add a py sdk example for a proxy backend

sdk/python/examples/proxy/proxy.py

@@ -0,0 +1,114 @@
+import zrok
+from zrok.model import ShareRequest
+import requests
+import atexit
+import urllib.parse
+import logging
+import sys
+from waitress import serve
+from flask import Flask, request, Response
+
+# Setup logging
+logging.basicConfig(
+    level=logging.INFO,
+    format='%(asctime)s - %(levelname)s - %(message)s'
+)
+logger = logging.getLogger(__name__)
+
+app = Flask(__name__)
+target_url = None
+zrok_opts = {}
+bindPort = 18081
+
+# List of hop-by-hop headers that should not be forwarded
+HOP_BY_HOP_HEADERS = {
+    'connection',
+    'keep-alive',
+    'proxy-authenticate',
+    'proxy-authorization',
+    'te',
+    'trailers',
+    'transfer-encoding',
+    'upgrade'
+}
+
+
+@app.route('/', defaults={'path': ''}, methods=['GET', 'POST', 'PUT', 'DELETE', 'HEAD', 'OPTIONS', 'PATCH'])
+@app.route('/<path:path>', methods=['GET', 'POST', 'PUT', 'DELETE', 'HEAD', 'OPTIONS', 'PATCH'])
+def proxy(path):
+    global target_url
+    logger.info(f"Incoming {request.method} request to {request.path}")
+    logger.info(f"Headers: {dict(request.headers)}")
+
+    # Forward the request to target URL
+    full_url = urllib.parse.urljoin(target_url, request.path)
+    logger.info(f"Forwarding to: {full_url}")
+
+    # Copy request headers, excluding hop-by-hop headers
+    headers = {k: v for k, v in request.headers.items() if k.lower() not in HOP_BY_HOP_HEADERS and k.lower() != 'host'}
+
+    try:
+        response = requests.request(
+            method=request.method,
+            url=full_url,
+            headers=headers,
+            data=request.get_data(),
+            stream=True
+        )
+
+        logger.info(f"Response status: {response.status_code}")
+        logger.info(f"Response headers: {dict(response.headers)}")
+
+        # Filter out hop-by-hop headers from the response
+        filtered_headers = {k: v for k, v in response.headers.items() if k.lower() not in HOP_BY_HOP_HEADERS}
+
+        return Response(
+            response.iter_content(chunk_size=8192),
+            status=response.status_code,
+            headers=filtered_headers
+        )
+
+    except Exception as e:
+        logger.error(f"Proxy error: {str(e)}", exc_info=True)
+        return str(e), 502
+
+
+@zrok.decor.zrok(opts=zrok_opts)
+def run_proxy():
+    # the port is only used to integrate Zrok with frameworks that expect a "hostname:port" combo
+    serve(app, port=bindPort)
+
+
+if __name__ == '__main__':
+    if len(sys.argv) != 2:
+        print("Usage: proxy.py <target_url>")
+        sys.exit(1)
+
+    target_url = sys.argv[1]
+    logger.info("=== Starting proxy server ===")
+    logger.info(f"Target URL: {target_url}")
+    logger.info(f"Logging level: {logger.getEffectiveLevel()}")
+
+    root = zrok.environment.root.Load()
+    try:
+        shr = zrok.share.CreateShare(root=root, request=ShareRequest(
+            BackendMode=zrok.model.PROXY_BACKEND_MODE,
+            ShareMode=zrok.model.PUBLIC_SHARE_MODE,
+            Frontends=['public'],
+            Target="http-proxy"
+        ))
+        shrToken = shr.Token
+        print("Access proxy at: ", "\n".join(shr.FrontendEndpoints))
+
+        def cleanup():
+            zrok.share.DeleteShare(root=root, shr=shr)
+            print("Share deleted")
+        atexit.register(cleanup)
+
+        zrok_opts['cfg'] = zrok.decor.Opts(root=root, shrToken=shrToken, bindPort=bindPort)
+
+        run_proxy()
+
+    except Exception as e:
+        print("Error:", e)
+        sys.exit(1)