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:
- 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:
Warning
Caution: Ceilometer does not accept complex value data structure for
value and metadata configurations. Therefore,
if you are extracting a complex data structure (Object, list, map, or
others), you can take advantage of the
Operations on extracted attributes feature to transform the
object into a simple value (string or number)
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
clusteras 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.
It is also possible to reference the sample itself using
"." (dot); the self reference of the sample is interesting
in cases when the attribute might not exist. Therefore, together with
the operations options, one can first check if it exist before
retrieving it (example:
". | value['some_field'] if 'some_field' in value else ''").
In our magnum example, we can usestatusas 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 usecontainer-infra. Other
values are accepted such asvolumefor cinder endpoints,
object-storefor 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_paththat we want to retrieve. To use a nested value
one can simply use
attribute1.attribute2.<asMuchAsNeeded>.lastattribute.
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 thevalue_attributethat 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 thevalue_mappingconfiguration.
This attribute is only used whenvalue_mappingis 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. Themetadata_mappingcan 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 isTrue.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_keyis 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>.lastattributeuser_id_attribute: optional parameter. The default
value isuser_id. The name of the attribute in the entries
that are processed fromresponse_entries_keyelements that
will be mapped touser_idattribute that is sent to
Gnocchi.project_id_attribute: optional parameter. The default
value isproject_id. The name of the attribute in the
entries that are processed fromresponse_entries_key
elements that will be mapped toproject_idattribute that
is sent to Gnocchi.resource_id_attribute: optional parameter. The default
value isid. The name of the attribute in the entries that
are processed fromresponse_entries_keyelements that will
be mapped toidattribute that is sent to Gnocchi.headers: optional parameter. It is a map (similar to
the metadata_mapping) of key and value that can be used to customize the
header of the request that is executed against the URL. This
configuration works for both OpenStack and non-OpenStack dynamic
pollster configuration.
headers: "x-openstack-nova-api-version": "2.46"
timeout: optional parameter. Defines the request
timeout for the requests executed by the dynamic pollsters to gather
data. The default timeout value is 30 seconds. If it is set to None, this means that the request never times
out on the client side. Therefore, one might have problems if the server
never closes the connection. The pollsters are executed serially, one
after the other. Therefore, if the request hangs, all pollsters
(including the non-dynamic ones) will stop executing.
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: 0The
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 (in addition to the original ones) 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
awsauthpython module.authentication_object: mandatory parameter. The name of
the class that we can find in themodulethat Ceilometer
will use as the authentication object in the request. For instance, when
using theawsauthpython 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 theS3Authclass, the
authentication_parameterscan 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 theauthentication_parameters.
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
Multi
metric dynamic pollsters (handling attribute values with list of
objects)
The initial idea for this feature comes from the categories fields that we can find in the summary object of the RadosGW API. Each user
has a categories attribute in the
response; in the categories list, we can
find the object that presents in a granular fashion the consumption of
different RadosGW API operations such as GET, PUT, POST, and may
others.
As follows we present an example of such a JSON response.
{
"entries": [
{
"buckets": [
{
"bucket": "",
"categories": [
{
"bytes_received": 0,
"bytes_sent": 40,
"category": "list_buckets",
"ops": 2,
"successful_ops": 2
}
],
"epoch": 1572969600,
"owner": "user",
"time": "2019-11-21 00:00:00.000000Z"
},
{
"bucket": "-",
"categories": [
{
"bytes_received": 0,
"bytes_sent": 0,
"category": "get_obj",
"ops": 1,
"successful_ops": 0
}
],
"epoch": 1572969600,
"owner": "someOtherUser",
"time": "2019-11-21 00:00:00.000000Z"
}
]
}
]
"summary": [
{
"categories": [
{
"bytes_received": 0,
"bytes_sent": 0,
"category": "create_bucket",
"ops": 2,
"successful_ops": 2
},
{
"bytes_received": 0,
"bytes_sent": 2120428,
"category": "get_obj",
"ops": 46,
"successful_ops": 46
},
{
"bytes_received": 0,
"bytes_sent": 21484,
"category": "list_bucket",
"ops": 8,
"successful_ops": 8
},
{
"bytes_received": 6889056,
"bytes_sent": 0,
"category": "put_obj",
"ops": 46,
"successful_ops": 46
}
],
"total": {
"bytes_received": 6889056,
"bytes_sent": 2141912,
"ops": 102,
"successful_ops": 102
},
"user": "user"
},
{
"categories": [
{
"bytes_received": 0,
"bytes_sent": 0,
"category": "create_bucket",
"ops": 1,
"successful_ops": 1
},
{
"bytes_received": 0,
"bytes_sent": 0,
"category": "delete_obj",
"ops": 23,
"successful_ops": 23
},
{
"bytes_received": 0,
"bytes_sent": 5371,
"category": "list_bucket",
"ops": 2,
"successful_ops": 2
},
{
"bytes_received": 3444350,
"bytes_sent": 0,
"category": "put_obj",
"ops": 23,
"successful_ops": 23
}
],
"total": {
"bytes_received": 3444350,
"bytes_sent": 5371,
"ops": 49,
"successful_ops": 49
},
"user": "someOtherUser"
}
]
}In that context, and having in mind that we have APIs with similar
data structures, we developed an extension for the dynamic pollster that
enables multi-metric processing for a single pollster. It works as
follows.
