BUG/MINOR: stats: drop srv refcount on early release

Server refcount is used to protect from server deletion while dumping a
server instance, for stats dump on both CLI and HTTP applet. However,
dump can be aborted prematurely before reaching the end. In this case,
server refcount is never decremented.

This bug can cause an inconsistency on servers refcount, preventing them
to be deleted even after "del server" success.

To fix this, implement release handler for both stats CLI and HTTP
applet. Drop server reference if dump was interrupted during servers
loop.

This should be backported up to 2.6.

diff --git a/src/stats.c b/src/stats.c
index 05b73d9b0f9b2139237c88d22015238faadba4c3..a6541a264ab47921490bdefa2462093a65a209aa 100644 (file)
--- a/src/stats.c
+++ b/src/stats.c
@@ -5049,6 +5049,14 @@ static int stats_dump_json_schema_to_buffer(struct appctx *appctx)
        return 1;
 }
 
+static void http_stats_release(struct appctx *appctx)
+{
+       struct show_stat_ctx *ctx = appctx->svcctx;
+
+       if (ctx->px_st == STAT_PX_ST_SV)
+               srv_drop(ctx->obj2);
+}
+
 static int cli_parse_clear_counters(char **args, char *payload, struct appctx *appctx, void *private)
 {
        struct proxy *px;
@@ -5267,6 +5275,14 @@ static int cli_io_handler_dump_stat(struct appctx *appctx)
        return stats_dump_stat_to_buffer(appctx_sc(appctx), NULL, NULL);
 }
 
+static void cli_io_handler_release_stat(struct appctx *appctx)
+{
+       struct show_stat_ctx *ctx = appctx->svcctx;
+
+       if (ctx->px_st == STAT_PX_ST_SV)
+               srv_drop(ctx->obj2);
+}
+
 static int cli_io_handler_dump_json_schema(struct appctx *appctx)
 {
        trash_chunk = b_make(trash.area, trash.size, 0, 0);
@@ -5512,7 +5528,7 @@ REGISTER_PER_THREAD_FREE(free_trash_counters);
 static struct cli_kw_list cli_kws = {{ },{
        { { "clear", "counters",  NULL },      "clear counters [all]                    : clear max statistics counters (or all counters)", cli_parse_clear_counters, NULL, NULL },
        { { "show", "info",  NULL },           "show info [desc|json|typed|float]*      : report information about the running process",    cli_parse_show_info, cli_io_handler_dump_info, NULL },
-       { { "show", "stat",  NULL },           "show stat [desc|json|no-maint|typed|up]*: report counters for each proxy and server",       cli_parse_show_stat, cli_io_handler_dump_stat, NULL },
+       { { "show", "stat",  NULL },           "show stat [desc|json|no-maint|typed|up]*: report counters for each proxy and server",       cli_parse_show_stat, cli_io_handler_dump_stat, cli_io_handler_release_stat },
        { { "show", "schema",  "json", NULL }, "show schema json                        : report schema used for stats",                    NULL, cli_io_handler_dump_json_schema, NULL },
        {{},}
 }};
@@ -5526,7 +5542,7 @@ struct applet http_stats_applet = {
        .rcv_buf = appctx_htx_rcv_buf,
        .snd_buf = appctx_htx_snd_buf,
        .fastfwd = http_stats_fastfwd,
-       .release = NULL,
+       .release = http_stats_release,
 };
 
 /*