Resolved an issue where the first streamed output could incorrectly return the input file.

Author: niekberenschot

CHANGELOG.md

@@ -2,6 +2,17 @@
 
 All notable changes to this project will be documented in this file.
 
+## [1.0.1] - 2025-12-20
+
+### Fixed
+
+- Resolved an issue where the first streamed output could incorrectly return the input file.
+
+### Added
+
+- Added S3 configuration documentation to the README.
+- Expanded README with an explanation of parallel processing behavior.
+
 ## [1.0.0] - 2025-12-20
 
 ### Added

README.md

@@ -15,6 +15,22 @@ You provide input files and FFmpeg commands; the API returns the results via **S
 
 `POST /v1/process`
 
+### API Example
+
+```bash
+curl -X POST http://localhost:8080/v1/process \
+  -H "Content-Type: application/json" \
+  -d '{
+    "input": {
+      "input.mp4": { "http": "https://example.com/video.mp4" }
+    },
+    "commands": [
+      ["-i", "input.mp4", "-vn", "output.mp3"]
+    ],
+    "output": { "base64": true }
+  }'
+```
+
 ## Request Structure
 
 ```json
@@ -91,24 +107,36 @@ Filenames reference input files or outputs from previous commands.
 }
 ```
 
-## Example
+## S3 Configuration
 
-```bash
-curl -X POST http://localhost:8080/v1/process \
-  -H "Content-Type: application/json" \
-  -d '{
-    "input": {
-      "input.mp4": { "http": "https://example.com/video.mp4" }
-    },
-    "commands": [
-      ["-i", "input.mp4", "-vn", "output.mp3"]
-    ],
-    "output": { "base64": true }
-  }'
+S3 access is configured **per request** using the `s3Config` object.
+
+* Works with:
+  * AWS S3
+  * S3-compatible providers (MinIO, DigitalOcean Spaces, Cloudflare R2, etc.)
+* The `endpoint` should **not** include a bucket name
+
+* `useSSL` defaults to **true** if omitted
+
+### Example
+
+```json
+{
+  "s3Config": {
+    "endpoint": "s3.amazonaws.com",
+    "region": "us-east-1",
+    "accessKey": "AKIA...",
+    "secretKey": "SECRET...",
+    "useSSL": true
+  }
+}
 ```
 
 ## Docker
 
+* FFmpeg is bundled
+* No external dependencies
+
 ### Image
 
 ```
@@ -127,10 +155,23 @@ API available at:
 http://localhost:8080
 ```
 
-## Notes
+## Scaling & Concurrency
 
-* FFmpeg is bundled
-* No external dependencies
-* Temporary files are cleaned automatically
-* S3 credentials are supplied per request
-* Go binary on scratch image
+Each request is handled independently by the HTTP server.
+
+* Input files are fetched **in parallel** (HTTP, S3, Base64 decoding).
+* FFmpeg is executed as a separate OS process per request.
+
+Concurrency comes from handling multiple HTTP requests simultaneously. FFmpeg’s own multithreading is fully supported and can be controlled via standard flags such as:
+
+```bash
+-threads 0   # auto
+-threads 4   # fixed
+```
+
+The service is stateless:
+
+* No shared filesystem state
+* No in-memory session data
+
+This makes it easy to scale **horizontally** by running multiple instances behind a load balancer, for example using **Kubernetes**, or a managed container service.

SECURITY.md

@@ -6,7 +6,8 @@ The following table outlines the versions of this project
 currently supported with security updates:
 
 | Version | Supported          |
-|---------| ------------------ |
+|---------|--------------------|
+| 1.0.1   | :white_check_mark: |
 | 1.0.0   | :white_check_mark: |
 
 ## Reporting a Vulnerability

cmd/main.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"encoding/base64"
 	"encoding/json"
-	"ffmpeg/internal"
 	"fmt"
 	"net/http"
 	"os"
@@ -17,12 +16,16 @@ import (
 	"github.com/google/uuid"
 
 	"ffmpeg/api"
+	"ffmpeg/internal"
 )
 
 func main() {
 	http.HandleFunc("/v1/process", handleProcess)
+	if err := http.ListenAndServe(":8080", nil); err != nil {
+		fmt.Println("server failed to start:", err)
+		os.Exit(1)
+	}
 	fmt.Println("Listening on :8080")
-	http.ListenAndServe(":8080", nil)
 }
 
 func handleProcess(w http.ResponseWriter, r *http.Request) {
@@ -54,7 +57,7 @@ func handleProcess(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if req.Output.InlineContentType != "" {
-		streamFirstFile(w, r, jobPath, req.Output.InlineContentType)
+		streamFirstResult(w, r, jobPath, req)
 		return
 	}
 
@@ -165,11 +168,14 @@ func collectResults(s3Client *s3.Client, req api.ProcessRequest, jobPath string)
 	return results, nil
 }
 
-func streamFirstFile(w http.ResponseWriter, r *http.Request, jobPath, contentType string) {
+func streamFirstResult(w http.ResponseWriter, r *http.Request, jobPath string, req api.ProcessRequest) {
 	files, _ := os.ReadDir(jobPath)
 	for _, f := range files {
 		if !f.IsDir() {
-			w.Header().Set("Content-Type", contentType)
+			if _, isInput := req.Inputs[f.Name()]; isInput {
+				continue
+			}
+			w.Header().Set("Content-Type", req.Output.InlineContentType)
 			http.ServeFile(w, r, filepath.Join(jobPath, f.Name()))
 			return
 		}