package envoy.extensions.load_balancing_policies.least_request.v3

Get desktop application:
View/edit binary Protocol Buffers messages

This configuration allows the built-in LEAST_REQUEST LB policy to be configured via the LB policy extension point. See the :ref:`load balancing architecture overview <arch_overview_load_balancing_types>` for more information. [#next-free-field: 7]

• optional google.protobuf.UInt32Value choice_count = 1

  The number of random healthy hosts from which the host with the fewest active requests will be chosen. Defaults to 2 so that we perform two-choice selection if the field is not set. Only applies to the ``N_CHOICES`` selection method.

• optional config.core.v3.RuntimeDouble active_request_bias = 2

  The following formula is used to calculate the dynamic weights when hosts have different load balancing weights: ``weight = load_balancing_weight / (active_requests + 1)^active_request_bias`` The larger the active request bias is, the more aggressively active requests will lower the effective weight when all host weights are not equal. ``active_request_bias`` must be greater than or equal to 0.0. When ``active_request_bias == 0.0`` the Least Request Load Balancer doesn't consider the number of active requests at the time it picks a host and behaves like the Round Robin Load Balancer. When ``active_request_bias > 0.0`` the Least Request Load Balancer scales the load balancing weight by the number of active requests at the time it does a pick. The value is cached for performance reasons and refreshed whenever one of the Load Balancer's host sets changes, e.g., whenever there is a host membership update or a host load balancing weight change. .. note:: This setting only takes effect if all host weights are not equal.

• optional common.v3.SlowStartConfig slow_start_config = 3

  Configuration for slow start mode. If this configuration is not set, slow start will not be not enabled.

• optional common.v3.LocalityLbConfig locality_lb_config = 4

  Configuration for local zone aware load balancing or locality weighted load balancing.

• optional google.protobuf.BoolValue enable_full_scan = 5

  [#not-implemented-hide:] Unused. Replaced by the `selection_method` enum for better extensibility.

• LeastRequest.SelectionMethod selection_method = 6

  Method for selecting the host set from which to return the host with the fewest active requests. Defaults to ``N_CHOICES``.

Available methods for selecting the host set from which to return the host with the fewest active requests.

Used in: LeastRequest

• N_CHOICES = 0

  Return host with fewest requests from a set of ``choice_count`` randomly selected hosts. Best selection method for most scenarios.

• FULL_SCAN = 1

  Return host with fewest requests from all hosts. Useful in some niche use cases involving low request rates and one of: (example 1) low request limits on workloads, or (example 2) few hosts. Example 1: Consider a workload type that can only accept one connection at a time. If such workloads are deployed across many hosts, only a small percentage of those workloads have zero connections at any given time, and the rate of new connections is low, the ``FULL_SCAN`` method is more likely to select a suitable host than ``N_CHOICES``. Example 2: Consider a workload type that is only deployed on 2 hosts. With default settings, the ``N_CHOICES`` method will return the host with more active requests 25% of the time. If the request rate is sufficiently low, the behavior of always selecting the host with least requests as of the last metrics refresh may be preferable.