worked around by stopping and starting rabbitmq as a dependency of the ironic-neutron-agent service. This ensure only queues for active agent uuid's are present, and those queues will be consumed.
-- Harald Jensås
[1] https://bugs.launchpad.net/oslo.messaging/+bug/1814544 [2] https://storyboard.openstack.org/#!/story/2004933 [3] https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/trans...
Cool thanks for the summary. You seem to have this under control so I might bravely run away. I definitely think these are issues that deserve a backport when the time comes.
Michael
On Tue, Feb 5, 2019 at 1:52 PM Harald Jensås hjensas@redhat.com wrote:
On Tue, 2019-02-05 at 09:54 +1100, Michael Still wrote:
Hi,
I’ve been chasing a bug in ironic’s neutron agent for the last few days and I think its time to ask for some advice.
I'm working on the same issue. (In fact there are two issues.)
Specifically, I was asked to debug why a set of controllers was using so much RAM, and the answer was that rabbitmq had a queue called ironic-neutron-agent-heartbeat.info with 800,000 messages enqueued. This notification queue is used by ironic’s neutron agent to calculate the hash ring. I have been able to duplicate this issue in a stock kolla-ansible install with ironic turned on but no bare metal nodes enrolled in ironic. About 0.6 messages are queued per second.
I added some debugging code (hence the thread yesterday about mangling the code kolla deploys), and I can see that the messages in the queue are being read by the ironic neutron agent and acked correctly. However, they are not removed from the queue.
You can see your queue size while using kolla with this command:
docker exec rabbitmq rabbitmqctl list_queues messages name messages_ready consumers | sort -n | tail -1
My stock install that’s been running for about 12 hours currently has 8,244 messages in that queue.
Where I’m a bit stumped is I had assumed that the messages weren’t being acked correctly, which is not the case. Is there something obvious about notification queues like them being persistent that I’ve missed in my general ignorance of the underlying implementation of notifications?
I opened a oslo.messaging bug[1] yesterday. When using notifications and all consumers use one or more pools. The ironic-neutron-agent does use pools for all listeners in it's hash-ring member manager. And the result is that notifications are published to the 'ironic-neutron- agent-heartbeat.info' queue and they are never consumed.
The second issue, each instance of the agent uses it's own pool to ensure all agents are notified about the existance of peer-agents. The pools use a uuid that is generated at startup (and re-generated on restart, stop/start etc). In the case where `[oslo_messaging_rabbit]/amqp_auto_delete = false` in neutron config these uuid queues are not automatically removed. So after a restart of the ironic-neutron-agent the queue with the old UUID is left in the message broker without no consumers, growing ...
I intend to push patches to fix both issues. As a workaround (or the permanent solution) will create another listener consuming the notifications without a pool. This should fix the first issue.
Second change will set amqp_auto_delete for these specific queues to 'true' no matter. What I'm currently stuck on here is that I need to change the control_exchange for the transport. According to oslo.messaging documentation it should be possible to override the control_exchange in the transport_url[3]. The idea is to set amqp_auto_delete and a ironic-neutron-agent specific exchange on the url when setting up the transport for notifications, but so far I belive the doc string on the control_exchange option is wrong.
NOTE: The second issue can be worked around by stopping and starting rabbitmq as a dependency of the ironic-neutron-agent service. This ensure only queues for active agent uuid's are present, and those queues will be consumed.
-- Harald Jensås
[1] https://bugs.launchpad.net/oslo.messaging/+bug/1814544 [2] https://storyboard.openstack.org/#!/story/2004933 [3]
https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/trans...
On 2/4/19, Harald Jensås hjensas@redhat.com wrote:
On Tue, 2019-02-05 at 09:54 +1100, Michael Still wrote:
Hi,
I’ve been chasing a bug in ironic’s neutron agent for the last few days and I think its time to ask for some advice.
I'm working on the same issue. (In fact there are two issues.)
