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Health Check
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
destinations:
- match:
kuma.io/service: backend
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 checksexpectedStatuses
(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
- only statuses in the range
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 headervalue
(optional) - the value of the header
TCP
send
- Base64 encoded content of the message which should be sent during the health checksreceive
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
.