traefik/docs/index.md

<p align="center">
<img src="http://traefik.github.io/traefik.logo.svg" alt="Træfɪk" title="Træfɪk" />
</p>

# <a id="top"></a> Documentation

- [Basics](#basics)
- [Launch configuration](#launch)
- [Global configuration](#global)
- [File backend](#file)
- [API backend](#api)
- [Docker backend](#docker)
- [Mesos/Marathon backend](#marathon)
- [Consul backend](#consul)
- [Consul catalog backend](#consulcatalog)
- [Etcd backend](#etcd)
- [Zookeeper backend](#zk)
- [Boltdb backend](#boltdb)
- [Atomic configuration changes](#atomicconfig)
- [Benchmarks](#benchmarks)


## <a id="basics"></a> Basics


Træfɪk is a modern HTTP reverse proxy and load balancer made to deploy microservices with ease.
It supports several backends ([Docker :whale:](https://www.docker.com/), [Mesos/Marathon](https://mesosphere.github.io/marathon/), [Consul](https://consul.io/), [Etcd](https://coreos.com/etcd/), Rest API, file...) to manage its configuration automatically and dynamically.

Basically, Træfɪk is a http router, which sends traffic from frontends to http backends, following rules you have configured.

### <a id="frontends"></a> Frontends

Frontends can be defined using the following rules:

- `Headers`: Headers adds a matcher for request header values. It accepts a sequence of key/value pairs to be matched. For example: `application/json`
- `HeadersRegexp`: Regular expressions can be used with headers as well. It accepts a sequence of key/value pairs, where the value has regex support. For example: `application/(text|json)`
- `Host`: Host adds a matcher for the URL host. It accepts a template with zero or more URL variables enclosed by `{}`. Variables can define an optional regexp pattern to be matched: `www.traefik.io`, `{subdomain:[a-z]+}.traefik.io`
- `Methods`: Methods adds a matcher for HTTP methods. It accepts a sequence of one or more methods to be matched, e.g.: `GET`, `POST`, `PUT`
- `Path`: Path adds a matcher for the URL path. It accepts a template with zero or more URL variables enclosed by `{}`. The template must start with a `/`. For exemple `/products/` `/articles/{category}/{id:[0-9]+}`
- `PathStrip`: Same as `Path` but strip the given prefix from the request URL's Path.
- `PathPrefix`: PathPrefix adds a matcher for the URL path prefix. This matches if the given template is a prefix of the full URL path.
- `PathPrefixStrip`: Same as `PathPrefix` but strip the given prefix from the request URL's Path.


 A frontend is a set of rules that forwards the incoming http traffic to a backend.
 You can optionally enable `passHostHeader` to forward client `Host` header to the backend.

### HTTP Backends

A backend is responsible to load-balance the traffic coming from one or more frontends to a set of http servers.
Various methods of load-balancing is supported:

- `wrr`: Weighted Round Robin
- `drr`: Dynamic Round Robin: increases weights on servers that perform better than others. It also rolls back to original weights if the servers have changed.

A circuit breaker can also be applied to a backend, preventing high loads on failing servers.
Initial state is Standby. CB observes the statistics and does not modify the request.
In case if condition matches, CB enters Tripped state, where it responds with predefines code or redirects to another frontend.
Once Tripped timer expires, CB enters Recovering state and resets all stats.
In case if the condition does not match and recovery timer expries, CB enters Standby state.

It can be configured using:

- Methods: `LatencyAtQuantileMS`, `NetworkErrorRatio`, `ResponseCodeRatio`
- Operators:  `AND`, `OR`, `EQ`, `NEQ`, `LT`, `LE`, `GT`, `GE`

For example:
- `NetworkErrorRatio() > 0.5`: watch error ratio over 10 second sliding window for a frontend
- `LatencyAtQuantileMS(50.0) > 50`:  watch latency at quantile in milliseconds.
- `ResponseCodeRatio(500, 600, 0, 600) > 0.5`: ratio of response codes in range [500-600) to  [0-600)


## <a id="launch"></a> Launch configuration

Træfɪk can be configured using a TOML file configuration, arguments, or both.
By default, Træfɪk will try to find a `traefik.toml` in the following places:
- `/etc/traefik/`
- `$HOME/.traefik/`
- `.` the working directory

You can override this by setting a `configFile` argument:

```bash
$ traefik --configFile=foo/bar/myconfigfile.toml
```

Træfɪk uses the following precedence order. Each item takes precedence over the item below it:

- arguments
- configuration file
- default

It means that arguments overrides configuration file.
Each argument is described in the help section:

```bash
$ traefik --help
traefik is a modern HTTP reverse proxy and load balancer made to deploy microservices with ease.
Complete documentation is available at http://traefik.io

Usage:
  traefik [flags]
  traefik [command]

Available Commands:
  version     Print version

Flags:
      --accessLogsFile string                Access logs file (default "log/access.log")
      --boltdb                               Enable Boltdb backend
      --boltdb.endpoint string               Boltdb server endpoint (default "127.0.0.1:4001")
      --boltdb.filename string               Override default configuration template. For advanced users :)
      --boltdb.prefix string                 Prefix used for KV store (default "/traefik")
      --boltdb.watch                         Watch provider (default true)
  -c, --configFile string                    Configuration file to use (TOML, JSON, YAML, HCL).
      --consul                               Enable Consul backend
      --consul.endpoint string               Comma sepparated Consul server endpoints (default "127.0.0.1:8500")
      --consul.filename string               Override default configuration template. For advanced users :)
      --consul.prefix string                 Prefix used for KV store (default "/traefik")
      --consul.tls                           Enable Consul TLS support
      --consul.tls.ca string                 TLS CA
      --consul.tls.cert string               TLS cert
      --consul.tls.insecureSkipVerify        TLS insecure skip verify
      --consul.tls.key string                TLS key
      --consul.watch                         Watch provider (default true)
      --consulCatalog                        Enable Consul catalog backend
      --consulCatalog.domain string          Default domain used
      --consulCatalog.endpoint string        Consul server endpoint (default "127.0.0.1:8500")
      --defaultEntryPoints value             Entrypoints to be used by frontends that do not specify any entrypoint (default &main.DefaultEntryPoints(nil))
      --docker                               Enable Docker backend
      --docker.domain string                 Default domain used
      --docker.endpoint string               Docker server endpoint. Can be a tcp or a unix socket endpoint (default "unix:///var/run/docker.sock")
      --docker.filename string               Override default configuration template. For advanced users :)
      --docker.tls                           Enable Docker TLS support
      --docker.tls.ca string                 TLS CA
      --docker.tls.cert string               TLS cert
      --docker.tls.insecureSkipVerify        TLS insecure skip verify
      --docker.tls.key string                TLS key
      --docker.watch                         Watch provider (default true)
      --entryPoints value                    Entrypoints definition using format: --entryPoints='Name:http Address::8000 Redirect.EntryPoint:https' --entryPoints='Name:https Address::4442 TLS:tests/traefik.crt,tests/traefik.key'
      --etcd                                 Enable Etcd backend
      --etcd.endpoint string                 Comma sepparated Etcd server endpoints (default "127.0.0.1:4001")
      --etcd.filename string                 Override default configuration template. For advanced users :)
      --etcd.prefix string                   Prefix used for KV store (default "/traefik")
      --etcd.tls                             Enable Etcd TLS support
      --etcd.tls.ca string                   TLS CA
      --etcd.tls.cert string                 TLS cert
      --etcd.tls.insecureSkipVerify          TLS insecure skip verify
      --etcd.tls.key string                  TLS key
      --etcd.watch                           Watch provider (default true)
      --file                                 Enable File backend
      --file.filename string                 Override default configuration template. For advanced users :)
      --file.watch                           Watch provider (default true)
  -g, --graceTimeOut string                  Timeout in seconds. Duration to give active requests a chance to finish during hot-reloads (default "10")
  -l, --logLevel string                      Log level (default "ERROR")
      --marathon                             Enable Marathon backend
      --marathon.domain string               Default domain used
      --marathon.endpoint string             Marathon server endpoint. You can also specify multiple endpoint for Marathon (default "http://127.0.0.1:8080")
      --marathon.exposedByDefault            Expose Marathon apps by default (default true)
      --marathon.filename string             Override default configuration template. For advanced users :)
      --marathon.watch                       Watch provider (default true)
      --maxIdleConnsPerHost int              If non-zero, controls the maximum idle (keep-alive) to keep per-host.  If zero, DefaultMaxIdleConnsPerHost is used
      --providersThrottleDuration duration   Backends throttle duration: minimum duration between 2 events from providers before applying a new configuration. It avoids unnecessary reloads if multiples events are sent in a short amount of time. (default 2s)
      --traefikLogsFile string               Traefik logs file (default "log/traefik.log")
      --web                                  Enable Web backend
      --web.address string                   Web administration port (default ":8080")
      --web.cerFile string                   SSL certificate
      --web.keyFile string                   SSL certificate
      --web.readOnly                         Enable read only API
      --zookeeper                            Enable Zookeeper backend
      --zookeeper.endpoint string            Comma sepparated Zookeeper server endpoints (default "127.0.0.1:2181")
      --zookeeper.filename string            Override default configuration template. For advanced users :)
      --zookeeper.prefix string              Prefix used for KV store (default "/traefik")
      --zookeeper.watch                      Watch provider (default true)

Use "traefik [command] --help" for more information about a command.
```