Specifically, I was asked to debug why a set of controllers was using so much RAM, and the answer was that rabbitmq had a queue called ironic-neutron-agent-heartbeat.info with 800,000 messages enqueued. This notification queue is used by ironic’s neutron agent to calculate the hash ring. I have been able to duplicate this issue in a stock kolla-ansible install with ironic turned on but no bare metal nodes enrolled in ironic. About 0.6 messages are queued per second.
I added some debugging code (hence the thread yesterday about mangling the code kolla deploys), and I can see that the messages in the queue are being read by the ironic neutron agent and acked correctly. However, they are not removed from the queue.
You can see your queue size while using kolla with this command:
docker exec rabbitmq rabbitmqctl list_queues messages name messages_ready consumers | sort -n | tail -1
My stock install that’s been running for about 12 hours currently has 8,244 messages in that queue.
Where I’m a bit stumped is I had assumed that the messages weren’t being acked correctly, which is not the case. Is there something obvious about notification queues like them being persistent that I’ve missed in my general ignorance of the underlying implementation of notifications?
I opened a oslo.messaging bug[1] yesterday. When using notifications and all consumers use one or more pools. The ironic-neutron-agent does use pools for all listeners in it's hash-ring member manager. And the result is that notifications are published to the 'ironic-neutron- agent-heartbeat.info' queue and they are never consumed.
This is an issue with the design of the notification pool feature.
The Notification service is designed so notification events can be sent even though there may currently be no consumers. It supports the ability for events to be queued until a consumer(s) is ready to process them. So when a notifier issues an event and there are no consumers subscribed, a queue must be provisioned to hold that event until consumers appear.
For notification pools the pool identifier is supplied by the notification listener when it subscribes. The value of any pool id is not known beforehand by the notifier, which is important because pool ids can be dynamically created by the listeners. And in many cases pool ids are not even used.
So notifications are always published to a non-pooled queue. If there are pooled subscriptions we rely on the broker to do the fanout. This means that the application should always have at least one non-pooled listener for the topic, since any events that may be published _before_ the listeners are established will be stored on a non-pooled queue.
The documentation doesn't make that clear AFAIKT - that needs to be fixed.
The second issue, each instance of the agent uses it's own pool to ensure all agents are notified about the existance of peer-agents. The pools use a uuid that is generated at startup (and re-generated on restart, stop/start etc). In the case where `[oslo_messaging_rabbit]/amqp_auto_delete = false` in neutron config these uuid queues are not automatically removed. So after a restart of the ironic-neutron-agent the queue with the old UUID is left in the message broker without no consumers, growing ...
I intend to push patches to fix both issues. As a workaround (or the permanent solution) will create another listener consuming the notifications without a pool. This should fix the first issue.
Second change will set amqp_auto_delete for these specific queues to 'true' no matter. What I'm currently stuck on here is that I need to change the control_exchange for the transport. According to oslo.messaging documentation it should be possible to override the control_exchange in the transport_url[3]. The idea is to set amqp_auto_delete and a ironic-neutron-agent specific exchange on the url when setting up the transport for notifications, but so far I belive the doc string on the control_exchange option is wrong.
Yes the doc string is wrong - you can override the default control_exchange via the Target's exchange field:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
At least that's the intent...
... however the Notifier API does not take a Target, it takes a list of topic _strings_:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
Which seems wrong, especially since the notification Listener subscribes to a list of Targets:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
I've opened a bug for this and will provide a patch for review shortly:
https://bugs.launchpad.net/oslo.messaging/+bug/1814797
NOTE: The second issue can be worked around by stopping and starting rabbitmq as a dependency of the ironic-neutron-agent service. This ensure only queues for active agent uuid's are present, and those queues will be consumed.
-- Harald Jensås
[1] https://bugs.launchpad.net/oslo.messaging/+bug/1814544 [2] https://storyboard.openstack.org/#!/story/2004933 [3] https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/trans...
