Implement Actions interface and update rule handling in Server

Introduced an Actions interface for plugins in 'action.go' and implemented a corresponding registry in 'registry.go'. Additionally, adjusted rule related behavior in 'Server' to account for actions, with relevant new fields in Ruleset and Rule. This enables multiple actions on a log message based on defined rules and further modularises the codebase, paving the path for addition of more plugin actions.

cmd/server/main.go

@@ -35,10 +35,15 @@ func main() {
 		os.Exit(1)
 	}
 
-	s := logranger.New(c)
+	s, err := logranger.New(c)
+	if err != nil {
+		l.Error("failed to create new server", LogErrKey, err)
+		os.Exit(1)
+	}
+
 	go func() {
 		if err = s.Run(); err != nil {
-			l.Error("failed to start logranger: %s", LogErrKey, err)
+			l.Error("failed to start logranger", LogErrKey, err)
 			os.Exit(1)
 		}
 	}()

connection.go

@@ -6,6 +6,8 @@ package logranger
 
 import (
 	"bufio"
+	"fmt"
+	"math/rand"
 	"net"
 )
 
@@ -23,9 +25,15 @@ type Connection struct {
 func NewConnection(nc net.Conn) *Connection {
 	c := &Connection{
 		conn: nc,
-		id:   "foo",
+		id:   NewConnectionID(),
 		rb:   bufio.NewReader(nc),
 		wb:   bufio.NewWriter(nc),
 	}
 	return c
 }
+
+// NewConnectionID generates a new unique message ID using a random number generator
+// and returns it as a hexadecimal string.
+func NewConnectionID() string {
+	return fmt.Sprintf("%x", rand.Int63())
+}

plugins/action.go

@@ -0,0 +1,18 @@
+// SPDX-FileCopyrightText: 2023 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
+package plugins
+
+import (
+	"github.com/wneessen/go-parsesyslog"
+)
+
+// Action is an interface that defines the behavior of an action to be performed
+// on a log message.
+//
+// The Process method takes a log message, a slice of match groups, and a
+// configuration map, and returns an error if any occurs during processing.
+type Action interface {
+	Process(logmessage parsesyslog.LogMsg, matchgroup []string, confmap map[string]any) error
+}

plugins/actions/all/all.go

@@ -0,0 +1,5 @@
+// SPDX-FileCopyrightText: 2023 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
+package all

plugins/actions/all/file.go

@@ -0,0 +1,7 @@
+// SPDX-FileCopyrightText: 2023 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
+package all
+
+import _ "github.com/wneessen/logranger/plugins/actions/file" // register plugin

plugins/actions/file/file.go

@@ -0,0 +1,71 @@
+// SPDX-FileCopyrightText: 2023 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
+package file
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/wneessen/go-parsesyslog"
+
+	"github.com/wneessen/logranger/plugins/actions"
+	"github.com/wneessen/logranger/template"
+)
+
+// File represents a file action that can be performed on a log message.
+type File struct{}
+
+// Process satisfies the plugins.Action interface for the File type
+// It takes in the log message (lm), match groups (mg), and configuration map (cm).
+func (f *File) Process(lm parsesyslog.LogMsg, mg []string, cm map[string]any) error {
+	if cm["file"] == nil {
+		return nil
+	}
+	c, ok := cm["file"].(map[string]any)
+	if !ok {
+		return fmt.Errorf("missing configuration for file action")
+	}
+	ot, ok := c["output_template"].(string)
+	if !ok || ot == "" {
+		return fmt.Errorf("not output_template configured for file action")
+	}
+
+	fn, ok := c["output_filepath"].(string)
+	if !ok || fn == "" {
+		return fmt.Errorf("no output_filename configured for file action")
+	}
+
+	of := os.O_APPEND | os.O_CREATE | os.O_WRONLY
+	if ow, ok := c["overwrite"].(bool); ok && ow {
+		of = os.O_WRONLY | os.O_CREATE
+	}
+
+	fh, err := os.OpenFile(fn, of, 0o600)
+	if err != nil {
+		return fmt.Errorf("failed to open file for writing in file action: %w", err)
+	}
+	defer func() {
+		_ = fh.Close()
+	}()
+
+	t, err := template.Compile(lm, mg, ot)
+	if err != nil {
+		return err
+	}
+	_, err = fh.WriteString(t)
+	if err != nil {
+		return fmt.Errorf("failed to write log message to file %q: %w", fn, err)
+	}
+	if err := fh.Sync(); err != nil {
+		return fmt.Errorf("failed to sync memory to file %q: %w", fn, err)
+	}
+
+	return nil
+}
+
+// init registers the "file" action with the Actions map.
+func init() {
+	actions.Add("file", &File{})
+}

