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Telemetry with Gnocchi, Ceph and Redis example

The default openstack-ansible installation configures gnocchi to use a file as storage backend. When you already have a pre-installed ceph, you can use this as backend for gnocchi. This documentation will guide you how to set up gnocchi to use your ceph as storage backend.

Ceph as metric storage

gnocchi_storage_driver: ceph

You have to add some pip packages to your gnocchi setup:

gnocchi_pip_packages:
- cryptography
- gnocchiclient
# this is what we want:
#  - "gnocchi[mysql,ceph,ceph_alternative_lib,redis]"
# but as there is no librados >=12.2 pip package we have to first install ceph without alternative support
# after adding the ceph repo to gnocchi container, python-rados>=12.2.0 is installed and linked automatically
# and gnocchi will automatically take up the features present in the used rados lib.
- "gnocchi[mysql,ceph,redis]"
- keystonemiddleware
- python-memcached

But when your setup grows, gnocchi might slow down or block your ceph installation. You might experience slow requests and stuck PGs in your Ceph. As this might have multiple causes, take a look at the presentations linked in the Performance Tests for Gnocchi section. They also include various parameters which you might tune.

Redis as measure storage

One solution to possible performance problems is to use an incoming measure storage for your gnocchi installation. The supported storage systems are:

  • File (default)

  • Ceph (preferred)

  • OpenStack Swift

  • Amazon S3

  • Redis

When your Swift installation uses Ceph as backend, the only one left for this setup is Redis.

So first of all setup a redis server/cluster, e.g. with this ansible role. Next, you have to configure Gnocchi with OpenStack-Ansible to use the Redis Cluster as incoming storage:

gnocchi_conf_overrides:
  incoming:
    driver: redis
    redis_url: redis://{{ hostvars[groups['redis-master'][0]]['ansible_default_ipv4']['address'] }}:{{ hostvars[groups['redis-master'][0]]['redis_sentinel_port'] }}?sentinel=master01{% for host in groups['redis-slave'] %}&sentinel_fallback={{ hostvars[host]['ansible_default_ipv4']['address'] }}:{{ hostvars[host]['redis_sentinel_port'] }}{% endfor %}

You also have to install additional pip/distro packages to use the redis cluster:

gnocchi_distro_packages:
- apache2
- apache2-utils
- libapache2-mod-wsgi
- git
- build-essential
- python-dev
- libpq-dev
- python-rados
# additional package for python redis client
- python-redis
gnocchi_pip_packages:
- cryptography
- gnocchiclient
# this is what we want:
#  - "gnocchi[mysql,ceph,ceph_alternative_lib,redis]"
# but as there is no librados >=12.2 pip package we have to first install ceph without alternative support
# after adding the ceph repo to gnocchi container, python-rados>=12.2.0 is installed and linked automatically
# and gnocchi will automatically take up the features present in the used rados lib.
- "gnocchi[mysql,ceph,redis]"
- keystonemiddleware
- python-memcached
- redis

Note

A word of caution: the name of the Ceph alternative lib implementation (ceph_alternative_lib) varies between Gnocchi versions.

Zookeeper for coordination

When you deployed Gnocchi on multiple servers to distribute the work, add Zookeeper as coordination backend. To setup Zookeeper, you can use this ansible role.

Create containers for Zookeeper:

## conf.d
zookeeper_hosts:
{% for server in groups['control_nodes'] %}
{{ server }}:
  ip: {{ hostvars[server]['ansible_default_ipv4']['address'] }}
{% endfor%}
## env.d
component_skel:
  zookeeper_server:
    belongs_to:
      - zookeeper_all

container_skel:
  zookeeper_container:
    belongs_to:
      - infra_containers
      - shared-infra_containers
    contains:
      - zookeeper_server
    properties:
      service_name: zookeeper

Now you can set up Zookeeper as coordination backend for Gnocchi:

gnocchi_coordination_url: "zookeeper://{% for host in groups['zookeeper_all'] %}{{ hostvars[host]['container_address'] }}:2181{% if not loop.last %},{% endif %}{% endfor %}"

You also have to install additional packages:

gnocchi_pip_packages:
- cryptography
- gnocchiclient
# this is what we want:
#  - "gnocchi[mysql,ceph,ceph_alternative_lib,redis]"
# but as there is no librados >=12.2 pip package we have to first install ceph without alternative support
# after adding the ceph repo to gnocchi container, python-rados>=12.2.0 is installed and linked automatically
# and gnocchi will automatically take up the features present in the used rados lib.
- "gnocchi[mysql,ceph,redis]"
- keystonemiddleware
- python-memcached
- redis
# addiitional pip packages needed for zookeeper coordination backend
- tooz
- lz4
- kazoo

Performance Tests for Gnocchi

For more ideas how to tune your Gnocchi stack, take a look at these presentations: