s3: Cache results of finding printer names

With hundreds of printers or on a slow machine, this can become expensive.

Problem reported and patch sponsored by DESY, Hamburg (www.desy.de)

diff --git a/source3/rpc_server/srv_spoolss_nt.c b/source3/rpc_server/srv_spoolss_nt.c
index 5df20d4f08341523e688e74ffdbe3538c76e4f25..4e971227360c146673d4b3a7db589fa1995c2740 100644 (file)
--- a/source3/rpc_server/srv_spoolss_nt.c
+++ b/source3/rpc_server/srv_spoolss_nt.c
@@ -470,6 +470,14 @@ static bool set_printer_hnd_name(TALLOC_CTX *mem_ctx,
        struct spoolss_PrinterInfo2 *info2 = NULL;
        WERROR result;
 
+       /*
+        * Hopefully nobody names his printers like this. Maybe \ or ,
+        * are illegal in printer names even?
+        */
+       const char printer_not_found[] = "Printer \\, !@#$%^&*( not found";
+       char *cache_key;
+       char *tmp;
+
        DEBUG(4,("Setting printer name=%s (len=%lu)\n", handlename,
                (unsigned long)strlen(handlename)));
 
@@ -509,6 +517,27 @@ static bool set_printer_hnd_name(TALLOC_CTX *mem_ctx,
                found = true;
        }
 
+       /*
+        * With hundreds of printers, the "for" loop iterating all
+        * shares can be quite expensive, as it is done on every
+        * OpenPrinter. The loop maps "aprinter" to "sname", the
+        * result of which we cache in gencache.
+        */
+
+       cache_key = talloc_asprintf(talloc_tos(), "PRINTERNAME/%s",
+                                   aprinter);
+       if ((cache_key != NULL) && gencache_get(cache_key, &tmp, NULL)) {
+
+               found = (strcmp(tmp, printer_not_found) != 0);
+               if (!found) {
+                       DEBUG(4, ("Printer %s not found\n", aprinter));
+                       SAFE_FREE(tmp);
+                       return false;
+               }
+               fstrcpy(sname, tmp);
+               SAFE_FREE(tmp);
+       }
+
        /* Search all sharenames first as this is easier than pulling
           the printer_info_2 off of disk. Don't use find_service() since
           that calls out to map_username() */
@@ -569,10 +598,20 @@ static bool set_printer_hnd_name(TALLOC_CTX *mem_ctx,
        }
 
        if ( !found ) {
+               if (cache_key != NULL) {
+                       gencache_set(cache_key, printer_not_found,
+                                    time(NULL)+300);
+                       TALLOC_FREE(cache_key);
+               }
                DEBUGADD(4,("Printer not found\n"));
                return false;
        }
 
+       if (cache_key != NULL) {
+               gencache_set(cache_key, sname, time(NULL)+300);
+               TALLOC_FREE(cache_key);
+       }
+
        DEBUGADD(4,("set_printer_hnd_name: Printer found: %s -> %s\n", aprinter, sname));
 
        fstrcpy(Printer->sharename, sname);