feat: configure Traefik readiness healthchecks based on app.json config

Closes #6834

docs/networking/proxies/traefik.md

@@ -32,6 +32,42 @@ The Traefik plugin has specific rules for routing requests:
 - If no `https:443` mapping is found, the first `https` port mapping is used for https requests.
 - If no `https` mapping is found, the container port from `http:80` will be used for https requests.
 - Requests are routed as soon as the container is running and passing healthchecks.
+- Readiness healthchecks defined in `app.json` with a `path` property are automatically transformed into Traefik healthcheck labels.
+
+### Healthchecks
+
+When an app has a readiness healthcheck defined in its `app.json` file with a `path` property, Dokku automatically generates Traefik healthcheck labels. These labels configure Traefik to perform health checks on the container before routing traffic to it.
+
+The following `app.json` healthcheck properties are mapped to Traefik labels:
+
+| app.json Property | Traefik Label Property | Description |
+|-------------------|------------------------|-------------|
+| `path`            | `healthcheck.path`     | The HTTP path to check (required) |
+| `scheme`          | `healthcheck.scheme`   | The scheme to use (`http` or `https`) |
+| `port`            | `healthcheck.port`     | The port to check |
+| `timeout`         | `healthcheck.timeout`  | Timeout in seconds (formatted as `Xs`) |
+| `wait`            | `healthcheck.interval` | Interval between checks in seconds (formatted as `Xs`) |
+
+Example `app.json` configuration:
+
+```json
+{
+  "healthchecks": {
+    "web": [
+      {
+        "name": "web readiness check",
+        "path": "/health",
+        "timeout": 5,
+        "type": "readiness",
+        "wait": 10
+      }
+    ]
+  }
+}
+```
+
+> [!NOTE]
+> Only the first readiness healthcheck with a `path` property is used. Liveness, startup, and command-based healthchecks are not transformed into Traefik labels.
 
 ### Switching to Traefik
 

plugins/traefik-vhosts/docker-args-process-deploy

@@ -129,6 +129,33 @@ trigger-traefik-vhosts-docker-args-process-deploy() {
         output="$output --label \"traefik.http.routers.$APP-$PROC_TYPE-https.rule=$traefik_domains\""
       fi
     fi
+
+    local app_json hc_path hc_scheme hc_port hc_timeout hc_interval hc_filter
+    app_json="$(plugn trigger app-json-get-content "$APP" 2>/dev/null || echo "{}")"
+    hc_filter='.healthchecks.web // [] | map(select(.type == "readiness" and .path != null and .path != "")) | .[0]'
+    hc_path=$(echo "$app_json" | jq -r "$hc_filter | .path // empty")
+    if [[ -n "$hc_path" ]]; then
+      hc_scheme=$(echo "$app_json" | jq -r "$hc_filter | .scheme // empty")
+      hc_port=$(echo "$app_json" | jq -r "$hc_filter | .port // empty")
+      hc_timeout=$(echo "$app_json" | jq -r "$hc_filter | .timeout // empty")
+      hc_interval=$(echo "$app_json" | jq -r "$hc_filter | .wait // empty")
+
+      if [[ -n "$proxy_container_http_port" ]]; then
+        output="$output --label traefik.http.services.$APP-$PROC_TYPE-http.loadbalancer.healthcheck.path=$hc_path"
+        [[ -n "$hc_scheme" ]] && output="$output --label traefik.http.services.$APP-$PROC_TYPE-http.loadbalancer.healthcheck.scheme=$hc_scheme"
+        [[ -n "$hc_port" ]] && output="$output --label traefik.http.services.$APP-$PROC_TYPE-http.loadbalancer.healthcheck.port=$hc_port"
+        [[ -n "$hc_timeout" ]] && output="$output --label traefik.http.services.$APP-$PROC_TYPE-http.loadbalancer.healthcheck.timeout=${hc_timeout}s"
+        [[ -n "$hc_interval" ]] && output="$output --label traefik.http.services.$APP-$PROC_TYPE-http.loadbalancer.healthcheck.interval=${hc_interval}s"
+      fi
+
+      if [[ -n "$proxy_container_https_port" ]]; then
+        output="$output --label traefik.http.services.$APP-$PROC_TYPE-https.loadbalancer.healthcheck.path=$hc_path"
+        [[ -n "$hc_scheme" ]] && output="$output --label traefik.http.services.$APP-$PROC_TYPE-https.loadbalancer.healthcheck.scheme=$hc_scheme"
+        [[ -n "$hc_port" ]] && output="$output --label traefik.http.services.$APP-$PROC_TYPE-https.loadbalancer.healthcheck.port=$hc_port"
+        [[ -n "$hc_timeout" ]] && output="$output --label traefik.http.services.$APP-$PROC_TYPE-https.loadbalancer.healthcheck.timeout=${hc_timeout}s"
+        [[ -n "$hc_interval" ]] && output="$output --label traefik.http.services.$APP-$PROC_TYPE-https.loadbalancer.healthcheck.interval=${hc_interval}s"
+      fi
+    fi
   fi
 
   local proxy_labels_file_path=$(fn-proxy-get-labels-file-path "traefik" "$APP")

tests/apps/python/app-traefik.json

@@ -0,0 +1,13 @@
+{
+  "healthchecks": {
+    "web": [
+      {
+        "name": "web readiness check",
+        "path": "/",
+        "timeout": 5,
+        "type": "readiness",
+        "wait": 2
+      }
+    ]
+  }
+}

tests/unit/traefik.bats

@@ -734,3 +734,61 @@ teardown() {
   run /bin/bash -c "dokku traefik:set --global dns-provider-cf_api_email"
   run /bin/bash -c "dokku traefik:set --global dns-provider-cf_api_key"
 }
+
+
+@test "(traefik) healthcheck labels from app.json" {
+  run /bin/bash -c "dokku proxy:set $TEST_APP traefik"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run deploy_app python dokku@$DOKKU_DOMAIN:$TEST_APP setup_traefik_healthcheck
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "docker inspect $TEST_APP.web.1 --format '{{ index .Config.Labels \"traefik.http.services.$TEST_APP-web-http.loadbalancer.healthcheck.path\" }}'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "/"
+
+  run /bin/bash -c "docker inspect $TEST_APP.web.1 --format '{{ index .Config.Labels \"traefik.http.services.$TEST_APP-web-http.loadbalancer.healthcheck.timeout\" }}'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "5s"
+
+  run /bin/bash -c "docker inspect $TEST_APP.web.1 --format '{{ index .Config.Labels \"traefik.http.services.$TEST_APP-web-http.loadbalancer.healthcheck.interval\" }}'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "2s"
+}
+
+@test "(traefik) no healthcheck labels without readiness check" {
+  run /bin/bash -c "dokku proxy:set $TEST_APP traefik"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run deploy_app python dokku@$DOKKU_DOMAIN:$TEST_APP
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "docker inspect $TEST_APP.web.1 --format '{{ index .Config.Labels \"traefik.http.services.$TEST_APP-web-http.loadbalancer.healthcheck.path\" }}'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output_not_exists
+}
+
+setup_traefik_healthcheck() {
+  local APP="$1"
+  local APP_REPO_DIR="$2"
+  [[ -z "$APP" ]] && local APP="$TEST_APP"
+  APP_REPO_DIR="$(realpath "$APP_REPO_DIR")"
+
+  mv "$APP_REPO_DIR/app-traefik.json" "$APP_REPO_DIR/app.json"
+}