Chapter 2. Configuring auto scaling for Compute instances
Chapter 2. Configuring auto scaling for Compute instances Automatically scale out your Compute instances in response to heavy system use. You can add pre-defined rules that consider factors such as CPU or memory use and you can configure Orchestration (heat) to add and remove additional instances automatically, when they are needed. 2.1. Overview of auto scaling architecture 2.1.1. Orchestration The core component providing auto scaling is Orchestration (heat). Use Orchestration to define rules using human-readable YAML templates. These rules are applied to evaluate system load based on Telemetry data to find out whether you need to add more instances into the stack. When the load drops, Orchestration can automatically remove the unused instances again. 2.1.2. Telemetry Telemetry monitors the performance of your Red Hat OpenStack Platform environment, collecting data on CPU, storage, and memory utilization for instances and physical hosts. Orchestration templates examine Telemetry data to assess whether any pre-defined action should start. 2.1.3. Key terms Stack A collection of resources that are necessary to operate an application. A stack can be as simple as a single instance and its resources, or as complex as multiple instances with all the resource dependencies that comprise a multi-tier application. Templates YAML scripts that define a series of tasks for heat to execute. For example, it is preferable to use separate templates for certain functions: Template file: Define thresholds that Telemetry should respond to, and define the auto scaling group. Environment file: Defines the build information for your environment: which flavor and image to use, how to configure the virtual network, and what software to install. 2.2. Example: Auto scaling based on CPU use In this example, Orchestration examines Telemetry data, and automatically increases the number of instances in response to high CPU use. Create a stack template and environment template to define the rules and subsequent configuration. This example uses existing resources, such as networks), and uses names that might be different to those in your own environment. Note The cpu_util metric was deprecated and removed from Red Hat OpenStack Platform. Procedure Create the environment template, describing the instance flavor, networking configuration, and image type. Save the template in the /home/<user>/stacks/example1/cirros.yaml file. Replace the <user> variable with a real user name. heat_template_version: 2016-10-14 description: Template to spawn an cirros instance. parameters: metadata: type: json image: type: string description: image used to create instance default: cirros flavor: type: string description: instance flavor to be used default: m1.tiny key_name: type: string description: keypair to be used default: mykeypair network: type: string description: project network to attach instance to default: internal1 external_network: type: string description: network used for floating IPs default: external_network resources: server: type: OS::Nova::Server properties: block_device_mapping: - device_name: vda delete_on_termination: true volume_id: { get_resource: volume } flavor: {get_param: flavor} key_name: {get_param: key_name} metadata: {get_param: metadata} networks: - port: { get_resource: port } port: type: OS::Neutron::Port properties: network: {get_param: network} security_groups: - default floating_ip: type: OS::Neutron::FloatingIP properties: floating_network: {get_param: external_network} floating_ip_assoc: type: OS::Neutron::FloatingIPAssociation properties: floatingip_id: { get_resource: floating_ip } port_id: { get_resource: port } volume: type: OS::Cinder::Volume properties: image: {get_param: image} size: 1 Register the Orchestration resource in ~/stacks/example1/environment.yaml : resource_registry: "OS::Nova::Server::Cirros": ~/stacks/example1/cirros.yaml Create the stack template. Describe the CPU thresholds to watch for and how many instances to add. An instance group is also created that defines the minimum and maximum number of instances that can participate in this template. Note The cpu_util metric was deprecated and removed from Red Hat OpenStack Platform. To obtain the equivalent functionality, use the cumulative cpu metric and an archive policy that includes the rate:mean aggregation method. For example, ceilometer-high-rate and