Introduction to dynamic pollster subsystem

The dynamic pollster feature allows system administrators to create/update REST API pollsters on the fly (without changing code). The system reads YAML configures that are found in pollsters_definitions_dirs parameter, which has the default at /etc/ceilometer/pollsters.d. Operators can use a single file per dynamic pollster or multiple dynamic pollsters per file.

Current limitations of the dynamic pollster system

Currently, the following types of APIs are not supported by the dynamic pollster system:

  • Paging APIs: if a user configures a dynamic pollster to gather data from a paging API, the pollster will use only the entries from the first page.

  • Tenant APIs: Tenant APIs are the ones that need to be polled in a tenant fashion. This feature is “a nice” to have, but is currently not implemented.

The dynamic pollsters system configuration (for OpenStack APIs)

Each YAML file in the dynamic pollster feature can use the following attributes to define a dynamic pollster:

  • name: mandatory field. It specifies the name/key of the dynamic pollster. For instance, a pollster for magnum can use the name dynamic.magnum.cluster;

  • sample_type: mandatory field; it defines the sample type. It must be one of the values: gauge, delta, cumulative;

  • unit: mandatory field; defines the unit of the metric that is being collected. For magnum, for instance, one can use cluster as the unit or some other meaningful String value;

  • value_attribute: mandatory attribute; defines the attribute in the JSON response from the URL of the component being polled. We also accept nested values dictionaries. To use a nested value one can simply use attribute1.attribute2.<asMuchAsNeeded>.lastattribute. In our magnum example, we can use status as the value attribute;

  • endpoint_type: mandatory field; defines the endpoint type that is used to discover the base URL of the component to be monitored; for magnum, one can use container-infra. Other values are accepted such as volume for cinder endpoints, object-store for swift, and so on;

  • url_path: mandatory attribute. It defines the path of the request that we execute on the endpoint to gather data. For example, to gather data from magnum, one can use v1/clusters/detail;

  • metadata_fields: optional field. It is a list of all fields that the response of the request executed with url_path that we want to retrieve. As an example, for magnum, one can use the following values:

metadata_fields:
  - "labels"
  - "updated_at"
  - "keypair"
  - "master_flavor_id"
  - "api_address"
  - "master_addresses"
  - "node_count"
  - "docker_volume_size"
  - "master_count"
  - "node_addresses"
  - "status_reason"
  - "coe_version"
  - "cluster_template_id"
  - "name"
  - "stack_id"
  - "created_at"
  - "discovery_url"
  - "container_version"
  • skip_sample_values: optional field. It defines the values that might come in the value_attribute that we want to ignore. For magnun, one could for instance, ignore some of the status it has for clusters. Therefore, data is not gathered for clusters in the defined status.

skip_sample_values:
  - "CREATE_FAILED"
  - "DELETE_FAILED"
  • value_mapping: optional attribute. It defines a mapping for the values that the dynamic pollster is handling. This is the actual value that is sent to Gnocchi or other backends. If there is no mapping specified, we will use the raw value that is obtained with the use of value_attribute. An example for magnum, one can use:

value_mapping:
  CREATE_IN_PROGRESS: "0"
  CREATE_FAILED: "1"
  CREATE_COMPLETE: "2"
  UPDATE_IN_PROGRESS: "3"
  UPDATE_FAILED: "4"
  UPDATE_COMPLETE: "5"
  DELETE_IN_PROGRESS: "6"
  DELETE_FAILED: "7"
  DELETE_COMPLETE: "8"
  RESUME_COMPLETE: "9"
  RESUME_FAILED: "10"
  RESTORE_COMPLETE: "11"
  ROLLBACK_IN_PROGRESS: "12"
  ROLLBACK_FAILED: "13"
  ROLLBACK_COMPLETE: "14"
  SNAPSHOT_COMPLETE: "15"
  CHECK_COMPLETE: "16"
  ADOPT_COMPLETE: "17"
  • default_value: optional parameter. The default value for the value mapping in case the variable value receives data that is not mapped to something in the value_mapping configuration. This attribute is only used when value_mapping is defined. Moreover, it has a default of -1.

