如何在GAE的webapp2中将子目录映射至其他服务器？

Absolutely, you can pull this off using App Engine's app.yaml routing and a webapp2 proxy handler—no Apache or .htaccess needed. Here's a step-by-step breakdown to make it work:

1. Configure app.yaml for Routing #

First, update your app.yaml to prioritize requests to /forum/* and route them to a separate webapp2 app (we'll build this next). Make sure this handler comes before your main site's catch-all route, since App Engine matches routes in order:

runtime: python27
api_version: 1
threadsafe: true

# Route forum traffic first
handlers:
- url: /forum/.*
  script: forum_proxy.app

# Main site routes (keep your existing main app handler here)
- url: /.*
  script: main.app

2. Build the webapp2 Proxy Handler #

Create a new file called forum_proxy.py—this will act as a reverse proxy, forwarding all /forum/ requests to your GCE forum instance. We'll use App Engine's built-in urlfetch service to handle the forwarding:

import webapp2
from google.appengine.api import urlfetch

class ForumProxyHandler(webapp2.RequestHandler):
    def _proxy_request(self, path, method):
        # Replace this with your GCE forum's actual base URL (include port if needed)
        GCE_FORUM_BASE = "http://your-gce-instance-ip-or-internal-domain"
        target_url = f"{GCE_FORUM_BASE}/forum/{path}"

        try:
            # Fetch the resource from GCE
            payload = self.request.body if method in (urlfetch.POST, urlfetch.PUT) else None
            response = urlfetch.fetch(
                url=target_url,
                method=method,
                payload=payload,
                headers=self.request.headers,
                follow_redirects=False
            )

            # Pass through response headers to the client
            for header_name, header_value in response.headers.items():
                self.response.headers[header_name] = header_value

            # Fix internal redirects to point to your subdirectory instead of GCE's URL
            if "Location" in self.response.headers:
                old_location = self.response.headers["Location"]
                self.response.headers["Location"] = old_location.replace(
                    f"{GCE_FORUM_BASE}/forum",
                    "https://example.com/forum"  # Replace with your actual domain/subdirectory
                )

            # Pass through status code and content
            self.response.status_int = response.status_code
            self.response.write(response.content)

        except urlfetch.Error:
            self.response.status_int = 500
            self.response.write("Failed to connect to the forum server.")

    # Handle all common HTTP methods
    def get(self, path):
        self._proxy_request(path, urlfetch.GET)

    def post(self, path):
        self._proxy_request(path, urlfetch.POST)

    def put(self, path):
        self._proxy_request(path, urlfetch.PUT)

    def delete(self, path):
        self._proxy_request(path, urlfetch.DELETE)

# Define the route pattern for forum requests
app = webapp2.WSGIApplication([
    (r"/forum/(.*)", ForumProxyHandler),
], debug=False)  # Disable debug in production!

3. Critical Setup Notes #

• Network Access: Ensure your GCE instance allows incoming traffic from App Engine. If your GCE is in a VPC, configure serverless VPC access so App Engine can reach it. Alternatively, set firewall rules to allow traffic from App Engine's IP ranges.
• HTTPS: If your main GAE domain uses HTTPS, make sure your GCE forum either supports HTTPS or you configure the proxy to forward over HTTPS (update GCE_FORUM_BASE to use https://). Otherwise, browsers will throw mixed-content warnings.
• Static Assets: The proxy will handle static files (CSS, JS, images) automatically, but consider adding caching headers in your GCE forum's response to reduce redundant proxy requests.
• Session/Cookies: If your forum uses cookies, ensure the Domain attribute of the cookies is set to example.com (not your GCE's IP) so they work across the subdirectory.

4. Test It Out #

Deploy your updated GAE app, then visit https://example.com/forum—you should see your GCE-hosted forum load as if it's part of your main domain's subdirectory.

内容的提问来源于stack exchange，提问作者Occam