[PATCH] reset r->cache->valid_sec for following the redirect

[Sangdeuk Kwon]

# HG changeset patch
# User Sangdeuk Kwon <dark264sh at gmail.com>
# Date 1557288704 -32400
#      Wed May 08 13:11:44 2019 +0900
# Node ID c4e1be885640a8302dcbf97162b3cbdc21710a84
# Parent  16a1adadf43751f59257ba419f6bacd530dd19d3
reset r->cache->valid_sec for following the redirect

this config:

http {
    proxy_intercept_errors on;

    proxy_cache_path /cache0 levels=1:2 keys_zone=STATIC:10m max_size=10g
inactive=60m use_temp_path=off;
    proxy_cache_key "$host$uri";
    proxy_cache STATIC;

    upstream up_servers {
        server 127.0.0.2:8080;
    }

    server {
        listen 127.0.0.1:8000;

        location / {
            proxy_pass http://up_servers;
            proxy_set_header Host $host;
            proxy_http_version 1.1;
            add_header X-Cached $upstream_cache_status;

            proxy_intercept_errors on;
            error_page 301 302 303 307 308 = @handle_redirects;
        }

        location @handle_redirects {
            set $orig_loc $upstream_http_location;
            proxy_pass $orig_loc;
        }
    }
}

When origin server does not send cache time header (max-age or expires),
nginx can follow the redirect with location header.
But, if origin server sends cache time header,
nginx can't follow the redirect and nginx send 302 response without
location header to a client.
So the client also can't follow the redirect because of absenting location
header.

diff -r 16a1adadf437 -r c4e1be885640 src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c  Wed Apr 24 16:38:56 2019 +0300
+++ b/src/http/ngx_http_upstream.c  Wed May 08 13:11:44 2019 +0900
@@ -2645,6 +2645,15 @@
                     if (valid) {
                         r->cache->error = status;
                     }
+
+                    if (status == NGX_HTTP_MOVED_PERMANENTLY
+                        || status == NGX_HTTP_MOVED_TEMPORARILY
+                        || status == NGX_HTTP_SEE_OTHER
+                        || status == NGX_HTTP_TEMPORARY_REDIRECT
+                        || status == NGX_HTTP_PERMANENT_REDIRECT)
+                    {
+                        r->cache->valid_sec = 0;
+                    }
                 }

                 ngx_http_file_cache_free(r->cache, u->pipe->temp_file);
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