  • metadata_mapping: optional parameter. The map used to create new metadata fields. The key is a metadata name that exists in the response of the request we make, and the value of this map is the new desired metadata field that will be created with the content of the metadata that we are mapping. The metadata_mapping can be created as follows:

metadata_mapping:
  name: "display_name"
  some_attribute: "new_attribute_name"
  • preserve_mapped_metadata: optional parameter. It indicates if we preserve the old metadata name when it gets mapped to a new one. The default value is True.

  • response_entries_key: optional parameter. This value is used to define the “key” of the response that will be used to look-up the entries used in the dynamic pollster processing. If no response_entries_key is informed by the operator, we will use the first we find. Moreover, if the response contains a list, instead of an object where one of its attributes is a list of entries, we use the list directly. Therefore, this option will be ignored when the API is returning the list/array of entries to be processed directly. We also accept nested values dictionaries. To use a nested value one can simply use attribute1.attribute2.<asMuchAsNeeded>.lastattribute

The complete YAML configuration to gather data from Magnum (that has been used as an example) is the following:

---

- name: "dynamic.magnum.cluster"
  sample_type: "gauge"
  unit: "cluster"
  value_attribute: "status"
  endpoint_type: "container-infra"
  url_path: "v1/clusters/detail"
  metadata_fields:
    - "labels"
    - "updated_at"
    - "keypair"
    - "master_flavor_id"
    - "api_address"
    - "master_addresses"
    - "node_count"
    - "docker_volume_size"
    - "master_count"
    - "node_addresses"
    - "status_reason"
    - "coe_version"
    - "cluster_template_id"
    - "name"
    - "stack_id"
    - "created_at"
    - "discovery_url"
    - "container_version"
  value_mapping:
    CREATE_IN_PROGRESS: "0"
    CREATE_FAILED: "1"
    CREATE_COMPLETE: "2"
    UPDATE_IN_PROGRESS: "3"
    UPDATE_FAILED: "4"
    UPDATE_COMPLETE: "5"
    DELETE_IN_PROGRESS: "6"
    DELETE_FAILED: "7"
    DELETE_COMPLETE: "8"
    RESUME_COMPLETE: "9"
    RESUME_FAILED: "10"
    RESTORE_COMPLETE: "11"
    ROLLBACK_IN_PROGRESS: "12"
    ROLLBACK_FAILED: "13"
    ROLLBACK_COMPLETE: "14"
    SNAPSHOT_COMPLETE: "15"
    CHECK_COMPLETE: "16"
    ADOPT_COMPLETE: "17"

We can also replicate and enhance some hardcoded pollsters. For instance, the pollster to gather VPN connections. Currently, it is always persisting 1 for all of the VPN connections it finds. However, the VPN connection can have multiple statuses, and we should normally only bill for active resources, and not resources on ERROR states. An example to gather VPN connections data is the following (this is just an example, and one can adapt and configure as he/she desires):

---

- name: "dynamic.network.services.vpn.connection"
sample_type: "gauge"
unit: "ipsec_site_connection"
value_attribute: "status"
endpoint_type: "network"
url_path: "v2.0/vpn/ipsec-site-connections"
metadata_fields:
  - "name"
  - "vpnservice_id"
  - "description"
  - "status"
  - "peer_address"
value_mapping:
  ACTIVE: "1"
metadata_mapping:
  name: "display_name"
default_value: 0

The dynamic pollsters system configuration (for non-OpenStack APIs)

The dynamic pollster system can also be used for non-OpenStack APIs. to configure non-OpenStack APIs, one can use all but one attribute of the Dynamic pollster system. The attribute that is not supported is the endpoint_type. The dynamic pollster system for non-OpenStack APIs is activated automatically when one uses the configurations module.

The extra parameters that are available when using the Non-OpenStack dynamic pollster sub-subsystem are the following:

  • module: required parameter. It is the python module name that Ceilometer has to load to use the authentication object when executing requests against the API. For instance, if one wants to create a pollster to gather data from RadosGW, he/she can use the awsauth python module.

