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Retry
This policy enables Kuma to know how to behave if there is a failed scenario (i.e. HTTP request) which could be retried.
Usage
As usual, we can apply sources
and destinations
selectors to determine how retries will be performed across our data plane proxies.
The policy let you configure retry behaviour for HTTP
, GRPC
and TCP
protocols.
Example
apiVersion: kuma.io/v1alpha1
kind: Retry
mesh: default
metadata:
name: web-to-backend-retry-policy
spec:
sources:
- match:
kuma.io/service: web
destinations:
- match:
kuma.io/service: backend
conf:
http:
numRetries: 5
perTryTimeout: 200ms
backOff:
baseInterval: 20ms
maxInterval: 1s
retriableStatusCodes:
- 500
- 504
grpc:
numRetries: 5
perTryTimeout: 200ms
backOff:
baseInterval: 20ms
maxInterval: 1s
retryOn:
- cancelled
- deadline_exceeded
- internal
- resource_exhausted
- unavailable
tcp:
maxConnectAttempts: 3
We will apply the configuration with kubectl apply -f [..]
.
HTTP
-
numRetries
(optional)Amount of attempts which will be made on failed (and retriable) requests
-
perTryTimeout
(optional)Amount of time after which retry attempt should timeout (i.e. all the values:
30000000ns
,30ms
,0.03s
,0.0005m
are equivalent and can be used to express the same timeout value, equal to30ms
) -
backOff
(optional)Configuration of durations which will be used in exponential backoff strategy between retries
-
baseDuration
(required)Base amount of time which should be taken between retries (i.e.
30ms
,0.03s
,0.0005m
) -
maxInterval
(optional)A maximal amount of time which will be taken between retries (i.e.
1s
,0.5m
)
-
-
retriableStatusCodes
(optional)A list of status codes which will cause the request to be retried. When this field will be provided it will overwrite the default behaviour of accepting as retriable codes:
502
,503
and504
and if they also should be considered asretriable
you have to manually place them in the listFor example to add a status code
418
:retriableStatusCodes: - 418 - 502 - 503 - 504
Note that if you won’t provide
retriableStatusCodes
, the default behaviour of the policy is to retry:- when server responds with one of status codes:
502
,503
or504
, - when server won’t respond at all (disconnect/reset/read timeout),
- when server resets the stream with a
REFUSED_STREAM
error code.
- when server responds with one of status codes:
GRPC
You can configure your GRPC Retry policy in similar fashion as the HTTP one with the only difference of the retryOn
property which replace the retriableStatusCodes
from the HTTP policy
-
retryOn
(optional)List of values which will cause retry.
Acceptable values
cancelled
deadline_exceeded
internal
resource_exhausted
unavailable
Note that if
retryOn
is not defined or if it’s empty, the policy will default to all values and is equivalent to:retryOn: - cancelled - deadline_exceeded - internal - resource_exhausted - unavailable
TCP
-
maxConnectAmount
(required)A maximal amount of TCP connection attempts which will be made before giving up
This policy will make attempt to retry the TCP connection which fail to be established and will be applied in the scenario when both, the dataplane, and the TCP service matched as a destination will be down.
Matching
Retry
is an Outbound Connection Policy.
The only supported value for destinations.match
is kuma.io/service
.