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Health Check

New to Kuma? You don’t need this policy, check MeshHealthCheck instead. If you want to use the HealthCheck policy, remember that it requires the TrafficRoute policy to function properly.

Health Check is an outbound policy. Dataplanes whose configuration is modified are in the sources matcher.

This policy enables Kuma to keep track of the health of every data plane proxy, with the goal of minimizing the number of failed requests in case a data plane proxy is temporarily unhealthy.

By creating an HealthCheck resource we can instruct a data plane proxy to keep track of the health status for any other data plane proxy. When health-checks are properly configured, a data plane proxy will never send a request to another data plane proxy that is considered unhealthy. When an unhealthy proxy returns to a healthy state, Kuma will resume sending requests to it again.

This policy provides active checks. If you want to configure passive checks, please utilize the Circuit Breaker policy. Data plane proxies with active checks will explicitly send requests to other data plane proxies to determine if target proxies are healthy or not. This mode generates extra traffic to other proxies and services as described in the policy configuration.

Usage

As usual, we can apply sources and destinations selectors to determine how health-checks will be performed across our data plane proxies.

The HealthCheck policy supports both L4/TCP (default) and L7/HTTP checks.

Examples

apiVersion: kuma.io/v1alpha1
kind: HealthCheck
mesh: default
metadata:
  name: web-to-backend-check
spec:
  sources:
  - match:
      kuma.io/service: web_default_svc_80
  destinations:
  - match:
      kuma.io/service: backend_default_svc_80
  conf:
    interval: 10s
    timeout: 2s
    unhealthyThreshold: 3
    healthyThreshold: 1
    initialJitter: 5s # optional
    intervalJitter: 6s # optional
    intervalJitterPercent: 10 # optional
    healthyPanicThreshold: 60 # optional, by default 50
    failTrafficOnPanic: true # optional, by default false
    noTrafficInterval: 10s # optional, by default 60s
    eventLogPath: "/tmp/health-check.log" # optional
    alwaysLogHealthCheckFailures: true # optional, by default false
    reuseConnection: false # optional, by default true
    tcp: # only one of tcp or http can be defined
      send: Zm9v
      receive:
      - YmFy
      - YmF6
    http:
      path: /health
      requestHeadersToAdd:
      - append: false
        header:
          key: Content-Type
          value: application/json
      - header:
          key: Accept
          value: application/json
      expectedStatuses: [200, 201]

We will apply the configuration with kubectl apply -f [..].

HTTP

HTTP health checks are executed using HTTP 2

  • path - HTTP path which will be requested during the health checks
  • expectedStatuses (optional) - list of status codes which should be considered as a healthy during the checks
    • only statuses in the range [100, 600) are allowed
    • by default, when this property is not provided only responses with status code 200 are being considered healthy
  • requestHeadersToAdd (optional) - list of headers which should be added to every health check request:
    • append (default, optional) - should the value of the provided header be appended to already existing headers (if present)
    • header:
      • key - the name of the header
      • value (optional) - the value of the header

TCP

  • send - Base64 encoded content of the message which should be sent during the health checks
  • receive list of Base64 encoded blocks of strings which should be found in the returning message which should be considered as healthy
    • when checking the response, “fuzzy” matching is performed such that each block must be found, and in the order specified, but not necessarily contiguous;
    • if receive section won’t be provided or will be empty, checks will be performed as “connect only” and will be marked as successful when TCP connection will be successfully established.

Matching

HealthCheck is an Outbound Connection Policy. The only supported value for destinations.match is kuma.io/service.

All options

$schema: http://json-schema.org/draft-04/schema#

$ref: #/definitions/HealthCheck

definitions

HealthCheck

  • ## Health Check

  • HealthCheck defines configuration for health checking.

  • Type: object

  • This schema accepts additional properties.

  • Properties

  • ## Conf

  • Conf defines configuration for various types of health checking.

  • Type: object

  • This schema accepts additional properties.