On Tue, 2019-02-05 at 11:43 -0500, Ken Giusti wrote:
On 2/4/19, Harald Jensås hjensas@redhat.com wrote:
I opened a oslo.messaging bug[1] yesterday. When using notifications and all consumers use one or more pools. The ironic-neutron-agent does use pools for all listeners in it's hash-ring member manager. And the result is that notifications are published to the 'ironic-neutron- agent-heartbeat.info' queue and they are never consumed.
This is an issue with the design of the notification pool feature.
The Notification service is designed so notification events can be sent even though there may currently be no consumers. It supports the ability for events to be queued until a consumer(s) is ready to process them. So when a notifier issues an event and there are no consumers subscribed, a queue must be provisioned to hold that event until consumers appear.
For notification pools the pool identifier is supplied by the notification listener when it subscribes. The value of any pool id is not known beforehand by the notifier, which is important because pool ids can be dynamically created by the listeners. And in many cases pool ids are not even used.
So notifications are always published to a non-pooled queue. If there are pooled subscriptions we rely on the broker to do the fanout. This means that the application should always have at least one non-pooled listener for the topic, since any events that may be published _before_ the listeners are established will be stored on a non-pooled queue.
From what I observer any message published _before_ or _after_ pool
listeners are established are stored on the non-pooled queue.
The documentation doesn't make that clear AFAIKT - that needs to be fixed.
I agree with your conclusion here. This is not clear in the documentation. And it should be updated to reflect the requirement of at least one non-pool listener to consume the non-pooled queue.
The second issue, each instance of the agent uses it's own pool to ensure all agents are notified about the existance of peer-agents. The pools use a uuid that is generated at startup (and re-generated on restart, stop/start etc). In the case where `[oslo_messaging_rabbit]/amqp_auto_delete = false` in neutron config these uuid queues are not automatically removed. So after a restart of the ironic-neutron-agent the queue with the old UUID is left in the message broker without no consumers, growing ...
I intend to push patches to fix both issues. As a workaround (or the permanent solution) will create another listener consuming the notifications without a pool. This should fix the first issue.
Second change will set amqp_auto_delete for these specific queues to 'true' no matter. What I'm currently stuck on here is that I need to change the control_exchange for the transport. According to oslo.messaging documentation it should be possible to override the control_exchange in the transport_url[3]. The idea is to set amqp_auto_delete and a ironic-neutron-agent specific exchange on the url when setting up the transport for notifications, but so far I belive the doc string on the control_exchange option is wrong.
Yes the doc string is wrong - you can override the default control_exchange via the Target's exchange field:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
At least that's the intent...
... however the Notifier API does not take a Target, it takes a list of topic _strings_:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
Which seems wrong, especially since the notification Listener subscribes to a list of Targets:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
I've opened a bug for this and will provide a patch for review shortly:
Thanks, this makes sense.
One question, in target I can see that there is the 'fanout' parameter.
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
""" Clients may request that a copy of the message be delivered to all servers listening on a topic by setting fanout to ``True``, rather than just one of them. """
In my usecase I actually want exactly that. So once your patch lands I can drop the use of pools and just set fanout=true on the target instead?
NOTE: The second issue can be worked around by stopping and starting rabbitmq as a dependency of the ironic-neutron-agent service. This ensure only queues for active agent uuid's are present, and those queues will be consumed.
-- Harald Jensås
[1] https://bugs.launchpad.net/oslo.messaging/+bug/1814544 [2] https://storyboard.openstack.org/#!/story/2004933 [3]
https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/trans...
On 2/5/19, Harald Jensås hjensas@redhat.com wrote:
On Tue, 2019-02-05 at 11:43 -0500, Ken Giusti wrote:
On 2/4/19, Harald Jensås hjensas@redhat.com wrote:
I opened a oslo.messaging bug[1] yesterday. When using notifications and all consumers use one or more pools. The ironic-neutron-agent does use pools for all listeners in it's hash-ring member manager. And the result is that notifications are published to the 'ironic-neutron- agent-heartbeat.info' queue and they are never consumed.
