[v9.5.x] SQL Datasources: Update behavior of default connection limits (#67465)

* SQL Datasources: Update behavior of default connection limits (#66687)

* Update behavior of defaults in connection limits

* Refactor to use config object instead

* Refactor remove unneeded function

---------

Co-authored-by: Zoltán Bedi <zoltan.bedi@gmail.com>
(cherry picked from commit 1fbac96bd4)

* SQL Datasources: Update behavior of default connection limits (#66687)

* Update behavior of defaults in connection limits

* Refactor to use config object instead

* Refactor remove unneeded function

---------

Co-authored-by: Zoltán Bedi <zoltan.bedi@gmail.com>
(cherry picked from commit 1fbac96bd4)

---------

Co-authored-by: Kyle Cunningham <codeincarnate@users.noreply.github.com>
Co-authored-by: Kyle Cunningham <kyle@codeincarnate.com>

pkg/api/dtos/frontend_settings.go

@@ -121,6 +121,12 @@ type FrontendSettingsWhitelabelingDTO struct {
 	PublicDashboardFooter *FrontendSettingsPublicDashboardFooterConfigDTO `json:"publicDashboardFooter,omitempty"` // PR TODO: type this properly
 }
 
+type FrontendSettingsSqlConnectionLimitsDTO struct {
+	MaxOpenConns    int `json:"maxOpenConns"`
+	MaxIdleConns    int `json:"maxIdleConns"`
+	ConnMaxLifetime int `json:"connMaxLifetime"`
+}
+
 type FrontendSettingsDTO struct {
 	DefaultDatasource          string                           `json:"defaultDatasource"`
 	Datasources                map[string]plugins.DataSourceDTO `json:"datasources"`
@@ -223,6 +229,8 @@ type FrontendSettingsDTO struct {
 
 	PluginsCDNBaseURL string `json:"pluginsCDNBaseURL,omitempty"`
 
+	SqlConnectionLimits FrontendSettingsSqlConnectionLimitsDTO `json:"sqlConnectionLimits"`
+
 	// Enterprise
 	Licensing     *FrontendSettingsLicensingDTO     `json:"licensing,omitempty"`
 	Whitelabeling *FrontendSettingsWhitelabelingDTO `json:"whitelabeling,omitempty"`

pkg/api/frontendsettings.go

@@ -215,6 +215,12 @@ func (hs *HTTPServer) getFrontendSettings(c *contextmodel.ReqContext) (*dtos.Fro
 		TokenExpirationDayLimit: hs.Cfg.SATokenExpirationDayLimit,
 
 		SnapshotEnabled: hs.Cfg.SnapshotEnabled,
+
+		SqlConnectionLimits: dtos.FrontendSettingsSqlConnectionLimitsDTO{
+			MaxOpenConns:    hs.Cfg.SqlDatasourceMaxOpenConnsDefault,
+			MaxIdleConns:    hs.Cfg.SqlDatasourceMaxIdleConnsDefault,
+			ConnMaxLifetime: hs.Cfg.SqlDatasourceMaxConnLifetimeDefault,
+		},
 	}
 
 	if hs.Cfg.UnifiedAlerting.Enabled != nil {