Implement -promote & -if-candidate flags on run command (#305)

Author: benbjohnson

cmd/litefs/config.go

@@ -0,0 +1,253 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"os"
+	"os/user"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/superfly/litefs"
+	"github.com/superfly/litefs/http"
+	"gopkg.in/yaml.v3"
+)
+
+// NOTE: Update etc/litefs.yml configuration file after changing the structure below.
+
+// Config represents a configuration for the binary process.
+type Config struct {
+	Exec         string `yaml:"exec"`
+	ExitOnError  bool   `yaml:"exit-on-error"`
+	SkipSync     bool   `yaml:"skip-sync"`
+	StrictVerify bool   `yaml:"strict-verify"`
+
+	Data    DataConfig    `yaml:"data"`
+	FUSE    FUSEConfig    `yaml:"fuse"`
+	HTTP    HTTPConfig    `yaml:"http"`
+	Proxy   ProxyConfig   `yaml:"proxy"`
+	Lease   LeaseConfig   `yaml:"lease"`
+	Tracing TracingConfig `yaml:"tracing"`
+}
+
+// NewConfig returns a new instance of Config with defaults set.
+func NewConfig() Config {
+	var config Config
+	config.ExitOnError = true
+
+	config.Data.Compress = true
+	config.Data.Retention = litefs.DefaultRetention
+	config.Data.RetentionMonitorInterval = litefs.DefaultRetentionMonitorInterval
+
+	config.HTTP.Addr = http.DefaultAddr
+
+	config.Lease.Candidate = true
+	config.Lease.ReconnectDelay = litefs.DefaultReconnectDelay
+	config.Lease.DemoteDelay = litefs.DefaultDemoteDelay
+
+	config.Tracing.MaxSize = DefaultTracingMaxSize
+	config.Tracing.MaxCount = DefaultTracingMaxCount
+	config.Tracing.Compress = DefaultTracingCompress
+
+	return config
+}
+
+// DataConfig represents the configuration for internal LiteFS data. This
+// includes database files as well as LTX transaction files.
+type DataConfig struct {
+	Dir      string `yaml:"dir"`
+	Compress bool   `yaml:"compress"`
+
+	Retention                time.Duration `yaml:"retention"`
+	RetentionMonitorInterval time.Duration `yaml:"retention-monitor-interval"`
+}
+
+// FUSEConfig represents the configuration for the FUSE file system.
+type FUSEConfig struct {
+	Dir        string `yaml:"dir"`
+	AllowOther bool   `yaml:"allow-other"`
+	Debug      bool   `yaml:"debug"`
+}
+
+// HTTPConfig represents the configuration for the HTTP server.
+type HTTPConfig struct {
+	Addr string `yaml:"addr"`
+}
+
+// ProxyConfig represents the configuration for the HTTP proxy server.
+type ProxyConfig struct {
+	Addr        string   `yaml:"addr"`
+	Target      string   `yaml:"target"`
+	DB          string   `yaml:"db"`
+	Debug       bool     `yaml:"debug"`
+	Passthrough []string `yaml:"passthrough"`
+}
+
+// LeaseConfig represents a generic configuration for all lease types.
+type LeaseConfig struct {
+	// Specifies the type of leasing to use: "consul" or "static"
+	Type string `yaml:"type"`
+
+	// The hostname of this node. Used by the application to forward requests.
+	Hostname string `yaml:"hostname"`
+
+	// URL for other nodes to access this node's API.
+	AdvertiseURL string `yaml:"advertise-url"`
+
+	// Specifies if this node can become primary. Defaults to true.
+	//
+	// If using a "static" lease, setting this to true makes it the primary.
+	// Replicas in a state lease should set this to false.
+	Candidate bool `yaml:"candidate"`
+
+	// After disconnect, time before node tries to reconnect to primary or
+	// becomes primary itself.
+	ReconnectDelay time.Duration `yaml:"reconnect-delay"`
+
+	// Amount of time to wait after a forced demotion before attempting to
+	// become primary again.
+	DemoteDelay time.Duration `yaml:"demote-delay"`
+
+	// Consul lease settings.
+	Consul struct {
+		URL       string        `yaml:"url"`
+		Key       string        `yaml:"key"`
+		TTL       time.Duration `yaml:"ttl"`
+		LockDelay time.Duration `yaml:"lock-delay"`
+	} `yaml:"consul"`
+}
+
+// Tracing configuration defaults.
+const (
+	DefaultTracingMaxSize  = 64 // MB
+	DefaultTracingMaxCount = 8
+	DefaultTracingCompress = true
+)
+
