chore: establish local platform baseline

internal/externalprobe/postgres.go

@@ -0,0 +1,75 @@
+package externalprobe
+
+import (
+	"context"
+	"errors"
+	"regexp"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+var (
+	serviceNamePattern = regexp.MustCompile(`^[a-z][a-z0-9-]{1,31}$`)
+	dependencyPattern  = regexp.MustCompile(`^[a-z][a-z0-9_]{1,63}$`)
+)
+
+func PostgresObserver(pool *pgxpool.Pool, serviceName string) (Observer, error) {
+	if pool == nil || !serviceNamePattern.MatchString(serviceName) {
+		return nil, errors.New("external probe database and service name are required")
+	}
+	return func(ctx context.Context, observation Observation) error {
+		if !dependencyPattern.MatchString(observation.Dependency) {
+			return errors.New("external probe dependency name is invalid")
+		}
+		if observation.Interval <= 0 {
+			return errors.New("external probe interval is required")
+		}
+		latencyMS := observation.Latency.Milliseconds()
+		if latencyMS < 0 {
+			latencyMS = 0
+		}
+		intervalMS := observation.Interval.Milliseconds()
+		if intervalMS < 1 {
+			intervalMS = 1
+		}
+		checkedAt := observation.CheckedAt.UTC()
+		if checkedAt.IsZero() {
+			checkedAt = time.Now().UTC()
+		}
+		status := "AVAILABLE"
+		if !observation.Available {
+			status = "UNAVAILABLE"
+			if observation.ErrorCode == "" {
+				observation.ErrorCode = "PROBE_FAILED"
+			}
+		}
+		_, err := pool.Exec(ctx, `
+			INSERT INTO external_dependency_probe_state(service_name,dependency,status,checked_at,last_success_at,last_failure_at,last_error_code,latency_ms,probe_interval_ms,consecutive_failures)
+			VALUES($1,$2,$3::varchar,$4::timestamptz,CASE WHEN $3::varchar='AVAILABLE' THEN $4::timestamptz END,CASE WHEN $3::varchar='UNAVAILABLE' THEN $4::timestamptz END,NULLIF($5::varchar,''),$6,$7,CASE WHEN $3::varchar='UNAVAILABLE' THEN 1 ELSE 0 END)
+			ON CONFLICT(service_name,dependency) DO UPDATE SET
+				status=EXCLUDED.status,
+				checked_at=EXCLUDED.checked_at,
+				last_success_at=CASE WHEN EXCLUDED.status='AVAILABLE' THEN EXCLUDED.checked_at ELSE external_dependency_probe_state.last_success_at END,
+				last_failure_at=CASE WHEN EXCLUDED.status='UNAVAILABLE' THEN EXCLUDED.checked_at ELSE external_dependency_probe_state.last_failure_at END,
+				last_error_code=EXCLUDED.last_error_code,
+				latency_ms=EXCLUDED.latency_ms,
+				probe_interval_ms=EXCLUDED.probe_interval_ms,
+				consecutive_failures=CASE WHEN EXCLUDED.status='AVAILABLE' THEN 0 ELSE external_dependency_probe_state.consecutive_failures+1 END,
+				updated_at=now()`, serviceName, observation.Dependency, status, checkedAt, observation.ErrorCode, latencyMS, intervalMS)
+		return err
+	}, nil
+}
+
+func ReconcilePostgresState(ctx context.Context, pool *pgxpool.Pool, serviceName string, dependencies []string) error {
+	if pool == nil || !serviceNamePattern.MatchString(serviceName) {
+		return errors.New("external probe database and service name are required")
+	}
+	for _, dependency := range dependencies {
+		if !dependencyPattern.MatchString(dependency) {
+			return errors.New("external probe dependency name is invalid")
+		}
+	}
+	_, err := pool.Exec(ctx, `DELETE FROM external_dependency_probe_state WHERE service_name=$1 AND NOT (dependency=ANY(COALESCE($2::text[],ARRAY[]::text[])))`, serviceName, dependencies)
+	return err
+}