initial

Signed-off-by: Lars Thoms <lars.thoms@uni-hamburg.de>

README.md

+# HLS Subscriber Stats
+
+To get meaningful statistics of a HTTP Live Stream (HLS), such as the current number of subscribers, it is necessary to analyze a *modified* `access.log`.
+
+
+## Requirements
+
+- golang
+
+
+## Build
+
+```shell
+go build hls-subscriber-stats.go
+```
+
+
+## Usage (nginx)
+
+1.  Add an additional `log_format` to your `http` section:  
+    ```nginx
+    http {
+        log_format hls-subscriber-stats "$msec $request_filename";
+    }
+    ```
+
+2.  Activate `access_log` in your `server` section:  
+    ```nginx
+    server {
+        access_log /path-log/hls-access.log hls-subscriber-stats;
+    }
+    ```
+
+3.  Execute *Go* program in your `application` section:
+    ```nginx
+    application stream {
+        live on;
+        hls  on;
+        exec_push /path-bin/hls-subscriber-stats -input /path-log/hls-access.log -output "/path-www/$name.json" -name "$name" -interval 10 -segments 3
+    }
+    ```

hls-subscriber-stats.go

+/*******************************************************************************
+ * parse access.log to receive the current number of HLS subscribers
+ * 
+ * logformat: [UNIX TIMESTAMP (or msec)] [FILE]
+ * e.g.:      1639399770.294 /srv/domain.tld/hls/stream-name-12.ts
+ * 
+ * @author Lars Thoms
+ * @date   2021-12-15 
+ ******************************************************************************/
+
+package main
+
+import (
+    "bufio"
+    "flag"
+    "log"
+    "os"
+    "regexp"
+    "strconv"
+    "time"
+)
+
+
+/*******************************************************************************
+ * distribution struct
+ ******************************************************************************/
+
+type distribution struct {
+    dist map[uint64]uint64
+    max uint64 
+}
+
+
+func (d * distribution) Init() {
+    d.dist = make(map[uint64]uint64)
+}
+
+
+func (d *distribution) Count(i uint64) {
+    d.dist[i]++
+    if d.max < i {
+        d.max = i
+    }
+}
+
+
+func (d *distribution) Get(i uint64) uint64 {
+    return d.dist[i]
+}
+
+
+/*******************************************************************************
+ * functions
+ ******************************************************************************/
+
+/**
+ * @brief      Parse access.log and generate a distribution
+ *
+ * @param      path    Path to access.log
+ * @param      stream  Name of the stream
+ * @param      dist    Distribution
+ */
+func ParseLog(path *string, stream *string, dist *distribution) {
+    
+    // open access.log
+    file, err := os.Open(*path)
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer file.Close()
+
+    // prepare filter
+    time := time.Now().Unix() / 100
+    time = 16393997
+    regex := regexp.MustCompile(
+        "^" + strconv.FormatInt(time, 10) + "[\\d]{2}\\.[\\d]+.*?" + regexp.QuoteMeta(*stream) + "-([\\d]+).ts$")
+
+    // iterate trough logfile
+    scanner := bufio.NewScanner(file)
+    for scanner.Scan() {
+        matches := regex.FindStringSubmatch(scanner.Text())
+        if matches != nil {
+            i, _ := strconv.ParseUint(matches[1], 10, 64)
+            dist.Count(i)
+        } else {
+            continue
+        }
+    }
+
+    if err := scanner.Err(); err != nil {
+        log.Fatal(err)
+    }
+}
+
+
+/**
+ * @brief      Generate stats.json with the current number of subscribers
+ *
+ * @param      dist      Distribution
+ * @param      path      Path to stats.json
+ * @param      segments  Number of stream segments to analyse
+ */
+func GenerateStat(dist *distribution, path *string, segments uint64) {
+    var subscribers uint64
+
+    for i := uint64(0); i < segments; i++ {
+        if s := dist.Get(dist.max - i); subscribers < s {
+            subscribers = s
+        }
+    }
+
+    // write stats as JSON to file
+    err := os.WriteFile(*path, []byte("{\"subscribers\":" + strconv.FormatUint(subscribers, 10) + "}"), 0644)
+    if err != nil {
+        log.Fatal(err)
+    }
+}
+
+
+/**
+ * @brief      HLS Subscriber Stats
+ */
+func main() {
+    // CLI arguments
+    logfilePtr   := flag.String("input", "access.log", "Path to access.log")
+    statsfilePtr := flag.String("output", "stream.json", "Path to stats.json")
+    streamPtr    := flag.String("name", "stream", "Name of the stream")
+    segmentsPtr  := flag.Uint64("segments", 3, "Number of stream segments to analyse")
+    intervalPtr  := flag.Int("interval", 10, "Pause between parsing operations in seconds")
+    flag.Parse()
+
+    // parse log all n seconds
+    for {
+        distPtr := new(distribution)
+        distPtr.Init()
+        ParseLog(logfilePtr, streamPtr, distPtr)
+        GenerateStat(distPtr, statsfilePtr, *segmentsPtr)
+
+        time.Sleep(time.Duration(*intervalPtr) * time.Second)
+    }
+}