## <a id="global"></a> Global configuration

```toml
# traefik.toml
################################################################
# Global configuration
################################################################

# Timeout in seconds.
# Duration to give active requests a chance to finish during hot-reloads
#
# Optional
# Default: 10
#
# graceTimeOut = 10

# Traefik logs file
# If not defined, logs to stdout
#
# Optional
#
# traefikLogsFile = "log/traefik.log"

# Access logs file
#
# Optional
#
# accessLogsFile = "log/access.log"

# Log level
#
# Optional
# Default: "ERROR"
#
# logLevel = "ERROR"

# Backends throttle duration: minimum duration between 2 events from providers
# before applying a new configuration. It avoids unnecessary reloads if multiples events
# are sent in a short amount of time.
#
# Optional
# Default: "2s"
#
# ProvidersThrottleDuration = "5s"

# If non-zero, controls the maximum idle (keep-alive) to keep per-host.  If zero, DefaultMaxIdleConnsPerHost is used.
# If you encounter 'too many open files' errors, you can either change this value, or change `ulimit` value.
#
# Optional
# Default: http.DefaultMaxIdleConnsPerHost
#
# MaxIdleConnsPerHost = 200

# Entrypoints to be used by frontends that do not specify any entrypoint.
# Each frontend can specify its own entrypoints.
#
# Optional
# Default: ["http"]
#
# defaultEntryPoints = ["http", "https"]

# Enable ACME (Let's Encrypt): automatic SSL
#
# Optional
#
# [acme]

# Email address used for registration
#
# Required
#
# email = "test@traefik.io"

# File used for certificates storage.
# WARNING, if you use Traefik in Docker, don't forget to mount this file as a volume.
#
# Required
#
# storageFile = "acme.json"

# Entrypoint to proxy acme challenge to.
# WARNING, must point to an entrypoint on port 443 
#
# Required
#
# entryPoint = "https"

# Enable on demand certificate. This will request a certificate from Let's Encrypt during the first TLS handshake for a hostname that does not yet have a certificate.
# WARNING, TLS handshakes will be slow when requesting a hostname certificate for the first time, this can leads to DoS attacks.
# WARNING, Take note that Let's Encrypt have rate limiting: https://community.letsencrypt.org/t/quick-start-guide/1631
#
# Optional
#
# onDemand = true

# CA server to use
# Uncomment the line to run on the staging let's encrypt server
# Leave comment to go to prod
#
# Optional
#
# caServer = "https://acme-staging.api.letsencrypt.org/directory"

# Domains list
# You can provide SANs (alternative domains) to each main domain
# WARNING, Take note that Let's Encrypt have rate limiting: https://community.letsencrypt.org/t/quick-start-guide/1631
# Each domain & SANs will lead to a certificate request.
#
# [[acme.domains]]
#   main = "local1.com"
#   sans = ["test1.local1.com", "test2.local1.com"]
# [[acme.domains]]
#   main = "local2.com"
#   sans = ["test1.local2.com", "test2x.local2.com"]
# [[acme.domains]]
#   main = "local3.com"
# [[acme.domains]]
#   main = "local4.com"


# Entrypoints definition
#
# Optional
# Default:
# [entryPoints]
#   [entryPoints.http]
#   address = ":80"
#
# To redirect an http entrypoint to an https entrypoint (with SNI support):
# [entryPoints]
#   [entryPoints.http]
#   address = ":80"
#     [entryPoints.http.redirect]
#       entryPoint = "https"
#   [entryPoints.https]
#   address = ":443"
#     [entryPoints.https.tls]
#       [[entryPoints.https.tls.certificates]]
#       CertFile = "integration/fixtures/https/snitest.com.cert"
#       KeyFile = "integration/fixtures/https/snitest.com.key"
#       [[entryPoints.https.tls.certificates]]
#       CertFile = "integration/fixtures/https/snitest.org.cert"
#       KeyFile = "integration/fixtures/https/snitest.org.key"
#
# To redirect an entrypoint rewriting the URL:
# [entryPoints]
#   [entryPoints.http]
#   address = ":80"
#     [entryPoints.http.redirect]
#       regex = "^http://localhost/(.*)"
#       replacement = "http://mydomain/$1"
```

### Samples

#### HTTP only

```
defaultEntryPoints = ["http"]
[entryPoints]
  [entryPoints.http]
  address = ":80"
```

### HTTP + HTTPS (with SNI)

```
defaultEntryPoints = ["http", "https"]
[entryPoints]
  [entryPoints.http]
  address = ":80"
  [entryPoints.https]
  address = ":443"
    [entryPoints.https.tls]
      [[entryPoints.https.tls.certificates]]
      CertFile = "integration/fixtures/https/snitest.com.cert"
      KeyFile = "integration/fixtures/https/snitest.com.key"
      [[entryPoints.https.tls.certificates]]
      CertFile = "integration/fixtures/https/snitest.org.cert"
      KeyFile = "integration/fixtures/https/snitest.org.key"
```

### HTTP redirect on HTTPS

```
defaultEntryPoints = ["http", "https"]
[entryPoints]
  [entryPoints.http]
  address = ":80"
    [entryPoints.http.redirect]
    entryPoint = "https"
  [entryPoints.https]
  address = ":443"
    [entryPoints.https.tls]
      [[entryPoints.https.tls.certificates]]
      certFile = "tests/traefik.crt"
      keyFile = "tests/traefik.key"
```

### Let's Encrypt support

```
[entryPoints]
  [entryPoints.https]
  address = ":443"
    [entryPoints.https.tls]
      # certs used as default certs
      [[entryPoints.https.tls.certificates]]
      certFile = "tests/traefik.crt"
      keyFile = "tests/traefik.key"
[acme]
email = "test@traefik.io"
storageFile = "acme.json"
onDemand = true
caServer = "http://172.18.0.1:4000/directory"
entryPoint = "https"

[[acme.domains]]
  main = "local1.com"
  sans = ["test1.local1.com", "test2.local1.com"]
[[acme.domains]]
  main = "local2.com"
  sans = ["test1.local2.com", "test2x.local2.com"]
[[acme.domains]]
  main = "local3.com"
[[acme.domains]]
  main = "local4.com"
```

### Override entrypoints in frontends

```
[frontends]
  [frontends.frontend1]
  backend = "backend2"
    [frontends.frontend1.routes.test_1]
    rule = "Host"
    value = "test.localhost"
  [frontends.frontend2]
  backend = "backend1"
  passHostHeader = true
  entrypoints = ["https"] # overrides defaultEntryPoints
    [frontends.frontend2.routes.test_1]
    rule = "Host"
    value = "{subdomain:[a-z]+}.localhost"
  [frontends.frontend3]
  entrypoints = ["http", "https"] # overrides defaultEntryPoints
  backend = "backend2"
    rule = "Path"
    value = "/test"
```


## <a id="file"></a> File backend

Like any other reverse proxy, Træfɪk can be configured with a file. You have two choices:

