traefik/docs/content/middlewares/http/inflightreq.md
2023-05-10 15:28:05 +02:00

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---
title: "Traefik InFlightReq Documentation"
description: "Traefik Proxy's HTTP middleware lets you limit the number of simultaneous in-flight requests. Read the technical documentation."
---
# 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, the number of allowed simultaneous in-flight requests can be limited.
## Configuration Examples
```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"
# Limiting to 10 simultaneous connections
- "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10"
```
```yaml tab="File (YAML)"
# Limiting to 10 simultaneous connections
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
```
## 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).
```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"
# Limiting to 10 simultaneous connections
- "traefik.http.middlewares.test-inflightreq.inflightreq.amount=10"
```
```yaml tab="File (YAML)"
# Limiting to 10 simultaneous connections
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
```
### `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 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."
##### `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 "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
```
##### `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 "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"]
```
#### `sourceCriterion.requestHeaderName`
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"
```
#### `sourceCriterion.requestHost`
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
```