The pollster name will contain a placeholder for the variable that
identifies the “submetric”. E.g. dynamic.radosgw.api.request.{category}. The
placeholder {category} indicates the
object’s attribute that is in the list of objects that we use to load
the sub metric name. Then, we must use a special notation in the value_attribute configuration to indicate that
we are dealing with a list of objects. This is achieved via [] (brackets); for instance, in the dynamic.radosgw.api.request.{category}, we can
use [categories].ops as the value_attribute. This indicates that the value
we retrieve is a list of objects, and when the dynamic pollster
processes it, we want it (the pollster) to load the ops value for the sub metrics being
generated.
Examples on how to create multi-metric pollster to handle data from
RadosGW API are presented as follows:
---
- name: "dynamic.radosgw.api.request.{category}"
sample_type: "gauge"
unit: "request"
value_attribute: "[categories].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('$')[0]"
project_id_attribute: "user | value.split('$') | value[0]"
resource_id_attribute: "user | value.split('$') | value[0]"
response_entries_key: "summary"
- name: "dynamic.radosgw.api.request.successful_ops.{category}"
sample_type: "gauge"
unit: "request"
value_attribute: "[categories].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('$')[0]"
project_id_attribute: "user | value.split('$') | value[0]"
resource_id_attribute: "user | value.split('$') | value[0]"
response_entries_key: "summary"
- name: "dynamic.radosgw.api.bytes_sent.{category}"
sample_type: "gauge"
unit: "request"
value_attribute: "[categories].bytes_sent"
url_path: "http://rgw.service.stage.i.ewcs.ch/admin/usage"
module: "awsauth"
authentication_object: "S3Auth"
authentication_parameters: "<access_key>, <secret_key>,<rados_gateway_server>"
user_id_attribute: "user | value.split('$')[0]"
project_id_attribute: "user | value.split('$') | value[0]"
resource_id_attribute: "user | value.split('$') | value[0]"
response_entries_key: "summary"
- name: "dynamic.radosgw.api.bytes_received.{category}"
sample_type: "gauge"
unit: "request"
value_attribute: "[categories].bytes_received"
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('$')[0]"
project_id_attribute: "user | value.split('$') | value[0]"
resource_id_attribute: "user | value.split('$') | value[0]"
response_entries_key: "summary"Handling linked API
responses
If the consumed API returns a linked response which contains a link
to the next response set (page), the Dynamic pollsters can be configured
to follow these links and join all linked responses into a single
one.
To enable this behavior the operator will need to configure the
parameter next_sample_url_attribute that
must contain a mapper to the response attribute that contains the link
to the next response page. This parameter also supports operations like
the others *_attribute dynamic pollster’s
parameters.
Examples on how to create a pollster to handle linked API responses
are presented as follows:
-
Example of a simple linked response:
- API response:
{ "server_link": "http://test.com/v1/test-volumes/marker=c3", "servers": [ { "volume": [ { "name": "a", "tmp": "ra" } ], "id": 1, "name": "a1" }, { "volume": [ { "name": "b", "tmp": "rb" } ], "id": 2, "name": "b2" }, { "volume": [ { "name": "c", "tmp": "rc" } ], "id": 3, "name": "c3" } ] }- Pollster configuration:
--- - name: "dynamic.linked.response" sample_type: "gauge" unit: "request" value_attribute: "[volume].tmp" url_path: "v1/test-volumes" response_entries_key: "servers" next_sample_url_attribute: "server_link" -
Example of a complex linked response:
- API response:
{ "server_link": [ { "href": "http://test.com/v1/test-volumes/marker=c3", "rel": "next" }, { "href": "http://test.com/v1/test-volumes/marker=b1", "rel": "prev" } ], "servers": [ { "volume": [ { "name": "a", "tmp": "ra" } ], "id": 1, "name": "a1" }, { "volume": [ { "name": "b", "tmp": "rb" } ], "id": 2, "name": "b2" }, { "volume": [ { "name": "c", "tmp": "rc" } ], "id": 3, "name": "c3" } ] }- Pollster configuration:
--- - name: "dynamic.linked.response" sample_type: "gauge" unit: "request" value_attribute: "[volume].tmp" url_path: "v1/test-volumes" response_entries_key: "servers" next_sample_url_attribute: "server_link | filter(lambda v: v.get('rel') == 'next', value) | list(value) | value[0] | value.get('href')"
OpenStack
Dynamic pollsters metadata enrichment with other OpenStack API’s
data
Sometimes we want/need to add/gather extra metadata for the samples
being handled by Ceilometer Dynamic pollsters, such as the project name,
domain id, domain name, and other metadata that are not always
accessible via the OpenStack component where the sample is gathered.
For instance, when gathering the status of virtual machines (VMs)
from Nova, we only have the tenant_id,
which must be used as the project_id.