- simply add your configuration at the end of the global configuration file `traefik.toml` :

```toml
# traefik.toml
defaultEntryPoints = ["http", "https"]
[entryPoints]
  [entryPoints.http]
  address = ":80"
    [entryPoints.http.redirect]
      entryPoint = "https"
  [entryPoints.https]
  address = ":443"
    [entryPoints.https.tls]
      [[entryPoints.https.tls.certificates]]
      CertFile = "integration/fixtures/https/snitest.com.cert"
      KeyFile = "integration/fixtures/https/snitest.com.key"
      [[entryPoints.https.tls.certificates]]
      CertFile = "integration/fixtures/https/snitest.org.cert"
      KeyFile = "integration/fixtures/https/snitest.org.key"
graceTimeOut = 10
logLevel = "DEBUG"

[file]

# rules
[backends]
  [backends.backend1]
    [backends.backend1.circuitbreaker]
      expression = "NetworkErrorRatio() > 0.5"
    [backends.backend1.servers.server1]
    url = "http://172.17.0.2:80"
    weight = 10
    [backends.backend1.servers.server2]
    url = "http://172.17.0.3:80"
    weight = 1
  [backends.backend2]
    [backends.backend2.LoadBalancer]
      method = "drr"
    [backends.backend2.servers.server1]
    url = "http://172.17.0.4:80"
    weight = 1
    [backends.backend2.servers.server2]
    url = "http://172.17.0.5:80"
    weight = 2

[frontends]
  [frontends.frontend1]
  backend = "backend2"
    [frontends.frontend1.routes.test_1]
    rule = "Host"
    value = "test.localhost"
  [frontends.frontend2]
  backend = "backend1"
  passHostHeader = true
  entrypoints = ["https"] # overrides defaultEntryPoints
    [frontends.frontend2.routes.test_1]
    rule = "Host"
    value = "{subdomain:[a-z]+}.localhost"
  [frontends.frontend3]
  entrypoints = ["http", "https"] # overrides defaultEntryPoints
  backend = "backend2"
    rule = "Path"
    value = "/test"
```

- or put your rules in a separate file, for example `rules.tml`:

```toml
# traefik.toml
[entryPoints]
  [entryPoints.http]
  address = ":80"
    [entryPoints.http.redirect]
      entryPoint = "https"
  [entryPoints.https]
  address = ":443"
    [entryPoints.https.tls]
      [[entryPoints.https.tls.certificates]]
      CertFile = "integration/fixtures/https/snitest.com.cert"
      KeyFile = "integration/fixtures/https/snitest.com.key"
      [[entryPoints.https.tls.certificates]]
      CertFile = "integration/fixtures/https/snitest.org.cert"
      KeyFile = "integration/fixtures/https/snitest.org.key"
graceTimeOut = 10
logLevel = "DEBUG"

[file]
filename = "rules.toml"
```

```toml
# rules.toml
[backends]
  [backends.backend1]
    [backends.backend1.circuitbreaker]
      expression = "NetworkErrorRatio() > 0.5"
    [backends.backend1.servers.server1]
    url = "http://172.17.0.2:80"
    weight = 10
    [backends.backend1.servers.server2]
    url = "http://172.17.0.3:80"
    weight = 1
  [backends.backend2]
    [backends.backend2.LoadBalancer]
      method = "drr"
    [backends.backend2.servers.server1]
    url = "http://172.17.0.4:80"
    weight = 1
    [backends.backend2.servers.server2]
    url = "http://172.17.0.5:80"
    weight = 2

[frontends]
  [frontends.frontend1]
  backend = "backend2"
    [frontends.frontend1.routes.test_1]
    rule = "Host"
    value = "test.localhost"
  [frontends.frontend2]
  backend = "backend1"
  passHostHeader = true
  entrypoints = ["https"] # overrides defaultEntryPoints
    [frontends.frontend2.routes.test_1]
    rule = "Host"
    value = "{subdomain:[a-z]+}.localhost"
  [frontends.frontend3]
  entrypoints = ["http", "https"] # overrides defaultEntryPoints
  backend = "backend2"
    rule = "Path"
    value = "/test"
```

If you want Træfɪk to watch file changes automatically, just add:

```toml
[file]
watch = true
```

## <a id="api"></a> API backend

Træfik can be configured using a restful api.
To enable it:

```toml
[web]
address = ":8080"

# SSL certificate and key used
#
# Optional
#
# CertFile = "traefik.crt"
# KeyFile = "traefik.key"
#
# Set REST API to read-only mode
#
# Optional
# ReadOnly = false
```

- `/`: provides a simple HTML frontend of Træfik

![Web UI Providers](img/web.frontend.png)
![Web UI Health](img/traefik-health.png)

- `/health`: `GET` json metrics

```sh
$ curl -s "http://localhost:8080/health" | jq .
{
  // Træfɪk PID
  "pid": 2458,
  // Træfɪk server uptime (formated time)
  "uptime": "39m6.885931127s",
  //  Træfɪk server uptime in seconds
  "uptime_sec": 2346.885931127,
  // current server date
  "time": "2015-10-07 18:32:24.362238909 +0200 CEST",
  // current server date in seconds
  "unixtime": 1444235544,
  // count HTTP response status code in realtime
  "status_code_count": {
    "502": 1
  },
  // count HTTP response status code since Træfɪk started
  "total_status_code_count": {
    "200": 7,
    "404": 21,
    "502": 13
  },
  // count HTTP response
  "count": 1,
  // count HTTP response
  "total_count": 41,
  // sum of all response time (formated time)
  "total_response_time": "35.456865605s",
  // sum of all response time in seconds
  "total_response_time_sec": 35.456865605,
  // average response time (formated time)
  "average_response_time": "864.8016ms",
  // average response time in seconds
  "average_response_time_sec": 0.8648016000000001
}
```

