InFlightReq

The InFlightReq middleware proactively prevents services from being overwhelmed with high load.

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Configuration Example

Middleware InFlightReq

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apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: test-inflightreq
spec:
  inFlightReq:
    sourceCriterion:
      ipStrategy:
        # Use the second IP from the X-Forwarded-For header as clientIP
        depth: 2
        ipv6Subnet: 64

Configuration Options

Field	Description	Default	Required
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).	0	No
sourceCriterion.requestHost	Whether to consider the request host as the source. More information about sourceCriterionhere.	false	No
sourceCriterion.requestHeaderName	Name of the header used to group incoming requests. More information about sourceCriterionhere.	""	No
sourceCriterion.ipStrategy.depth	Depth position of the IP to select in the X-Forwarded-For header (starting from the right). 0 means no depth. If greater than the total number of IPs in X-Forwarded-For, then the client IP is empty If higher than 0, the excludedIPs options is not evaluated. More information about sourceCriterion, ipStrategy](#ipstrategy), and [depth` below.	0	No
sourceCriterion.ipStrategy.excludedIPs	Allows Traefik to scan the X-Forwarded-For header and select the first IP not in the list. If depth is specified, excludedIPs is ignored. More information about sourceCriterion, ipStrategy](#ipstrategy), and [excludedIPs` below.		No
sourceCriterion.ipStrategy.ipv6Subnet	If ipv6Subnet is provided and the selected IP is IPv6, the IP is transformed into the first IP of the subnet it belongs to. More information about sourceCriterion, ipStrategy.ipv6Subnet, and excludedIPs below.		No

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.

ipStrategy

The ipStrategy option defines three parameters that configures how Traefik determines the client IP: depth, excludedIPs and ipv6Subnet.

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.ipv6Subnet

This strategy applies to Depth and RemoteAddr strategy only. If ipv6Subnet is provided and the selected IP is IPv6, the IP is transformed into the first IP of the subnet it belongs to.

This is useful for grouping IPv6 addresses into subnets to prevent bypassing this middleware by obtaining a new IPv6.

• ipv6Subnet is ignored if its value is outside of 0-128 interval

Example of ipv6Subnet

If ipv6Subnet is provided, the IP is transformed in the following way.

IP	ipv6Subnet	clientIP
"::abcd:1111:2222:3333"	64	"::0:0:0:0"
"::abcd:1111:2222:3333"	80	"::abcd:0:0:0:0"
"::abcd:1111:2222:3333"	96	"::abcd:1111:0:0:0"

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	""

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"	""