InFlightReq

Limiting the Number of Simultaneous In-Flight Requests

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

Configuration Examples

Docker & Swarm

labels:
  - "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10"

Kubernetes

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

Consul Catalog

# Limiting to 10 simultaneous connections
- "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10"

File (YAML)

# Limiting to 10 simultaneous connections
http:
  middlewares:
    test-inflightreq:
      inFlightReq:
        amount: 10

File (TOML)

# Limiting to 10 simultaneous connections
[http.middlewares]
  [http.middlewares.test-inflightreq.inFlightReq]
    amount = 10

Configuration Options

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).

Docker & Swarm

labels:
  - "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10"

Kubernetes

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

Consul Catalog

# Limiting to 10 simultaneous connections
- "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10"

File (YAML)

# Limiting to 10 simultaneous connections
http:
  middlewares:
    test-inflightreq:
      inFlightReq:
        amount: 10

File (TOML)

# Limiting to 10 simultaneous connections
[http.middlewares]
  [http.middlewares.test-inflightreq.inFlightReq]
    amount = 10

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

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, i.e. 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

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.

If ipStrategy.ipv6Subnet is provided and the selected IP is IPv6, the IP is transformed into the first IP of the subnet it belongs to.
See ipStrategy.ipv6Subnet for more details.

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	""

Docker & Swarm

labels:
  - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.depth=2"

Kubernetes

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

Consul Catalog

- "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.depth=2"

File (YAML)

http:
  middlewares:
    test-inflightreq:
      inFlightReq:
        sourceCriterion:
          ipStrategy:
            depth: 2

File (TOML)

[http.middlewares]
  [http.middlewares.test-inflightreq.inflightreq]
    [http.middlewares.test-inflightreq.inFlightReq.sourceCriterion.ipStrategy]
      depth = 2

ipStrategy.excludedIPs

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

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"	""

Docker & Swarm

labels:
  - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.excludedips=127.0.0.1/32, 192.168.1.7"

Kubernetes

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

Consul Catalog

- "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.excludedips=127.0.0.1/32, 192.168.1.7"

File (YAML)

http:
  middlewares:
    test-inflightreq:
      inFlightReq:
        sourceCriterion:
          ipStrategy:
            excludedIPs:
              - "127.0.0.1/32"
              - "192.168.1.7"

File (TOML)

[http.middlewares]
  [http.middlewares.test-inflightreq.inflightreq]
    [http.middlewares.test-inflightreq.inFlightReq.sourceCriterion.ipStrategy]
      excludedIPs = ["127.0.0.1/32", "192.168.1.7"]

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"

Docker & Swarm

labels:
  - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.ipv6Subnet=64"

Kubernetes

apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: test-inflightreq
spec:
  inFlightReq:
    sourceCriterion:
      ipStrategy:
        ipv6Subnet: 64

Consul Catalog

- "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.ipv6Subnet=64"

File (YAML)

http:
  middlewares:
    test-inflightreq:
      inFlightReq:
        sourceCriterion:
          ipStrategy:
            ipv6Subnet: 64

File (TOML)

[http.middlewares]
  [http.middlewares.test-inflightreq.inflightreq]
    [http.middlewares.test-inflightreq.inFlightReq.sourceCriterion.ipStrategy]
      ipv6Subnet = 64

sourceCriterion.requestHeaderName

Name of the header used to group incoming requests.

Docker & Swarm

labels:
  - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requestheadername=username"

Kubernetes

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

Consul Catalog

- "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requestheadername=username"

File (YAML)

http:
  middlewares:
    test-inflightreq:
      inFlightReq:
        sourceCriterion:
          requestHeaderName: username

File (TOML)

[http.middlewares]
  [http.middlewares.test-inflightreq.inflightreq]
    [http.middlewares.test-inflightreq.inFlightReq.sourceCriterion]
      requestHeaderName = "username"

sourceCriterion.requestHost

Whether to consider the request host as the source.

Docker & Swarm

labels:
  - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requesthost=true"

Kubernetes

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

Consul Catalog

- "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requesthost=true"

File (YAML)

http:
  middlewares:
    test-inflightreq:
      inFlightReq:
        sourceCriterion:
          requestHost: true

File (TOML)

[http.middlewares]
  [http.middlewares.test-inflightreq.inflightreq]
    [http.middlewares.test-inflightreq.inFlightReq.sourceCriterion]
      requestHost = true