feat: add ability to deploy process types in parallel

docs/deployment/schedulers/docker-local.md

@@ -37,6 +37,29 @@ Once set, you may re-enable it by setting a blank value for `disable-chown`:
 dokku scheduler-docker-local:set node-js-app disable-chown
 ```
 
+### Deploying Process Types in parallel
+
+> New as of 25.5
+
+By default, Dokku deploys an app's processes one-by-one in order, with the `web` process being deployed first. Deployment parallelism may be achieved by setting the `parallel-schedule-count` property, which defaults to `1`. Increasing this number increases the number of process types that may be deployed in parallel (with the web process being the exception).
+
+```shell
+# Increase parallelism from 1 process type at a time to 4 process types at a time.
+dokku scheduler-docker-local:set node-js-app parallel-schedule-count 4
+```
+
+Once set, you may reset it by setting a blank value for `parallel-schedule-count`:
+
+```shell
+dokku scheduler-docker-local:set node-js-app parallel-schedule-count
+```
+
+If the value of `parallel-schedule-count` is increased and a given process type fails to schedule successfully, then any in-flight process types will continue to be processed, while all process types that have not been scheduled will be skipped before the deployment finally fails.
+
+Container scheduling output is shown in the order it is received, and thus may be out of order in case of output to stderr.
+
+Note that increasing the value of `parallel-schedule-count` may significantly impact CPU utilization on your host as your app containers - and their respective processes - start up. Setting a value higher than the number of available CPUs is discouraged. It is recommended that users carefully set this value so as not to overburden their server.
+
 ## Implemented Triggers
 
 This plugin implements various functionality through `plugn` triggers to integrate with Docker for running apps on a single server. The following functionality is supported by the `scheduler-docker-local` plugin.

plugins/scheduler-docker-local/bin/scheduler-deploy-process

@@ -8,6 +8,7 @@ main() {
   declare APP="$1" IMAGE_SOURCE_TYPE="$2" IMAGE="$3" IMAGE_TAG="$4" PROC_TYPE="$5" PROC_COUNT="$6"
   local CONTAINER_INDEX=1
 
+  dokku_log_info1 "Deploying $PROC_TYPE (count=$PROC_COUNT)"
   DOKKU_CHECKS_DISABLED="$(is_app_proctype_checks_disabled "$APP" "$PROC_TYPE")"
   if [[ "$DOKKU_CHECKS_DISABLED" == "true" ]]; then
     dokku_log_verbose "Zero downtime is disabled, stopping currently running containers  ($PROC_TYPE)"

plugins/scheduler-docker-local/internal-functions

@@ -38,6 +38,7 @@ cmd-scheduler-docker-local-report-single() {
   verify_app_name "$APP"
   local flag_map=(
     "--scheduler-docker-local-disable-chown: $(fn-plugin-property-get "scheduler-docker-local" "$APP" "disable-chown" "")"
+    "--scheduler-docker-local-parallel-schedule-count: $(fn-plugin-property-get "scheduler-docker-local" "$APP" "parallel-schedule-count" "")"
   )
 
   if [[ -z "$INFO_FLAG" ]]; then