- `/api`: `GET` configuration for all providers

```sh
$ curl -s "http://localhost:8080/api" | jq .
{
  "file": {
    "frontends": {
      "frontend2": {
        "routes": {
          "test_2": {
            "value": "/test",
            "rule": "Path"
          }
        },
        "backend": "backend1"
      },
      "frontend1": {
        "routes": {
          "test_1": {
            "value": "test.localhost",
            "rule": "Host"
          }
        },
        "backend": "backend2"
      }
    },
    "backends": {
      "backend2": {
        "loadBalancer": {
          "method": "drr"
        },
        "servers": {
          "server2": {
            "weight": 2,
            "URL": "http://172.17.0.5:80"
          },
          "server1": {
            "weight": 1,
            "url": "http://172.17.0.4:80"
          }
        }
      },
      "backend1": {
        "loadBalancer": {
          "method": "wrr"
        },
        "circuitBreaker": {
          "expression": "NetworkErrorRatio() > 0.5"
        },
        "servers": {
          "server2": {
            "weight": 1,
            "url": "http://172.17.0.3:80"
          },
          "server1": {
            "weight": 10,
            "url": "http://172.17.0.2:80"
          }
        }
      }
    }
  }
}
```

- `/api/providers`: `GET` providers
- `/api/providers/{provider}`: `GET` or `PUT` provider
- `/api/providers/{provider}/backends`: `GET` backends
- `/api/providers/{provider}/backends/{backend}`: `GET` a backend
- `/api/providers/{provider}/backends/{backend}/servers`: `GET` servers in a backend
- `/api/providers/{provider}/backends/{backend}/servers/{server}`: `GET` a server in a backend
- `/api/providers/{provider}/frontends`: `GET` frontends
- `/api/providers/{provider}/frontends/{frontend}`: `GET` a frontend
- `/api/providers/{provider}/frontends/{frontend}/routes`: `GET` routes in a frontend
- `/api/providers/{provider}/frontends/{frontend}/routes/{route}`: `GET` a route in a frontend


## <a id="docker"></a> Docker backend

Træfɪk can be configured to use Docker as a backend configuration:

```toml
################################################################
# Docker configuration backend
################################################################

# Enable Docker configuration backend
#
# Optional
#
[docker]

# Docker server endpoint. Can be a tcp or a unix socket endpoint.
#
# Required
#
endpoint = "unix:///var/run/docker.sock"

# Default domain used.
# Can be overridden by setting the "traefik.domain" label on a container.
#
# Required
#
domain = "docker.localhost"

# Enable watch docker changes
#
# Optional
#
watch = true

# Override default configuration template. For advanced users :)
#
# Optional
#
# filename = "docker.tmpl"

# Enable docker TLS connection
#
#  [docker.tls]
#  ca = "/etc/ssl/ca.crt"
#  cert = "/etc/ssl/docker.crt"
#  key = "/etc/ssl/docker.key"
#  insecureskipverify = true
```

Labels can be used on containers to override default behaviour:

- `traefik.backend=foo`: assign the container to `foo` backend
- `traefik.port=80`: register this port. Useful when the container exposes multiples ports.
- `traefik.protocol=https`: override the default `http` protocol
- `traefik.weight=10`: assign this weight to the container
- `traefik.enable=false`: disable this container in Træfɪk
- `traefik.frontend.rule=Host`: override the default frontend rule (Default: Host). See [frontends](#frontends).
- `traefik.frontend.value=test.example.com`: override the default frontend value (Default: `{containerName}.{domain}`) See [frontends](#frontends). Must be associated with label traefik.frontend.rule.
- `traefik.frontend.passHostHeader=true`: forward client `Host` header to the backend.
- `traefik.frontend.entryPoints=http,https`: assign this frontend to entry points `http` and `https`. Overrides `defaultEntryPoints`.
* `traefik.domain=traefik.localhost`: override the default domain


## <a id="marathon"></a> Marathon backend

Træfɪk can be configured to use Marathon as a backend configuration:


```toml
################################################################
# Mesos/Marathon configuration backend
################################################################

# Enable Marathon configuration backend
#
# Optional
#
[marathon]

# Marathon server endpoint.
# You can also specify multiple endpoint for Marathon:
# endpoint := "http://10.241.1.71:8080,10.241.1.72:8080,10.241.1.73:8080"
#
# Required
#
endpoint = "http://127.0.0.1:8080"

# Enable watch Marathon changes
#
# Optional
#
watch = true

# Default domain used.
# Can be overridden by setting the "traefik.domain" label on an application.
#
# Required
#
domain = "marathon.localhost"

# Override default configuration template. For advanced users :)
#
# Optional
#
# filename = "marathon.tmpl"

# Expose Marathon apps by default in traefik
#
# Optional
# Default: false
#
# ExposedByDefault = true

# Enable Marathon basic authentication
#
# Optional
#
#  [marathon.basic]
#  httpBasicAuthUser = "foo"
#  httpBasicPassword = "bar"

# TLS client configuration. https://golang.org/pkg/crypto/tls/#Config
#
# Optional
#
# [marathon.TLS]
# InsecureSkipVerify = true
```

Labels can be used on containers to override default behaviour:

- `traefik.backend=foo`: assign the application to `foo` backend
- `traefik.portIndex=1`: register port by index in the application's ports array. Useful when the application exposes multiple ports.
- `traefik.port=80`: register the explicit application port value. Cannot be used alongside `traefik.portIndex`.
- `traefik.protocol=https`: override the default `http` protocol
- `traefik.weight=10`: assign this weight to the application
- `traefik.enable=false`: disable this application in Træfɪk
- `traefik.frontend.rule=Host`: override the default frontend rule (Default: Host). See [frontends](#frontends).
- `traefik.frontend.value=test.example.com`: override the default frontend value (Default: `{appName}.{domain}`) See [frontends](#frontends). Must be associated with label traefik.frontend.rule.
- `traefik.frontend.passHostHeader=true`: forward client `Host` header to the backend.
- `traefik.frontend.entryPoints=http,https`: assign this frontend to entry points `http` and `https`. Overrides `defaultEntryPoints`.
* `traefik.domain=traefik.localhost`: override the default domain

## <a id="consul"></a> Consul backend

Træfɪk can be configured to use Consul as a backend configuration:

```toml
################################################################
# Consul KV configuration backend
################################################################

# Enable Consul KV configuration backend
#
# Optional
#
[consul]

# Consul server endpoint
#
# Required
#
endpoint = "127.0.0.1:8500"

# Enable watch Consul changes
#
# Optional
#
watch = true

# Prefix used for KV store.
#
# Optional
#
prefix = "traefik"

# Override default configuration template. For advanced users :)
#
# Optional
#
# filename = "consul.tmpl"

# Enable consul TLS connection
#
# Optional
#
# [consul.tls]
# ca = "/etc/ssl/ca.crt"
# cert = "/etc/ssl/consul.crt"
# key = "/etc/ssl/consul.key"
# insecureskipverify = true
```

The Keys-Values structure should look (using `prefix = "/traefik"`):

- backend 1

| Key                                                    | Value                       |
|--------------------------------------------------------|-----------------------------|
| `/traefik/backends/backend1/circuitbreaker/expression` | `NetworkErrorRatio() > 0.5` |
| `/traefik/backends/backend1/servers/server1/url`       | `http://172.17.0.2:80`      |
| `/traefik/backends/backend1/servers/server1/weight`    | `10`                        |
| `/traefik/backends/backend1/servers/server2/url`       | `http://172.17.0.3:80`      |
| `/traefik/backends/backend1/servers/server2/weight`    | `1`                         |

- backend 2

| Key                                                 | Value                  |
|-----------------------------------------------------|------------------------|
| `/traefik/backends/backend2/loadbalancer/method`    | `drr`                  |
| `/traefik/backends/backend2/servers/server1/url`    | `http://172.17.0.4:80` |
| `/traefik/backends/backend2/servers/server1/weight` | `1`                    |
| `/traefik/backends/backend2/servers/server2/url`    | `http://172.17.0.5:80` |
| `/traefik/backends/backend2/servers/server2/weight` | `2`                    |

- frontend 1

| Key                                                | Value            |
|----------------------------------------------------|------------------|
| `/traefik/frontends/frontend1/backend`             | `backend2`       |
| `/traefik/frontends/frontend1/routes/test_1/rule`  | `Host`           |
| `/traefik/frontends/frontend1/routes/test_1/value` | `test.localhost` |

- frontend 2

| Key                                                | Value      |
|----------------------------------------------------|------------|
| `/traefik/frontends/frontend2/backend`             | `backend1` |
| `/traefik/frontends/frontend2/passHostHeader`      | `true`     |
| `/traefik/frontends/frontend2/entrypoints`         |`http,https`|
| `/traefik/frontends/frontend2/routes/test_2/rule`  | `Path`     |
| `/traefik/frontends/frontend2/routes/test_2/value` | `/test`    |


## <a id="etcd"></a> Etcd backend

Træfɪk can be configured to use Etcd as a backend configuration:

```toml
################################################################
# Etcd configuration backend
################################################################

# Enable Etcd configuration backend
#
# Optional
#
# [etcd]

# Etcd server endpoint
#
# Required
#
# endpoint = "127.0.0.1:4001"

# Enable watch Etcd changes
#
# Optional
#
# watch = true

# Prefix used for KV store.
#
# Optional
#
# prefix = "/traefik"

# Override default configuration template. For advanced users :)
#
# Optional
#
# filename = "etcd.tmpl"

# Enable etcd TLS connection
#
# Optional
#
# [etcd.tls]
# ca = "/etc/ssl/ca.crt"
# cert = "/etc/ssl/etcd.crt"
# key = "/etc/ssl/etcd.key"
# insecureskipverify = true
```

The Keys-Values structure should look (using `prefix = "/traefik"`):

- backend 1

| Key                                                    | Value                       |
|--------------------------------------------------------|-----------------------------|
| `/traefik/backends/backend1/circuitbreaker/expression` | `NetworkErrorRatio() > 0.5` |
| `/traefik/backends/backend1/servers/server1/url`       | `http://172.17.0.2:80`      |
| `/traefik/backends/backend1/servers/server1/weight`    | `10`                        |
| `/traefik/backends/backend1/servers/server2/url`       | `http://172.17.0.3:80`      |
| `/traefik/backends/backend1/servers/server2/weight`    | `1`                         |

- backend 2

| Key                                                 | Value                  |
|-----------------------------------------------------|------------------------|
| `/traefik/backends/backend2/loadbalancer/method`    | `drr`                  |
| `/traefik/backends/backend2/servers/server1/url`    | `http://172.17.0.4:80` |
| `/traefik/backends/backend2/servers/server1/weight` | `1`                    |
| `/traefik/backends/backend2/servers/server2/url`    | `http://172.17.0.5:80` |
| `/traefik/backends/backend2/servers/server2/weight` | `2`                    |

