Description of AverageLatencySchedulingPolicy fields - Alibaba Cloud Service Mesh

This topic describes the fields of AverageLatencySchedulingPolicy.

AverageLatencySchedulingPolicySpec

Field	Type	Description
load_scheduling_core	LoadSchedulingCore	The scheduler configuration.

LoadSchedulingCore

Field	Type	Description
aimd_load_scheduler	AimdLoadScheduler	The configuration of the Additive Increase Multiplicative Decrease (AIMD) scheduler.

Selector

Traffic flows are selected based on control point, flow label, agent group, and service.

control_point: ingress
label_matcher:
  match_labels:
    user_tier: gold
  match_expressions:
    - key: query
      operator: In
      values:
        - insert
        - delete
  expression:
    label_matches:
      - label: user_agent
        regex: ^(?!.*Chrome).*Safari

Field	Type	Description
control_point	string	This field identifies the location within services where policies take effect for traffic flows. You can set this field to ingress, egress, a specific listener, or a specific filter chain. Default value: ingress.
label_matcher	LabelMatcher	This field can be used to match traffic flows based on flow labels.
service	string	The Fully Qualified Domain Name (FQDN) of the service to select. Default value: any.

LabelMatcher

It provides three methods to define requirements:

Match labels
Match expressions
Arbitrary expression

If multiple requirements are set, they are all combined by using the logical AND operator. An empty label matcher always matches any requests.

Field	Type	Description
expression	Expression	An expression to be evaluated on the labels.
match_labels	map[string]string	A map of key-value pairs that represent the labels to be matched.
match_list	MatchRequirement	The list of labels matching requirements.

Expression

Expression allows multiple variants, and only one of the fields can be configured.

Field	Type	Description
all	ExpressionList	The expression is true when all subexpressions are true, which is equivalent to the logical AND operation.
any	ExpressionList	The expression is `true` when any subexpression is `true`, which is equivalent to the logical `OR` operation.
label_equals	EqualExpression	The expression is `true` when the value of the specified label equals the given value.
label_exists	string	The expression is `true` when a label with the given name exists.
label_matches	MatchesExpression	The expression is `true` when the specified label matches the given regular expression.
not	Expression	The expression negates the result of the subexpression.

ExpressionList

Field	Type	Description
of	[]Expression	The list of subexpressions of the match expression.

EqualExpression

Field	Type	Description
label	string	The label key. This field is required.
value	string	The label value.

MatchesExpression

Field	Type	Description
label	string	The name of the label to match the regular expression. This field is required.
regex	string	A regular expression that should match the label value. This field is required. For more information, see Regular expression syntax of Go.

MatchRequirement

Field	Type	Description
key	string	The label key that the selector applies to. This field is required.
operator	Enumeration	Valid values: In, NotIn, Exists, and DoesNotExist. This field is required.
values	[]string	An array of string values that relates to the key by an operator. If the operator is Exists or DoesNotExist, the values array must be empty.

AimdLoadScheduler

Field	Type	Description
gradient	GradientControllerParameters	The parameters for the gradient controller. This field is required.
load_multiplier_linear_increment	float64	The minimum value is 0 and the default value is `0.025`. This field specifies the linear increment to the load multiplier every 10 seconds when the system is not in the overloaded state, until `max_load_multiplier` is reached.
load_scheduler	LoadSchedulerParameters	The parameters for the load scheduler. This field is required.
max_load_multiplier	float64	The minimum value is 0. The default value is 2. The field specifies the maximum load multiplier that can be reached during recovery from an overloaded state. This field helps protect the service from request bursts when the system is still recovering. Once the value of this field is reached, the scheduler enters the pass-through mode. This mode allows requests to bypass the scheduler and be sent directly to the service. The pass-through mode is disabled if the system enters the overloaded state again.

GradientControllerParameters

The following table describes the gradient parameters.

Field

Type

Description

max_gradient

float64

Default value: 1.

min_gradient

float64

Default value: 0.1.

slope

float64

Default value: -1.

The slope field controls the aggressiveness and direction of the gradient controller. This field is used as exponent on the signal to setpoint ratio in computation of the gradient. Example:

slope = 1: When the signal is too high, increase the control variable.
slope = -1: When the signal is too high, decrease the control variable.
slope = -0.5: When the signal is too high, decrease the control variable gradually.

It is recommended that the absolute value of slope does not exceed 1.

LoadSchedulerParameters

Field	Type	Description
scheduler	Scheduler	The configuration of the Weighted Fair Queuing-based workload scheduler.
selectors	[]Selector	The selectors for the Weighted Fair Queuing-based workload scheduler.
workload_latency_based_tokens	bool	Default value: false. The size of traffic flows within each workload is automatically estimated based on historical latency. The number of tokens for each workload is set to the average latency of traffic flows in the workload during the last few seconds (the exact duration of this average can change). This setting is useful in concurrency limiting scenarios, where the concurrency is calculated by using the following formula: Concurrency = avg.latency × in-flight flows. The value of tokens estimated takes a lower precedence than the value of tokens specified in the workload definition and the value of tokens explicitly specified in the flow labels.

Scheduler

Field	Type	Description
workloads	[]SchedulerWorkload	The list of workloads to be used.

SchedulerWorkload

Field	Type	Description
label_matcher	LabelMatcher	The label matcher to select a workload based on flow labels.
Name	string	The workload name.
Parameters	SchedulerWorkloadParameters	The parameters associated with traffic flows matching the label matcher.

SchedulerWorkloadParameters

Field	Type	Description
priority	float64	The priority.
queue_timeout	string	The timeout for the traffic flows in the workload.
tokens	float64	The tokens field determines the cost of admitting a single traffic flow in the workload, which is typically defined as milliseconds of flow latency (time to response or duration of a feature) or simply equal to 1 if the resource being accessed is constrained by the number of traffic flows (third-party rate limiters). This override is applicable only if the number of tokens is not specified in the flow labels.