plugins/scheduler-docker-local/scheduler-deploy

@@ -44,24 +44,28 @@ trigger-scheduler-docker-local-scheduler-deploy() {
 
   local WAIT="${DOKKU_WAIT_TO_RETIRE:-60}"
 
+  local TMP_FILE=$(mktemp "/tmp/dokku-${DOKKU_PID}-${FUNCNAME[0]}.XXXXXX")
+  trap "rm -rf '$TMP_FILE' >/dev/null" RETURN INT TERM
+
   local line
   local PROC_TYPE
   local PROC_COUNT
-  local CONTAINER_INDEX
   while read -r line || [[ -n "$line" ]]; do
-    PROC_TYPE=${line%%=*}
-    PROC_COUNT=${line#*=}
+    local PROC_TYPE=${line%%=*}
+    local PROC_COUNT=${line#*=}
 
-    dokku_log_info1 "Deploying $PROC_TYPE (count=$PROC_COUNT)"
-    export DOKKU_NETWORK_BIND_ALL="$DOKKU_NETWORK_BIND_ALL"
-    export DOKKU_HEROKUISH="$DOKKU_HEROKUISH"
-    export DOKKU_CNB="$DOKKU_CNB"
-    export DOCKER_RUN_LABEL_ARGS="$DOCKER_RUN_LABEL_ARGS"
-    export DOKKU_START_CMD="$DOKKU_START_CMD"
-    export DOCKER_STOP_TIME_ARG="$DOCKER_STOP_TIME_ARG"
-    "$PLUGIN_AVAILABLE_PATH/scheduler-docker-local/bin/scheduler-deploy-process" "$APP" "$IMAGE_SOURCE_TYPE" "$IMAGE" "$IMAGE_TAG" "$PROC_TYPE" "$PROC_COUNT"
+    if [[ "$PROC_TYPE" != "web" ]]; then
+      echo "$PLUGIN_AVAILABLE_PATH/scheduler-docker-local/bin/scheduler-deploy-process $APP $IMAGE_SOURCE_TYPE $IMAGE $IMAGE_TAG $PROC_TYPE $PROC_COUNT" >> "$TMP_FILE"
+      continue
+    fi
+
+    DOKKU_NETWORK_BIND_ALL="$DOKKU_NETWORK_BIND_ALL" DOKKU_HEROKUISH="$DOKKU_HEROKUISH" DOKKU_CNB="$DOKKU_CNB" DOCKER_RUN_LABEL_ARGS="$DOCKER_RUN_LABEL_ARGS" DOKKU_START_CMD="$DOKKU_START_CMD" DOCKER_STOP_TIME_ARG="$DOCKER_STOP_TIME_ARG" "$PLUGIN_AVAILABLE_PATH/scheduler-docker-local/bin/scheduler-deploy-process" "$APP" "$IMAGE_SOURCE_TYPE" "$IMAGE" "$IMAGE_TAG" "$PROC_TYPE" "$PROC_COUNT"
   done < <(plugn trigger ps-current-scale "$APP")
 
+  PARALLEL_DEPLOY_COUNT="$(fn-plugin-property-get "scheduler-docker-local" "$APP" "parallel-schedule-count" "1")"
+
+  DOKKU_NETWORK_BIND_ALL="$DOKKU_NETWORK_BIND_ALL" DOKKU_HEROKUISH="$DOKKU_HEROKUISH" DOKKU_CNB="$DOKKU_CNB" DOCKER_RUN_LABEL_ARGS="$DOCKER_RUN_LABEL_ARGS" DOKKU_START_CMD="$DOKKU_START_CMD" DOCKER_STOP_TIME_ARG="$DOCKER_STOP_TIME_ARG" parallel --halt soon,fail=1 --jobs "$PARALLEL_DEPLOY_COUNT" --ungroup < "$TMP_FILE"
+
   dokku_log_info1 "Running post-deploy"
   plugn trigger core-post-deploy "$APP" "$port" "$ipaddr" "$IMAGE_TAG"
   plugn trigger post-deploy "$APP" "$port" "$ipaddr" "$IMAGE_TAG"

plugins/scheduler-docker-local/subcommands/set

@@ -9,13 +9,13 @@ cmd-scheduler-docker-local-set() {
   declare cmd="scheduler-docker-local:set"
   [[ "$1" == "$cmd" ]] && shift 1
   declare APP="$1" KEY="$2" VALUE="$3"
-  local VALID_KEYS=("disable-chown")
+  local VALID_KEYS=("disable-chown" "parallel-schedule-count")
   verify_app_name "$APP"
 
   [[ -z "$KEY" ]] && dokku_log_fail "No key specified"
 
   if ! fn-in-array "$KEY" "${VALID_KEYS[@]}"; then
-    dokku_log_fail "Invalid key specified, valid keys include: disable-chown"
+    dokku_log_fail "Invalid key specified, valid keys include: disable-chown, parallel-schedule-count"
   fi
 
   if [[ -n "$VALUE" ]]; then