ceilometer-low-rate . You must convert the threshold value from % to ns to use the cpu metric for the CPU utilisation alarm. The formula is: time_ns = 1,000,000,000 x {granularity} x {percentage_in_decimal}. For example, for a threshold of 80% with a granularity of 1s, the threshold is 1,000,000,000 x 1 x 0.8 = 800,000,000.0 Save the following values in ~/stacks/example1/template.yaml : heat_template_version: 2016-10-14 description: Example auto scale group, policy and alarm resources: scaleup_group: type: OS::Heat::AutoScalingGroup properties: cooldown: 300 desired_capacity: 1 max_size: 3 min_size: 1 resource: type: OS::Nova::Server::Cirros properties: metadata: {"metering.server_group": {get_param: "OS::stack_id"}} scaleup_policy: type: OS::Heat::ScalingPolicy properties: adjustment_type: change_in_capacity auto_scaling_group_id: { get_resource: scaleup_group } cooldown: 300 scaling_adjustment: 1 scaledown_policy: type: OS::Heat::ScalingPolicy properties: adjustment_type: change_in_capacity auto_scaling_group_id: { get_resource: scaleup_group } cooldown: 300 scaling_adjustment: -1 cpu_alarm_high: type: OS::Aodh::GnocchiAggregationByResourcesAlarm properties: description: Scale up if CPU > 80% metric: cpu aggregation_method: rate:mean granularity: 1 evaluation_periods: 3 threshold: 800000000.0 resource_type: instance comparison_operator: gt alarm_actions: - str_replace: template: trust+url params: url: {get_attr: [scaleup_policy, signal_url]} query: str_replace: template: '{"=": {"server_group": "stack_id"}}' params: stack_id: {get_param: "OS::stack_id"} cpu_alarm_low: type: OS::Aodh::GnocchiAggregationByResourcesAlarm properties: metric: cpu aggregation_method: rate:mean granularity: 1 evaluation_periods: 3 threshold: 200000000.0 resource_type: instance comparison_operator: lt alarm_actions: - str_replace: template: trust+url params: url: {get_attr: [scaledown_policy, signal_url]} query: str_replace: template: '{"=": {"server_group": "stack_id"}}' params: stack_id: {get_param: "OS::stack_id"} outputs: scaleup_policy_signal_url: value: {get_attr: [scaleup_policy, signal_url]} scaledown_policy_signal_url: value: {get_attr: [scaledown_policy, signal_url]} Enter the following command to build the environment and deploy the instance: Orchestration creates the stack and launches a defined minimum number of cirros instances, as defined in the min_size parameter of the scaleup_group definition. Verify that the instances were created successfully: Orchestration also creates two cpu alarms which are used to trigger scale-up or scale-down events, as defined in cpu_alarm_high and cpu_alarm_low . Verify that the triggers exist: 2.2.1. Testing auto scaling up instances Orchestration can scale instances automatically based on the cpu_alarm_high threshold definition. When the CPU use reaches a value defined in the threshold parameter, another instance starts up to balance the load. The threshold value in the above template.yaml file is set to 80%. Procedure Log on to the instance and run several dd commands to generate the load: You can expect to have 100% CPU use in the cirros instance. Verify that the alarm has triggered: After approximately 60 seconds, Orchestration starts another instance and adds it into the group. To verify this, enter the following command: After another short period of time, observe that Orchestration has auto scaled again to three instances. The configuration is set to a maximum of three instances, so it cannot scale any higher. Use the following command to verify that Orchestration has auto-scaled again to three instances: 2.2.2. Automatically scaling down instances Orchestration can automatically scale down instances based on the cpu_alarm_low threshold. In this example, the instances scale down when CPU use is below 5%. Procedure Terminate the running dd processes and observe Orchestration begin to scale the instances down: When you stop the dd processes, the cpu_alarm_low event triggers. As a result, Orchestration begins to automatically scale down and remove the instances. Verify that the corresponding alarm has triggered: After several minutes, Orchestration continually reduces the number of instances to the minimum value defined in the min_size parameter of the scaleup_group definition. In this scenario, the min_size parameter is set to 1 . 2.2.3. Troubleshooting the setup If your environment is not working properly, you can look for errors in the log files and history records. To view information on state transitions, you can list the stack event records: To read the alarm history log: To see the records of scale-out or scale-down operations that heat collects for the existing stack, use the awk command to parse the heat-engine.log : To view aodh -related information, examine the evaluator.log :