plugins/actions/registry.go

@@ -0,0 +1,17 @@
+// SPDX-FileCopyrightText: 2023 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
+package actions
+
+import (
+	"github.com/wneessen/logranger/plugins"
+)
+
+// Actions is a variable that represents a map of string keys to Action values. The keys are used to identify different actions, and the corresponding values are the functions that define
+var Actions = map[string]plugins.Action{}
+
+// Add adds an action with the given name to the Actions map. The action function must implement the Action interface.
+func Add(name string, action plugins.Action) {
+	Actions[name] = action
+}

rule.go

@@ -14,12 +14,17 @@ import (
 	"github.com/kkyr/fig"
 )
 
+// Ruleset represents a collection of rules.
 type Ruleset struct {
-	Rule []struct {
+	Rule []Rule `fig:"rule"`
+}
+
+// Rule represents a rule with its properties.
+type Rule struct {
 	ID        string         `fig:"id" validate:"required"`
 	Regexp    *regexp.Regexp `fig:"regexp" validate:"required"`
-		HostMatch *string        `fig:"host_match"`
-	} `fig:"rule"`
+	HostMatch *regexp.Regexp `fig:"host_match"`
+	Actions   map[string]any `fig:"actions"`
 }
 
 // NewRuleset initializes a new Ruleset based on the provided Config.

server.go

@@ -18,6 +18,9 @@ import (
 	"github.com/wneessen/go-parsesyslog"
 	_ "github.com/wneessen/go-parsesyslog/rfc3164"
 	_ "github.com/wneessen/go-parsesyslog/rfc5424"
+
+	"github.com/wneessen/logranger/plugins/actions"
+	_ "github.com/wneessen/logranger/plugins/actions/all"
 )
 
 const (
@@ -42,12 +45,28 @@ type Server struct {
 }
 
 // New creates a new instance of Server based on the provided Config
-func New(c *Config) *Server {
+func New(c *Config) (*Server, error) {
 	s := &Server{
 		conf: c,
 	}
+
 	s.setLogLevel()
-	return s
+
+	if err := s.setRules(); err != nil {
+		return s, err
+	}
+
+	p, err := parsesyslog.New(s.conf.internal.ParserType)
+	if err != nil {
+		return s, fmt.Errorf("failed to initialize syslog parser: %w", err)
+	}
+	s.parser = p
+
+	if len(actions.Actions) <= 0 {
+		return s, fmt.Errorf("no action plugins found/configured")
+	}
+
+	return s, nil
 }
 
 // Run starts the logranger Server by creating a new listener using the NewListener
@@ -57,31 +76,6 @@ func (s *Server) Run() error {
 	if err != nil {
 		return err
 	}
-
-	p, err := parsesyslog.New(s.conf.internal.ParserType)
-	if err != nil {
-		return fmt.Errorf("failed to initialize syslog parser: %w", err)
-	}
-	s.parser = p
-
-	rs, err := NewRuleset(s.conf)
-	if err != nil {
-		return fmt.Errorf("failed to read ruleset: %w", err)
-	}
-	s.ruleset = rs
-	for _, r := range rs.Rule {
-		s.log.Debug("found rule", slog.String("ID", r.ID))
-		if r.HostMatch != nil {
-			s.log.Debug("host match enabled", slog.String("host", *r.HostMatch))
-		}
-		if r.Regexp != nil {
-			foo := r.Regexp.FindAllStringSubmatch("test_foo23", -1)
-			if len(foo) > 0 {
-				s.log.Debug("matched", slog.Any("groups", foo))
-			}
-		}
-	}
-
 	return s.RunWithListener(l)
 }
 
