implemented rate limiting

backend/backend.go

@@ -1,6 +1,7 @@
 package backend
 
 import (
+	"embed"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -13,7 +14,6 @@ import (
 	"slices"
 	"strings"
 	"time"
-	"embed"
 
 	"git.noctra.dev/noctra/servtex/globals"
 	"github.com/fsnotify/fsnotify"
@@ -22,9 +22,15 @@ import (
 //go:embed default_config.json
 var defaultConfig embed.FS
 
+// There are no errors if I can't see them
+func Must[T any](object T, err error) T {
+	return object
+}
+
+
 // Returns the current time in the timezone specified in the config file
 func GetLocalTime() time.Time {
-	timezone, _ := time.LoadLocation(globals.AppConfig.Timezone)
+	timezone := Must(time.LoadLocation(globals.AppConfig.Timezone))
 	return time.Now().In(timezone)
 }
 
@@ -57,7 +63,7 @@ func LogLine(message string, level int) {
 	globals.LogFile.WriteString(logline)
 }
 
-// Logs client info. Configured log level sets the verbosity.
+// Logs client info. Configured log level sets the verbosity. Logs only up to level INFO
 //
 // Bad Request if err != nil
 func VerifyLogRequest(request *http.Request) (err error) {
@@ -66,16 +72,16 @@ func VerifyLogRequest(request *http.Request) (err error) {
 
 	if client.Proxied && globals.AppConfig.LogLevelNumeric > 1 {
 		LogLine(fmt.Sprintf(
-				"Request: %s via %s - %s %s",
+				"httpR: %s via %s - %s %s",
 				client.ClientIP, 
 				client.Proxy,
 				client.RequestType, 
 				client.RequestPath, 
 			), 
-			4,
+			2,
 		)
 	} else {
-		LogLine(fmt.Sprintf("Request: %s - %s %s", client.ClientIP, client.RequestType, client.RequestPath), 4)
+		LogLine(fmt.Sprintf("httpR: %s - %s %s", client.ClientIP, client.RequestType, client.RequestPath), 2)
 	}
 
 	return nil
@@ -84,7 +90,7 @@ func VerifyLogRequest(request *http.Request) (err error) {
 
 // Writes a configuration file populated with defaults
 func createConfigWithDefaults(path string) error {
-	config, _ := defaultConfig.ReadFile("default_config.json")
+	config := Must(defaultConfig.ReadFile("default_config.json"))
 	err := os.WriteFile(path, config, 0644)
 	return err
 }
@@ -122,7 +128,7 @@ func configReaderParse(filePath string, configOptionStorage *globals.Config) err
 
 // populates the appconfig with default values
 func configPopulator(configOptionStorage *globals.Config) {
-	jsonData, _ := defaultConfig.ReadFile("default_config.json")
+	jsonData := Must(defaultConfig.ReadFile("default_config.json"))
 	json.Unmarshal(jsonData, &configOptionStorage)
 }
 
@@ -175,7 +181,6 @@ func watchLoop(watcher *fsnotify.Watcher, callOnChange func() error) {
 	defer watcher.Close()
 	for {
 		select {
-			// Errors
 		case err, ok := <-watcher.Errors:
 			if !ok {
 				LogLine(fmt.Sprintf("Watcher crashed on error, manual compile only: %s", err), 4)
@@ -183,7 +188,6 @@ func watchLoop(watcher *fsnotify.Watcher, callOnChange func() error) {
 			}
 			LogLine(fmt.Sprintf("Watcher Error: %s", err), 3)
 
-			// Events
 		case event, ok := <-watcher.Events:
 			if !ok {
 				LogLine(fmt.Sprintf("Watcher crashed on event, manual compile only: %s", event), 4)
@@ -204,6 +208,7 @@ func watchLoop(watcher *fsnotify.Watcher, callOnChange func() error) {
 }
 
 
+// Returns a list of all .tex files recursively found in the passed directory
 func texFinder(path string) []string {
 	var texFiles []string
 	err := filepath.WalkDir(path, func(path string, d fs.DirEntry, err error) error {
@@ -216,7 +221,7 @@ func texFinder(path string) []string {
 		return nil
 	})
 	if err != nil {
-		LogLine("Some paths could not be traversed while search for .tex files", 3)
+		LogLine(fmt.Sprintf("Some paths could not be traversed while search for .tex files: %s", err), 3)
 	}
 	return texFiles
 }
@@ -249,19 +254,40 @@ func updateExecutionTimestamp(execution *globals.LatexExecution) {
 	execution.TimestampRFC = GetLocalTimeRFC()
 }
 
