[
https://issues.apache.org/jira/browse/AMQ-3331?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Stirling Chow updated AMQ-3331:
-------------------------------
Description:
Symptom
=======
Broker A produces messages to two queues, Q1 and Q2. Broker B consumes
messages from two queues, Q1 and Q2. Broker A is connected by a demand
forwarding bridge, over TCP, to Broker B so that messages produced to Q1/Q2
will be forwarded to the consumers on Broker B.
At some point, Broker B's instance of Q2 becomes full (e.g., because the Q2
consumer is slow), and this triggers producer flow control to halt new messages
being sent to Broker B's Q2 over the bridge. Broker A's instances of Q1/Q2 are
not full, so the producers on Broker A are not blocked.
If the messages produced by Broker A are *persistent*, we see this behaviour
over the course of the production of 1000 messages to both Q1/Q2, where Broker
B's Q2 becomes full on the 500th message:
{noformat}
Broker A Bridge Broker B
======== ========
0->1000->0 ------> 0->1000->...
0->1000->500 0->500->...
{noformat}
The above results, which assume network and consumer prefetch sizes of 1, are
what we expected, namely:
# Broker A produces 1000 messages to Q1 without blocking and all of these
messages are forwarded to Broker B's Q1 without blocking, eventually being
consumed by Broker B's Q1 consumer.
# Broker A produces 1000 messages to Q2 without blocking and 500 of these
messages are forwarded to Broker B's Q2 before producer flow control blocks the
flow until Broker B's Q2 consumer can start reducing the queue size.
This is good because the bridge treats Q1 and Q2 independently (i.e., producer
flow control on Q2 does not block the messages forwarded to Q1).
If the messages produced by Broker A are *non-persistent*, we see this
behaviour:
{noformat}
Broker A Bridge Broker B
======== ========
0->1000->500 ------> 0->500->...
0->1000->500 0->500->...
{noformat}
The above results, which assume network and consumer prefetch sizes of 1, are
not what we expected, namely: producer flow control on Broker B's instance of
Q2 blocks the forwarding of messages to Broker B's instance of Q1.
This is not good because producer flow control on Q2 essentially triggers
producer flow control on Q1, even though Q1 is *not* full.
It also seems strange (and almost non-intuitive until you understand the
cause), that peristent messages should behave better than non-persistent
messages. The same difference in behaviour can also be observed with
persistent messages if Broker A these outside a JMS transaction (e.g.,
AUTO_ACKNOWLEDGE) versus inside a JMS transaction: outside behaves
appropriately, with Q1 independent of Q2, but inside behaves the same as the
non-persistent case with Q1 blocked by Q2.
These observations are contrary to the AMQ 5.0 documentation regarding producer
flow control: {quote}As of ActiveMQ 5.0, we can now individually flow control
each producer on a shared connection without having to suspend the entire
connection.{quote}
Cause
=====
The difference in behaviour between persistent and non-persistent (and
transactionaly/non-transactional) is due to the two ways that
org.apache.activemq.broker.region.Queue implements producer flow control:
{code:title=Queue#send(...)}
// We can avoid blocking due to low usage if the producer is
// sending
// a sync message or if it is using a producer window
if (producerInfo.getWindowSize() > 0 || message.isResponseRequired()) {
{code}
and
{code:title=Queue#send(...)}
} else
if (memoryUsage.isFull()) {
waitForSpace(context, memoryUsage, "Usage Manager Memory Limit is full.
Producer ("
+ message.getProducerId() + ") stopped to
prevent flooding "
+ getActiveMQDestination().getQualifiedName() +
"."
+ " See
http://activemq.apache.org/producer-flow-control.html for more info");
}
{code}
There is only a single transport thread that services the TCP socket on Broker
B. This TCP socket is the "remote" end of the A->B bridge and is responsible
for *sequentially* enqueueing to Broker B's queues all messages from Broker A.
When a non-persistent or transactional message is sent to Broker A's queues, it
has +responseRequired=true+, which is preserved when the bridge forwards the
message to Broker B's queues. If producer flow control is triggered on Broker
B's queue, the first method of producer flow control will be used: the
transport thread will not block, but the repsonse will be held back until the
queue has room. As a result, the transport thread is free to continue
enqueueing messages from the bridge, particularly those destined for queues
that are not full (NOTE: since the network prefetch is 1 no new messages to the
full queue will be forwarded until the response is returned).
When a persistent or non-transactional message is sent to Broker A's queues, it
has +responseRequired=false+, which is preserved when the bridge forwards the
message to Broker B's queues. If producer flow control is triggered on Broker
B's queue, the second method of producer flow control will be used: the
transport thread will be blocked. As a result, no other messages from the
bridge will be forwarded, even those destined for queues that are not full.