This is an issue with the design of the notification pool feature.
The Notification service is designed so notification events can be sent even though there may currently be no consumers. It supports the ability for events to be queued until a consumer(s) is ready to process them. So when a notifier issues an event and there are no consumers subscribed, a queue must be provisioned to hold that event until consumers appear.
For notification pools the pool identifier is supplied by the notification listener when it subscribes. The value of any pool id is not known beforehand by the notifier, which is important because pool ids can be dynamically created by the listeners. And in many cases pool ids are not even used.
So notifications are always published to a non-pooled queue. If there are pooled subscriptions we rely on the broker to do the fanout. This means that the application should always have at least one non-pooled listener for the topic, since any events that may be published _before_ the listeners are established will be stored on a non-pooled queue.
From what I observer any message published _before_ or _after_ pool listeners are established are stored on the non-pooled queue.
True that. Even if listeners are established before a notification is issued the notifier still doesn't know that and blindly creates a non pooled queue just in case there aren't any listeners.
Not intuitive I agree.
The documentation doesn't make that clear AFAIKT - that needs to be fixed.
I agree with your conclusion here. This is not clear in the documentation. And it should be updated to reflect the requirement of at least one non-pool listener to consume the non-pooled queue.
+1 I can do that.
The second issue, each instance of the agent uses it's own pool to ensure all agents are notified about the existance of peer-agents. The pools use a uuid that is generated at startup (and re-generated on restart, stop/start etc). In the case where `[oslo_messaging_rabbit]/amqp_auto_delete = false` in neutron config these uuid queues are not automatically removed. So after a restart of the ironic-neutron-agent the queue with the old UUID is left in the message broker without no consumers, growing ...
I intend to push patches to fix both issues. As a workaround (or the permanent solution) will create another listener consuming the notifications without a pool. This should fix the first issue.
Second change will set amqp_auto_delete for these specific queues to 'true' no matter. What I'm currently stuck on here is that I need to change the control_exchange for the transport. According to oslo.messaging documentation it should be possible to override the control_exchange in the transport_url[3]. The idea is to set amqp_auto_delete and a ironic-neutron-agent specific exchange on the url when setting up the transport for notifications, but so far I belive the doc string on the control_exchange option is wrong.
Yes the doc string is wrong - you can override the default control_exchange via the Target's exchange field:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
At least that's the intent...
... however the Notifier API does not take a Target, it takes a list of topic _strings_:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
Which seems wrong, especially since the notification Listener subscribes to a list of Targets:
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
I've opened a bug for this and will provide a patch for review shortly:
Thanks, this makes sense.
I've hacked in the ability to override the default exchange for notifiers, but I don't think it would help in your case. In rabbitmq exchange and queue names are scoped independently. This means that if you have an exchange named "openstack' and another named 'my-exchange' but use the same topic (say 'foo') you end up with a single instance of queue 'foo' bound to both exchanges. IOW declaring one listener on exchange=openstack and topic=foo, and another listener on exchange=my-exchange and topic=foo they will compete for messages because they are consuming from the same queue (foo). So if your intent is to partition notification traffic you'd still need unique topics as well.
One question, in target I can see that there is the 'fanout' parameter.
https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/...
""" Clients may request that a copy of the message be delivered to all servers listening on a topic by setting fanout to ``True``, rather than just one of them. """
In my usecase I actually want exactly that. So once your patch lands I can drop the use of pools and just set fanout=true on the target instead?
The 'fanout' attribute is only used with RPC messaging, not Notifications.
Can you use RPC fanout instead of Notifications? RPC fanout ('cast' as the API calls it) is different from 'normal' RPC in that no reply is returned to the caller. So it's a lot like Notifications in that regard. However RPC fanout is different from Notifications in two important ways: 1) RPC fanout messages are sent 'least effort', meaning they can be silently discarded, and 2) RPC fanout messages are not stored - they are only delivered to active subscribers (listeners).
