[+] add metric list command for exporting metric definitions (#1165)

Supports listing all metrics/presets or filtering by name(s).
Outputs YAML format suitable for creating custom `metrics.yaml` files.
Returns errors for non-existent metric or preset names.

Author: pashagolub

internal/cmdopts/cmdmetric.go

@@ -4,20 +4,23 @@ import (
 	"context"
 	"fmt"
 	"math"
-	"slices"
+
+	"gopkg.in/yaml.v3"
 )
 
 type MetricCommand struct {
 	owner     *Options
 	PrintInit MetricPrintInitCommand `command:"print-init" description:"Get and print init SQL for a given metric or preset"`
 	PrintSQL  MetricPrintSQLCommand  `command:"print-sql" description:"Get and print SQL for a given metric"`
+	List      MetricListCommand      `command:"list" description:"List available metrics and presets"`
 }
 
 func NewMetricCommand(owner *Options) *MetricCommand {
 	return &MetricCommand{
 		owner:     owner,
 		PrintInit: MetricPrintInitCommand{owner: owner},
 		PrintSQL:  MetricPrintSQLCommand{owner: owner},
+		List:      MetricListCommand{owner: owner},
 	}
 }
 
@@ -34,21 +37,15 @@ func (cmd *MetricPrintInitCommand) Execute(args []string) error {
 	if err != nil {
 		return err
 	}
-	w := cmd.owner.OutputWriter
-	for _, name := range args {
-		if preset, ok := metrics.PresetDefs[name]; ok {
-			for k := range preset.Metrics {
-				args = append(args, k)
-			}
-		}
+	metrics, err = metrics.FilterByNames(args)
+	if err != nil {
+		return err
 	}
-	slices.Sort(args)
-	args = slices.Compact(args)
-	for _, mname := range args {
-		if m, ok := metrics.MetricDefs[mname]; ok && m.InitSQL != "" {
-
+	w := cmd.owner.OutputWriter
+	for mname, mdef := range metrics.MetricDefs {
+		if mdef.InitSQL > "" {
 			fmt.Fprintln(w, "--", mname)
-			fmt.Fprintln(w, m.InitSQL)
+			fmt.Fprintln(w, mdef.InitSQL)
 		}
 	}
 	cmd.owner.CompleteCommand(ExitCodeOK)
@@ -69,6 +66,10 @@ func (cmd *MetricPrintSQLCommand) Execute(args []string) error {
 	if err != nil {
 		return err
 	}
+	metrics, err = metrics.FilterByNames(args)
+	if err != nil {
+		return err
+	}
 	w := cmd.owner.OutputWriter
 	if cmd.Version == 0 {
 		cmd.Version = math.MaxInt32
@@ -84,3 +85,28 @@ func (cmd *MetricPrintSQLCommand) Execute(args []string) error {
 	cmd.owner.CompleteCommand(ExitCodeOK)
 	return nil
 }
+
+type MetricListCommand struct {
+	owner *Options
+}
+
+func (cmd *MetricListCommand) Execute(args []string) error {
+	err := cmd.owner.InitMetricReader(context.Background())
+	if err != nil {
+		return err
+	}
+	allMetrics, err := cmd.owner.MetricsReaderWriter.GetMetrics()
+	if err != nil {
+		return err
+	}
+	result, err := allMetrics.FilterByNames(args)
+	if err != nil {
+		return err
+	}
+	w := cmd.owner.OutputWriter
+
+	yamlData, _ := yaml.Marshal(result)
+	fmt.Fprint(w, string(yamlData))
+	cmd.owner.CompleteCommand(ExitCodeOK)
+	return nil
+}

internal/cmdopts/cmdmetric_test.go

@@ -15,8 +15,8 @@ func TestMetricPrintInit_Execute(t *testing.T) {
 	w := &strings.Builder{}
 	os.Args = []string{0: "config_test", "metric", "print-init", "test1"}
 	_, err = New(w)
-	assert.Empty(t, w.String())
-	assert.NoError(t, err, "should not error when no metrics found")
+	assert.Error(t, err, "should error when metric not found")
+	assert.Contains(t, err.Error(), "not found")
 
 	w.Reset()
 	os.Args = []string{0: "config_test", "metric", "print-init", "cpu_load"}
@@ -45,8 +45,8 @@ func TestMetricPrintSQL_Execute(t *testing.T) {
 	w := &strings.Builder{}
 	os.Args = []string{0: "config_test", "metric", "print-sql", "test1"}
 	_, err = New(w)
-	assert.Empty(t, w.String())
-	assert.NoError(t, err, "should not error when no metrics found")
+	assert.Error(t, err, "should error when metric not found")
+	assert.Contains(t, err.Error(), "not found")
 