The preservation of the {{responseRequired}} flag occurs in
org.apache.activemq.network.DemandForwardingBridgeSupport:
{code:title=DemandForwardingBridgeSupport#serviceLocalCommand(...)}
if (!message.isResponseRequired()) {
// If the message was originally sent using async
// send, we will preserve that QOS
// by bridging it using an async send (small chance
// of message loss).
try {
remoteBroker.oneway(message);
localBroker.oneway(new MessageAck(md, MessageAck.INDIVIDUAL_ACK_TYPE,
1));
dequeueCounter.incrementAndGet();
} finally {
sub.decrementOutstandingResponses();
}
} else {
// The message was not sent using async send, so we
// should only ack the local
// broker when we get confirmation that the remote
// broker has received the message.
ResponseCallback callback = new ResponseCallback() {
public void onCompletion(FutureResponse future) {
try {
Response response = future.getResult();
if (response.isException()) {
ExceptionResponse er = (ExceptionResponse) response;
serviceLocalException(er.getException());
} else {
localBroker.oneway(new MessageAck(md,
MessageAck.INDIVIDUAL_ACK_TYPE, 1));
dequeueCounter.incrementAndGet();
}
} catch (IOException e) {
serviceLocalException(e);
} finally {
sub.decrementOutstandingResponses();
}
}
};
remoteBroker.asyncRequest(message, callback);
}
{code}
was:
Symptom
=======
Broker A produces messages to two queues, Q1 and Q2. Broker B consumes
messages from two queues, Q1 and Q2. Broker A is connected by a demand
forwarding bridge, over TCP, to Broker B so that messages produced to Q1/Q2
will be forwarded to the consumers on Broker B.
At some point, Broker B's instance of Q2 becomes full (e.g., because the Q2
consumer is slow), and this triggers producer flow control to halt new messages
being sent to Broker B's Q2 over the bridge. Broker A's instances of Q1/Q2 are
not full, so the producers on Broker A are not blocked.
If the messages produced by Broker A are *persistent*, we see this behaviour
over the course of the production of 1000 messages to both Q1/Q2, where Broker
B's Q2 becomes full on the 500th message:
{noformat}
Broker A Bridge Broker B
======== ========
0->1000->0 ------> 0->1000->...
0->1000->500 0->500->...
{noformat}
The above results, which assume network and consumer prefetch sizes of 1, are
what we expected, namely:
# Broker A produces 1000 messages to Q1 without blocking and all of these
messages are forwarded to Broker B's Q1 without blocking, eventually being
consumed by Broker B's Q1 consumer.
# Broker A produces 1000 messages to Q2 without blocking and 500 of these
messages are forwarded to Broker B's Q2 before producer flow control blocks the
flow until Broker B's Q2 consumer can start reducing the queue size.
This is good because the bridge treats Q1 and Q2 independently (i.e., producer
flow control on Q2 does not block the messages forwarded to Q1).
If the messages produced by Broker A are *non-persistent*, we see this
behaviour:
{noformat}
Broker A Bridge Broker B
======== ========
0->1000->500 ------> 0->500->...
0->1000->500 0->500->...
{noformat}
The above results, which assume network and consumer prefetch sizes of 1, are
not what we expected, namely: producer flow control on Broker B's instance of
Q2 blocks the forwarding of messages to Broker B's instance of Q1.
This is not good because producer flow control on Q2 essentially triggers
producer flow control on Q1, even though Q1 is *not* full.
It also seems strange (and almost non-intuitive until you understand the
cause), that peristent messages should behave better than non-persistent
messages. The same difference in behaviour can also be observed with
persistent messages if Broker A these outside a JMS transaction (e.g.,
AUTO_ACKNOWLEDGE) versus inside a JMS transaction: outside behaves
appropriately, with Q1 independent of Q2, but inside behaves the same as the
non-persistent case with Q1 blocked by Q2.
These observations are contrary to the AMQ 5.0 documentation regarding producer
flow control: {quote}As of ActiveMQ 5.0, we can now individually flow control
each producer on a shared connection without having to suspend the entire
connection.{quote}
Cause
=====
The difference in behaviour between persistent and non-persistent (and
transactionaly/non-transactional) is due to the two ways that
org.apache.activemq.broker.region.Queue implements producer flow control:
{code:title=Queue#send(...)}
// We can avoid blocking due to low usage if the producer is
// sending
// a sync message or if it is using a producer window
if (producerInfo.getWindowSize() > 0 || message.isResponseRequired()) {
{code}
and
{code:title=Queue#send(...)}
} else
if (memoryUsage.isFull()) {
waitForSpace(context, memoryUsage, "Usage Manager Memory Limit is full.
