Read POSTGRES_DATABASE_SCHEME variable from app when setting DATABASE_URL

README.md

@@ -130,6 +130,33 @@ dokku postgres:clone lolipop new_database
 dokku postgres:destroy lolipop
 ```
 
+## Changing database adapter
+
+It's possible to change the protocol for DATABASE_URL by setting
+the environment variable POSTGRES_DATABASE_SCHEME on the app:
+
+```
+dokku config:set playground POSTGRES_DATABASE_SCHEME=postgres2
+dokku postgres:link lolipop playground
+```
+
+Will cause DATABASE_URL to be set as
+postgres2://postgres:SOME_PASSWORD@dokku-postgres-lolipop:5432/lolipop
+
+CAUTION: Changing POSTGRES_DATABASE_SCHEME after linking will cause dokku to
+believe the postgres is not linked when attempting to use `dokku postgres:unlink`
+or `dokku postgres:promote`.
+You should be able to fix this by
+
+- Changing DATABASE_URL manually to the new value.
+
+OR
+
+- Set POSTGRES_DATABASE_SCHEME back to its original setting
+- Unlink the service
+- Change POSTGRES_DATABASE_SCHEME to the desired setting
+- Relink the service
+
 ## upgrade/downgrade
 
 At the moment a database can’t be upgraded  (or downgraded) inplace. Instead a clone has to be made, like this:

functions

@@ -1,6 +1,7 @@
 #!/usr/bin/env bash
 set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 source "$(dirname "$0")/config"
+source "$PLUGIN_AVAILABLE_PATH/config/functions"
 
 get_random_ports() {
   local iterations="${1:-1}"
@@ -70,6 +71,7 @@ service_exposed_ports() {
 service_link() {
   local APP="$2"
   local SERVICE="$1"
+  update_plugin_scheme_for_app "$APP"
   local SERVICE_URL=$(service_url "$SERVICE")
   local SERVICE_NAME=$(get_service_name "$SERVICE")
   local SERVICE_ROOT="$PLUGIN_DATA_ROOT/$SERVICE"
@@ -253,6 +255,7 @@ service_stop() {
 service_unlink() {
   local APP="$2"
   local SERVICE="$1"
+  update_plugin_scheme_for_app "$APP"
   local SERVICE_URL=$(service_url "$SERVICE")
   local SERVICE_NAME=$(get_service_name "$SERVICE")
   local EXISTING_CONFIG=$(dokku config "$APP")
@@ -316,6 +319,7 @@ promote() {
   local APP="$2"
   local PLUGIN_DEFAULT_CONFIG_VAR="${PLUGIN_DEFAULT_ALIAS}_URL"
   local EXISTING_CONFIG=$(dokku config "$APP")
+  update_plugin_scheme_for_app "$APP"
   local SERVICE_URL=$(service_url "$SERVICE")
   local CONFIG_VARS=($(echo "$EXISTING_CONFIG" | grep "$SERVICE_URL" | cut -d: -f1)) || true
   local PREVIOUS_DEFAULT_URL=$(get_url_from_config "$EXISTING_CONFIG" "$PLUGIN_DEFAULT_CONFIG_VAR")
@@ -357,3 +361,9 @@ service_linked_apps() {
 
   tr '\n' ' ' < "$LINKS_FILE"
 }
+
+update_plugin_scheme_for_app() {
+  local APP=$1
+  local POSTGRES_DATABASE_SCHEME=$(config_get $APP POSTGRES_DATABASE_SCHEME)
+  PLUGIN_SCHEME=${POSTGRES_DATABASE_SCHEME:-$PLUGIN_SCHEME}
+}

tests/service_link.bats

@@ -59,3 +59,12 @@ teardown() {
   assert_contains "${lines[*]}" "--link dokku.postgres.l:dokku-postgres-l"
   dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
 }
+
+@test "($PLUGIN_COMMAND_PREFIX:link) uses apps POSTGRES_DATABASE_SCHEME variable" {
+  dokku config:set my_app POSTGRES_DATABASE_SCHEME=postgres2
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app
+  url=$(dokku config:get my_app DATABASE_URL)
+  password="$(cat "$PLUGIN_DATA_ROOT/l/PASSWORD")"
+  assert_contains "$url" "postgres2://postgres:$password@dokku-postgres-l:5432/l"
+  dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
+}

tests/service_promote.bats

@@ -53,3 +53,10 @@ teardown() {
   run dokku config my_app
   assert_contains "${lines[*]}" "DOKKU_POSTGRES_"
 }
+@test "($PLUGIN_COMMAND_PREFIX:promote) uses POSTGRES_DATABASE_SCHEME variable" {
+  password="$(cat "$PLUGIN_DATA_ROOT/l/PASSWORD")"
+  dokku config:set my_app "POSTGRES_DATABASE_SCHEME=postgres2" "DATABASE_URL=postgres://u:p@host:5432/db" "DOKKU_POSTGRES_BLUE_URL=postgres2://postgres:$password@dokku-postgres-l:5432/l"
+  dokku "$PLUGIN_COMMAND_PREFIX:promote" l my_app
+  url=$(dokku config:get my_app DATABASE_URL)
+  assert_contains "$url" "postgres2://postgres:$password@dokku-postgres-l:5432/l"
+}