- frontend 1

| Key                                                | Value            |
|----------------------------------------------------|------------------|
| `/traefik/frontends/frontend1/backend`             | `backend2`       |
| `/traefik/frontends/frontend1/routes/test_1/rule`  | `Host`           |
| `/traefik/frontends/frontend1/routes/test_1/value` | `test.localhost` |

- frontend 2

| Key                                                | Value      |
|----------------------------------------------------|------------|
| `/traefik/frontends/frontend2/backend`             | `backend1` |
| `/traefik/frontends/frontend2/passHostHeader`      | `true`     |
| `/traefik/frontends/frontend2/entrypoints`         |`http,https`|
| `/traefik/frontends/frontend2/routes/test_2/rule`  | `Path`     |
| `/traefik/frontends/frontend2/routes/test_2/value` | `/test`    |


## <a id="consulcatalog"></a> Consul catalog backend

Træfɪk can be configured to use service discovery catalog of Consul as a backend configuration:

```toml
################################################################
# Consul Catalog configuration backend
################################################################

# Enable Consul Catalog configuration backend
#
# Optional
#
[consulCatalog]

# Consul server endpoint
#
# Required
#
endpoint = "127.0.0.1:8500"

# Default domain used.
#
# Optional
#
domain = "consul.localhost"
```

This backend will create routes matching on hostname based on the service name
used in consul.

## <a id="zk"></a> Zookeeper backend

Træfɪk can be configured to use Zookeeper as a backend configuration:

```toml
################################################################
# Zookeeper configuration backend
################################################################

# Enable Zookeeperconfiguration backend
#
# Optional
#
# [zookeeper]

# Zookeeper server endpoint
#
# Required
#
# endpoint = "127.0.0.1:2181"

# Enable watch Zookeeper changes
#
# Optional
#
# watch = true

# Prefix used for KV store.
#
# Optional
#
# prefix = "/traefik"

# Override default configuration template. For advanced users :)
#
# Optional
#
# filename = "zookeeper.tmpl"
```
The Keys-Values structure should look (using `prefix = "/traefik"`):

- backend 1

| Key                                                    | Value                       |
|--------------------------------------------------------|-----------------------------|
| `/traefik/backends/backend1/circuitbreaker/expression` | `NetworkErrorRatio() > 0.5` |
| `/traefik/backends/backend1/servers/server1/url`       | `http://172.17.0.2:80`      |
| `/traefik/backends/backend1/servers/server1/weight`    | `10`                        |
| `/traefik/backends/backend1/servers/server2/url`       | `http://172.17.0.3:80`      |
| `/traefik/backends/backend1/servers/server2/weight`    | `1`                         |

- backend 2

| Key                                                 | Value                  |
|-----------------------------------------------------|------------------------|
| `/traefik/backends/backend2/loadbalancer/method`    | `drr`                  |
| `/traefik/backends/backend2/servers/server1/url`    | `http://172.17.0.4:80` |
| `/traefik/backends/backend2/servers/server1/weight` | `1`                    |
| `/traefik/backends/backend2/servers/server2/url`    | `http://172.17.0.5:80` |
| `/traefik/backends/backend2/servers/server2/weight` | `2`                    |

- frontend 1

| Key                                               | Value            |
|---------------------------------------------------|------------------|
| `/traefik/frontends/frontend1/backend             | `backend2`       |
| `/traefik/frontends/frontend1/routes/test_1/rule  | `Host`           |
| `/traefik/frontends/frontend1/routes/test_1/value | `test.localhost` |

- frontend 2

| Key                                                | Value      |
|----------------------------------------------------|------------|
| `/traefik/frontends/frontend2/backend`             | `backend1` |
| `/traefik/frontends/frontend2/passHostHeader`      | `true`     |
| `/traefik/frontends/frontend2/entrypoints`         |`http,https`|
| `/traefik/frontends/frontend2/routes/test_2/rule`  | `Path`     |
| `/traefik/frontends/frontend2/routes/test_2/value` | `/test`    |


## <a id="boltdb"></a> BoltDB backend

Træfɪk can be configured to use BoltDB as a backend configuration:

```toml
################################################################
# BoltDB configuration backend
################################################################

# Enable BoltDB configuration backend
#
# Optional
#
# [boltdb]

# BoltDB file
#
# Required
#
# endpoint = "/my.db"

# Enable watch BoltDB changes
#
# Optional
#
# watch = true

# Prefix used for KV store.
#
# Optional
#
# prefix = "/traefik"

# Override default configuration template. For advanced users :)
#
# Optional
#
# filename = "boltdb.tmpl"
```

## <a id="atomicconfig"></a> Atomic configuration changes

The [Etcd](https://github.com/coreos/etcd/issues/860) and [Consul](https://github.com/hashicorp/consul/issues/886) backends do not support updating multiple keys atomically. As a result, it may be possible for Træfɪk to read an intermediate configuration state despite judicious use of the `--providersThrottleDuration` flag. To solve this problem, Træfɪk supports a special key called `/traefik/alias`. If set, Træfɪk use the value as an alternative key prefix.

