refactor logger config via env

README.md

@@ -8,15 +8,18 @@ This repository contains a helper zap.Logger constructor that injects a mandator
 
 Basically, the logger is configured with the [zap.NewProductionLogger](https://github.com/uber-go/zap/blob/d6ce3b9b283401bc6cf975de6ac3e5ed5aec5341/config.go#L115) with modified logs timestamps as RFC3339-formatted string with nanosecond precision.
 
-For the default logger configuration the logging level is set using an env variable `LOGGER_LEVEL`. According to the [zap.Logger docs](https://github.com/uber-go/zap/blob/d6ce3b9b283401bc6cf975de6ac3e5ed5aec5341/level.go#L28), the expected `LOGGER_LEVEL` values are (the `dpanic`/`DPANIC` level is omitted, higher levels are more important):
+For the default logger configuration the logging level is set using an env variable `LOGGER_LEVEL`. According to the [zap.Logger docs](https://github.com/uber-go/zap/blob/d6ce3b9b283401bc6cf975de6ac3e5ed5aec5341/level.go#L28), the expected `LOGGER_LEVEL` values are (higher levels are more important):
 - `debug` or `DEBUG` — typically voluminous logs that are usually disabled in production;
 - `info` or `INFO` — the default logging priority;
 - `warn` or `WARN` — logs that are more important than Info, but don't need individual human review;
 - `error` or `ERROR` — high-priority logs. If an application is running smoothly, it shouldn't generate any error-level logs;
+- `dpanic` or `DPANIC` — logs a message, then panics. Works only if logger's development field set to true;
 - `panic` or `PANIC` — logs a message, then panics;
 - `fatal` or `FATAL` — logs a message, then calls os.Exit(1).
 
-Although the default cfg is made for logger instantiation and usage simplicity, a user can still configure the logger the way the [zap.Config](https://github.com/uber-go/zap/blob/d6ce3b9b283401bc6cf975de6ac3e5ed5aec5341/config.go#L45) allows it by assigning a path to a config file to the `LOGGER_CFG_PATH` env variable. Supported extensions for the config file are `.json`, `.yml` and `.yaml`. Configuration made by the config file overwrites the `LOGGER_LEVEL` and should contain comprehensive configuration (this is why the example file below is so detailed although it doesn't contain all the configurable fields).
+Although the default cfg is introduced for logger instantiation and usage simplicity, a user can still configure the logger the way the [zap.Config](https://github.com/uber-go/zap/blob/d6ce3b9b283401bc6cf975de6ac3e5ed5aec5341/config.go#L45) allows it via _setting_ env variables. If no value is set to an env variable, the production logger config value is used by default. See the [env configuration example](#configuration-via-env-variables) for details.
+
+Reminder: a _set_ env variable is a variable of any value stored in the system, even an empty one. So, e.g. `export LOGGER_ENCODERCONFIG_TIMEKEY=` will not apply a default value to the logger, but will result in the timestamp key absence. To set a default value, use `unset LOGGER_ENCODERCONFIG_TIMEKEY`. This is true for all config parameters.
 
 ## Examples
 
@@ -50,41 +53,17 @@ results in (stack trace and caller messages are removed for simplicity):
 {"level":"error","ts":"2022-09-27T09:00:19.78001+03:00","msg":"error","context":"my_application"}
 ```
 
-### Providing a cfg file
-
-define a `cfg.json` (you can use the following as a boilerplate):
-```json
-{
-    "level": "warn",
-    "outputPaths": [
-        "stderr"
-    ],
-    "errorOutputPaths": [
-        "stderr"
-    ],
-    "encoding": "console",
-    "sampling": {
-        "initial": 100,
-        "thereafter": 100
-    },
-    "encoderConfig": {
-        "timeKey": "ts",
-        "levelKey": "level",
-        "nameKey": "logger",
-        "callerKey": "caller",
-        "messageKey": "msg",
-        "stacktraceKey": "stacktrace",
-        "lineEnding": "\n",
-        "timeEncoder": "ISO8601"
-    }
-}
-```
+### Configuration via env variables
 
-make the config file available via `LOGGER_CFG_PATH` env variable
+configure all needed logger parameters by exporting corresponding env variables, e.g.:
 ```bash
-export LOGGER_CFG_PATH=cfg.json
+export LOGGER_LEVEL=warn
+export LOGGER_ENCODING=console
+export LOGGER_ENCODERCONFIG_ENCODETIME=ISO8601
 ```
 
+As you can see, just like LOGGER_LEVEL, all logger-related env variables are prefixed with `LOGGER_` and then writen solidly with `_` as structure level separator.
+
 ```go
 package main
 

