openstack/tripleo-heat-templates
Code Issues Proposed changes

Add ERL args parameter for rabbit and set the busy wait threshold to none

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Additional argument to be able to customize the ERL command line
arguments. This allows the operator to specify some arguments to the
Erlang VM. By default we are now passing '+sbwt none' to set the
the erlang scheduler busy wait threshold. This threshold determines how
long schedulers are to busy wait when running out of work before going
to sleep. On most of our deployments where rabbitmq shares a node with
a lot of other services it makes little sense to busy wait when out of
work in order to improve latency as other processes are more likely to
fail to do work due to CPUs being overused by rabbit,

We have measured a three-fold reduction of CPU usage with this option
with no other observable impact.

We can observe the change in the beam.smp params:
root         346  0.0  0.0  11680  1468 ?        S    18:29   0:00  \_ /bin/sh /usr/sbin/rabbitmq-server
root         367  0.0  0.0  81940  2060 ?        S    18:29   0:00      \_ su rabbitmq -s /bin/sh -c /usr/lib/rabbitmq/bin/rabbitmq-server
rabbitmq     372  0.0  0.0   9672  1520 ?        Ss   18:29   0:00          \_ /bin/sh /usr/lib/rabbitmq/bin/rabbitmq-server
rabbitmq     561  2.6  0.5 2365936 122036 ?      Sl   18:29   1:04              \_ /usr/lib64/erlang/erts-7.3.1.4/bin/beam.smp -W w -A 64 -K true -P 1048576 -K true -sbwt none -B i -- -root /usr/lib64/erlang -progname erl -- -home /var/lib/rabbitmq -- -pa /usr/lib/rabbitmq/lib/rabbitmq_server-3.6.15/ebin -noshell -noinput -s rabbit boot -sname rabbit@controller-0 -boot start_sasl -config /etc/rabbitmq/rabbitmq -kernel inet_default_connect_options [{nodelay,true}] -kernel inet_default_connect_options [{nodelay,true}] -sasl errlog_type error -sasl sasl_error_logger false -rabbit error_logger {file,"/var/log/rabbitmq/rabbit@controller-0.log"} -rabbit sasl_error_logger {file,"/var/log/rabbitmq/rabbit@controller-0-sasl.log"} -rabbit enabled_plugins_file "/etc/rabbitmq/enabled_plugins" -rabbit plugins_dir "/usr/lib/rabbitmq/plugins:/usr/lib/rabbitmq/lib/rabbitmq_server-3.6.15/plugins" -rabbit plugins_expand_dir "/var/lib/rabbitmq/mnesia/rabbit@controller-0-plugins-expand" -os_mon start_cpu_sup false -os_mon start_disksup false -os_mon start_memsup false -mnesia dir "/var/lib/rabbitmq/mnesia/rabbit@controller-0"
rabbitmq     703  0.0  0.0  11588   448 ?        Ss   18:29   0:00                  \_ inet_gethost 4
rabbitmq     704  0.0  0.0  13712   708 ?        S    18:29   0:00                      \_ inet_gethost 4

Change-Id: I0ce91ed9132afe305c60036837c702c2611fa7c2
This commit is contained in:
Michele Baldessari 2018-09-12 18:18:53 +02:00
parent 860c9a33f7
commit 06b66a8094
2 changed files with 17 additions and 0 deletions
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9
puppet/services/rabbitmq.yaml
View File

@ -63,6 +63,14 @@ parameters:
net_ticktime kernel variable.
default: 15
type: number
RabbitAdditionalErlArgs:
description:
Additional parameters passed to the Erlang subsystem. The string
needs to be enclosed in quotes twice. We default to +sbwt none
in order to have the erlang vm be less busy on spinlocks, but
we allow a simple way of overriding it.
default: "'+sbwt none'"
type: string
MonitoringSubscriptionRabbitmq:
default: 'overcloud-rabbitmq'
type: string
@ -104,6 +112,7 @@ outputs:
NODE_IP_ADDRESS: ''
RABBITMQ_NODENAME: "rabbit@%{::hostname}"
RABBITMQ_SERVER_ERL_ARGS: '"+K true +P 1048576 -kernel inet_default_connect_options [{nodelay,true}]"'
RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS: {get_param: RabbitAdditionalErlArgs}
'export ERL_EPMD_ADDRESS': "%{hiera('rabbitmq::interface')}"
rabbitmq_kernel_variables:
inet_dist_listen_min: '25672'

8
releasenotes/notes/rabbitmq-erl-args-9029cf4605d63dd9.yaml Normal file
View File

@ -0,0 +1,8 @@
---
other:
- |
A new parameter called 'RabbitAdditionalErlArgs' that specifies additional arguments
to the Erlang VM has been added. It now defaults to "'+sbwt none'" (http://erlang.org/doc/man/erl.html#+sbwt)
This threshold determines how long schedulers are to busy wait when running out of work before going to sleep.
By setting it to none we let the erlang threads go to sleep right away when they do not have any work to
do.