Given the key structure below, Træfɪk will use the `http://172.17.0.2:80` as its only backend (frontend keys have been omitted for brevity).

| Key                                                                     | Value                       |
|-------------------------------------------------------------------------|-----------------------------|
| `/traefik/alias`                                                        | `/traefik_configurations/1` |
| `/traefik_configurations/1/backends/backend1/servers/server1/url`       | `http://172.17.0.2:80`      |
| `/traefik_configurations/1/backends/backend1/servers/server1/weight`    | `10`                        |

When an atomic configuration change is required, you may write a new configuration at an alternative prefix. Here, although the `/traefik_configurations/2/...` keys have been set, the old configuration is still active because the `/traefik/alias` key still points to `/traefik_configurations/1`:

| Key                                                                     | Value                       |
|-------------------------------------------------------------------------|-----------------------------|
| `/traefik/alias`                                                        | `/traefik_configurations/1` |
| `/traefik_configurations/1/backends/backend1/servers/server1/url`       | `http://172.17.0.2:80`      |
| `/traefik_configurations/1/backends/backend1/servers/server1/weight`    | `10`                        |
| `/traefik_configurations/2/backends/backend1/servers/server1/url`       | `http://172.17.0.2:80`      |
| `/traefik_configurations/2/backends/backend1/servers/server1/weight`    | `5`                        |
| `/traefik_configurations/2/backends/backend1/servers/server2/url`       | `http://172.17.0.3:80`      |
| `/traefik_configurations/2/backends/backend1/servers/server2/weight`    | `5`                        |

Once the `/traefik/alias` key is updated, the new `/traefik_configurations/2` configuration becomes active atomically. Here, we have a 50% balance between the `http://172.17.0.3:80` and the `http://172.17.0.4:80` hosts while no traffic is sent to the `172.17.0.2:80` host:

| Key                                                                     | Value                       |
|-------------------------------------------------------------------------|-----------------------------|
| `/traefik/alias`                                                        | `/traefik_configurations/2` |
| `/traefik_configurations/1/backends/backend1/servers/server1/url`       | `http://172.17.0.2:80`      |
| `/traefik_configurations/1/backends/backend1/servers/server1/weight`    | `10`                        |
| `/traefik_configurations/2/backends/backend1/servers/server1/url`       | `http://172.17.0.3:80`      |
| `/traefik_configurations/2/backends/backend1/servers/server1/weight`    | `5`                        |
| `/traefik_configurations/2/backends/backend1/servers/server2/url`       | `http://172.17.0.4:80`      |
| `/traefik_configurations/2/backends/backend1/servers/server2/weight`    | `5`                        |

Note that Træfɪk *will not watch for key changes in the `/traefik_configurations` prefix*. It will only watch for changes in the `/traefik` prefix. Further, if the `/traefik/alias` key is set, all other sibling keys with the `/traefik` prefix are ignored.


## <a id="benchmarks"></a> Benchmarks

Here are some early Benchmarks between Nginx, HA-Proxy and Træfɪk acting as simple load balancers between two servers.

- Nginx:

```sh
$ docker run -d -e VIRTUAL_HOST=test.nginx.localhost emilevauge/whoami
$ docker run -d -e VIRTUAL_HOST=test.nginx.localhost emilevauge/whoami
$ docker run --log-driver=none -d -p 80:80 -v /var/run/docker.sock:/tmp/docker.sock:ro jwilder/nginx-proxy
$ wrk -t12 -c400 -d60s -H "Host: test.nginx.localhost" --latency http://127.0.0.1:80
Running 1m test @ http://127.0.0.1:80
  12 threads and 400 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency   162.61ms  203.34ms   1.72s    91.07%
    Req/Sec   277.57    107.67   790.00     67.53%
  Latency Distribution
     50%  128.19ms
     75%  218.22ms
     90%  342.12ms
     99%    1.08s 
  197991 requests in 1.00m, 82.32MB read
  Socket errors: connect 0, read 0, write 0, timeout 18
Requests/sec:   3296.04
Transfer/sec:      1.37MB
```

- HA-Proxy:

```
$ docker run -d --name web1 -e VIRTUAL_HOST=test.haproxy.localhost emilevauge/whoami
$ docker run -d --name web2 -e VIRTUAL_HOST=test.haproxy.localhost emilevauge/whoami
$ docker run -d -p 80:80 --link web1:web1 --link web2:web2 dockercloud/haproxy
$ wrk -t12 -c400 -d60s -H "Host: test.haproxy.localhost" --latency http://127.0.0.1:80
Running 1m test @ http://127.0.0.1:80
  12 threads and 400 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency   158.08ms  187.88ms   1.75s    89.61%
    Req/Sec   281.33    120.47     0.98k    65.88%
  Latency Distribution
     50%  121.77ms
     75%  227.10ms
     90%  351.98ms
     99%    1.01s 
  200462 requests in 1.00m, 59.65MB read
Requests/sec:   3337.66
Transfer/sec:      0.99MB
```

- Træfɪk:

```sh
$ docker run -d -l traefik.backend=test1 -l traefik.frontend.rule=Host -l traefik.frontend.value=test.traefik.localhost emilevauge/whoami
$ docker run -d -l traefik.backend=test1 -l traefik.frontend.rule=Host -l traefik.frontend.value=test.traefik.localhost emilevauge/whoami
$ docker run -d -p 8080:8080 -p 80:80 -v $PWD/traefik.toml:/traefik.toml -v /var/run/docker.sock:/var/run/docker.sock containous/traefik
$ wrk -t12 -c400 -d60s -H "Host: test.traefik.localhost" --latency http://127.0.0.1:80
Running 1m test @ http://127.0.0.1:80
  12 threads and 400 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency   132.93ms  121.89ms   1.20s    66.62%
    Req/Sec   280.95    104.88   740.00     68.26%
  Latency Distribution
     50%  128.71ms
     75%  214.15ms
     90%  281.45ms
     99%  498.44ms
  200734 requests in 1.00m, 80.02MB read
Requests/sec:   3340.13
Transfer/sec:      1.33MB
```