bugfix: balancer keepalive connections were never reused with proxy_bind.

When proxy_bind sets the local address and balancer_by_lua* enables
keepalive without calling balancer.bind_to_local_addr(), pc->local holds
the proxy_bind address while bp->local is NULL. free_peer hashed the
saved connection with bp->local, but get_cached_item looks it up with
pc->local, so the lookup never matched: every connection was saved,
never reused, and closed when it idled out.

Hash with pc->local, which is the address the connection was bound to
and the one stored in item->local_sockaddr.

Since nginx 1.29.7 the "keepalive" directive is enabled by default and
its cache takes the connections before the Lua pool, so the test turns
it off with "keepalive 0" on those versions.

Author: setnicka

src/ngx_http_lua_balancer.c

@@ -660,7 +660,7 @@ ngx_http_lua_balancer_free_peer(ngx_peer_connection_t *pc, void *data,
             ngx_queue_insert_head(&lscf->balancer.cache, q);
             hash = ngx_http_lua_balancer_calc_hash(host,
                                                    bp->sockaddr, bp->socklen,
-                                                   bp->local);
+                                                   pc->local);
             item->hash = hash;
             hash %= lscf->balancer.bucket_cnt;
             ngx_queue_insert_head(&lscf->balancer.buckets[hash], &item->hnode);

t/188-balancer_keepalive_pool_max_retry.t

@@ -6,7 +6,7 @@ use Cwd qw(cwd);
 log_level('info');
 repeat_each(1);
 
-plan tests => repeat_each() * (blocks() * 6 - 1);
+plan tests => repeat_each() * (blocks() * 6 + 5);
 
 my $pwd = cwd();
 
@@ -214,3 +214,45 @@ qr/\A\Q$first\E(?:\Q$extra\E)?\z/
 --- no_error_log
 retry storm guard
 [alert]
+
+
+
+=== TEST 3: reuse keepalive connections per proxy_bind address
+proxy_bind sets the local address of the upstream connection, while
+balancer.bind_to_local_addr() is not called.
+--- http_config eval
+# Since nginx version 1.29.7, the "keepalive" directive is enabled by
+# default and its cache takes the connections before the Lua pool sees them.
+my $keepalive = $Test::Nginx::Util::NginxVersion >= 1.029007 ?
+                "keepalive 0;" : "";
+
+qq{
+    upstream backend {
+        server 0.0.0.1;
+        $keepalive
+        balancer_by_lua_block {
+            local b = require "ngx.balancer"
+            assert(b.set_current_peer("127.0.0.1", \$TEST_NGINX_RAND_PORT_1))
+            assert(b.enable_keepalive())
+        }
+    }
+
+    server {
+        listen 127.0.0.1:\$TEST_NGINX_RAND_PORT_1;
+        return 200 "\$remote_addr \$connection_requests";
+    }
+}
+--- config
+    location = /t {
+        proxy_bind $arg_bind;
+        proxy_pass http://backend;
+        proxy_http_version 1.1;
+        proxy_set_header Connection "";
+    }
+--- request eval
+["GET /t?bind=127.0.0.1", "GET /t?bind=127.0.0.2",
+ "GET /t?bind=127.0.0.1", "GET /t?bind=127.0.0.2"]
+--- response_body eval
+["127.0.0.1 1", "127.0.0.2 1", "127.0.0.1 2", "127.0.0.2 2"]
+--- no_error_log
+[error]