@@ -177,13 +171,33 @@ ReadLoop:
 				continue ReadLoop
 			}
 		}
-		s.log.Debug("log message successfully received",
-			slog.String("message", lm.Message.String()),
-			slog.String("facility", lm.Facility.String()),
-			slog.String("severity", lm.Severity.String()),
-			slog.Time("server_time", lm.Timestamp))
+		if err = s.processMessage(lm); err != nil {
+			s.log.Error("failed to process actions on log message", LogErrKey, err)
 		}
 	}
+}
+
+func (s *Server) processMessage(lm parsesyslog.LogMsg) error {
+	if s.ruleset != nil {
+		for _, r := range s.ruleset.Rule {
+			if !r.Regexp.MatchString(lm.Message.String()) {
+				continue
+			}
+			if r.HostMatch != nil && !r.HostMatch.MatchString(lm.Hostname) {
+				continue
+			}
+			mg := r.Regexp.FindStringSubmatch(lm.Message.String())
+			for n, a := range actions.Actions {
+				s.log.Debug("trying to execute action", slog.String("action_name", n))
+				if err := a.Process(lm, mg, r.Actions); err != nil {
+					s.log.Error("failed to process action", LogErrKey, err,
+						slog.String("action", n), slog.String("rule_id", r.ID))
+				}
+			}
+		}
+	}
+	return nil
+}
 
 // setLogLevel sets the log level based on the value of `s.conf.Log.Level`.
 // It creates a new `slog.HandlerOptions` and assigns the corresponding `slog.Level`
@@ -209,3 +223,16 @@ func (s *Server) setLogLevel() {
 	lh := slog.NewJSONHandler(os.Stdout, &lo)
 	s.log = slog.New(lh).With(slog.String("context", "logranger"))
 }
+
+// setRules initializes/updates the ruleset for the logranger Server by
+// calling NewRuleset with the config and assigns the returned ruleset
+// to the Server's ruleset field.
+// It returns an error if there is a failure in reading or loading the ruleset.
+func (s *Server) setRules() error {
+	rs, err := NewRuleset(s.conf)
+	if err != nil {
+		return fmt.Errorf("failed to read ruleset: %w", err)
+	}
+	s.ruleset = rs
+	return nil
+}

template/template.go

@@ -0,0 +1,75 @@
+// SPDX-FileCopyrightText: 2023 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
+package template
+
+import (
+	"fmt"
+	"strings"
+	"text/template"
+	"time"
+
+	"github.com/wneessen/go-parsesyslog"
+)
+
+// FuncMap represents a mapping of function names to their corresponding
+// functions.
+// It is used to define custom functions that can be accessed in Go
+// templates.
+type FuncMap struct{}
+
+// Compile compiles a template string using a given LogMsg, match group,
+// and output template.
+// It replaces special characters in the output template and creates a
+// new template, named "template", with custom template functions from
+// the FuncMap. It then populates a map with values from the LogMsg
+// and current time and executes the template using the map as the
+// data source. The compiled template result or an error is returned.
+func Compile(lm parsesyslog.LogMsg, mg []string, ot string) (string, error) {
+	pt := strings.Builder{}
+	fm := NewTemplateFuncMap()
+
+	ot = strings.ReplaceAll(ot, `\n`, "\n")
+	ot = strings.ReplaceAll(ot, `\t`, "\t")
+	ot = strings.ReplaceAll(ot, `\r`, "\r")
+	tpl, err := template.New("template").Funcs(fm).Parse(ot)
+	if err != nil {
+		return pt.String(), fmt.Errorf("failed to create template: %w", err)
+	}
+
+	dm := make(map[string]any)
+	dm["match"] = mg
+	dm["hostname"] = lm.Hostname
+	dm["timestamp"] = lm.Timestamp
+	dm["now_rfc3339"] = time.Now().Format(time.RFC3339)
+	dm["now_unix"] = time.Now().Unix()
+	dm["severity"] = lm.Severity.String()
+	dm["facility"] = lm.Facility.String()
+	dm["appname"] = lm.AppName
+	dm["original_message"] = lm.Message
+
+	if err = tpl.Execute(&pt, dm); err != nil {
+		return pt.String(), fmt.Errorf("failed to compile template: %w", err)
+	}
+	return pt.String(), nil
+}
+
+// NewTemplateFuncMap creates a new template function map by returning a
+// template.FuncMap.
+func NewTemplateFuncMap() template.FuncMap {
+	fm := FuncMap{}
+	return template.FuncMap{
+		"_ToLower": fm.ToLower,
+	}
+}
+
+// ToLower returns a given string as lower-case representation
+func (*FuncMap) ToLower(s string) string {
+	return strings.ToLower(s)
+}
+
+// ToUpper returns a given string as upper-case representation
+func (*FuncMap) ToUpper(s string) string {
+	return strings.ToUpper(s)
+}