Project: Traefik (Orchestration & Management / API Gateway)
File: inflightreq.md

title: "Traefik InFlightReq Documentation" description: "Traefik Proxy's HTTP middleware lets you limit the number of simultaneous in-flight requests. Read the technical documentation." Limiting the Number of Simultaneous In-Flight Requests {: .subtitle } To proactively prevent services from being overwhelmed with high load, the number of allowed simultaneous in-flight requests can be limited. ```yaml tab="Docker & Swarm" labels: "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10" ``` ```yaml tab="Kubernetes" apiVersion: traefik.io/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: amount: 10 ``` ```yaml tab="Consul Catalog" "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10" ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: amount: 10 ``` ```toml tab="File (TOML)" [http.middlewares] [http.middlewares.test-inflightreq.inFlightReq] amount = 10 ``` 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). ```yaml tab="Docker & Swarm" labels: "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10" ``` ```yaml tab="Kubernetes" apiVersion: traefik.io/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: amount: 10 ``` ```yaml tab="Consul Catalog" "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10" ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: amount: 10 ``` ```toml tab="File (TOML)" [http.middlewares] [http.middlewares.test-inflightreq.inFlightReq] amount = 10 ``` 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`. 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, 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." 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

!!! example "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` | `""` | ```yaml tab="Docker & Swarm" labels: "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.depth=2" ``` ```yaml tab="Kubernetes" apiVersion: traefik.io/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: sourceCriterion: ipStrategy: depth: 2 ``` ```yaml tab="Consul Catalog" "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.depth=2" ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: sourceCriterion: ipStrategy: depth: 2 ``` ```toml tab="File (TOML)" [http.middlewares] [http.middlewares.test-inflightreq.inflightreq] [http.middlewares.test-inflightreq.inFlightReq.sourceCriterion.ipStrategy] depth = 2 ``` `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 "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"` | `""` | ```yaml tab="Docker & Swarm" labels: "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.excludedips=127.0.0.1/32, 192.168.1.7" ``` ```yaml tab="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 ``` ```yaml tab="Consul Catalog" "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.excludedips=127.0.0.1/32, 192.168.1.7" ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: sourceCriterion: ipStrategy: excludedIPs: "127.0.0.1/32" "192.168.1.7" ``` ```toml tab="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"] ``` Name of the header used to group incoming requests. ```yaml tab="Docker & Swarm" labels: "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requestheadername=username" ``` ```yaml tab="Kubernetes" apiVersion: traefik.io/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: sourceCriterion: requestHeaderName: username ``` ```yaml tab="Consul Catalog" "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requestheadername=username" ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: sourceCriterion: requestHeaderName: username ``` ```toml tab="File (TOML)" [http.middlewares] [http.middlewares.test-inflightreq.inflightreq] [http.middlewares.test-inflightreq.inFlightReq.sourceCriterion] requestHeaderName = "username" ``` Whether to consider the request host as the source. ```yaml tab="Docker & Swarm" labels: "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requesthost=true" ``` ```yaml tab="Kubernetes" apiVersion: traefik.io/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: sourceCriterion: requestHost: true ``` ```yaml tab="Cosul Catalog" "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requesthost=true" ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: sourceCriterion: requestHost: true ``` ```toml tab="File (TOML)" [http.middlewares] [http.middlewares.test-inflightreq.inflightreq] [http.middlewares.test-inflightreq.inFlightReq.sourceCriterion] requestHost = true ```