Let’s break down why your Nginx caching for https://p.rmiao.top/proxy/bing/HPImageArchive.aspx?format=js&idx=0&n=2 isn’t working, even after ignoring Cache-Control and Set-Cookie headers. I’ve debugged dozens of similar issues, so let’s walk through targeted checks step by step.

1. Validate Your Core Cache Configuration #

First, double-check that your foundational caching setup is correct—this is where most folks stumble:

• You must define a proxy_cache_path in your http block to tell Nginx where to store cache files. If this is missing, caching won’t work at all:

  http {
      # Example: Creates a cache zone named "bing_cache" with 10MB metadata storage, max 10GB total cache, expires after 72h of inactivity
      proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=bing_cache:10m max_size=10g inactive=72h use_temp_path=off;
  }
  

• Make sure you’ve enabled caching in your target location block with proxy_cache bing_cache; (matching the zone name from proxy_cache_path).
• Watch out for accidental proxy_no_cache or proxy_cache_bypass rules that always evaluate to true—these will completely bypass the cache. For example, if you have proxy_no_cache $http_pragma;, check if the Pragma header is being sent with every request to your proxy URL.

2. Fix How You Override Upstream Cache Headers #

Ignoring Cache-Control and Set-Cookie isn’t enough on its own—you need to explicitly tell Nginx how long to cache the response. If you don’t set a TTL, Nginx won’t know when to keep the cache entry. Update your location block like this:

location /proxy/bing/ {
    proxy_cache bing_cache;
    # Ignore upstream headers that block caching
    proxy_ignore_headers Cache-Control Set-Cookie Expires;
    # Set explicit cache durations for successful responses
    proxy_cache_valid 200 4h;
    # Fallback cache duration for non-200 responses (optional but useful)
    proxy_cache_valid any 1h;
    # Optional: Tell client browsers to cache the response too
    add_header Cache-Control "public, max-age=14400";
    
    # Don't forget your proxy_pass directive to Bing
    proxy_pass https://www.bing.com/;
    proxy_pass_request_uri on;
}

3. Check for Hidden Upstream Headers Blocking Caching #

Even with proxy_ignore_headers, some upstream headers can still interfere. Use curl to fetch the raw Bing endpoint response and look for:

• Vary: *: This tells Nginx the response varies for every request, so it won’t cache by default. Fix this by either ignoring the Vary header or adding varying values to your cache key.
• X-Cache or other custom headers that might signal the upstream doesn’t allow caching.

Run this command to inspect upstream headers:

curl -I "https://www.bing.com/HPImageArchive.aspx?format=js&idx=0&n=2"

4. Ensure Your Cache Key Is Consistent #

Nginx’s default cache key ($scheme$proxy_host$request_uri) works for most cases, but subtle request differences (like reordered query params or hidden headers) can create unique keys for identical requests. Explicitly define a cache key to force consistency:

proxy_cache_key "$scheme$host$request_uri";

You can also verify if cache files are being created by checking the directory you set in proxy_cache_path (e.g., /var/cache/nginx). If you see files there after making requests, the cache is being written—if not, Nginx is skipping caching entirely.

5. Enable Cache Logging for Debugging #

Add cache-specific logging to get concrete data on why requests aren’t hitting the cache. Update your http or server block:

log_format cache_log '$remote_addr - $remote_user [$time_local] '
                    '"$request" $status $body_bytes_sent '
                    '"$http_referer" "$http_user_agent" '
                    'cache_status=$upstream_cache_status';

access_log /var/log/nginx/cache_access.log cache_log;

The $upstream_cache_status value will tell you exactly what’s happening:

• HIT: Request served from cache (success!)
• MISS: Request wasn’t in cache (should be cached after first hit)
• BYPASS: Cache was bypassed due to your configuration
• EXPIRED: Cache entry expired (adjust proxy_cache_valid if needed)

Check the logs in real-time with:

tail -f /var/log/nginx/cache_access.log

6. Verify Your Proxy Pass Setup #

Make sure your proxy_pass directive isn’t mangling the request. For example, if you’re using proxy_pass https://www.bing.com/HPImageArchive.aspx;, you might be stripping the query string accidentally. Use proxy_pass_request_uri on; to preserve the full request path and params, as shown in step 2.

内容的提问来源于stack exchange，提问作者Ryan Miao