go.mod

@@ -3,8 +3,8 @@ module github.com/neutron-org/neutron-logger
 go 1.18
 
 require (
+	github.com/kelseyhightower/envconfig v1.4.0
 	go.uber.org/zap v1.23.0
-	gopkg.in/yaml.v2 v2.4.0
 )
 
 require (

go.sum

@@ -2,6 +2,8 @@ github.com/benbjohnson/clock v1.1.0 h1:Q92kusRqC1XV2MjkWETPvjJVqKetz1OzxZB7mHJLj
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/kelseyhightower/envconfig v1.4.0 h1:Im6hONhd3pLkfDFsbRgu68RDNkGF1r3dvMUtDTo2cv8=
+github.com/kelseyhightower/envconfig v1.4.0/go.mod h1:cccZRl6mQpaq41TPp5QxidR+Sa3axMbJDNb//FQX6Gg=
 github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
@@ -15,8 +17,4 @@ go.uber.org/multierr v1.6.0 h1:y6IPFStTAIT5Ytl7/XYmHvzXQ7S3g/IeZW9hyZ5thw4=
 go.uber.org/multierr v1.6.0/go.mod h1:cdWPpRnG4AhwMwsgIHip0KRBQjJy5kYEpYjJxpXp9iU=
 go.uber.org/zap v1.23.0 h1:OjGQ5KQDEUawVHxNwQgPpiypGHOxo2mNZsOqTak4fFY=
 go.uber.org/zap v1.23.0/go.mod h1:D+nX8jyLsMHMYrln8A0rJjFt/T/9/bGgIhAqxv5URuY=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
-gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

logger.go

@@ -1,26 +1,19 @@
 package logger
 
 import (
-	"fmt"
-	"io/ioutil"
-	"os"
-
+	"github.com/kelseyhightower/envconfig"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
 )
 
-var (
-	// loggerCfgPath is the path to a logger configuration file. Expected to be either json or yaml.
-	loggerCfgPath = os.Getenv("LOGGER_CFG_PATH")
-	// loggerLevel defines the logger logging level.
-	loggerLevel = os.Getenv("LOGGER_LEVEL")
-)
+// loggerPrefix is the prefix for env variables that configure the logger.
+const loggerPrefix = "LOGGER"
 
 // NewForContext returns a new zap logger with an injected "context" field that is always
 // presented in the logger messages. If a LOGGER_CFG_PATH env variable is defined, the logger
 // config is build using the given file. Otherwise, a default simple config is used.
 func NewForContext(context string) (*zap.Logger, error) {
-	cfg, err := loadCfg()
+	cfg, err := loadConfig()
 	if err != nil {
 		return nil, err
 	}
@@ -32,51 +25,14 @@ func NewForContext(context string) (*zap.Logger, error) {
 	return l, nil
 }
 
-// loadCfg loads logger configuration from the given config file or, if it's empty, returns the
-// default config.
-func loadCfg() (*zap.Config, error) {
-	if loggerCfgPath == "" {
-		return defaultLoggerCfg(), nil
-	}
-	cfg, err := cfgFromFile()
-	if err != nil {
-		return nil, fmt.Errorf("failed to build logger config from provided file %s: %w", loggerCfgPath, err)
-	}
-	return cfg, nil
-}
-
-// defaultLoggerCfg creates a default logger config.
-func defaultLoggerCfg() *zap.Config {
+// loadConfig initializes a default production logger config with parameters overwritten by
+// corresponding env vars if set.
+func loadConfig() (*zap.Config, error) {
 	cfg := zap.NewProductionConfig()
-	cfg.Level = zap.NewAtomicLevelAt(parseLevel())
 	cfg.EncoderConfig.EncodeTime = zapcore.RFC3339NanoTimeEncoder
-	return &cfg
-}
-
-// cfgFromFile loads logger configuration from loggerCfgPath.
-func cfgFromFile() (*zap.Config, error) {
-	unmarshalFn, err := getCfgUnmarshaller(loggerCfgPath)
+	err := envconfig.Process(loggerPrefix, &cfg)
 	if err != nil {
 		return nil, err
 	}
-
-	cfgData, err := ioutil.ReadFile(loggerCfgPath)
-	if err != nil {
-		return nil, fmt.Errorf("read cfg file error: %w", err)
-	}
-	cfg, err := unmarshalFn(cfgData)
-	if err != nil {
-		return nil, fmt.Errorf("unmarshal error: %w", err)
-	}
-	return cfg, nil
-}
-
-// parseLevel parses logger level env into zapcore.Level. The env value is expected to contain one of
-// the zapcore.Level const values. On an unexpected value, an Info level is returned.
-func parseLevel() zapcore.Level {
-	var level zapcore.Level
-	if err := level.UnmarshalText([]byte(loggerLevel)); err != nil {
-		return zapcore.InfoLevel
-	}
-	return level
+	return &cfg, nil
 }