  • Properties

    • interval
      • Interval between consecutive health checks.
      • Type: string
      • String format must be a "regex"
      • The value must match this pattern: ^([0-9]+\.?[0-9]*|\.[0-9]+)s$
    • timeout
      • Maximum time to wait for a health check response.
      • Type: string
      • String format must be a "regex"
      • The value must match this pattern: ^([0-9]+\.?[0-9]*|\.[0-9]+)s$
    • unhealthy_threshold
      • Number of consecutive unhealthy checks before considering a host unhealthy.
      • Type: integer
    • healthy_threshold
      • Number of consecutive healthy checks before considering a host healthy.
      • Type: integer
    • initial_jitter
      • If specified, Envoy will start health checking after for a random time in ms between 0 and initial_jitter. This only applies to the first health check.
      • Type: string
      • String format must be a "regex"
      • The value must match this pattern: ^([0-9]+\.?[0-9]*|\.[0-9]+)s$
    • interval_jitter
      • If specified, during every interval Envoy will add interval_jitter to the wait time.
      • Type: string
      • String format must be a "regex"
      • The value must match this pattern: ^([0-9]+\.?[0-9]*|\.[0-9]+)s$
    • intervaljitterpercent
      • *If specified, during every interval Envoy will add intervalms * intervaljitterpercent / 100 to the wait time. If intervaljitterms and intervaljitter_percent are both set, both of them will be used to increase the wait time.*
      • Type: integer
    • healthypanicthreshold
      • Allows to configure panic threshold for Envoy cluster. If not specified, the default is 50%. To disable panic mode, set to 0%.
      • Type: number
    • failtrafficon_panic
      • If set to true, Envoy will not consider any hosts when the cluster is in 'panic mode'. Instead, the cluster will fail all requests as if all hosts are unhealthy. This can help avoid potentially overwhelming a failing service.
      • Type: boolean
    • eventlogpath
      • Specifies the path to the file where Envoy can log health check events. If empty, no event log will be written.
      • Type: string
    • alwaysloghealthcheckfailures
      • If set to true, health check failure events will always be logged. If set to false, only the initial health check failure event will be logged. The default value is false.
      • Type: boolean
    • notrafficinterval
      • The "no traffic interval" is a special health check interval that is used when a cluster has never had traffic routed to it. This lower interval allows cluster information to be kept up to date, without sending a potentially large amount of active health checking traffic for no reason. Once a cluster has been used for traffic routing, Envoy will shift back to using the standard health check interval that is defined. Note that this interval takes precedence over any other. The default value for "no traffic interval" is 60 seconds.
      • Type: string
      • String format must be a "regex"
      • The value must match this pattern: ^([0-9]+\.?[0-9]*|\.[0-9]+)s$
    • tcp
    • http
    • reuse_connection
      • Reuse health check connection between health checks. Default is true.
      • Type: boolean kuma.mesh.v1alpha1.HealthCheck.Conf.Http

  • ## Http

  • Http defines optional Http configuration which will instruct the service the health check will be made for is an http service. It's mutually exclusive with the Tcp block so when provided you can't provide the Tcp configuration

  • Type: object

  • This schema accepts additional properties.

  • Properties

    • path
      • The HTTP path which will be requested during the health check (ie. /health) +required
      • Type: string
    • requestheadersto_add
    • expected_statuses
      • List of HTTP response statuses which are considered healthy +optional
      • Type: array
        • Items
        • ##### U Int 32 Value
        • Wrapper message for uint32. The JSON representation for UInt32Value is JSON number.
        • Type: integer kuma.mesh.v1alpha1.HealthCheck.Conf.Http.HeaderValue

  • ## Header Value

  • Type: object

  • This schema accepts additional properties.

  • Properties

    • key
      • Header name +required
      • Type: string
    • value
      • Header value +optional
      • Type: string kuma.mesh.v1alpha1.HealthCheck.Conf.Http.HeaderValueOption

  • ## Header Value Option

  • Type: object

  • This schema accepts additional properties.

  • Properties

    • header
    • append
      • The bool value which if true (default) will mean the header values should be appended to already present ones +optional
      • Type: boolean kuma.mesh.v1alpha1.HealthCheck.Conf.Tcp

  • ## Tcp

  • Tcp defines optional configuration for specifying bytes to send and expected response during the health check

  • Type: object

  • This schema accepts additional properties.

  • Properties

    • send
      • Bytes which will be send during the health check to the target
      • Type: string
    • receive
      • Bytes blocks expected as a response. When checking the response, “fuzzy” matching is performed such that each block must be found, and in the order specified, but not necessarily contiguous.
      • Type: array
        • Items
        • ##### Bytes Value
        • Wrapper message for bytes. The JSON representation for BytesValue is JSON string.
        • Type: string kuma.mesh.v1alpha1.Selector

  • ## Selector

  • Selector defines structure for selecting tags for given dataplane

  • Type: object

  • This schema accepts additional properties.

  • Properties

    • match
      • Tags to match, can be used for both source and destinations
      • Type: object
      • This schema accepts additional properties.
      • Properties

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