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feat: improve logging #8

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feat: improve logging #8

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0cf6cf1
improve logging
Oct 20, 2025
3b1a068
fix json
Oct 20, 2025
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136 changes: 125 additions & 11 deletions main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ limitations under the License.
package main

import (
"encoding/json"
"fmt"
"io"
"log"
Expand Down Expand Up @@ -76,6 +77,9 @@ func init() {
}

func main() {
// Configure logger to output raw JSON without timestamp prefix for Datadog
log.SetFlags(0)

errFilesPath := "/www"
if os.Getenv(ErrFilesPathVar) != "" {
errFilesPath = os.Getenv(ErrFilesPathVar)
Expand Down Expand Up @@ -107,6 +111,28 @@ func errorHandler(path, defaultFormat string) func(http.ResponseWriter, *http.Re
return func(w http.ResponseWriter, r *http.Request) {
start := time.Now()
ext := defaultExt
var logJSON []byte // Declare logJSON variable for reuse throughout function

// Log request details in JSON format with debug level
requestLog := map[string]interface{}{
"timestamp": start.Format(time.RFC3339),
"level": "debug", // Set log level to debug for Datadog categorization
"method": r.Method,
"path": r.URL.Path,
"query": r.URL.RawQuery,
"host": r.Host,
"remote_addr": r.RemoteAddr,
"user_agent": r.Header.Get("User-Agent"),
"original_uri": r.Header.Get(OriginalURI),
"namespace": r.Header.Get(Namespace),
"ingress_name": r.Header.Get(IngressName),
"service_name": r.Header.Get(ServiceName),
"service_port": r.Header.Get(ServicePort),
"request_id": r.Header.Get(RequestId),
"x_code": r.Header.Get(CodeHeader),
"x_format": r.Header.Get(FormatHeader),
"accept": r.Header.Get("Accept"),
}

if os.Getenv("DEBUG") != "" {
w.Header().Set(FormatHeader, r.Header.Get(FormatHeader))
Expand All @@ -123,25 +149,75 @@ func errorHandler(path, defaultFormat string) func(http.ResponseWriter, *http.Re
format := r.Header.Get(FormatHeader)
if format == "" {
format = defaultFormat
log.Printf("format not specified. Using %v", format)
if os.Getenv("DEBUG") != "" {
// Log debug message in JSON format for Datadog
debugLog := map[string]interface{}{
"timestamp": time.Now().Format(time.RFC3339),
"level": "debug",
"message": fmt.Sprintf("format not specified. Using %v", format),
"context": "format_selection",
}
logJSON, _ = json.Marshal(debugLog)
log.Printf("%s", logJSON)
}
}

cext, err := mime.ExtensionsByType(format)
if err != nil {
log.Printf("unexpected error reading media type extension: %v. Using %v", err, ext)
// Log error message in JSON format for Datadog
errorLog := map[string]interface{}{
"timestamp": time.Now().Format(time.RFC3339),
"level": "debug",
"message": fmt.Sprintf("unexpected error reading media type extension: %v. Using %v", err, ext),
"context": "mime_type_parsing",
"error": err.Error(),
}
logJSON, _ = json.Marshal(errorLog)
log.Printf("%s", logJSON)
format = defaultFormat
} else if len(cext) == 0 {
log.Printf("couldn't get media type extension. Using %v", ext)
// Log warning message in JSON format for Datadog
warnLog := map[string]interface{}{
"timestamp": time.Now().Format(time.RFC3339),
"level": "debug",
"message": fmt.Sprintf("couldn't get media type extension. Using %v", ext),
"context": "mime_extension_lookup",
}
logJSON, _ = json.Marshal(warnLog)
log.Printf("%s", logJSON)
} else {
ext = cext[0]
}
w.Header().Set(ContentType, format)

errCode := r.Header.Get(CodeHeader)
code, err := strconv.Atoi(errCode)
if err != nil {
code = 404
log.Printf("unexpected error reading return code: %v. Using %v", err, code)
code := 404 // Default code
if errCode != "" {
parsedCode, err := strconv.Atoi(errCode)
if err != nil {
// Log error message in JSON format for Datadog
errorLog := map[string]interface{}{
"timestamp": time.Now().Format(time.RFC3339),
"level": "debug",
"message": fmt.Sprintf("invalid return code %q: %v. Using %v", errCode, err, code),
"context": "return_code_parsing",
"error": err.Error(),
}
logJSON, _ = json.Marshal(errorLog)
log.Printf("%s", logJSON)
} else {
code = parsedCode
}
} else if os.Getenv("DEBUG") != "" {
// Log debug message in JSON format for Datadog
debugLog := map[string]interface{}{
"timestamp": time.Now().Format(time.RFC3339),
"level": "debug",
"message": fmt.Sprintf("return code not specified. Using %v", code),
"context": "return_code_default",
}
logJSON, _ = json.Marshal(debugLog)
log.Printf("%s", logJSON)
}
w.WriteHeader(code)

Expand All @@ -155,22 +231,47 @@ func errorHandler(path, defaultFormat string) func(http.ResponseWriter, *http.Re
file := fmt.Sprintf("%v/%v%v", path, code, ext)
f, err := os.Open(file)
if err != nil {
log.Printf("unexpected error opening file: %v", err)
// Log error message in JSON format for Datadog
errorLog := map[string]interface{}{
"timestamp": time.Now().Format(time.RFC3339),
"level": "debug",
"message": fmt.Sprintf("unexpected error opening file: %v", err),
"context": "file_opening",
"error": err.Error(),
}
logJSON, _ = json.Marshal(errorLog)
log.Printf("%s", logJSON)
scode := strconv.Itoa(code)
file := fmt.Sprintf("%v/%cxx%v", path, scode[0], ext)
f, err := os.Open(file)
if err != nil {
log.Printf("unexpected error opening file: %v", err)
// Log error message in JSON format for Datadog
errorLog := map[string]interface{}{
"timestamp": time.Now().Format(time.RFC3339),
"level": "debug",
"message": fmt.Sprintf("unexpected error opening file: %v", err),
"context": "file_opening",
"error": err.Error(),
}
logJSON, _ = json.Marshal(errorLog)
log.Printf("%s", logJSON)
http.NotFound(w, r)
return
}
defer f.Close()
log.Printf("serving custom error response for code %v and format %v from file %v", code, format, file)
// Log info message in JSON format for Datadog
infoLog := map[string]interface{}{
"timestamp": time.Now().Format(time.RFC3339),
"level": "debug",
"message": fmt.Sprintf("serving custom error response for code %v and format %v from file %v", code, format, file),
"context": "custom_error_response",
}
logJSON, _ = json.Marshal(infoLog)
log.Printf("%s", logJSON)
io.Copy(w, f)
return
}
defer f.Close()
log.Printf("serving custom error response for code %v and format %v from file %v", code, format, file)
io.Copy(w, f)

duration := time.Now().Sub(start).Seconds()
Expand All @@ -180,5 +281,18 @@ func errorHandler(path, defaultFormat string) func(http.ResponseWriter, *http.Re

requestCount.WithLabelValues(proto).Inc()
requestDuration.WithLabelValues(proto).Observe(duration)

// Add response details to log
requestLog["status_code"] = code
requestLog["content_type"] = format
requestLog["response_file"] = file
requestLog["duration_seconds"] = duration
requestLog["protocol"] = proto
requestLog["message"] = fmt.Sprintf("HTTP %s %s - %d", r.Method, r.URL.Path, code)
requestLog["context"] = "http_request"

// Output JSON log with debug level for Datadog
logJSON, _ = json.Marshal(requestLog)
log.Printf("%s", logJSON)
}
}