pkg/rulefmt: Add rule group parsing

pkg/rulefmt/rulefmt.go

@@ -0,0 +1,98 @@
+package rulefmt
+
+import (
+	"io/ioutil"
+
+	"github.com/ghodss/yaml"
+	"github.com/pkg/errors"
+	"github.com/prometheus/prometheus/promql"
+)
+
+// Error represents semantical errors on parsing rule groups.
+type Error struct {
+	Group string
+	Rule  int
+	Err   error
+}
+
+func (err *Error) Error() string {
+	return errors.Wrapf(err, "group %q, rule %d", err.Group, err.Rule).Error()
+}
+
+// RuleGroups is a set of rule groups that are typically exposed in a file.
+type RuleGroups struct {
+	Version int         `json:"version"`
+	Groups  []RuleGroup `json:"groups"`
+}
+
+// Validate validates all rules in the rule groups.
+func (g *RuleGroups) Validate() (errs []error) {
+	if g.Version != 1 {
+		errs = append(errs, errors.Errorf("invalid rule group version %d", g.Version))
+	}
+	for _, g := range g.Groups {
+		for i, r := range g.Rules {
+			for _, err := range r.Validate() {
+				errs = append(errs, &Error{
+					Group: g.Name,
+					Rule:  i,
+					Err:   err,
+				})
+			}
+		}
+	}
+	return errs
+}
+
+// RuleGroup is a list of sequentially evaluated recording and alerting rules.
+type RuleGroup struct {
+	Name  string `json:"name"`
+	Rules []Rule `json:"rules"`
+}
+
+// Rule describes an alerting or recording rule.
+type Rule struct {
+	Record      string            `json:"record"`
+	Alert       string            `json:"alert"`
+	Expr        string            `json:"expr"`
+	For         string            `json:"for"`
+	Labels      map[string]string `json:"labels"`
+	Annotations map[string]string `json:"annotations"`
+}
+
+// Validate the rule and return a list of encountered errors.
+func (r *Rule) Validate() (errs []error) {
+	if r.Record != "" && r.Alert != "" {
+		errs = append(errs, errors.Errorf("only one of 'record' and 'alert' must be set"))
+	}
+	if r.Record == "" && r.Alert == "" {
+		errs = append(errs, errors.Errorf("one of 'record' or 'alert' must be set"))
+	}
+	if r.Expr == "" {
+		errs = append(errs, errors.Errorf("field 'expr' must be set in rule"))
+	} else if _, err := promql.ParseExpr(r.Expr); err != nil {
+		errs = append(errs, errors.Errorf("could not parse expression: %s", err))
+	}
+	if r.Record != "" {
+		if len(r.Annotations) > 0 {
+			errs = append(errs, errors.Errorf("invalid field 'annotations' in recording rule"))
+		}
+		if r.For != "" {
+			errs = append(errs, errors.Errorf("invalid field 'for' in recording rule"))
+		}
+	}
+	return errs
+}
+
+// ParseFile parses the rule file and validates it.
+func ParseFile(file string) (*RuleGroups, []error) {
+	b, err := ioutil.ReadFile(file)
+	if err != nil {
+		return nil, []error{err}
+	}
+	var groups RuleGroups
+	if err := yaml.Unmarshal(b, &groups); err != nil {
+		return nil, []error{err}
+	}
+	return &groups, groups.Validate()
+}

pkg/rulefmt/rulefmt_test.go

@@ -0,0 +1,12 @@
+package rulefmt
+
+import "testing"
+
+func TestParseFileSuccess(t *testing.T) {
+	if _, errs := ParseFile("testdata/test.yaml"); len(errs) > 0 {
+		t.Errorf("unexpected errors parsing file")
+		for _, err := range errs {
+			t.Error(err)
+		}
+	}
+}

pkg/rulefmt/testdata/test.yaml

@@ -0,0 +1,59 @@
+version: 1
+groups:
+- name: my-group-name
+  interval: 30s   # defaults to global interval
+  rules:
+  - alert: HighErrors
+    expr: |
+      sum without(instance) (rate(errors_total[5m]))
+      / sum without(instance) (rate(requests_total[5m]))
+    for: 5m
+    labels:
+      severity: critical
+    annotations:
+      description: "stuff's happening with {{ $.labels.service }}"
+
+  # Mix recording rules in the same list
+  - record: "new_metric"
+    expr: |
+      sum without(instance) (rate(errors_total[5m]))
+      / sum without(instance) (rate(requests_total[5m]))
+    labels:
+      abc: edf
+      uvw: xyz
+
+  - alert: HighErrors
+    expr: | 
+      sum without(instance) (rate(errors_total[5m]))
+      / sum without(instance) (rate(requests_total[5m]))
+    for: 5m
+    labels:
+      severity: critical
+    annotations:
+      description: "stuff's happening with {{ $.labels.service }}"
+      
+- name: my-group-name
+  interval: 30s   # defaults to global interval
+  rules:
+  - alert: HighErrors
+    expr: | 
+      sum without(instance) (rate(errors_total[5m]))
+      / sum without(instance) (rate(requests_total[5m]))
+    for: 5m
+    labels:
+      severity: critical
+
+  - record: "new_metric"
+    expr: |
+      sum without(instance) (rate(errors_total[5m]))
+      / sum without(instance) (rate(requests_total[5m]))
+
+  - alert: HighErrors
+    expr: | 
+      sum without(instance) (rate(errors_total[5m]))
+      / sum without(instance) (rate(requests_total[5m]))
+    for: 5m
+    labels:
+      severity: critical
+    annotations:
+      description: "stuff's happening with {{ $.labels.service }}"