PR #1001: Postgres Connection Pooling Control

internal/cmd/base/servers.go

@@ -88,8 +88,9 @@ type Server struct {
 	DevTargetSessionMaxSeconds      int
 	DevTargetSessionConnectionLimit int
 
-	DatabaseUrl            string
-	DevDatabaseCleanupFunc func() error
+	DatabaseUrl                string
+	DatabaseMaxOpenConnections int
+	DevDatabaseCleanupFunc     func() error
 
 	Database *gorm.DB
 }
@@ -453,7 +454,11 @@ func (b *Server) ConnectToDatabase(dialect string) error {
 	if err != nil {
 		return fmt.Errorf("unable to create db object with dialect %s: %w", dialect, err)
 	}
-
+	if b.DatabaseMaxOpenConnections == 1 {
+		return fmt.Errorf("unable to create db object with dialect %s: %s", dialect, "max_open_connections must be unlimited by setting 0 or at least 2")
+	} else {
+		dbase.DB().SetMaxOpenConns(b.DatabaseMaxOpenConnections)
+	}
 	b.Database = dbase
 	if os.Getenv("BOUNDARY_DISABLE_GORM_FORMATTER") == "" {
 		gorm.LogFormatter = db.GetGormLogFormatter(b.Logger)

internal/cmd/commands/server/server.go

@@ -366,6 +366,8 @@ func (c *Command) Run(args []string) int {
 			c.UI.Error(fmt.Errorf("Error parsing database url: %w", err).Error())
 			return base.CommandUserError
 		}
+		c.DatabaseMaxOpenConnections = c.Config.Controller.Database.MaxOpenConnections
+
 		if err := c.ConnectToDatabase("postgres"); err != nil {
 			c.UI.Error(fmt.Errorf("Error connecting to database: %w", err).Error())
 			return base.CommandCliError

internal/cmd/config/config.go

@@ -133,8 +133,9 @@ type Worker struct {
 }
 
 type Database struct {
-	Url          string `hcl:"url"`
-	MigrationUrl string `hcl:"migration_url"`
+	Url                string `hcl:"url"`
+	MigrationUrl       string `hcl:"migration_url"`
+	MaxOpenConnections int    `hcl:"max_open_connections"`
 }
 
 // DevWorker is a Config that is used for dev mode of Boundary

website/content/docs/configuration/controller.mdx

@@ -15,6 +15,7 @@ controller {
   description = "An example controller"
   database {
     url = "postgresql://<username>:<password>@10.0.0.1:5432/<database_name>"
+    max_open_connections = 2
   }
 }
 ```
@@ -28,6 +29,13 @@ controller {
   - `url` - Configures the URL for connecting to Postgres
   - `migration_url` - Can be used to specify a different URL for migrations, as that
     usually requires higher privileges.
+  - `max_open_connections` - Can be used to control the maximum number of
+    connections that can be opened by the controller. The minimum number of
+    connections required is 2. Every controller requires 1 non-pooled
+    shared lock connection (which is held for the lifetime of the controller) and
+    a minimum of 1 pooled connection which is used for all other database
+    requests. Setting this value to 0 will allow the controller to open as many
+    connections as needed.
 
   Either can refer to a file on disk (file://) from which a URL will be read; an env
   var (env://) from which the URL will be read; or a direct database URL (postgres://).