MINOR: server: yield during "purge all servers"

Extend "purge all servers" handler to yield after 50 iterations. The
objective is to avoid to consume too much time under thread isolation.

When yielding must be performed, applet_have_more_data() is manually
called. This is necessary as the applet is not blocked on buffer output.
Without it, CLI handler won't be called again.

diff --git a/src/server.c b/src/server.c
index 2bab37dfd790add1363ce588d0abcf5548202b70..76b0d9bfa2d01027158aefca8d4557770d0b689f 100644 (file)
--- a/src/server.c
+++ b/src/server.c
@@ -7184,6 +7184,11 @@ static int cli_parse_purge_server(char **args, char *payload, struct appctx *app
 
 struct purge_all_servers_ctx {
        char *bename;
+
+       struct server *srv;
+       struct watcher srv_watch;
+
+       int c0, c1, c2;
 };
 
 /* Parser for "purge all servers" CLI command. Prepare context for performing
@@ -7195,6 +7200,7 @@ struct purge_all_servers_ctx {
 static int cli_parse_purge_all_servers(char **args, char *payload, struct appctx *appctx, void *private)
 {
        struct purge_all_servers_ctx *ctx = applet_reserve_svcctx(appctx, sizeof(*ctx));
+       struct proxy *be;
 
        if (!cli_has_level(appctx, ACCESS_LVL_ADMIN))
                return 1;
@@ -7202,25 +7208,33 @@ static int cli_parse_purge_all_servers(char **args, char *payload, struct appctx
        if (!*args[3])
                return cli_err(appctx, "A backend name is expected.\n");
 
-       /* Perform a first lookup to immediately detect a non existing backend. */
-       if (!proxy_be_by_name(args[3]))
+       be = proxy_be_by_name(args[3]);
+       if (!be)
                return cli_err(appctx, "No such backend.\n");
 
        ctx->bename = strdup(args[3]);
        if (!ctx->bename)
                return cli_err(appctx, "Out of memory.\n");
 
+       watcher_init(&ctx->srv_watch, &ctx->srv,
+                    offsetof(struct server, watcher_list));
+       watcher_attach(&ctx->srv_watch, proxy_first_server(be));
+
        return 0;
 }
 
-/* Handler for "purge all servers" CLI command. */
+/* Handler for "purge all servers" CLI command. Only runs over a fixed number
+ * of servers with yield in between.
+ *
+ * Returns 1 when all work is performed or 0 on yield.
+ */
 static int cli_io_handler_purge_all_server(struct appctx *appctx)
 {
        struct purge_all_servers_ctx *ctx = applet_reserve_svcctx(appctx, sizeof(*ctx));
        struct proxy *be;
-       struct server *srv, *srvtmp;
-       int c0 = 0, c1 = 0, c2 = 0;
-       int ret;
+       struct server *srv;
+       /* constant for max iterations before yield */
+       int ret, max_iter = 50;
 
        chunk_reset(&trash);
 
@@ -7233,31 +7247,44 @@ static int cli_io_handler_purge_all_server(struct appctx *appctx)
                goto out;
        }
 
-       list_for_each_entry_safe(srv, srvtmp, &be->servers, el_px) {
-               if (srv->flags & (SRV_F_NON_PURGEABLE | SRV_F_NAME_REFD)) {
-                       ++c2;
-                       continue;
+       while ((srv = ctx->srv)) {
+               if (!max_iter) {
+                       applet_have_more_data(appctx);
+                       ret = 0;
+                       goto out;
                }
 
-               if (!(srv->cur_admin & SRV_ADMF_MAINT))
-                       srv_adm_set_maint(srv);
-
-               if (srv_in_use(srv)) {
-                       if (!LIST_INLIST(&srv->el_alt))
-                               LIST_APPEND(&be->servers_purge, &srv->el_alt);
-                       srv->flags |= SRV_F_TO_PURGE;
-                       ha_notice("Server '%s/%s' flagged for deletion.\n", be->id, srv->id);
-                       ++c1;
+               if (srv->flags & (SRV_F_NON_PURGEABLE | SRV_F_NAME_REFD)) {
+                       ++ctx->c2;
                }
                else {
-                       srv_unregister(srv);
-                       ha_notice("Server '%s/%s' deleted.\n", be->id, srv->id);
-                       srv_drop(srv);
-                       ++c0;
+                       if (!(srv->cur_admin & SRV_ADMF_MAINT))
+                               srv_adm_set_maint(srv);
+
+                       if (srv_in_use(srv)) {
+                               if (!LIST_INLIST(&srv->el_alt))
+                                       LIST_APPEND(&be->servers_purge, &srv->el_alt);
+                               srv->flags |= SRV_F_TO_PURGE;
+                               ha_notice("Server '%s/%s' flagged for deletion.\n", be->id, srv->id);
+                               ++ctx->c1;
+                       }
+                       else {
+                               srv_unregister(srv);
+                               ha_notice("Server '%s/%s' deleted.\n", be->id, srv->id);
+                               srv_drop(srv);
+                               ++ctx->c0;
+                               srv = NULL;
+                       }
                }
+
+               --max_iter;
+
+               /* if srv_unregister() has been performed, watcher is already updated to next server */
+               if (srv)
+                       watcher_next(&ctx->srv_watch, proxy_next_server(srv));
        }
 
-       if (c1) {
+       if (ctx->c1) {
                if (!tick_isset(be->purge_task->expire))
                        be->purge_task->expire = tick_add(now_ms, 1000);
                task_queue(be->purge_task);
@@ -7265,12 +7292,12 @@ static int cli_io_handler_purge_all_server(struct appctx *appctx)
 
        chunk_printf(&trash, "Servers backend iteration performed: "
                             "%d removed, %d scheduled, %d skipped.\n",
-                            c0, c1, c2);
+                            ctx->c0, ctx->c1, ctx->c2);
        ret = 1;
 
  out:
-       if (applet_putchk(appctx, &trash) < 0)
-               ret = 0;
+       if (ret)
+               applet_putchk(appctx, &trash);
        thread_release();
        return ret;
 }
@@ -7279,6 +7306,7 @@ static void cli_release_purge_all_servers(struct appctx *appctx)
 {
        struct purge_all_servers_ctx *ctx = applet_reserve_svcctx(appctx, sizeof(*ctx));
        ha_free(&ctx->bename);
+       watcher_detach(&ctx->srv_watch);
 }
 
 /* Reset the statistics counters of a single server, invoked from the