 	w.Reset()
 	os.Args = []string{0: "config_test", "metric", "print-sql", "cpu_load"}
@@ -68,3 +68,54 @@ func TestMetricPrintSQL_Execute(t *testing.T) {
 	_, err = New(w)
 	assert.Error(t, err, "should error when no config database found")
 }
+
+func TestMetricList_Execute(t *testing.T) {
+	var err error
+
+	// Test: List all metrics and presets (no argument)
+	w := &strings.Builder{}
+	os.Args = []string{0: "config_test", "metric", "list"}
+	_, err = New(w)
+	assert.NoError(t, err, "should not error when listing all metrics")
+	assert.Contains(t, w.String(), "metrics:")
+	assert.Contains(t, w.String(), "presets:")
+	assert.Contains(t, w.String(), "cpu_load")
+	assert.Contains(t, w.String(), "standard")
+
+	// Test: List specific metric
+	w.Reset()
+	os.Args = []string{0: "config_test", "metric", "list", "cpu_load"}
+	_, err = New(w)
+	assert.NoError(t, err, "should not error when listing specific metric")
+	assert.Contains(t, w.String(), "cpu_load")
+	assert.Contains(t, w.String(), "metrics:")
+	// Should not contain other metrics
+	assert.NotContains(t, w.String(), "presets:")
+
+	// Test: List specific preset
+	w.Reset()
+	os.Args = []string{0: "config_test", "metric", "list", "standard"}
+	_, err = New(w)
+	assert.NoError(t, err, "should not error when listing preset")
+	assert.Contains(t, w.String(), "presets:")
+	assert.Contains(t, w.String(), "standard")
+	assert.Contains(t, w.String(), "metrics:")
+	// Should contain metrics from the preset
+	assert.Contains(t, w.String(), "cpu_load")
+
+	// Test: List non-existent metric/preset
+	w.Reset()
+	os.Args = []string{0: "config_test", "metric", "list", "nonexistent"}
+	_, err = New(w)
+	assert.Error(t, err, "should error when metric/preset not found")
+	assert.Contains(t, err.Error(), "not found")
+
+	// Test: Error handling - invalid metrics path
+	os.Args = []string{0: "config_test", "--metrics=foo", "metric", "list"}
+	_, err = New(w)
+	assert.Error(t, err, "should error when no metric definitions found")
+
+	os.Args = []string{0: "config_test", "--metrics=postgresql://foo@bar/fail", "metric", "list"}
+	_, err = New(w)
+	assert.Error(t, err, "should error when no config database found")
+}

internal/metrics/types.go

@@ -1,6 +1,7 @@
 package metrics
 
 import (
+	"fmt"
 	"maps"
 	"time"
 
@@ -154,9 +155,46 @@ type MeasurementEnvelope struct {
 }
 
 type Metrics struct {
-	MetricDefs MetricDefs `yaml:"metrics"`
-	PresetDefs PresetDefs `yaml:"presets"`
+	MetricDefs MetricDefs `yaml:"metrics,omitempty"`
+	PresetDefs PresetDefs `yaml:"presets,omitempty"`
+}
+
+// FilterByNames returns a new Metrics struct containing only the specified metrics and/or presets.
+// When a preset is requested, it includes both the preset definition and all its metrics.
+// If names is empty, returns a full copy of all metrics and presets.
+// Returns an error if any name is not found.
+func (m *Metrics) FilterByNames(names []string) (*Metrics, error) {
+	result := &Metrics{
+		MetricDefs: make(MetricDefs),
+		PresetDefs: make(PresetDefs),
+	}
+
+	// If no names provided, return full copy
+	if len(names) == 0 {
+		maps.Copy(result.MetricDefs, m.MetricDefs)
+		maps.Copy(result.PresetDefs, m.PresetDefs)
+		return result, nil
+	}
+
+	for _, name := range names {
+		if preset, ok := m.PresetDefs[name]; ok {
+			result.PresetDefs[name] = preset
+			// Include all metrics from the preset
+			for metricName := range preset.Metrics {
+				if metric, exists := m.MetricDefs[metricName]; exists {
+					result.MetricDefs[metricName] = metric
+				}
+			}
+		} else if metric, ok := m.MetricDefs[name]; ok {
+			result.MetricDefs[name] = metric
+		} else {
+			return nil, fmt.Errorf("metric or preset '%s' not found", name)
+		}
+	}
+
+	return result, nil
 }
+
 type Reader interface {
 	GetMetrics() (*Metrics, error)
 }