heat_template_version: 2016-10-14 description: Template to spawn an cirros instance. parameters: metadata: type: json image: type: string description: image used to create instance default: cirros flavor: type: string description: instance flavor to be used default: m1.tiny key_name: type: string description: keypair to be used default: mykeypair network: type: string description: project network to attach instance to default: internal1 external_network: type: string description: network used for floating IPs default: external_network resources: server: type: OS::Nova::Server properties: block_device_mapping: - device_name: vda delete_on_termination: true volume_id: { get_resource: volume } flavor: {get_param: flavor} key_name: {get_param: key_name} metadata: {get_param: metadata} networks: - port: { get_resource: port } port: type: OS::Neutron::Port properties: network: {get_param: network} security_groups: - default floating_ip: type: OS::Neutron::FloatingIP properties: floating_network: {get_param: external_network} floating_ip_assoc: type: OS::Neutron::FloatingIPAssociation properties: floatingip_id: { get_resource: floating_ip } port_id: { get_resource: port } volume: type: OS::Cinder::Volume properties: image: {get_param: image} size: 1 resource_registry: "OS::Nova::Server::Cirros": ~/stacks/example1/cirros.yaml heat_template_version: 2016-10-14 description: Example auto scale group, policy and alarm resources: scaleup_group: type: OS::Heat::AutoScalingGroup properties: cooldown: 300 desired_capacity: 1 max_size: 3 min_size: 1 resource: type: OS::Nova::Server::Cirros properties: metadata: {"metering.server_group": {get_param: "OS::stack_id"}} scaleup_policy: type: OS::Heat::ScalingPolicy properties: adjustment_type: change_in_capacity auto_scaling_group_id: { get_resource: scaleup_group } cooldown: 300 scaling_adjustment: 1 scaledown_policy: type: OS::Heat::ScalingPolicy properties: adjustment_type: change_in_capacity auto_scaling_group_id: { get_resource: scaleup_group } cooldown: 300 scaling_adjustment: -1 cpu_alarm_high: type: OS::Aodh::GnocchiAggregationByResourcesAlarm properties: description: Scale up if CPU > 80% metric: cpu aggregation_method: rate:mean granularity: 1 evaluation_periods: 3 threshold: 800000000.0 resource_type: instance comparison_operator: gt alarm_actions: - str_replace: template: trust+url params: url: {get_attr: [scaleup_policy, signal_url]} query: str_replace: template: '{"=": {"server_group": "stack_id"}}' params: stack_id: {get_param: "OS::stack_id"} cpu_alarm_low: type: OS::Aodh::GnocchiAggregationByResourcesAlarm properties: metric: cpu aggregation_method: rate:mean granularity: 1 evaluation_periods: 3 threshold: 200000000.0 resource_type: instance comparison_operator: lt alarm_actions: - str_replace: template: trust+url params: url: {get_attr: [scaledown_policy, signal_url]} query: str_replace: template: '{"=": {"server_group": "stack_id"}}' params: stack_id: {get_param: "OS::stack_id"} outputs: scaleup_policy_signal_url: value: {get_attr: [scaleup_policy, signal_url]} scaledown_policy_signal_url: value: {get_attr: [scaledown_policy, signal_url]} openstack stack create -t template.yaml -e environment.yaml example +---------------------+--------------------------------------------+ | Field | Value | +---------------------+--------------------------------------------+ | id | 248a98bb-f56e-4934-a281-fffde62d78d8 | | stack_name | example | | description | Example auto scale group, policy and alarm | | creation_time | 2017-03-06T15:00:29Z | | updated_time | None | | stack_status | CREATE_IN_PROGRESS | | stack_status_reason | Stack CREATE started | +---------------------+--------------------------------------------+ openstack server list +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+-------------------------------------+ | ID | Name | Status | Task State | Power State | Networks | +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+-------------------------------------+ | e1524f65-5be6-49e4-8501-e5e5d812c612 | ex-3gax-5f3a4og5cwn2-png47w3u2vjd-server-vaajhuv4mj3j | ACTIVE | - | Running | internal1=10.10.10.9, 192.168.122.8 | +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+-------------------------------------+ openstack alarm list +--------------------------------------+--------------------------------------------+-------------------------------------+-------------------+----------+---------+ | alarm_id | type | name | state | severity | enabled | +--------------------------------------+--------------------------------------------+-------------------------------------+-------------------+----------+---------+ | 022f707d-46cc-4d39-a0b2-afd2fc7ab86a | gnocchi_aggregation_by_resources_threshold | example-cpu_alarm_high-odj77qpbld7j | insufficient data | low | True | | 46ed2c50-e05a-44d8-b6f6-f1ebd83af913 | gnocchi_aggregation_by_resources_threshold | example-cpu_alarm_low-m37jvnm56x2t | insufficient data | low | True | +--------------------------------------+--------------------------------------------+-------------------------------------+-------------------+----------+---------+ ssh -i ~/mykey.pem cirros@192.168.122.8 sudo dd if=/dev/zero of=/dev/null & sudo dd if=/dev/zero of=/dev/null & sudo dd if=/dev/zero of=/dev/null & openstack alarm list +--------------------------------------+--------------------------------------------+-------------------------------------+-------+----------+---------+ | alarm_id | type | name | state | severity | enabled | +--------------------------------------+--------------------------------------------+-------------------------------------+-------+----------+---------+ | 022f707d-46cc-4d39-a0b2-afd2fc7ab86a | gnocchi_aggregation_by_resources_threshold | example-cpu_alarm_high-odj77qpbld7j | alarm | low | True | | 46ed2c50-e05a-44d8-b6f6-f1ebd83af913 | gnocchi_aggregation_by_resources_threshold | example-cpu_alarm_low-m37jvnm56x2t | ok | low | True | +--------------------------------------+--------------------------------------------+-------------------------------------+-------+----------+---------+ openstack server list +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+---------------------------------------+ | ID | Name | Status | Task State | Power State | Networks | +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+---------------------------------------+ | 477ee1af-096c-477c-9a3f-b95b0e2d4ab5 | ex-3gax-4urpikl5koff-yrxk3zxzfmpf-server-2hde4tp4trnk | ACTIVE | - | Running | internal1=10.10.10.13, 192.168.122.17 | | e1524f65-5be6-49e4-8501-e5e5d812c612 | ex-3gax-5f3a4og5cwn2-png47w3u2vjd-server-vaajhuv4mj3j | ACTIVE | - | Running | internal1=10.10.10.9, 192.168.122.8 | +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+---------------------------------------+ openstack server list +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+---------------------------------------+ | ID | Name | Status | Task State | Power State | Networks | +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+---------------------------------------+ | 477ee1af-096c-477c-9a3f-b95b0e2d4ab5 | ex-3gax-4urpikl5koff-yrxk3zxzfmpf-server-2hde4tp4trnk | ACTIVE | - | Running | internal1=10.10.10.13, 192.168.122.17 | | e1524f65-5be6-49e4-8501-e5e5d812c612 | ex-3gax-5f3a4og5cwn2-png47w3u2vjd-server-vaajhuv4mj3j | ACTIVE | - | Running | internal1=10.10.10.9, 192.168.122.8 | | 6c88179e-c368-453d-a01a-555eae8cd77a | ex-3gax-fvxz3tr63j4o-36fhftuja3bw-server-rhl4sqkjuy5p | ACTIVE | - | Running | internal1=10.10.10.5, 192.168.122.5 | +--------------------------------------+-------------------------------------------------------+--------+------------+-------------+---------------------------------------+ killall dd openstack alarm list +--------------------------------------+--------------------------------------------+-------------------------------------+-------+----------+---------+ | alarm_id | type | name | state | severity | enabled | +--------------------------------------+--------------------------------------------+-------------------------------------+-------+----------+---------+ | 022f707d-46cc-4d39-a0b2-afd2fc7ab86a | gnocchi_aggregation_by_resources_threshold | example-cpu_alarm_high-odj77qpbld7j | ok | low | True | | 46ed2c50-e05a-44d8-b6f6-f1ebd83af913 | gnocchi_aggregation_by_resources_threshold | example-cpu_alarm_low-m37jvnm56x2t | alarm | low | True | +--------------------------------------+--------------------------------------------+-------------------------------------+-------+----------+---------+ openstack stack event list example 