[QPID-7677] [C++ broker] broker requires much more memory for AMQP1.0 subscription than for 0-10 one

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.32, qpid-cpp-1.36.0
• Fix Version/s: qpid-cpp-1.37.0
• Component/s: C++ Broker
• Labels: memory
• Assignee: Alan Conway
• Reporter: Pavel Moravec
• Created: 19/Feb/17 19:45
• Updated: 22/Nov/17 10:33
• Resolved: 23/Feb/17 22:58

Description

Having an AMQP 1.0 consumer of a queue increases memory usage of qpidd by much more than having an AMQP 0-10 consumer - the difference is approx. 0.5MB.

This affects scalable usage of the broker, where having thousands of 1.0 consumers require gigabytes of memory.

Trivial test:

qpid-config add queue qqq

for i in $(seq 1 10); do qpid-receive -a qqq -f & sleep 0.1; done

# this added small 26kB VSZ and 75kB RSS per one consumer/receiver

for i in $(seq 1 10); do qpid-receive -a qqq -f --connection-options "{protocol:'amqp1.0'}" & sleep 0.1; done

# this added 640kB VSZ and 805kB RSS per one consumer/receiver

Better test: have multiple consumers on the same AMQP connection (I can provide such program in case of interest).

Running such scenario under valgrind/massif showed the extra memory is consumed by:

->91.90% (143,361,792B) 0x5D544F1: qpid::broker::amqp::OutgoingFromQueue::OutgoingFromQueue(qpid::broker::Broker&, std::string const&, std::string const&, boost::shared_ptr<qpid::broker::Queue>, pn_link_t*, qpid::broker::amqp::Session&, qpid::sys::OutputControl&, qpid::broker::SubscriptionType, bool, bool) (Outgoing.h:57)

And really, when I changed in:

https://github.com/apache/qpid-cpp/blob/master/src/qpid/broker/amqp/Outgoing.cpp#L68

the "deliveries(5000)" to "deliveries(50)", memory consumption dramatically decreased.

I don't understand this part of code, but please make the "CircularArray<Record> deliveries(5000)" more memory efficient.