use hclog as the default logger

Inject hclog as the default logger in the main binary.

internal/logging/logging.go

@@ -1,12 +1,15 @@
 package logging
 
 import (
+	"fmt"
 	"io"
 	"io/ioutil"
 	"log"
 	"os"
 	"strings"
 	"syscall"
+
+	"github.com/hashicorp/go-hclog"
 )
 
 // These are the environmental variables that determine if we log, and if
@@ -19,39 +22,38 @@ const (
 // ValidLevels are the log level names that Terraform recognizes.
 var ValidLevels = []LogLevel{"TRACE", "DEBUG", "INFO", "WARN", "ERROR"}
 
-// LogOutput determines where we should send logs (if anywhere) and the log level.
-func LogOutput() (logOutput io.Writer, err error) {
-	logOutput = ioutil.Discard
+// logger is the global hclog logger
+var logger hclog.Logger
 
+func init() {
+	logOutput := io.Writer(os.Stderr)
 	logLevel := CurrentLogLevel()
 	if logLevel == "" {
-		return
+		logOutput = ioutil.Discard
 	}
 
-	logOutput = os.Stderr
 	if logPath := os.Getenv(EnvLogFile); logPath != "" {
-		var err error
-		logOutput, err = os.OpenFile(logPath, syscall.O_CREAT|syscall.O_RDWR|syscall.O_APPEND, 0666)
+		f, err := os.OpenFile(logPath, syscall.O_CREAT|syscall.O_RDWR|syscall.O_APPEND, 0666)
 		if err != nil {
-			return nil, err
+			fmt.Fprintf(os.Stderr, "Error opening log file: %v\n", err)
+		} else {
+			logOutput = f
 		}
 	}
 
-	if logLevel == "TRACE" {
-		// Just pass through logs directly then, without any level filtering at all.
-		return logOutput, nil
+	logger = hclog.New(&hclog.LoggerOptions{
+		Level:  hclog.LevelFromString(logLevel),
+		Output: logOutput,
+	})
 }
 
-	// Otherwise we'll use our level filter, which is a heuristic-based
-	// best effort thing that is not totally reliable but helps to reduce
-	// the volume of logs in some cases.
-	logOutput = &LevelFilter{
-		Levels:   ValidLevels,
-		MinLevel: LogLevel(logLevel),
-		Writer:   logOutput,
+// LogOutput determines where we should send logs (if anywhere) and the log level.
+func LogOutput() (logOutput io.Writer, err error) {
+	return logger.StandardWriter(&hclog.StandardLoggerOptions{InferLevels: true}), nil
 }
 
-	return logOutput, nil
+func HCLogger() hclog.Logger {
+	return logger
 }
 
 // SetOutput checks for a log destination with LogOutput, and calls
@@ -67,20 +69,22 @@ func SetOutput() {
 		out = ioutil.Discard
 	}
 
+	// the hclog logger will add the prefix info
+	log.SetFlags(0)
+	log.SetPrefix("")
 	log.SetOutput(out)
 }
 
 // CurrentLogLevel returns the current log level string based the environment vars
 func CurrentLogLevel() string {
-	envLevel := os.Getenv(EnvLog)
+	envLevel := strings.ToUpper(os.Getenv(EnvLog))
 	if envLevel == "" {
 		return ""
 	}
 
 	logLevel := "TRACE"
 	if isValidLogLevel(envLevel) {
-		// allow following for better ux: info, Info or INFO
-		logLevel = strings.ToUpper(envLevel)
+		logLevel = envLevel
 	} else {
 		log.Printf("[WARN] Invalid log level: %q. Defaulting to level: TRACE. Valid levels are: %+v",
 			envLevel, ValidLevels)
@@ -100,7 +104,7 @@ func IsDebugOrHigher() bool {
 
 func isValidLogLevel(level string) bool {
 	for _, l := range ValidLevels {
-		if strings.ToUpper(level) == string(l) {
+		if level == string(l) {
 			return true
 		}
 	}

main.go

@@ -19,7 +19,6 @@ import (
 	"github.com/hashicorp/terraform/command/cliconfig"
 	"github.com/hashicorp/terraform/command/format"
 	"github.com/hashicorp/terraform/httpclient"
-	"github.com/hashicorp/terraform/internal/logging"
 	"github.com/hashicorp/terraform/version"
 	"github.com/mattn/go-colorable"
 	"github.com/mattn/go-shellwords"
@@ -37,8 +36,6 @@ const (
 )
 
 func main() {
-	// Override global prefix set by go-dynect during init()
-	log.SetPrefix("")
 	os.Exit(realMain())
 }
 
@@ -51,13 +48,6 @@ func realMain() int {
 	}
 
 	if !panicwrap.Wrapped(&wrapConfig) {
-		// Determine where logs should go in general (requested by the user)
-		logWriter, err := logging.LogOutput()
-		if err != nil {
-			fmt.Fprintf(os.Stderr, "Couldn't setup log output: %s", err)
-			return 1
-		}
-
 		// We always send logs to a temporary file that we use in case
 		// there is a panic. Otherwise, we delete it.
 		logTempFile, err := ioutil.TempFile("", "terraform-log")
@@ -76,7 +66,7 @@ func realMain() int {
 
 		// Create the configuration for panicwrap and wrap our executable
 		wrapConfig.Handler = panicHandler(logTempFile)
-		wrapConfig.Writer = io.MultiWriter(logTempFile, logWriter)
+		wrapConfig.Writer = os.Stderr
 		wrapConfig.Stdout = outW
 		wrapConfig.IgnoreSignals = ignoreSignals
 		wrapConfig.ForwardSignals = forwardSignals
@@ -122,7 +112,6 @@ func init() {
 func wrappedMain() int {
 	var err error
 
-	log.SetOutput(os.Stderr)
 	log.Printf(
 		"[INFO] Terraform version: %s %s %s",
 		Version, VersionPrerelease, GitCommit)

plugin/client.go

@@ -4,8 +4,8 @@ import (
 	"os"
 	"os/exec"
 
-	hclog "github.com/hashicorp/go-hclog"
 	plugin "github.com/hashicorp/go-plugin"
+	"github.com/hashicorp/terraform/internal/logging"
 	"github.com/hashicorp/terraform/plugin/discovery"
 )
 
@@ -17,11 +17,7 @@ var enableAutoMTLS = os.Getenv("TF_DISABLE_PLUGIN_TLS") == ""
 // ClientConfig returns a configuration object that can be used to instantiate
 // a client for the plugin described by the given metadata.
 func ClientConfig(m discovery.PluginMeta) *plugin.ClientConfig {
-	logger := hclog.New(&hclog.LoggerOptions{
-		Name:   "plugin",
-		Level:  hclog.Trace,
-		Output: os.Stderr,
-	})
+	logger := logging.HCLogger()
 
 	return &plugin.ClientConfig{
 		Cmd:              exec.Command(m.Path),

terraform/context.go

@@ -10,6 +10,7 @@ import (
 	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/instances"
+	"github.com/hashicorp/terraform/internal/logging"
 	"github.com/hashicorp/terraform/lang"
 	"github.com/hashicorp/terraform/plans"
 	"github.com/hashicorp/terraform/providers"
@@ -20,6 +21,10 @@ import (
 	"github.com/zclconf/go-cty/cty"
 )
 
+func init() {
+	logging.SetOutput()
+}
+
 // InputMode defines what sort of input will be asked for when Input
 // is called on Context.
 type InputMode byte