fix: prevent overlapping remote writes

By adding configuration validatation to prevent possibility of
overlapping end and start of two separate write attempts.

Also does additional basic validations:

- ensures that WriteRetryMinInt < WriteRetryMaxInt
- ensures that MetricsWALPath is defined
- ensures that WriteUrl is defined

Signed-off-by: Petr Vobornik <[email protected]>

config/config_validator.go

@@ -0,0 +1,40 @@
+package config
+
+import (
+	"fmt"
+	"time"
+)
+
+type Validator interface {
+	Validate() error
+}
+
+type ConfigValidator struct {
+	config *Config
+}
+
+func NewConfigValidator(config *Config) *ConfigValidator {
+	return &ConfigValidator{config}
+}
+
+func (cv *ConfigValidator) Validate() error {
+	c := cv.config
+
+	if c.WriteUrl == "" {
+		return fmt.Errorf("WriteURL must be defined")
+	}
+
+	if c.WriteInterval <= time.Duration(c.WriteRetryAttempts)*(c.WriteRetryMaxInt+c.WriteTimeout) {
+		return fmt.Errorf("WriteInterval must be bigger than WriteRetryAttempts * ( WriteRetryMaxInt + WriteTimeout )")
+	}
+
+	if c.WriteRetryMinInt >= c.WriteRetryMaxInt {
+		return fmt.Errorf("WriteRetryMinInt must be smaller than WriteRetryMaxInt")
+	}
+
+	if c.MetricsWALPath == "" {
+		return fmt.Errorf("MetricsWALPath must be defined")
+	}
+
+	return nil
+}

config/config_validator_test.go

@@ -0,0 +1,98 @@
+package config
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestConfigValidator(t *testing.T) {
+	t.Run("Validate Config", func(t *testing.T) {
+		t.Run("WriteURL must be defined", func(t *testing.T) {
+			// given
+			c := NewConfig()
+			c.WriteUrl = ""
+			cv := NewConfigValidator(c)
+
+			// when
+			err := cv.Validate()
+
+			// then
+			expectErrorContains(t, err, "WriteURL must be defined")
+		})
+
+		t.Run("overlapping requests", func(t *testing.T) {
+			// given
+			c := NewConfig()
+			c.WriteInterval = 80 * time.Second
+			c.WriteRetryAttempts = 8
+			c.WriteRetryMaxInt = 10 * time.Second
+			c.WriteTimeout = 60 * time.Second
+			cv := NewConfigValidator(c)
+
+			// when
+			err := cv.Validate()
+
+			// then
+			expectErrorContains(t, err, "WriteInterval must be bigger than WriteRetryAttempts * ( WriteRetryMaxInt + WriteTimeout )")
+		})
+
+		t.Run("WriteRetryMinInt to be smaller than WriteRetryMaxInt", func(t *testing.T) {
+			// given
+			c := NewConfig()
+			c.WriteRetryMinInt = 10 * time.Second
+			c.WriteRetryMaxInt = 1 * time.Second
+			cv := NewConfigValidator(c)
+
+			// when
+			err := cv.Validate()
+
+			// then
+			expectErrorContains(t, err, "WriteRetryMinInt must be smaller than WriteRetryMaxInt")
+		})
+
+		t.Run("MetricsWALPath must be defined", func(t *testing.T) {
+			// given
+			c := NewConfig()
+			c.MetricsWALPath = ""
+			cv := NewConfigValidator(c)
+
+			// when
+			err := cv.Validate()
+
+			// then
+			expectErrorContains(t, err, "MetricsWALPath must be defined")
+		})
+
+		t.Run("default config should be valid", func(t *testing.T) {
+			// given
+			c := NewConfig()
+			cv := NewConfigValidator(c)
+
+			// when
+			err := cv.Validate()
+
+			// then
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+		})
+	})
+}
+
+// Helpers
+
+func expectError(t *testing.T, err error) {
+	t.Helper()
+	if err == nil {
+		t.Fatalf("expected error, got nil")
+	}
+}
+
+func expectErrorContains(t *testing.T, err error, expected string) {
+	t.Helper()
+	expectError(t, err)
+	if !strings.Contains(err.Error(), expected) {
+		t.Fatalf("expected error to contain '%s', got '%s'", expected, err.Error())
+	}
+}

hack/host-metering.conf

@@ -11,7 +11,8 @@ host_cert_path=./hack/test-cert.crt
 host_cert_key_path=./hack/test-cert.key
 collect_interval_sec=0
 label_refresh_interval_sec=10
-write_retry_attempts=4
-write_retry_interval_sec=2
+write_timeout_sec=1
+write_retry_attempts=1
+write_retry_max_int_sec=2
 metrics_wal_path=./hack/cpumetrics
 log_level=DEBUG

main.go

@@ -59,6 +59,13 @@ func main() {
 		//print out the configuration
 		logger.Infoln(cfg.String())
 
+		cv := config.NewConfigValidator(cfg)
+		err = cv.Validate()
+		if err != nil {
+			logger.Errorf("Invalid configuration: %v\n", err.Error())
+			os.Exit(2)
+		}
+
 		d, err := daemon.NewDaemon(cfg)
 		if err != nil {
 			logger.Errorf("Failed to create daemon: %v\n", err.Error())