the notification can't send measures to gnocchi timely

[xuqiankun]

When I use ceilometer service（P or Q verion) for collecting measurements within OpenStack ，
I build 50 vms in my system, I find that samples in the rabbitmq can't be consumed timely.
The num samples of "ceilometer-pipe-meter_source:meter_sink-*" will always increase.

here is my config for notification
[notification]
workers = 10
workload_partitioning = True
batch_size = 50
pipeline_processing_queues = 30

Even though I config batch_size smaller(10) ,the num of samples will increase although slowly than pre,
result in that some samples will not send to gnocchi or send to gnocchi delay.

In M version
The default value of the batch_size for collector is 100, the batch_size of collector is 1.

In Q version
The notification and the collector merge to one process，The default value of the batch_size is 100

So i guess the num of the batch_size is related to this problem，
Then I config batch_size = 1, the rabbitmq send sample to gnocchi in time
(this also will increase pressure of gnocchi-api)

rabbitmqctl list_queues |grep ceilometer-pipe-meter
ceilometer-pipe-meter_source:meter_sink-27.sample 0
ceilometer-pipe-meter_source:meter_sink-17.sample 0
ceilometer-pipe-meter_source:meter_sink-4.sample 0
ceilometer-pipe-meter_source:meter_sink-3.sample 0
ceilometer-pipe-meter_source:meter_sink-5.sample 0
ceilometer-pipe-meter_source:meter_sink-12.sample 0
ceilometer-pipe-meter_source:meter_sink-26.sample 0
ceilometer-pipe-meter_source:meter_sink-28.sample 0
ceilometer-pipe-meter_source:meter_sink-23.sample 0
ceilometer-pipe-meter_source:meter_sink-21.sample 0
ceilometer-pipe-meter_source:meter_sink-1.sample 0
ceilometer-pipe-meter_source:meter_sink-11.sample 0
ceilometer-pipe-meter_source:meter_sink-16.sample 0
ceilometer-pipe-meter_source:meter_sink-24.sample 0

But when I config batch_size > 1, ,the num of samples will increase.

rabbitmqctl list_queues |grep ceilometer-pipe-meter
ceilometer-pipe-meter_source:meter_sink-27.sample 450
ceilometer-pipe-meter_source:meter_sink-17.sample 0
ceilometer-pipe-meter_source:meter_sink-4.sample 0
ceilometer-pipe-meter_source:meter_sink-3.sample 899
ceilometer-pipe-meter_source:meter_sink-5.sample 0
ceilometer-pipe-meter_source:meter_sink-12.sample 0
ceilometer-pipe-meter_source:meter_sink-26.sample 206
ceilometer-pipe-meter_source:meter_sink-28.sample 0
ceilometer-pipe-meter_source:meter_sink-23.sample 0
ceilometer-pipe-meter_source:meter_sink-21.sample 0
ceilometer-pipe-meter_source:meter_sink-1.sample 5
ceilometer-pipe-meter_source:meter_sink-11.sample 0
ceilometer-pipe-meter_source:meter_sink-16.sample 2627
ceilometer-pipe-meter_source:meter_sink-24.sample 0
ceilometer-pipe-meter_source:meter_sink-25.sample 0
ceilometer-pipe-meter_source:meter_sink-2.sample 0
ceilometer-pipe-meter_source:meter_sink-13.sample 3045
ceilometer-pipe-meter_source:meter_sink-29.sample 0
ceilometer-pipe-meter_source:meter_sink-10.sample 0
ceilometer-pipe-meter_source:meter_sink-19.sample 70
ceilometer-pipe-meter_source:meter_sink-0.sample 0
ceilometer-pipe-meter_source:meter_sink-18.sample 1845
ceilometer-pipe-meter_source:meter_sink-9.sample 0
ceilometer-pipe-meter_source:meter_sink-7.sample 0
ceilometer-pipe-meter_source:meter_sink-14.sample 1624
ceilometer-pipe-meter_source:meter_sink-6.sample 0
ceilometer-pipe-meter_source:meter_sink-15.sample 2195
ceilometer-pipe-meter_source:meter_sink-20.sample 0
ceilometer-pipe-meter_source:meter_sink-22.sample 0
ceilometer-pipe-meter_source:meter_sink-8.sample 0

Is this a bug for ceilometer?

[xuqiankun (xuqiankun)]

# NOTE(gordc): set single thread to process data sequentially
# if batching enabled.
batch = (1 if self.conf.notification.batch_size > 1
         else self.conf.max_parallel_requests)

I find this code ,but i don't know the reason.