Producer ("
+ message.getProducerId() + ") stopped to
prevent flooding "
+ getActiveMQDestination().getQualifiedName() +
"."
+ " See
http://activemq.apache.org/producer-flow-control.html for more info");
}
{code}
There is only a single transport thread that services the TCP socket on Broker
B. This TCP socket is the "remote" end of the A->B bridge and is responsible
for *sequentially* enqueueing to Broker B's queues all messages from Broker A.
When a non-persistent or transactional message is sent to Broker A's queues, it
has +responseRequired=true+, which is preserved when the bridge forwards the
message to Broker B's queues. If producer flow control is triggered on Broker
B's queue, the first method of producer flow control will be used: the
transport thread will not block, but the repsonse will be held back until the
queue has room. As a result, the transport thread is free to continue
enqueueing messages from the bridge, particularly those destined for queues
that are not full (NOTE: since the network prefetch is 1 no new messages to the
full queue will be forwarded until the response is returned).
When a persistent or non-transactional message is sent to Broker A's queues, it
has +responseRequired=false+, which is preserved when the bridge forwards the
message to Broker B's queues. If producer flow control is triggered on Broker
B's queue, the second method of producer flow control will be used: the
transport thread will be blocked. As a result, no other messages from the
bridge will be forwarded, even those destined for queues that are not full.
The preservation of the {{responseRequired}} flag occurs in
org.apache.activemq.network.DemandForwardingBridgeSupport:
{code:title=DemandForwardingBridgeSupport#serviceLocalCommand(...)}
if (!message.isResponseRequired()) {
// If the message was originally sent using async
// send, we will preserve that QOS
// by bridging it using an async send (small chance
// of message loss).
try {
remoteBroker.oneway(message);
localBroker.oneway(new MessageAck(md,
MessageAck.INDIVIDUAL_ACK_TYPE, 1));
dequeueCounter.incrementAndGet();
} finally {
sub.decrementOutstandingResponses();
}
} else {
// The message was not sent using async send, so we
// should only ack the local
// broker when we get confirmation that the remote
// broker has received the message.
ResponseCallback callback = new ResponseCallback() {
public void onCompletion(FutureResponse future)
{
try {
Response response = future.getResult();
if (response.isException()) {
ExceptionResponse er =
(ExceptionResponse) response;
serviceLocalException(er.getException());
} else {
localBroker.oneway(new
MessageAck(md, MessageAck.INDIVIDUAL_ACK_TYPE, 1));
dequeueCounter.incrementAndGet();
}
} catch (IOException e) {
serviceLocalException(e);
} finally {
sub.decrementOutstandingResponses();
}
}
};
remoteBroker.asyncRequest(message, callback);
}
{code}
> When a producer from a network bridge is blocked by producer flow control,
> all producers from the network bridge get blocked.
> -----------------------------------------------------------------------------------------------------------------------------
>
> Key: AMQ-3331
> URL: https://issues.apache.org/jira/browse/AMQ-3331
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker, Test Cases, Transport
> Affects Versions: 5.5.0
> Reporter: Stirling Chow
>
> Symptom
> =======
> Broker A produces messages to two queues, Q1 and Q2. Broker B consumes
> messages from two queues, Q1 and Q2. Broker A is connected by a demand
> forwarding bridge, over TCP, to Broker B so that messages produced to Q1/Q2
> will be forwarded to the consumers on Broker B.
> At some point, Broker B's instance of Q2 becomes full (e.g., because the Q2
> consumer is slow), and this triggers producer flow control to halt new
> messages being sent to Broker B's Q2 over the bridge. Broker A's instances
> of Q1/Q2 are not full, so the producers on Broker A are not blocked.
> If the messages produced by Broker A are *persistent*, we see this behaviour
> over the course of the production of 1000 messages to both Q1/Q2, where
> Broker B's Q2 becomes full on the 500th message:
> {noformat}
> Broker A Bridge Broker B
> ======== ========
> 0->1000->0 ------> 0->1000->...
> 0->1000->500 0->500->...
> {noformat}
> The above results, which assume network and consumer prefetch sizes of 1, are
> what we expected, namely:
> # Broker A produces 1000 messages to Q1 without blocking and all of these
> messages are forwarded to Broker B's Q1 without blocking, eventually being
> consumed by Broker B's Q1 consumer.
> # Broker A produces 1000 messages to Q2 without blocking and 500 of these
> messages are forwarded to Broker B's Q2 before producer flow control blocks
> the flow until Broker B's Q2 consumer can start reducing the queue size.
> This is good because the bridge treats Q1 and Q2 independently (i.e.,
> producer flow control on Q2 does not block the messages forwarded to Q1).
