grpclog: add GRPC_GO_COMPONENT_LOG_LEVEL for controling component logs

README.md

@@ -79,6 +79,28 @@ $ export GRPC_GO_LOG_VERBOSITY_LEVEL=99
 $ export GRPC_GO_LOG_SEVERITY_LEVEL=info
 ```
 
+Additionally, you can configure log severity levels for individual components
+using the `GRPC_GO_COMPONENT_LOG_LEVEL` environment variable. The format is a
+comma-separated list of `component:LEVEL` pairs like this:
+
+```console
+$ export GRPC_GO_COMPONENT_LOG_LEVEL=dns:ERROR,transport:WARNING
+```
+
+When both `GRPC_GO_LOG_SEVERITY_LEVEL` and `GRPC_GO_COMPONENT_LOG_LEVEL` are
+set, component-specific settings take precedence over `GRPC_GO_LOG_SEVERITY_LEVEL`
+for the specified components. Components not listed in
+`GRPC_GO_COMPONENT_LOG_LEVEL` will use the `GRPC_GO_LOG_SEVERITY_LEVEL` setting.
+For example:
+
+```console
+$ export GRPC_GO_LOG_SEVERITY_LEVEL=ERROR
+$ export GRPC_GO_COMPONENT_LOG_LEVEL=dns:INFO
+```
+
+In this case, the `dns` component will log at `INFO` level, while all other
+components will log at `ERROR` level.
+
 ### The RPC failed with error `"code = Unavailable desc = transport is closing"`
 
 This error means the connection the RPC is using was closed, and there are many

grpclog/component.go

@@ -20,33 +20,78 @@ package grpclog
 
 import (
 	"fmt"
+	"strings"
 )
 
+type severityLevel int
+
+const (
+	severityInfo severityLevel = iota
+	severityWarning
+	severityError
+	severityFatal
+)
+
+func parseComponentLogLevels(logLevel string) map[string]severityLevel {
+	if logLevel == "" {
+		return nil
+	}
+
+	logLevels := make(map[string]severityLevel)
+	for part := range strings.SplitSeq(logLevel, ",") {
+		kv := strings.Split(part, ":")
+		if len(kv) < 2 {
+			continue
+		}
+		component := kv[0]
+		if component == "" {
+			continue
+		}
+		level := kv[1]
+		switch level {
+		case "INFO", "info":
+			logLevels[component] = severityInfo
+		case "WARNING", "warning":
+			logLevels[component] = severityWarning
+		case "ERROR", "error":
+			logLevels[component] = severityError
+		default:
+			logLevels[component] = severityFatal
+		}
+	}
+	return logLevels
+}
+
 // componentData records the settings for a component.
 type componentData struct {
 	name string
+
+	infoDepth    func(depth int, args ...any)
+	warningDepth func(depth int, args ...any)
+	errorDepth   func(depth int, args ...any)
+	fatalDepth   func(depth int, args ...any)
 }
 
 var cache = map[string]*componentData{}
 
 func (c *componentData) InfoDepth(depth int, args ...any) {
 	args = append([]any{"[" + string(c.name) + "]"}, args...)
-	InfoDepth(depth+1, args...)
+	c.infoDepth(depth+1, args...)
 }
 
 func (c *componentData) WarningDepth(depth int, args ...any) {
 	args = append([]any{"[" + string(c.name) + "]"}, args...)
-	WarningDepth(depth+1, args...)
+	c.warningDepth(depth+1, args...)
 }
 
 func (c *componentData) ErrorDepth(depth int, args ...any) {
 	args = append([]any{"[" + string(c.name) + "]"}, args...)
-	ErrorDepth(depth+1, args...)
+	c.errorDepth(depth+1, args...)
 }
 
 func (c *componentData) FatalDepth(depth int, args ...any) {
 	args = append([]any{"[" + string(c.name) + "]"}, args...)
-	FatalDepth(depth+1, args...)
+	c.fatalDepth(depth+1, args...)
 }
 
 func (c *componentData) Info(args ...any) {
@@ -101,6 +146,9 @@ func (c *componentData) V(l int) bool {
 	return V(l)
 }
 
+func noopDepth(_ int, _ ...any) {
+}
+
 // Component creates a new component and returns it for logging. If a component
 // with the name already exists, nothing will be created and it will be
 // returned. SetLoggerV2 will panic if it is called with a logger created by
@@ -109,7 +157,50 @@ func Component(componentName string) DepthLoggerV2 {
 	if cData, ok := cache[componentName]; ok {
 		return cData
 	}
-	c := &componentData{componentName}
+	c := &componentData{
+		name:         componentName,
+		infoDepth:    InfoDepth,
+		warningDepth: WarningDepth,
+		errorDepth:   ErrorDepth,
+		fatalDepth:   FatalDepth,
+	}
+
+	if level, ok := componentLogLevels[componentName]; ok {
+		c.fatalDepth = func(depth int, args ...any) {
+			componentFatalDepth(depth+1, args...)
+		}
+		switch level {
+		case severityInfo:
+			c.infoDepth = func(depth int, args ...any) {
+				componentInfoDepth(depth+1, args...)
+			}
+			c.warningDepth = func(depth int, args ...any) {
+				componentWarningDepth(depth+1, args...)
+			}
+			c.errorDepth = func(depth int, args ...any) {
+				componentErrorDepth(depth+1, args...)
+			}
+		case severityWarning:
+			c.infoDepth = noopDepth
+			c.warningDepth = func(depth int, args ...any) {
+				componentWarningDepth(depth+1, args...)
+			}
+			c.errorDepth = func(depth int, args ...any) {
+				componentErrorDepth(depth+1, args...)
+			}
+		case severityError:
+			c.infoDepth = noopDepth
+			c.warningDepth = noopDepth
+			c.errorDepth = func(depth int, args ...any) {
+				componentErrorDepth(depth+1, args...)
+			}
+		case severityFatal:
+			c.infoDepth = noopDepth
+			c.warningDepth = noopDepth
+			c.errorDepth = noopDepth
+		}
+	}
+
 	cache[componentName] = c
 	return c
 }