internal/metrics/types_test.go

@@ -64,3 +64,141 @@ func TestMeasurements(t *testing.T) {
 	assert.NotEqual(t, m, m1, "deep copy should be different")
 	assert.True(t, time.Now().UnixNano()-m1.GetEpoch() < int64(time.Second), "epoch should be close to now")
 }
+
+func TestFilterByNames(t *testing.T) {
+	// Setup test data
+	metrics := &Metrics{
+		MetricDefs: MetricDefs{
+			"cpu_load": Metric{
+				Description: "CPU load metric",
+				InitSQL:     "CREATE FUNCTION cpu_load()",
+			},
+			"db_size": Metric{
+				Description: "Database size metric",
+			},
+			"db_stats": Metric{
+				Description: "Database stats metric",
+			},
+			"replication": Metric{
+				Description: "Replication metric",
+			},
+		},
+		PresetDefs: PresetDefs{
+			"minimal": Preset{
+				Description: "Minimal preset",
+				Metrics: map[string]float64{
+					"cpu_load": 60,
+					"db_size":  300,
+				},
+			},
+			"standard": Preset{
+				Description: "Standard preset",
+				Metrics: map[string]float64{
+					"cpu_load":    60,
+					"db_size":     300,
+					"db_stats":    60,
+					"replication": 120,
+				},
+			},
+		},
+	}
+
+	tests := []struct {
+		name          string
+		names         []string
+		wantMetrics   []string
+		wantPresets   []string
+		wantErr       bool
+		errContains   string
+	}{
+		{
+			name:        "empty names returns all",
+			names:       []string{},
+			wantMetrics: []string{"cpu_load", "db_size", "db_stats", "replication"},
+			wantPresets: []string{"minimal", "standard"},
+			wantErr:     false,
+		},
+		{
+			name:        "single metric",
+			names:       []string{"cpu_load"},
+			wantMetrics: []string{"cpu_load"},
+			wantPresets: []string{},
+			wantErr:     false,
+		},
+		{
+			name:        "multiple metrics",
+			names:       []string{"cpu_load", "db_size"},
+			wantMetrics: []string{"cpu_load", "db_size"},
+			wantPresets: []string{},
+			wantErr:     false,
+		},
+		{
+			name:        "single preset includes all its metrics",
+			names:       []string{"minimal"},
+			wantMetrics: []string{"cpu_load", "db_size"},
+			wantPresets: []string{"minimal"},
+			wantErr:     false,
+		},
+		{
+			name:        "multiple presets",
+			names:       []string{"minimal", "standard"},
+			wantMetrics: []string{"cpu_load", "db_size", "db_stats", "replication"},
+			wantPresets: []string{"minimal", "standard"},
+			wantErr:     false,
+		},
+		{
+			name:        "mix of metrics and presets",
+			names:       []string{"minimal", "replication"},
+			wantMetrics: []string{"cpu_load", "db_size", "replication"},
+			wantPresets: []string{"minimal"},
+			wantErr:     false,
+		},
+		{
+			name:        "non-existent metric",
+			names:       []string{"nonexistent"},
+			wantErr:     true,
+			errContains: "not found",
+		},
+		{
+			name:        "mix of existing and non-existing",
+			names:       []string{"cpu_load", "nonexistent"},
+			wantErr:     true,
+			errContains: "not found",
+		},
+		{
+			name:        "non-existent preset",
+			names:       []string{"nonexistent_preset"},
+			wantErr:     true,
+			errContains: "not found",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := metrics.FilterByNames(tt.names)
+
+			if tt.wantErr {
+				assert.Error(t, err)
+				if tt.errContains != "" {
+					assert.Contains(t, err.Error(), tt.errContains)
+				}
+				return
+			}
+
+			assert.NoError(t, err)
+			assert.NotNil(t, result)
+
+			// Check metrics
+			assert.Equal(t, len(tt.wantMetrics), len(result.MetricDefs), "metric count mismatch")
+			for _, metricName := range tt.wantMetrics {
+				assert.Contains(t, result.MetricDefs, metricName, "expected metric not found: "+metricName)
+			}
+
+			// Check presets
+			assert.Equal(t, len(tt.wantPresets), len(result.PresetDefs), "preset count mismatch")
+			for _, presetName := range tt.wantPresets {
+				assert.Contains(t, result.PresetDefs, presetName, "expected preset not found: "+presetName)
+			}
+		})
+	}
+}