## Autoscaling using Ceilometer/Aodh

updated: 2020-10-17 18:54

# Autoscaling using Ceilometer/Aodh

As a telemetry service, the ceilometer project consists of several sub-projects which provide metering, monitoring and alarming services in the telemetry space. This section walks you through the steps to build an auto-scaling solution by integrating senlin with ceilometer/aodh.

## Step 1: Create a VM cluster

The first step is to create a profile using a spec file like the following one and save it to a file, e.g. `sample_server.yaml`:

    type: os.nova.server
    version: 1.0
    properties:
      name: cirros_server
      flavor: m1.tiny
      image: cirros-0.3.5-x86_64-disk
      key_name: oskey
      networks:
        - network: private

Note this spec file assumes that you have a working nova key-pair named “`oskey`” and there is a network named “`private`”. You may need to change these values based your environment settings. To create a profile using this spec:

    $ openstack cluster profile create --spec-file sample_server.yaml pserver

Then you can create a cluster using the profile named “`pserver`”:

    $ openstack cluster create --profile pserver --desired-capacity 2 mycluster

You can show cluster details, using the command openstack cluster show mycluster

    $ openstack cluster show mycluster
    +------------------+--------------------------------------------------------------------------------+
    | Field            | Value                                                                          |
    +------------------+--------------------------------------------------------------------------------+
    | config           | {}                                                                             |
    | created_at       | 2016-08-01T02:14:38Z                                                           |
    | data             | {}                                                                             |
    | dependents       | {}                                                                             |
    | desired_capacity | 2                                                                              |
    | domain_id        | None                                                                           |
    | id               | 09e9b90c-03e3-41e3-8a31-e9bde6707585                                           |
    | init_at          | 2016-08-01T02:13:59Z                                                           |
    | location         | None                                                                           |
    | max_size         | -1                                                                             |
    | metadata         | {}                                                                             |
    | min_size         | 0                                                                              |
    | name             | mycluster                                                                      |
    | node_ids         | 78509587-fa74-49cb-984f-a2e033316a63                                           |
    |                  | 8ccc31e6-14a3-4882-b0ef-27108cdb238d                                           |
    | profile_id       | 8f81a3a5-e91b-4fd5-91f1-e4a04ddae20f                                           |
    | profile_name     | pserver                                                                        |
    | project_id       | e127900ee5d94ff5aff30173aa607765                                               |
    | status           | ACTIVE                                                                         |
    | status_reason    | CLUSTER_CREATE: number of active nodes is equal or above desired_capacity (2). |
    | timeout          | 3600                                                                           |
    | updated_at       | 2016-08-01T02:14:38Z                                                           |
    | user_id          | 3914a2df5b7e49e3acbba86044e820ef                                               |
    +------------------+--------------------------------------------------------------------------------+

This creates a cluster with 2 nodes created at the beginning. We export the cluster ID into an environment variable for convenience:

    $ export MYCLUSTER_ID=10c80bfe-41af-41f7-b9b1-9c81c9e5d21f

You may want to check the IP addresses assigned to each node. In the output from the following command, you will find the IP address for the specific node:

    $ openstack cluster node show 14936837-1459-416b-a1f3-dea026f6cffc --details
    ...
    | details | +-----------+--------------------------------------+ |
    |         | | property  | value                                | |
    |         | +-----------+--------------------------------------+ |
    |         | | addresses | {                                    | |
    |         | |           |   "private": [                       | |
    |         | |           |     {                                | |
    |         | |           |       "OS-EXT-IPS-MAC:mac-addr": ... | |
    |         | |           |       "OS-EXT-IPS:type": "fixed",    | |
    |         | |           |       "addr": "10.0.0.9",            | |
    |         | |           |       "version": 4                   | |
    |         | |           |     }                                | |
    |         | |           |   ]                                  | |
    |         | |           | }                                    | |
    |         | | flavor    | 1                                    | |
    |         | | id        | 362f57b2-c089-4aab-bab3-1a7ffd4e1834 | |
    ...

We will use these IP addresses later to generate workloads on each nova server.

## Step 2: Create Receivers

The next step is to create receivers for the cluster for triggering actions on the cluster. Each receiver is usually created for a specific purpose, so for different purposes you may need to create more than receivers.