I've always felt that notification pools are an attempt to implement a Publish/Subscribe messaging pattern on top of an event queuing service. That's hard to do since event queuing has strict delivery guarantees (avoid dropping) which Pub/Sub doesn't (drop if no consumers).
NOTE: The second issue can be worked around by stopping and starting rabbitmq as a dependency of the ironic-neutron-agent service. This ensure only queues for active agent uuid's are present, and those queues will be consumed.
-- Harald Jensås
[1] https://bugs.launchpad.net/oslo.messaging/+bug/1814544 [2] https://storyboard.openstack.org/#!/story/2004933 [3]
https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/trans...
Ken Giusti kgiusti@gmail.com writes:
On 2/4/19, Harald Jensås hjensas@redhat.com wrote:
On Tue, 2019-02-05 at 09:54 +1100, Michael Still wrote:
Hi,
I’ve been chasing a bug in ironic’s neutron agent for the last few days and I think its time to ask for some advice.
I'm working on the same issue. (In fact there are two issues.)
Specifically, I was asked to debug why a set of controllers was using so much RAM, and the answer was that rabbitmq had a queue called ironic-neutron-agent-heartbeat.info with 800,000 messages enqueued. This notification queue is used by ironic’s neutron agent to calculate the hash ring. I have been able to duplicate this issue in a stock kolla-ansible install with ironic turned on but no bare metal nodes enrolled in ironic. About 0.6 messages are queued per second.
I added some debugging code (hence the thread yesterday about mangling the code kolla deploys), and I can see that the messages in the queue are being read by the ironic neutron agent and acked correctly. However, they are not removed from the queue.
You can see your queue size while using kolla with this command:
docker exec rabbitmq rabbitmqctl list_queues messages name messages_ready consumers | sort -n | tail -1
My stock install that’s been running for about 12 hours currently has 8,244 messages in that queue.
Where I’m a bit stumped is I had assumed that the messages weren’t being acked correctly, which is not the case. Is there something obvious about notification queues like them being persistent that I’ve missed in my general ignorance of the underlying implementation of notifications?
I opened a oslo.messaging bug[1] yesterday. When using notifications and all consumers use one or more pools. The ironic-neutron-agent does use pools for all listeners in it's hash-ring member manager. And the result is that notifications are published to the 'ironic-neutron- agent-heartbeat.info' queue and they are never consumed.
This is an issue with the design of the notification pool feature.
The Notification service is designed so notification events can be sent even though there may currently be no consumers. It supports the ability for events to be queued until a consumer(s) is ready to process them. So when a notifier issues an event and there are no consumers subscribed, a queue must be provisioned to hold that event until consumers appear.
This has come up several times over the last few years, and it's always a surprise to whoever it has bitten. I wonder if we should change the default behavior to not create the consumer queue in the publisher?
I'm also interested in how we catch future instances of this. Is there something we can do in CI or in a runtime warning to let people know? I am sure there are plenty of ironic deployments out there consuming heaps more RAM than is required for this queue.
Michael
On Wed, Feb 6, 2019 at 8:41 AM Doug Hellmann doug@doughellmann.com wrote:
Ken Giusti kgiusti@gmail.com writes:
On 2/4/19, Harald Jensås hjensas@redhat.com wrote:
On Tue, 2019-02-05 at 09:54 +1100, Michael Still wrote:
Hi,
I’ve been chasing a bug in ironic’s neutron agent for the last few days and I think its time to ask for some advice.
I'm working on the same issue. (In fact there are two issues.)
Specifically, I was asked to debug why a set of controllers was using so much RAM, and the answer was that rabbitmq had a queue called ironic-neutron-agent-heartbeat.info with 800,000 messages enqueued. This notification queue is used by ironic’s neutron agent to calculate the hash ring. I have been able to duplicate this issue in a stock kolla-ansible install with ironic turned on but no bare metal nodes enrolled in ironic. About 0.6 messages are queued per second.
I added some debugging code (hence the thread yesterday about mangling the code kolla deploys), and I can see that the messages in the queue are being read by the ironic neutron agent and acked correctly. However, they are not removed from the queue.
You can see your queue size while using kolla with this command:
docker exec rabbitmq rabbitmqctl list_queues messages name messages_ready consumers | sort -n | tail -1
My stock install that’s been running for about 12 hours currently has 8,244 messages in that queue.
Where I’m a bit stumped is I had assumed that the messages weren’t being acked correctly, which is not the case. Is there something obvious about notification queues like them being persistent that I’ve missed in my general ignorance of the underlying implementation of notifications?
I opened a oslo.messaging bug[1] yesterday. When using notifications and all consumers use one or more pools. The ironic-neutron-agent does use pools for all listeners in it's hash-ring member manager. And the result is that notifications are published to the 'ironic-neutron- agent-heartbeat.info' queue and they are never consumed.
This is an issue with the design of the notification pool feature.
The Notification service is designed so notification events can be sent even though there may currently be no consumers. It supports the ability for events to be queued until a consumer(s) is ready to process them. So when a notifier issues an event and there are no consumers subscribed, a queue must be provisioned to hold that event until consumers appear.
This has come up several times over the last few years, and it's always a surprise to whoever it has bitten. I wonder if we should change the default behavior to not create the consumer queue in the publisher?
-- Doug
On 2/5/19, Doug Hellmann doug@doughellmann.com wrote:
Ken Giusti kgiusti@gmail.com writes:
On 2/4/19, Harald Jensås hjensas@redhat.com wrote:
On Tue, 2019-02-05 at 09:54 +1100, Michael Still wrote:
Hi,
I’ve been chasing a bug in ironic’s neutron agent for the last few days and I think its time to ask for some advice.
I'm working on the same issue. (In fact there are two issues.)
Specifically, I was asked to debug why a set of controllers was using so much RAM, and the answer was that rabbitmq had a queue called ironic-neutron-agent-heartbeat.info with 800,000 messages enqueued. This notification queue is used by ironic’s neutron agent to calculate the hash ring. I have been able to duplicate this issue in a stock kolla-ansible install with ironic turned on but no bare metal nodes enrolled in ironic. About 0.6 messages are queued per second.
I added some debugging code (hence the thread yesterday about mangling the code kolla deploys), and I can see that the messages in the queue are being read by the ironic neutron agent and acked correctly. However, they are not removed from the queue.
You can see your queue size while using kolla with this command:
docker exec rabbitmq rabbitmqctl list_queues messages name messages_ready consumers | sort -n | tail -1
My stock install that’s been running for about 12 hours currently has 8,244 messages in that queue.
Where I’m a bit stumped is I had assumed that the messages weren’t being acked correctly, which is not the case. Is there something obvious about notification queues like them being persistent that I’ve missed in my general ignorance of the underlying implementation of notifications?
I opened a oslo.messaging bug[1] yesterday. When using notifications and all consumers use one or more pools. The ironic-neutron-agent does use pools for all listeners in it's hash-ring member manager. And the result is that notifications are published to the 'ironic-neutron- agent-heartbeat.info' queue and they are never consumed.
This is an issue with the design of the notification pool feature.
The Notification service is designed so notification events can be sent even though there may currently be no consumers. It supports the ability for events to be queued until a consumer(s) is ready to process them. So when a notifier issues an event and there are no consumers subscribed, a queue must be provisioned to hold that event until consumers appear.
This has come up several times over the last few years, and it's always a surprise to whoever it has bitten. I wonder if we should change the default behavior to not create the consumer queue in the publisher?
+1
One possibility is to provide options on the Notifier constructor allowing the app to control the queue creation behavior. Something like "create_queue=True/False".
We can document this as a 'dead letter' queue feature for events published w/o active listeners.
-- Doug
participants (4)
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Doug Hellmann
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Harald Jensås
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Ken Giusti
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Michael Still