# InFlightReq Limiting the Number of Simultaneous In-Flight Requests {: .subtitle } ![InFlightReq](../assets/img/middleware/inflightreq.png) To proactively prevent services from being overwhelmed with high load, a limit on the number of simultaneous in-flight requests can be applied. ## Configuration Examples ```yaml tab="Docker" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10" ``` ```yaml tab="Kubernetes" apiVersion: traefik.containo.us/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: amount: 10 ``` ```json tab="Marathon" "labels": { "traefik.http.middlewares.test-inflightreq.inflightreq.amount": "10" } ``` ```yaml tab="Rancher" # Limiting to 10 simultaneous connections labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10" ``` ```toml tab="File (TOML)" # Limiting to 10 simultaneous connections [http.middlewares] [http.middlewares.test-inflightreq.inFlightReq] amount = 10 ``` ```yaml tab="File (YAML)" # Limiting to 10 simultaneous connections 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 will return an `HTTP 429 Too Many Requests` if there are already `amount` requests in progress (based on the same `sourceCriterion` strategy). ```yaml tab="Docker" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10" ``` ```yaml tab="Kubernetes" apiVersion: traefik.containo.us/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: amount: 10 ``` ```json tab="Marathon" "labels": { "traefik.http.middlewares.test-inflightreq.inflightreq.amount": "10" } ``` ```yaml tab="Rancher" # Limiting to 10 simultaneous connections labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10" ``` ```toml tab="File (TOML)" # Limiting to 10 simultaneous connections [http.middlewares] [http.middlewares.test-inflightreq.inFlightReq] amount = 10 ``` ```yaml tab="File (YAML)" # Limiting to 10 simultaneous connections http: middlewares: test-inflightreq: inFlightReq: amount: 10 ``` ### `sourceCriterion` SourceCriterion defines what criterion is used to group requests as originating from a common source. The precedence order is `ipStrategy`, then `requestHeaderName`, then `requestHost`. If none are set, the default is to use the `requestHost`. #### `sourceCriterion.ipStrategy` The `ipStrategy` option defines two parameters that sets how Traefik will determine the client IP: `depth`, and `excludedIPs`. ##### `ipStrategy.depth` The `depth` option tells Traefik to use the `X-Forwarded-For` header and take 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 will be empty. - `depth` is ignored if its value is lesser than or equal to 0. !!! example "Example of Depth & X-Forwarded-For" If `depth` was equal to 2, and the request `X-Forwarded-For` header was `"10.0.0.1,11.0.0.1,12.0.0.1,13.0.0.1"` then the "real" client IP would be `"10.0.0.1"` (at depth 4) but the IP used as the criterion would be `"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" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.depth=2" ``` ```yaml tab="Kubernetes" apiVersion: traefik.containo.us/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: sourceCriterion: ipStrategy: depth: 2 ``` ```yaml tab="Rancher" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.depth=2" ``` ```json tab="Marathon" "labels": { "traefik.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 ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: sourceCriterion: ipStrategy: depth: 2 ``` ##### `ipStrategy.excludedIPs` `excludedIPs` tells Traefik to scan the `X-Forwarded-For` header and pick 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" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.excludedips=127.0.0.1/32, 192.168.1.7" ``` ```yaml tab="Kubernetes" apiVersion: traefik.containo.us/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: sourceCriterion: ipStrategy: excludedIPs: - 127.0.0.1/32 - 192.168.1.7 ``` ```json tab="Marathon" "labels": { "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.ipstrategy.excludedips": "127.0.0.1/32, 192.168.1.7" } ``` ```yaml tab="Rancher" labels: - "traefik.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"] ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: sourceCriterion: ipStrategy: excludedIPs: - "127.0.0.1/32" - "192.168.1.7" ``` #### `sourceCriterion.requestHeaderName` Requests having the same value for the given header are grouped as coming from the same source. ```yaml tab="Docker" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requestheadername=username" ``` ```yaml tab="Kubernetes" apiVersion: traefik.containo.us/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: sourceCriterion: requestHeaderName: username ``` ```yaml tab="Rancher" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requestheadername=username" ``` ```json tab="Marathon" "labels": { "traefik.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" ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: sourceCriterion: requestHeaderName: username ``` #### `sourceCriterion.requestHost` Whether to consider the request host as the source. ```yaml tab="Docker" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requesthost=true" ``` ```yaml tab="Kubernetes" apiVersion: traefik.containo.us/v1alpha1 kind: Middleware metadata: name: test-inflightreq spec: inFlightReq: sourceCriterion: requestHost: true ``` ```yaml tab="Rancher" labels: - "traefik.http.middlewares.test-inflightreq.inflightreq.sourcecriterion.requesthost=true" ``` ```json tab="Marathon" "labels": { "traefik.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 ``` ```yaml tab="File (YAML)" http: middlewares: test-inflightreq: inFlightReq: sourceCriterion: requestHost: true ```