The following command creates a receiver for scaling out the specified cluster by two nodes every time it is triggered:

    $ openstack cluster receiver create --action CLUSTER_SCALE_OUT --params count=2 --cluster mycluster r_01
    +------------+---------------------------------------------------------------------------------+
    | Field      | Value                                                                           |
    +------------+---------------------------------------------------------------------------------+
    | action     | CLUSTER_SCALE_OUT                                                               |
    | actor      | {                                                                               |
    |            |   "trust_id": "432f81d339444cac959bab2fd9ba92fa"                                |
    |            | }                                                                               |
    | channel    | {                                                                               |
    |            |   "alarm_url": "http://node1:8778/v1/webhooks/ba...5a/trigger?V=2&count=2       |
    |            | }                                                                               |
    | cluster_id | b75d25e7-e84d-4742-abf7-d8a3001e25a9                                            |
    | created_at | 2016-08-01T02:17:14Z                                                            |
    | domain_id  | None                                                                            |
    | id         | ba13f7cd-7a95-4545-b646-6a833ba6505a                                            |
    | location   | None                                                                            |
    | name       | r_01                                                                            |
    | params     | {                                                                               |
    |            |   "count": "2"                                                                  |
    |            | }                                                                               |
    | project_id | 99185bcde62c478e8d05b702e52d8b8d                                                |
    | type       | webhook                                                                         |
    | updated_at | None                                                                            |
    | user_id    | 6c369aec78b74a4da413f86dadb0255e                                                |
    +------------+---------------------------------------------------------------------------------+

At present, all property values shown for a receiver are read only. You cannot change their values once the receiver is created. The only type of receivers senlin understands is “`webhook`”. For the “`action`” parameter, there are many choices:

- `CLUSTER_SCALE_OUT`

- `CLUSTER_SCALE_IN`

- `CLUSTER_RESIZE`

- `CLUSTER_CHECK`

- `CLUSTER_UPDATE`

- `CLUSTER_DELETE`

- `CLUSTER_ADD_NODES`

- `CLUSTER_DEL_NODES`

- `NODE_CREATE`

- `NODE_DELETE`

- `NODE_UPDATE`

- `NODE_CHECK`

- `NODE_RECOVER`

Senlin may add supports to more action types in future.

After a receiver is created, you can check its “`channel`” property value to find out how to trigger that receiver. For a receiver of type “`webhook`” (the default and the only supported type as for now), this means you will check the “`alarm_url`” value. We will use that value later for action triggering. For convenience, we export that value to an environment variable:

    $ export ALRM_URL01="http://node1:8778/v1/webhooks/ba...5a/trigger?V=2&count=2"

Similar to the example above, you can create other receivers for different kinds of cluster operations or the same cluster operation with different parameter values.

## Step 3: Creating Aodh Alarms

Once we have the cluster created and prepared to receive external signals, we can proceed to create alarms using the software/service you deployed. The following command creates a threshold alarm using aodh alarm service so that:

- aodh will evaluate the CPU utilization (i.e. `cpu_util`) metric across the specified cluster;

- aodh will compute the CPU utilization using the average value during a given period (i.e. 60 seconds here);

- aodh will perform evaluation at the end of every single period;

- aodh won’t trigger alarm actions repeatedly;

- aodh will do metric aggregation based on the specified metadata.

    $ aodh alarm create \
      --type gnocchi_resources_threshold --name cpu-high \
      --metric cpu_util --threshold 70 --comparison-operator gt \
      --description 'instance running hot' --evaluation-periods 1 \
      --aggregation-method mean --alarm-action $ALRM_URL01 \
      --granularity 600 --repeat-actions False \
      --query metadata.user_metadata.cluster_id=$MYCLUSTER_ID

Note that we are referencing the two environment variables `MYCLUSTER_ID` and `ALRM_URL01` in this command.

Note

To make aodh aware of the `cluster_id` metadata senlin injects into each and every VM server created, you may need to add the following line into your `/etc/ceilometer/ceilometer.conf` file:

    reserved_metadata_keys = cluster_id

Also note that to make sure your CPU utilization driven metrics are evaluated at least once per 60 seconds, you will need to change the `interval` value for the `cpu_source` in the file `/etc/ceilometer/pipeline.yaml`. For example, you can change it from the default value `600` to `60`:

    sources:
      <other stuff ...>
      - name: cpu_source
        interval: 600   <- change this to 60
        meters:
          - "cpu"
      <other stuff ...>

## Step 4: Run Workloads on Cluster Nodes

To examine the effect of cluster scaling under high CPU workload. You can now log into each cluster nodes and run some CPU burning workloads there to drive the CPU utilization high. For example:

    $ ssh cirros@10.0.0.9
    $ cat /dev/zero > /dev/null
    < Guest system "hang" here... >

When all nodes in the cluster have their CPU pressure boosted, you can check the CPU utilization on each node and finally proceed to the next step.

## Step 5: Verify Cluster Scaling

After a while after the CPU workloads on cluster nodes are started, you will notice that the cluster has been automatically scaled. Two new nodes are created and added to the cluster. This can be verified by running the following command:

    $ openstack cluster show $MYCLUSTER_ID

Optionally, you can use the following command to check if the anticipated action was triggered and executed:

    $ openstack cluster action list --filters target=$MYCLUSTER_ID

updated: 2020-10-17 18:54

Except where otherwise noted, this document is licensed under Creative Commons Attribution 3.0 License. See all OpenStack Legal Documents.

questions?