+// Returns the necessary time to sleep for rate limiting.
+//
+// Requires an RFC3339 timestamp. A dog will die if anything else is passed.
+func rateLimitTime(timestampRFC string) (sleepTime time.Duration) {
+	lastExeTime := Must(time.Parse(time.RFC3339, timestampRFC))
+	rateLimitInterval := Must(time.ParseDuration(fmt.Sprintf("%ds", globals.AppConfig.RateLimitSeconds)))
+	return time.Until(lastExeTime.Add(rateLimitInterval)).Round(time.Second)
+}
+
 // Intended to be run as goroutine
 func LatexCompile() error {
 	execution := &globals.LatexExec
 	config := globals.AppConfig
+
+	// check for already running compilation
 	if execution.ExecutionLock.TryLock() {
 		defer execution.ExecutionLock.Unlock()
 	} else {
-		LogLine("LaTeX execution already underway", 2)
+		LogLine("LaTeX: Already running", 2)
 		return errors.New("Execution already in progress")
 	}
 
-	LogLine("LaTeX execution started", 2)
+	// rate limit or start right away
+	rateLimit := rateLimitTime(execution.TimestampRFC)
+	if rateLimit.Seconds() > 0 {
+		LogLine(fmt.Sprintf("LaTeX: Rate limit: %d seconds", int(rateLimit.Seconds())), 3)
+		execution.ExecutionState = globals.LatexExecutionStateLimit
+		time.Sleep(rateLimit)
+	} else {
+		LogLine("LaTeX: Started", 3)
+		execution.ExecutionState = globals.LatexExecutionStateRunning
+	}
 
+	// build command
 	var latexCommand *exec.Cmd
 	switch config.LatexEngine {
 		case "lualatex":
@@ -277,10 +303,11 @@ func LatexCompile() error {
 			execution.Output = []byte{}
 			updateExecutionTimestamp(execution)
 
-			LogLine("Unsupported LaTeX Engine", 4)
+			LogLine("LaTeX: Unsupported engine", 4)
 			return errors.New("Unsupported LaTeX Engine")
 	}
 
+	// execute command
 	stdout, err := latexCommand.Output()
 	execution.Output = stdout
 	if err == nil { 
@@ -290,7 +317,7 @@ func LatexCompile() error {
 	}
 	updateExecutionTimestamp(execution)
 
-	LogLine("LaTeX execution finished", 2)
+	LogLine("LaTeX: Finished", 3)
 	return err
 }
 
@@ -317,7 +344,7 @@ func isTrustedProxy(proxy string, trustedProxies []string) (trusted bool, usedPr
 	// resolve trustedProxies in case a DNS name was configured
 	for _, trustedProxyDNS := range trustedProxies {
 		// get IPs of this dns name
-		trustedProxyIPs, err := net.LookupAddr(trustedProxyDNS)
+		trustedProxyIPs, err := net.LookupHost(trustedProxyDNS)
 		if err != nil { continue }
 
 		// set usedProxy to DNS name if proxy is trusted

backend/default_config.json

@@ -6,6 +6,7 @@
 	"latexEngine": "lualatex",
 	"latexSourceFilePath": "./latex/Example.tex",
 	"latexOutputPath": "./latex/output",
+	"rateLimitSeconds": 20,
 
 	"webserverDomain": "localhost",
 	"webserverPort": "8080",

config.json

@@ -1,11 +1,12 @@
 {
 	"timezone": "Europe/Berlin",
 	"logFilePath": "./servtex.log",
-	"logLevel": "debug",
+	"logLevel": "info",
 
 	"latexEngine": "lualatex",
 	"latexSourceFilePath": "./testfiles/Example.tex",
 	"latexOutputPath": "./testfiles/output",
+	"rateLimitSeconds": 0,
 
 	"webserverDomain": "localhost",
 	"webserverPort": "8080",

frontend/webserver.go

@@ -95,8 +95,9 @@ func SSEventHandler(writer http.ResponseWriter, request *http.Request) {
 				ssePing(&writer)
 			} else {
 				sseStatusSend(&writer)
+				if globals.LatexExec.ExecutionState != globals.LatexExecutionStateRunning {
 					sseOutputSend(&writer)	
-				// let client keep current pdf, if compile failed
+				}
 				if globals.LatexExec.ExecutionState != globals.LatexExecutionStateFailure {
 					ssePDFSend(&writer)
 				}

globals/memory.go

@@ -18,6 +18,7 @@ type Config struct {
 	LatexEngine		string		`json:"latexEngine"`
 	LatexSourceFilePath	string		`json:"latexSourceFilePath"`
 	LatexOutputPath		string		`json:"latexOutputPath"`
+	RateLimitSeconds	int		`json:"rateLimitSeconds"`
 
 	// webserver
 	WebserverDomain		string		`json:"webserverDomain"`
@@ -40,6 +41,8 @@ type LatexExecution struct {
 var LatexExec LatexExecution
 var LatexExecutionStateSuccess = "Success"
 var LatexExecutionStateFailure = "Failure"
+var LatexExecutionStateRunning = "Running"
+var LatexExecutionStateLimit   = "Running (rate limited)"
 
 // Creates a copy of a LatexExecution (without the Mutex)
 func (execution *LatexExecution) Copy() (exeCopy *LatexExecution) {