feat(backend): allow configuring default grid sort options

This will allow UI to get the defaults for grid sorting via the API

docs/CONFIGURATION.md

@@ -245,6 +245,61 @@ filters:
   default: []
 ```
 
+### Grid
+
+`grid` section allows customizing how alert grid is rendered in the UI.
+Sorting configuration can be overridden by each user via UI settings.
+Syntax:
+
+```YAML
+grid:
+  sorting:
+    order: string
+    reverse: bool
+    label: string
+```
+
+- `sorting:order` - default sort order for alert grid, valid values are:
+  - `disabled` - no sorting, alert groups are rendered in the order they are
+    returned by the API
+  - `startsAt` - sort by alert timestamps, most recent alert in each group will
+    be used when comparing each group
+  - `label` - sort by labels, if the label used for sorting is not shared by
+    all alerts in a group then the first alert in the group will be queried for
+    it
+- `sorting:reverse` - default value for reversed sort order
+- `sorting:label` - label name for sorting when `grid:sorting:order` is set
+  to `label`. Labels can be assigned custom values used only by sorting via
+  `labels:sorting:valueMapping`, see [Labels](#Labels) section for details.
+
+Defaults:
+
+```YAML
+grid:
+  sorting:
+    order: startsAt
+    reverse: true
+    label: alertname
+```
+
+Example with sorting using `severity` label, with extra option to map severity
+labels to numeric values for sorting:
+
+```YAML
+grid:
+  sorting:
+    order: label
+    reverse: false
+    label: severity
+labels:
+  sorting:
+    valueMapping:
+      severity:
+        critical: 1
+        warning: 2
+        info: 3
+```
+
 ### Labels
 
 `labels` section allows configuring how alert labels will be rendered in the
@@ -293,6 +348,8 @@ labels:
   To allow for more natural sorting `sorting:valueMapping` can be used to
   map label values to integer values which will be used for sorting instead
   of original string values.
+  Note: this option is not available via environment variables, you can only set
+  it via the config file.
 
 Example with static color for the `job` label (every `job` label will have the
 same color regardless of the value) and unique color for the `@receiver` label

internal/config/config.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/prymitive/karma/internal/slices"
 	"github.com/prymitive/karma/internal/uri"
 	"github.com/spf13/pflag"
 	"github.com/spf13/viper"
@@ -60,6 +61,10 @@ func init() {
 		"List of labels to keep, all other labels will be stripped")
 	pflag.StringSlice("labels.strip", []string{}, "List of labels to ignore")
 
+	pflag.String("grid.sorting.order", "startsAt", "Default sort order for alert grid")
+	pflag.Bool("grid.sorting.reverse", true, "Reverse sort order")
+	pflag.String("grid.sorting.label", "alertname", "Label name to use when sorting alert grid by label")
+
 	pflag.Bool("log.config", true, "Log used configuration to log on startup")
 	pflag.String("log.level", "info",
 		"Log level, one of: debug, info, warning, error, fatal and panic")
@@ -137,6 +142,9 @@ func (config *configSchema) Read() {
 	config.Custom.JS = v.GetString("custom.js")
 	config.Debug = v.GetBool("debug")
 	config.Filters.Default = v.GetStringSlice("filters.default")
+	config.Grid.Sorting.Order = v.GetString("grid.sorting.order")
+	config.Grid.Sorting.Reverse = v.GetBool("grid.sorting.reverse")
+	config.Grid.Sorting.Label = v.GetString("grid.sorting.label")
 	config.Labels.Color.Custom = map[string]map[string]string{}
 	config.Labels.Color.Static = v.GetStringSlice("labels.color.static")
 	config.Labels.Color.Unique = v.GetStringSlice("labels.color.unique")
@@ -172,6 +180,10 @@ func (config *configSchema) Read() {
 		log.Fatal(err)
 	}
 
+	if !slices.StringInSlice([]string{"disabled", "startsAt", "label"}, config.Grid.Sorting.Order) {
+		log.Fatalf("Invalid grid.sorting.order value '%s', allowed options: disabled, startsAt, label", config.Grid.Sorting.Order)
+	}
+
 	// accept single Alertmanager server from flag/env if nothing is set yet
 	if len(config.Alertmanager.Servers) == 0 && v.GetString("alertmanager.uri") != "" {
 		log.Info("Using simple config with a single Alertmanager server")

internal/config/config_test.go

@@ -82,6 +82,11 @@ filters:
   default:
   - '@state=active'
   - foo=bar
+grid:
+  sorting:
+    order: startsAt
+    reverse: true
+    label: alertname
 labels:
   keep:
   - foo

internal/config/models.go

@@ -43,6 +43,13 @@ type configSchema struct {
 	Filters struct {
 		Default []string
 	}
+	Grid struct {
+		Sorting struct {
+			Order   string
+			Reverse bool
+			Label   string
+		}
+	}
 	Labels struct {
 		Keep  []string
 		Strip []string

internal/models/api.go

@@ -155,8 +155,16 @@ func (ag *APIAlertGroup) DedupSharedMaps() {
 	}
 }
 
+// GridSettings exposes all grid settings from the config file
+type GridSettings struct {
+	Order   string `json:"order"`
+	Reverse bool   `json:"reverse"`
+	Label   string `json:"label"`
+}
+
 // SortSettings nests all settings specific to sorting
 type SortSettings struct {
+	Grid         GridSettings              `json:"grid"`
 	ValueMapping map[string]map[string]int `json:"valueMapping"`
 }
 

views.go

@@ -84,6 +84,11 @@ func alerts(c *gin.Context) {
 	resp.Upstreams = getUpstreams()
 	resp.Settings = models.Settings{
 		Sorting: models.SortSettings{
+			Grid: models.GridSettings{
+				Order:   config.Config.Grid.Sorting.Order,
+				Reverse: config.Config.Grid.Sorting.Reverse,
+				Label:   config.Config.Grid.Sorting.Label,
+			},
 			ValueMapping: map[string]map[string]int{},
 		},
 		StaticColorLabels:        config.Config.Labels.Color.Static,