> If the messages produced by Broker A are *non-persistent*, we see this
> behaviour:
> {noformat}
> Broker A Bridge Broker B
> ======== ========
> 0->1000->500 ------> 0->500->...
> 0->1000->500 0->500->...
> {noformat}
> The above results, which assume network and consumer prefetch sizes of 1, are
> not what we expected, namely: producer flow control on Broker B's instance of
> Q2 blocks the forwarding of messages to Broker B's instance of Q1.
> This is not good because producer flow control on Q2 essentially triggers
> producer flow control on Q1, even though Q1 is *not* full.
> It also seems strange (and almost non-intuitive until you understand the
> cause), that peristent messages should behave better than non-persistent
> messages. The same difference in behaviour can also be observed with
> persistent messages if Broker A these outside a JMS transaction (e.g.,
> AUTO_ACKNOWLEDGE) versus inside a JMS transaction: outside behaves
> appropriately, with Q1 independent of Q2, but inside behaves the same as the
> non-persistent case with Q1 blocked by Q2.
> These observations are contrary to the AMQ 5.0 documentation regarding
> producer flow control: {quote}As of ActiveMQ 5.0, we can now individually
> flow control each producer on a shared connection without having to suspend
> the entire connection.{quote}
> Cause
> =====
> The difference in behaviour between persistent and non-persistent (and
> transactionaly/non-transactional) is due to the two ways that
> org.apache.activemq.broker.region.Queue implements producer flow control:
> {code:title=Queue#send(...)}
> // We can avoid blocking due to low usage if the producer is
> // sending
> // a sync message or if it is using a producer window
> if (producerInfo.getWindowSize() > 0 || message.isResponseRequired()) {
> {code}
> and
> {code:title=Queue#send(...)}
> } else
> if (memoryUsage.isFull()) {
> waitForSpace(context, memoryUsage, "Usage Manager Memory Limit is full.
> Producer ("
> + message.getProducerId() + ") stopped to
> prevent flooding "
> + getActiveMQDestination().getQualifiedName()
> + "."
> + " See
> http://activemq.apache.org/producer-flow-control.html for more info");
> }
> {code}
> There is only a single transport thread that services the TCP socket on
> Broker B. This TCP socket is the "remote" end of the A->B bridge and is
> responsible for *sequentially* enqueueing to Broker B's queues all messages
> from Broker A. When a non-persistent or transactional message is sent to
> Broker A's queues, it has +responseRequired=true+, which is preserved when
> the bridge forwards the message to Broker B's queues. If producer flow
> control is triggered on Broker B's queue, the first method of producer flow
> control will be used: the transport thread will not block, but the repsonse
> will be held back until the queue has room. As a result, the transport
> thread is free to continue enqueueing messages from the bridge, particularly
> those destined for queues that are not full (NOTE: since the network prefetch
> is 1 no new messages to the full queue will be forwarded until the response
> is returned).
> When a persistent or non-transactional message is sent to Broker A's queues,
> it has +responseRequired=false+, which is preserved when the bridge forwards
> the message to Broker B's queues. If producer flow control is triggered on
> Broker B's queue, the second method of producer flow control will be used:
> the transport thread will be blocked. As a result, no other messages from
> the bridge will be forwarded, even those destined for queues that are not
> full.
> The preservation of the {{responseRequired}} flag occurs in
> org.apache.activemq.network.DemandForwardingBridgeSupport:
> {code:title=DemandForwardingBridgeSupport#serviceLocalCommand(...)}
> if (!message.isResponseRequired()) {
>
> // If the message was originally sent using async
> // send, we will preserve that QOS
> // by bridging it using an async send (small chance
> // of message loss).
> try {
> remoteBroker.oneway(message);
> localBroker.oneway(new MessageAck(md, MessageAck.INDIVIDUAL_ACK_TYPE,
> 1));
> dequeueCounter.incrementAndGet();
> } finally {
> sub.decrementOutstandingResponses();
> }
>
> } else {
>
> // The message was not sent using async send, so we
> // should only ack the local
> // broker when we get confirmation that the remote
> // broker has received the message.
> ResponseCallback callback = new ResponseCallback() {
> public void onCompletion(FutureResponse future) {
> try {
> Response response = future.getResult();
> if (response.isException()) {
> ExceptionResponse er = (ExceptionResponse) response;
> serviceLocalException(er.getException());
> } else {
> localBroker.oneway(new MessageAck(md,
> MessageAck.INDIVIDUAL_ACK_TYPE, 1));
> dequeueCounter.incrementAndGet();
> }
> } catch (IOException e) {
> serviceLocalException(e);
> } finally {
> sub.decrementOutstandingResponses();
> }
> }
> };
>
> remoteBroker.asyncRequest(message, callback);
> }
> {code}
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