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
+------------------+--------------------------------------+
| Field | Value |
+------------------+--------------------------------------+
| created_at | 2016-06-07T02:26:33Z |
| data | {} |
| desired_capacity | 2 |
| domain_id | None |
| id | 10c80bfe-41af-41f7-b9b1-9c81c9e5d21f |
| init_at | 2016-06-07T02:26:17Z |
| max_size | -1 |
| metadata | {} |
| min_size | 0 |
| name | mycluster |
| node_ids | 14936837-1459-416b-a1f3-dea026f6cffc |
| | 99ab3862-a230-4c09-af73-076dc0dec39b |
| profile_id | 1de5686a-09bb-4fb0-9502-34fa38833010 |
| profile_name | pserver |
| project_id | 99185bcde62c478e8d05b702e52d8b8d |
| status | ACTIVE |
| status_reason | Cluster creation succeeded. |
| timeout | 3600 |
| updated_at | 2016-06-13T02:42:47Z |
| user_id | 6c369aec78b74a4da413f86dadb0255e |
+------------------+--------------------------------------+
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=1&count=2" |
| | } |
| cluster_id | b75d25e7-e84d-4742-abf7-d8a3001e25a9 |
| created_at | 2016-08-01T02:17:14Z |
| domain_id | - |
| id | ba13f7cd-7a95-4545-b646-6a833ba6505a |
| location | - |
| name | r_01 |
| params | { |
| | "count": "2" |
| | } |
| project_id | 99185bcde62c478e8d05b702e52d8b8d |
| type | webhook |
| updated_at | - |
| 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_OUTCLUSTER_SCALE_INCLUSTER_RESIZECLUSTER_CHECKCLUSTER_UPDATECLUSTER_DELETECLUSTER_ADD_NODESCLUSTER_DEL_NODESNODE_CREATENODE_DELETENODE_UPDATENODE_CHECKNODE_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=1&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 \
-t threshold --statistic avg --name cpu-high \
-m cpu_util --threshold 70 --comparison-operator gt \
--period 60 --evaluation-periods 1 \
--alarm-action $ALRM_URL01 \
--repeat-actions False \
--query metadata.user_metadata.cluster_id=$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
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