2017-03-06 11:12:43Z [example]: CREATE_IN_PROGRESS Stack CREATE started 2017-03-06 11:12:43Z [example.scaleup_group]: CREATE_IN_PROGRESS state changed 2017-03-06 11:13:04Z [example.scaleup_group]: CREATE_COMPLETE state changed 2017-03-06 11:13:04Z [example.scaledown_policy]: CREATE_IN_PROGRESS state changed 2017-03-06 11:13:05Z [example.scaleup_policy]: CREATE_IN_PROGRESS state changed 2017-03-06 11:13:05Z [example.scaledown_policy]: CREATE_COMPLETE state changed 2017-03-06 11:13:05Z [example.scaleup_policy]: CREATE_COMPLETE state changed 2017-03-06 11:13:05Z [example.cpu_alarm_low]: CREATE_IN_PROGRESS state changed 2017-03-06 11:13:05Z [example.cpu_alarm_high]: CREATE_IN_PROGRESS state changed 2017-03-06 11:13:06Z [example.cpu_alarm_low]: CREATE_COMPLETE state changed 2017-03-06 11:13:07Z [example.cpu_alarm_high]: CREATE_COMPLETE state changed 2017-03-06 11:13:07Z [example]: CREATE_COMPLETE Stack CREATE completed successfully 2017-03-06 11:19:34Z [example.scaleup_policy]: SIGNAL_COMPLETE alarm state changed from alarm to alarm (Remaining as alarm due to 1 samples outside threshold, most recent: 95.4080102993) 2017-03-06 11:25:43Z [example.scaleup_policy]: SIGNAL_COMPLETE alarm state changed from alarm to alarm (Remaining as alarm due to 1 samples outside threshold, most recent: 95.8869217299) 2017-03-06 11:33:25Z [example.scaledown_policy]: SIGNAL_COMPLETE alarm state changed from ok to alarm (Transition to alarm due to 1 samples outside threshold, most recent: 2.73931707966) 2017-03-06 11:39:15Z [example.scaledown_policy]: SIGNAL_COMPLETE alarm state changed from alarm to alarm (Remaining as alarm due to 1 samples outside threshold, most recent: 2.78110858552) openstack alarm-history show 022f707d-46cc-4d39-a0b2-afd2fc7ab86a +----------------------------+------------------+-----------------------------------------------------------------------------------------------------+--------------------------------------+ | timestamp | type | detail | event_id | +----------------------------+------------------+-----------------------------------------------------------------------------------------------------+--------------------------------------+ | 2017-03-06T11:32:35.510000 | state transition | {"transition_reason": "Transition to ok due to 1 samples inside threshold, most recent: | 25e0e70b-3eda-466e-abac-42d9cf67e704 | | | | 2.73931707966", "state": "ok"} | | | 2017-03-06T11:17:35.403000 | state transition | {"transition_reason": "Transition to alarm due to 1 samples outside threshold, most recent: | 8322f62c-0d0a-4dc0-9279-435510f81039 | | | | 95.0964497325", "state": "alarm"} | | | 2017-03-06T11:15:35.723000 | state transition | {"transition_reason": "Transition to ok due to 1 samples inside threshold, most recent: | 1503bd81-7eba-474e-b74e-ded8a7b630a1 | | | | 3.59330523447", "state": "ok"} | | | 2017-03-06T11:13:06.413000 | creation | {"alarm_actions": ["trust+http://fca6e27e3d524ed68abdc0fd576aa848:delete@192.168.122.126:8004/v1/fd | 224f15c0-b6f1-4690-9a22-0c1d236e65f6 | | | | 1c345135be4ee587fef424c241719d/stacks/example/d9ef59ed-b8f8-4e90-bd9b- | | | | | ae87e73ef6e2/resources/scaleup_policy/signal"], "user_id": "a85f83b7f7784025b6acdc06ef0a8fd8", | | | | | "name": "example-cpu_alarm_high-odj77qpbld7j", "state": "insufficient data", "timestamp": | | | | | "2017-03-06T11:13:06.413455", "description": "Scale up if CPU > 80%", "enabled": true, | | | | | "state_timestamp": "2017-03-06T11:13:06.413455", "rule": {"evaluation_periods": 1, "metric": | | | | | "cpu_util", "aggregation_method": "mean", "granularity": 300, "threshold": 80.0, "query": "{\"=\": | | | | | {\"server_group\": \"d9ef59ed-b8f8-4e90-bd9b-ae87e73ef6e2\"}}", "comparison_operator": "gt", | | | | | "resource_type": "instance"}, "alarm_id": "022f707d-46cc-4d39-a0b2-afd2fc7ab86a", | | | | | "time_constraints": [], "insufficient_data_actions": null, "repeat_actions": true, "ok_actions": | | | | | null, "project_id": "fd1c345135be4ee587fef424c241719d", "type": | | | | | "gnocchi_aggregation_by_resources_threshold", "severity": "low"} | | +----------------------------+------------------+-----------------------------------------------------------------------------------------------------+------------------------------------- awk '/Stack UPDATE started/,/Stack CREATE completed successfully/ {print USD0}' /var/log/containers/heat/heat-engine.log grep -i alarm /var/log/containers/aodh/evaluator.log | grep -i transition