MeshLoadBalancingStrategy (beta)

This policy uses new policy matching algorithm and is in beta state.

This policy enables Kuma to configure the load balancing strategy for traffic between services in the mesh. Also, localityAwareLoadBalancing flag is going to be replaced by the current policy and will be deprecated in the future releases.

TargetRef support matrix

TargetRef typetop leveltofrom
Mesh✅✅❌
MeshSubset✅❌❌
MeshService✅✅❌
MeshServiceSubset✅❌❌
MeshGatewayRoute❌❌❌

To learn more about the information in this table, see the matching docs.

Configuration

LocalityAwareness

Locality-aware load balancing is enabled by default unlike its predecessor localityAwareLoadBalancing.

  • disabled – (optional) allows to disable locality-aware load balancing. When disabled requests are distributed across all endpoints regardless of locality.

LoadBalancer

  • type - available values are RoundRobin, LeastRequest, RingHash, Random, Maglev.

RoundRobin

RoundRobin is a load balancing algorithm that distributes requests across available upstream hosts in round-robin order.

LeastRequest

LeastRequest selects N random available hosts as specified in ‘choiceCount’ (2 by default) and picks the host which has the fewest active requests.

  • choiceCount - (optional) is the number of random healthy hosts from which the host with the fewest active requests will be chosen. Defaults to 2 so that Envoy performs two-choice selection if the field is not set.

RingHash

RingHash implements consistent hashing to upstream hosts. Each host is mapped onto a circle (the “ring”) by hashing its address; each request is then routed to a host by hashing some property of the request, and finding the nearest corresponding host clockwise around the ring.

  • hashFunction - (optional) available values are XX_HASH, MURMUR_HASH_2. Default is XX_HASH.
  • minRingSize - (optional) minimum hash ring size. The larger the ring is (that is, the more hashes there are for each provided host) the better the request distribution will reflect the desired weights. Defaults to 1024 entries, and limited to 8M entries.
  • maxRingSize - (optional) maximum hash ring size. Defaults to 8M entries, and limited to 8M entries, but can be lowered to further constrain resource use.
  • hashPolicies - (optional) specify a list of request/connection properties that are used to calculate a hash. These hash policies are executed in the specified order. If a hash policy has the “terminal” attribute set to true, and there is already a hash generated, the hash is returned immediately, ignoring the rest of the hash policy list.
    • type - available values are Header, Cookie, Connection, QueryParameter, FilterState
    • terminal - is a flag that short-circuits the hash computing. This field provides a ‘fallback’ style of configuration: “if a terminal policy doesn’t work, fallback to rest of the policy list”, it saves time when the terminal policy works. If true, and there is already a hash computed, ignore rest of the list of hash polices.
    • header:
      • name - the name of the request header that will be used to obtain the hash key.
    • cookie:
      • name - the name of the cookie that will be used to obtain the hash key.
      • ttl - (optional) if specified, a cookie with the TTL will be generated if the cookie is not present.
      • path - (optional) the name of the path for the cookie.
    • connection:
      • sourceIP - if true, then hashing is based on a source IP address.
    • queryParameter:
      • name - the name of the URL query parameter that will be used to obtain the hash key. If the parameter is not present, no hash will be produced. Query parameter names are case-sensitive.
    • filterState:
      • key – the name of the Object in the per-request filterState, which is an Envoy::Hashable object. If there is no data associated with the key, or the stored object is not Envoy::Hashable, no hash will be produced.

Random

Random selects a random available host. The random load balancer generally performs better than round-robin if no health checking policy is configured. Random selection avoids bias towards the host in the set that comes after a failed host.

Maglev

Maglev implements consistent hashing to upstream hosts. Maglev can be used as a drop in replacement for the ring hash load balancer any place in which consistent hashing is desired.

