InFlightReq

To proactively prevent services from being overwhelmed with high load, the number of allowed simultaneous in-flight requests can be limited.

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Configuration Options

amount

Field	Description
amount	The amount option defines the maximum amount of allowed simultaneous in-flight request. The middleware responds with HTTP 429 Too Many Requests if there are already amount requests in progress (based on the same sourceCriterion strategy).

Kubernetes CR

apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: test-inflightreq
spec:
  inFlightReq:
    amount: 10

sourceCriterion

Field	Description
sourceCriterion	The sourceCriterion option defines what criterion is used to group requests as originating from a common source. If several strategies are defined at the same time, an error will be raised. If none are set, the default is to use the requestHost.

sourceCriterion.ipStrategy

Field	Description
sourceCriterion.ipStrategy	The ipStrategy option defines two parameters that configures how Traefik determines the client IP: depth, and excludedIPs.

important

As a middleware, InFlightReq happens before the actual proxying to the backend takes place. In addition, the previous network hop only gets appended to X-Forwarded-For during the last stages of proxying, that is after it has already passed through the middleware.
Therefore, during InFlightReq, as the previous network hop is not yet present in X-Forwarded-For, it cannot be used and/or relied upon.

ipStrategy.depth

Field	Description
ipStrategy.depth	The depth option tells Traefik to use the X-Forwarded-For header and select the IP located at the depth position (starting from the right).

• If depth is greater than the total number of IPs in X-Forwarded-For, then the client IP is empty.
• depth is ignored if its value is less than or equal to 0.

Example of Depth & X-Forwarded-For

If depth is set to 2, and the request X-Forwarded-For header is "10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1" then the "real" client IP is "10.0.0.1" (at depth 4) but the IP used as the criterion is "12.0.0.1" (depth=2).

X-Forwarded-For	depth	clientIP
"10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1"	1	"13.0.0.1"
"10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1"	3	"11.0.0.1"
"10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1"	5	""

apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: test-inflightreq
spec:
  inFlightReq:
    sourceCriterion:
      ipStrategy:
        depth: 2

ipStrategy.excludedIPs

Field	Description
ipStrategy.excludedIPs	excludedIPs configures Traefik to scan the X-Forwarded-For header and select the first IP not in the list.

important

If depth is specified, excludedIPs is ignored.

Example of ExcludedIPs & X-Forwarded-For

X-Forwarded-For	excludedIPs	clientIP
"10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1"	"12.0.0.1,13.0.0.1"	"11.0.0.1"
"10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1"	"15.0.0.1,13.0.0.1"	"12.0.0.1"
"10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1"	"10.0.0.1,13.0.0.1"	"12.0.0.1"
"10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1"	"15.0.0.1,16.0.0.1"	"13.0.0.1"
"10.0.0.1,11.0.0.1"	"10.0.0.1,11.0.0.1"	""

apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: test-inflightreq
spec:
  inFlightReq:
    sourceCriterion:
      ipStrategy:
        excludedIPs:
        - 127.0.0.1/32
        - 192.168.1.7

sourceCriterion.requestHeaderName

Field	Description
sourceCriterion.requestHeaderName	Name of the header used to group incoming requests.

apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: test-inflightreq
spec:
  inFlightReq:
  sourceCriterion:
      requestHeaderName: username

sourceCriterion.requestHost

Field	Description
sourceCriterion.requestHost	Whether to consider the request host as the source.

apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: test-inflightreq
spec:
  inFlightReq:
    sourceCriterion:
      requestHost: true