However, for billing and later invoicing one might need/want the project
name, domain id, and other metadata that are available in Keystone (and
maybe some others that are scattered over other components). To achieve
that, one can use the OpenStack metadata enrichment option. This feature
is only available to OpenStack pollsters, and can only gather
extra metadata from OpenStack APIs. As follows we present an example
that shows a dynamic pollster configuration to gather virtual machine
(VM) status, and to enrich the data pushed to the storage backend (e.g.
Gnocchi) with project name, domain ID, and domain name.
--- - name: "dynamic_pollster.instance.status" next_sample_url_attribute: "server_links | filter(lambda v: v.get('rel') == 'next', value) | list(value) | value[0] | value.get('href') | value.replace('http:', 'https:')" sample_type: "gauge" unit: "server" value_attribute: "status" endpoint_type: "compute" url_path: "/v2.1/servers/detail?all_tenants=true" headers: "Openstack-API-Version": "compute 2.65" project_id_attribute: "tenant_id" metadata_fields: - "status" - "name" - "flavor.vcpus" - "flavor.ram" - "flavor.disk" - "flavor.ephemeral" - "flavor.swap" - "flavor.original_name" - "image | value or { 'id': '' } | value['id']" - "OS-EXT-AZ:availability_zone" - "OS-EXT-SRV-ATTR:host" - "user_id" - "tags | ','.join(value)" - "locked" value_mapping: ACTIVE: "1" default_value: 0 metadata_mapping: "OS-EXT-AZ:availability_zone": "dynamic_availability_zone" "OS-EXT-SRV-ATTR:host": "dynamic_host" "flavor.original_name": "dynamic_flavor_name" "flavor.vcpus": "dynamic_flavor_vcpus" "flavor.ram": "dynamic_flavor_ram" "flavor.disk": "dynamic_flavor_disk" "flavor.ephemeral": "dynamic_flavor_ephemeral" "flavor.swap": "dynamic_flavor_swap" "image | value or { 'id': '' } | value['id']": "dynamic_image_ref" "name": "dynamic_display_name" "locked": "dynamic_locked" "tags | ','.join(value)": "dynamic_tags" extra_metadata_fields_cache_seconds: 3600 extra_metadata_fields: - name: "project_name" endpoint_type: "identity" url_path: "'/v3/projects/' + str(sample['project_id'])" headers: "Openstack-API-Version": "identity latest" value: "name" extra_metadata_fields_cache_seconds: 1800 # overriding the default cache policy - name: "domain_id" endpoint_type: "identity" url_path: "'/v3/projects/' + str(sample['project_id'])" headers: "Openstack-API-Version": "identity latest" value: "domain_id" - name: "domain_name" endpoint_type: "identity" url_path: "'/v3/domains/' + str(extra_metadata_captured['domain_id'])" headers: "Openstack-API-Version": "identity latest" value: "name"
The above example can be used to gather and persist in the backend
the status of VMs. It will persist 1 in
the backend as a measure for every collecting period if the VM’s status
is ACTIVE, and 0 otherwise. This is quite useful to create
hashmap rating rules for running VMs in CloudKitty. Then, to enrich the
resource in the storage backend, we are adding extra metadata that are
collected in Keystone via the extra_metadata_fields options.
The metadata enrichment feature has the following options:
-
extra_metadata_fields_cache_seconds: optional
parameter. Defines the extra metadata request’s response cache. Some
requests, such as the ones executed against Keystone to retrieve extra
metadata are rather static. Therefore, one does not need to constantly
re-execute the request. That is the reason why we cache the response of
such requests. By default the cache time to live (TTL) for responses is
3600 seconds. However, this value can be
increased of decreased. -
extra_metadata_fields: optional parameter. This
option is a list of objects, where each one of its elements is an extra
metadata definition. Each one of the extra metadata definition can have
the options defined in the dynamic pollsters such as to handle paged
responses, operations on the extracted values, headers and so on. The
basic options that must be defined for an extra metadata definitions are
the following:name: This option is mandatory. The name of the extra
metadata. This is the name that is going to be used by the metadata. If
there is already any other metadata gathered via metadata_fields option or transformed via metadata_mapping configuration, this metadata
is going to be discarded.endpoint_type: The endpoint type that we want to
execute the call against. This option is mandatory. It works similarly
to the endpoint_type option in the
dynamic pollster definition.url_path: This option is mandatory. It works similarly
to the url_path option in the dynamic
pollster definition. However, this one enables
operators to execute/evaluate expressions in runtime, which `allows one
to retrieve the information from previously gathered metadata via
extra_metadata_captured
dictionary, or via the sample
itself.value: This configuration is mandatory. It works
similarly to the value_attribute option
in the dynamic pollster definition. It is the value we want to extract
from the response, and assign in the metadata being generated.headers: This option is optional. It works similarly to
the headers option in the dynamic
pollster definition.next_sample_url_attribute: This option is optional. It
works similarly to the next_sample_url_attribute option in the dynamic
pollster definition.response_entries_key: This option is optional. It works
similarly to the response_entries_key
option in the dynamic pollster definition.