docs, sticky session for Docker

docs/basics.md

@@ -222,6 +222,17 @@ For example:
 - Another possible value for `extractorfunc` is `client.ip` which will categorize requests based on client source ip.
 - Lastly `extractorfunc` can take the value of `request.header.ANY_HEADER` which will categorize requests based on `ANY_HEADER` that you provide.
 
+Sticky sessions are supported with both load balancers. When sticky sessions are enabled, a cookie called `_TRAEFIK_BACKEND` is set on the initial
+request. On subsequent requests, the client will be directed to the backend stored in the cookie if it is still healthy. If not, a new backend
+will be assigned.
+
+For example:
+```toml
+[backends]
+  [backends.backend1]
+    [backends.backend1.loadbalancer]
+      sticky = true
+```
 ## Servers
 
 Servers are simply defined using a `URL`. You can also apply a custom `weight` to each server (this will be used by load-balancing).

docs/toml.md

@@ -716,6 +716,7 @@ Labels can be used on containers to override default behaviour:
 - `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.stickysession=true`: enable backend sticky sessions
 - `traefik.frontend.rule=Host:test.traefik.io`: override the default frontend rule (Default: `Host:{containerName}.{domain}`).
 - `traefik.frontend.passHostHeader=true`: forward client `Host` header to the backend.
 - `traefik.frontend.priority=10`: override default frontend priority

provider/docker.go

@@ -439,6 +439,13 @@ func (provider *Docker) getWeight(container dockerData) string {
 	return "1"
 }
 
+func (provider *Docker) getSticky(container dockertypes.ContainerJSON) string {
+	if label, err := getLabel(container, "traefik.stickysession"); err == nil {
+		return true
+	}
+	return false
+}
+
 func (provider *Docker) getDomain(container dockerData) string {
 	if label, err := getLabel(container, "traefik.domain"); err == nil {
 		return label

templates/docker.tmpl

@@ -7,6 +7,7 @@
     {{if hasLoadBalancerLabel .}}
     [backends.backend-{{getBackend .}}.loadbalancer]
       method = "{{getLoadBalancerMethod .}}"
+      sticky = {{getSticky . }}
     {{end}}
 
     {{if hasMaxConnLabels .}}