+// TracingConfig represents the configuration the on-disk trace log.
+type TracingConfig struct {
+	Path     string `yaml:"path"`
+	MaxSize  int    `yaml:"max-size"`
+	MaxCount int    `yaml:"max-count"`
+	Compress bool   `yaml:"compress"`
+}
+
+// UnmarshalConfig unmarshals config from data.
+// If expandEnv is true then environment variables are expanded in the config.
+func UnmarshalConfig(config *Config, data []byte, expandEnv bool) error {
+	// Expand environment variables, if enabled.
+	if expandEnv {
+		data = []byte(ExpandEnv(string(data)))
+	}
+
+	dec := yaml.NewDecoder(bytes.NewReader(data))
+	dec.KnownFields(true) // strict checking
+	if err := dec.Decode(&config); err != nil {
+		return err
+	}
+	return nil
+}
+
+// ExpandEnv replaces environment variables just like os.ExpandEnv() but also
+// allows for equality/inequality binary expressions within the ${} form.
+func ExpandEnv(s string) string {
+	return os.Expand(s, func(v string) string {
+		v = strings.TrimSpace(v)
+
+		if a := expandExprSingleQuote.FindStringSubmatch(v); a != nil {
+			if a[2] == "==" {
+				return strconv.FormatBool(os.Getenv(a[1]) == a[3])
+			}
+			return strconv.FormatBool(os.Getenv(a[1]) != a[3])
+		}
+
+		if a := expandExprDoubleQuote.FindStringSubmatch(v); a != nil {
+			if a[2] == "==" {
+				return strconv.FormatBool(os.Getenv(a[1]) == a[3])
+			}
+			return strconv.FormatBool(os.Getenv(a[1]) != a[3])
+		}
+
+		if a := expandExprVar.FindStringSubmatch(v); a != nil {
+			if a[2] == "==" {
+				return strconv.FormatBool(os.Getenv(a[1]) == os.Getenv(a[3]))
+			}
+			return strconv.FormatBool(os.Getenv(a[1]) != os.Getenv(a[3]))
+		}
+
+		return os.Getenv(v)
+	})
+}
+
+var (
+	expandExprSingleQuote = regexp.MustCompile(`^(\w+)\s*(==|!=)\s*'(.*)'$`)
+	expandExprDoubleQuote = regexp.MustCompile(`^(\w+)\s*(==|!=)\s*"(.*)"$`)
+	expandExprVar         = regexp.MustCompile(`^(\w+)\s*(==|!=)\s*(\w+)$`)
+)
+
+// splitArgs returns the list of args before and after a "--" arg. If the double
+// dash is not specified, then args0 is args and args1 is empty.
+func splitArgs(args []string) (args0, args1 []string) {
+	for i, v := range args {
+		if v == "--" {
+			return args[:i], args[i+1:]
+		}
+	}
+	return args, nil
+}
+
+// ParseConfigPath parses the configuration file from configPath, if specified.
+// Returns ok true if a configuration file was successfully found.
+//
+// Otherwise searches the standard list of search paths. Returns an error if
+// no configuration files could be found.
+func ParseConfigPath(ctx context.Context, configPath string, expandEnv bool, config *Config) (err error) {
+	// Only read from explicit path, if specified. Report any error.
+	if configPath != "" {
+		// Read configuration.
+		buf, err := os.ReadFile(configPath)
+		if err != nil {
+			return err
+		}
+		return UnmarshalConfig(config, buf, expandEnv)
+	}
+
+	// Otherwise attempt to read each config path until we succeed.
+	for _, path := range configSearchPaths() {
+		if path, err = filepath.Abs(path); err != nil {
+			return err
+		}
+
+		buf, err := os.ReadFile(path)
+		if os.IsNotExist(err) {
+			continue
+		} else if err != nil {
+			return fmt.Errorf("cannot read config file at %s: %s", path, err)
+		}
+
+		if err := UnmarshalConfig(config, buf, expandEnv); err != nil {
+			return fmt.Errorf("cannot unmarshal config file at %s: %s", path, err)
+		}
+
+		fmt.Printf("config file read from %s\n", path)
+		return nil
+	}
+
+	return fmt.Errorf("config file not found")
+}
+
+// configSearchPaths returns paths to search for the config file. It starts with
+// the current directory, then home directory, if available. And finally it tries
+// to read from the /etc directory.
+func configSearchPaths() []string {
+	a := []string{"litefs.yml"}
+	if u, _ := user.Current(); u != nil && u.HomeDir != "" {
+		a = append(a, filepath.Join(u.HomeDir, "litefs.yml"))
+	}
+	a = append(a, "/etc/litefs.yml")
+	return a
+}