Add allowEmptyServices for Docker provider

docs/content/providers/docker.md

@@ -714,3 +714,30 @@ providers:
 ```bash tab="CLI"
 --providers.docker.tls.insecureSkipVerify=true
 ```
+
+### `allowEmptyServices`
+
+_Optional, Default=false_
+
+If the parameter is set to `true`,
+any [servers load balancer](../routing/services/index.md#servers-load-balancer) defined for Docker containers is created 
+regardless of the [healthiness](https://docs.docker.com/engine/reference/builder/#healthcheck) of the corresponding containers.
+It also then stays alive and responsive even at times when it becomes empty,
+i.e. when all its children containers become unhealthy.
+This results in `503` HTTP responses instead of `404` ones,
+in the above cases.
+
+```yaml tab="File (YAML)"
+providers:
+  docker:
+    allowEmptyServices: true
+```
+
+```toml tab="File (TOML)"
+[providers.docker]
+  allowEmptyServices = true
+```
+
+```bash tab="CLI"
+--providers.docker.allowEmptyServices=true
+```

docs/content/reference/static-configuration/cli-ref.md

@@ -519,6 +519,9 @@ Watch Consul API events. (Default: ```false```)
 `--providers.docker`:  
 Enable Docker backend with default settings. (Default: ```false```)
 
+`--providers.docker.allowemptyservices`:  
+Disregards the Docker containers health checks with respect to the creation or removal of the corresponding services. (Default: ```false```)
+
 `--providers.docker.constraints`:  
 Constraints is an expression that Traefik matches against the container's labels to determine whether to create any route for that container.
 

docs/content/reference/static-configuration/env-ref.md

@@ -519,6 +519,9 @@ KV Username
 `TRAEFIK_PROVIDERS_DOCKER`:  
 Enable Docker backend with default settings. (Default: ```false```)
 
+`TRAEFIK_PROVIDERS_DOCKER_ALLOWEMPTYSERVICES`:  
+Disregards the Docker containers health checks with respect to the creation or removal of the corresponding services. (Default: ```false```)
+
 `TRAEFIK_PROVIDERS_DOCKER_CONSTRAINTS`:  
 Constraints is an expression that Traefik matches against the container's labels to determine whether to create any route for that container.
 

docs/content/reference/static-configuration/file.toml

@@ -67,6 +67,7 @@
     network = "foobar"
     swarmModeRefreshSeconds = "42s"
     httpClientTimeout = "42s"
+    allowEmptyServices = true
     [providers.docker.tls]
       ca = "foobar"
       caOptional = true

docs/content/reference/static-configuration/file.yaml

@@ -79,6 +79,7 @@ providers:
     network: foobar
     swarmModeRefreshSeconds: 42s
     httpClientTimeout: 42s
+    allowEmptyServices: true
   file:
     directory: foobar
     watch: true