feat(lib): add log filtering rules

Closes #942

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/policy/expressions/logging.go

@@ -14,16 +14,11 @@ import (
 )
 
 var (
-	filterInvocations = promauto.NewGaugeVec(prometheus.GaugeOpts{
-		Namespace: "techaro",
-		Subsystem: "anubis",
-		Name:      "slog_filter_invocations",
-	}, []string{"name"})
-
 	filterExecutionTime = promauto.NewHistogramVec(prometheus.HistogramOpts{
-		Namespace: "techaro",
-		Subsystem: "anubis",
-		Name:      "slog_filter_execution_time_nanoseconds",
+		Namespace: "anubis",
+		Subsystem: "slog",
+		Name:      "filter_execution_time_nanoseconds",
+		Help:      "How long each log filter took to execute (nanoseconds)",
 		Buckets:   []float64{10, 50, 100, 200, 500, 1000, 2000, 5000, 10000, 20000, 50000, 100000, 200000, 500000, 1000000, 2000000, 5000000, 10000000}, // 10 nanoseconds to 10 milliseconds
 	}, []string{"name"})
 )
@@ -76,7 +71,6 @@ func (f Filter) Filter(ctx context.Context, r slog.Record) bool {
 	}
 	dur := time.Since(t0)
 	filterExecutionTime.WithLabelValues(f.name).Observe(float64(dur.Nanoseconds()))
-	filterInvocations.WithLabelValues(f.name).Inc()
 	//f.log.Debug("filter execution", "dur", dur.Nanoseconds())
 
 	if val, ok := result.(types.Bool); ok {

lib/policy/policy.go

@@ -8,8 +8,10 @@ import (
 	"log/slog"
 	"sync/atomic"
 
+	"github.com/TecharoHQ/anubis/lib/logging"
 	"github.com/TecharoHQ/anubis/lib/policy/checker"
 	"github.com/TecharoHQ/anubis/lib/policy/config"
+	"github.com/TecharoHQ/anubis/lib/policy/expressions"
 	"github.com/TecharoHQ/anubis/lib/store"
 	"github.com/TecharoHQ/anubis/lib/thoth"
 	"github.com/prometheus/client_golang/prometheus"
@@ -35,17 +37,42 @@ type ParsedConfig struct {
 	Thresholds        []*Threshold
 	DNSBL             bool
 	Impressum         *config.Impressum
+	Logging           *config.Logging
 	OpenGraph         config.OpenGraph
 	DefaultDifficulty int
 	StatusCodes       config.StatusCodes
 	Store             store.Interface
 }
 
+func (pc *ParsedConfig) ApplyLogFilters(base *slog.Logger) (*slog.Logger, error) {
+	var errs []error
+	var filters []logging.Filterer
+
+	for _, f := range pc.Logging.Filters {
+		filter, err := expressions.NewFilter(base, f.Name, f.Expression.String())
+		if err != nil {
+			errs = append(errs, fmt.Errorf("filter %s invalid: %w", f.Name, err))
+			continue
+		}
+		filters = append(filters, filter)
+	}
+
+	result := slog.New(logging.NewFilterHandler(base.Handler(), filters...))
+	slog.SetDefault(result)
+
+	if len(errs) != 0 {
+		return nil, errors.Join(errs...)
+	}
+
+	return result, nil
+}
+
 func newParsedConfig(orig *config.Config) *ParsedConfig {
 	return &ParsedConfig{
 		orig:        orig,
 		OpenGraph:   orig.OpenGraph,
 		StatusCodes: orig.StatusCodes,
+		Logging:     orig.Logging,
 	}
 }