  • authentication_object: mandatory parameter. The name of the class that we can find in the module that Ceilometer will use as the authentication object in the request. For instance, when using the awsauth python module to gather data from RadosGW, one can use the authentication object as S3Auth.

  • authentication_parameters: optional parameter. It is a comma separated value that will be used to instantiate the authentication_object. For instance, if we gather data from RadosGW, and we use the S3Auth class, the authentication_parameters can be configured as <rados_gw_access_key>, rados_gw_secret_key, rados_gw_host_name.

  • barbican_secret_id: optional parameter. The Barbican secret ID, from which, Ceilometer can retrieve the comma separated values of the authentication_parameters.

  • user_id_attribute: optional parameter. The name of the attribute in the entries that are processed from response_entries_key elements that will be mapped to user_id attribute that is sent to Gnocchi.

  • project_id_attribute: optional parameter. The name of the attribute in the entries that are processed from response_entries_key elements that will be mapped to project_id attribute that is sent to Gnocchi.

  • resource_id_attribute: optional parameter. The name of the attribute in the entries that are processed from response_entries_key elements that will be mapped to id attribute that is sent to Gnocchi.

As follows we present an example on how to convert the hard-coded pollster for radosgw.api.request metric to the dynamic pollster model:

---

- name: "dynamic.radosgw.api.request"
sample_type: "gauge"
unit: "request"
value_attribute: "total.ops"
url_path: "http://rgw.service.stage.i.ewcs.ch/admin/usage"
module: "awsauth"
authentication_object: "S3Auth"
authentication_parameters: "<access_key>, <secret_key>,
<rados_gateway_server>"
user_id_attribute: "user"
project_id_attribute: "user"
resource_id_attribute: "user"
response_entries_key: "summary"

We can take that example a bit further, and instead of gathering the total .ops variable, which counts for all the requests (even the unsuccessful ones), we can use the successful_ops.

---

- name: "dynamic.radosgw.api.request.successful_ops"
sample_type: "gauge"
unit: "request"
value_attribute: "total.successful_ops"
url_path: "http://rgw.service.stage.i.ewcs.ch/admin/usage"
module: "awsauth"
authentication_object: "S3Auth"
authentication_parameters: "<access_key>, <secret_key>,
<rados_gateway_server>"
user_id_attribute: "user"
project_id_attribute: "user"
resource_id_attribute: "user"
response_entries_key: "summary"

Operations on extracted attributes

The dynamic pollster system can execute Python operations to transform the attributes that are extracted from the JSON response that the system handles.

One example of use case is the RadosGW that uses <project_id$project_id> as the username (which is normally mapped to the Gnocchi resource_id). With this feature (operations on extracted attributes), one can create configurations in the dynamic pollster to clean/normalize that variable. It is as simple as defining resource_id_attribute: “user | value.split(‘$’)[0].strip()”

The operations are separated by | symbol. The first element of the expression is the key to be retrieved from the JSON object. The other elements are operations that can be applied to the value variable. The value variable is the variable we use to hold the data being extracted. The previous example can be rewritten as: resource_id_attribute: “user | value.split (‘$’) | value[0] | value.strip()”

As follows we present a complete configuration for a RadosGW dynamic pollster that is removing the $ symbol, and getting the first part of the String.

---

- name: "dynamic.radosgw.api.request.successful_ops"
sample_type: "gauge"
unit: "request"
value_attribute: "total.successful_ops"
url_path: "http://rgw.service.stage.i.ewcs.ch/admin/usage"
module: "awsauth"
authentication_object: "S3Auth"
authentication_parameters: "<access_key>, <secret_key>,
<rados_gateway_server>"
user_id_attribute: "user | value.split ('$') | value[0]"
project_id_attribute: "user | value.split ('$') | value[0]"
resource_id_attribute: "user | value.split ('$') | value[0]"
response_entries_key: "summary"

The Dynamic pollster configuration options that support this feature are the following:

  • value_attribute

  • response_entries_key

  • user_id_attribute

  • project_id_attribute

  • resource_id_attribute