  • tableSize - (optional) the table size for Maglev hashing. Maglev aims for “minimal disruption” rather than an absolute guarantee. Minimal disruption means that when the set of upstream hosts change, a connection will likely be sent to the same upstream as it was before. Increasing the table size reduces the amount of disruption. The table size must be prime number limited to 5000011. If it is not specified, the default is 65537.
  • hashPolicies - (optional) specify a list of request/connection properties that are used to calculate a hash. These hash policies are executed in the specified order. If a hash policy has the “terminal” attribute set to true, and there is already a hash generated, the hash is returned immediately, ignoring the rest of the hash policy list.
    • type - available values are Header, Cookie, Connection, QueryParameter, FilterState
    • terminal - is a flag that short-circuits the hash computing. This field provides a ‘fallback’ style of configuration: “if a terminal policy doesn’t work, fallback to rest of the policy list”, it saves time when the terminal policy works. If true, and there is already a hash computed, ignore rest of the list of hash polices.
    • header:
      • name - the name of the request header that will be used to obtain the hash key.
    • cookie:
      • name - the name of the cookie that will be used to obtain the hash key.
      • ttl - (optional) if specified, a cookie with the TTL will be generated if the cookie is not present.
      • path - (optional) the name of the path for the cookie.
    • connection:
      • sourceIP - if true, then hashing is based on a source IP address.
    • queryParameter:
      • name - the name of the URL query parameter that will be used to obtain the hash key. If the parameter is not present, no hash will be produced. Query parameter names are case-sensitive.
    • filterState:
      • key – the name of the Object in the per-request filterState, which is an Envoy::Hashable object. If there is no data associated with the key, or the stored object is not Envoy::Hashable, no hash will be produced.

Examples

RingHash load balancing from web to backend

Load balance requests from web to backend based on the HTTP header x-header:

  1. kind: MeshLoadBalancingStrategy
  2. apiVersion: kuma.io/v1alpha1
  3. metadata:
  4.   name: ring-hash
  5.   namespace: kuma-system
  6.   labels:
  7.     kuma.io/mesh: mesh-1
  8. spec:
  9.   targetRef:
  10.     kind: MeshService
  11.     name: web
  12.   to:
  13.     - targetRef:
  14.         kind: MeshService
  15.         name: backend
  16.       default:
  17.         loadBalancer:
  18.           type: RingHash
  19.           ringHash:
  20.             hashPolicies:
  21.               - type: Header
  22.                 header:
  23.                   name: x-header

Apply the configuration with kubectl apply -f [..].

  1. type: MeshLoadBalancingStrategy
  2. name: ring-hash
  3. mesh: mesh-1
  4. spec:
  5.   targetRef:
  6.     kind: MeshService
  7.     name: web
  8.   to:
  9.     - targetRef:
  10.         kind: MeshService
  11.         name: backend
  12.       default:
  13.         loadBalancer:
  14.           type: RingHash
  15.           ringHash:
  16.             hashPolicies:
  17.               - type: Header
  18.                 header:
  19.                   name: x-header

Apply the configuration with kumactl apply -f [..] or with the HTTP API.

Disable locality-aware load balancing for backend

Requests to backend will be spread evenly across all zones where backend is deployed.

  1. kind: MeshLoadBalancingStrategy
  2. apiVersion: kuma.io/v1alpha1
  3. metadata:
  4.   name: disable-la-to-backend
  5.   namespace: kuma-system
  6.   labels:
  7.     kuma.io/mesh: mesh-1
  8. spec:
  9.   targetRef:
  10.     kind: Mesh
  11.   to:
  12.     - targetRef:
  13.         kind: MeshService
  14.         name: backend
  15.       default:
  16.         localityAwareness:
  17.           disabled: true

Apply the configuration with kubectl apply -f [..].

  1. type: MeshLoadBalancingStrategy
  2. name: disable-la-to-backend
  3. mesh: mesh-1
  4. spec:
  5.   targetRef:
  6.     kind: Mesh
  7.   to:
  8.     - targetRef:
  9.         kind: MeshService
  10.         name: backend
  11.       default:
  12.         localityAwareness:
  13.           disabled: true

Apply the configuration with kumactl apply -f [..] or with the HTTP API.