config: reload: bin: Add opt-out option to ensure thread safety on hot reloading

include/fluent-bit/flb_config.h

@@ -257,6 +257,7 @@ struct flb_config {
 #endif /* FLB_HAVE_CHUNK_TRACE */
 
     int enable_hot_reload;
+    int ensure_thread_safety_on_hot_reloading;
 
     /* Co-routines */
     unsigned int coro_stack_size;
@@ -337,6 +338,7 @@ enum conf_type {
 #endif /* FLB_HAVE_CHUNK_TRACE */
 
 #define FLB_CONF_STR_HOT_RELOAD        "Hot_Reload"
+#define FLB_CONF_STR_HOT_RELOAD_ENSURE_THREAD_SAFETY  "Hot_Reload.Ensure_Thread_Safety"
 
 /* DNS */
 #define FLB_CONF_DNS_MODE              "dns.mode"

src/flb_config.c

@@ -177,6 +177,10 @@ struct flb_service_config service_configs[] = {
      FLB_CONF_TYPE_BOOL,
      offsetof(struct flb_config, enable_hot_reload)},
 
+    {FLB_CONF_STR_HOT_RELOAD_ENSURE_THREAD_SAFETY,
+     FLB_CONF_TYPE_BOOL,
+     offsetof(struct flb_config, ensure_thread_safety_on_hot_reloading)},
+
     {NULL, FLB_CONF_TYPE_OTHER, 0} /* end of array */
 };
 
@@ -268,6 +272,9 @@ struct flb_config *flb_config_init()
     config->sched_cap  = FLB_SCHED_CAP;
     config->sched_base = FLB_SCHED_BASE;
 
+    /* reload */
+    config->ensure_thread_safety_on_hot_reloading = FLB_TRUE;
+
 #ifdef FLB_HAVE_SQLDB
     mk_list_init(&config->sqldb_list);
 #endif

src/flb_reload.c

@@ -380,6 +380,10 @@ int flb_reload(flb_ctx_t *ctx, struct flb_cf *cf_opts)
         return -3;
     }
 
+    if (old_config->ensure_thread_safety_on_hot_reloading) {
+        old_config->grace = -1;
+    }
+
     /* Normally, we should create a service section before using this cf
      * context. However, this context of config format will be used
      * for copying contents from other one. So, we just need to create

src/fluent-bit.c

@@ -150,6 +150,7 @@ static void flb_help(int rc, struct flb_config *config)
     print_opt("-q, --quiet", "quiet mode");
     print_opt("-S, --sosreport", "support report for Enterprise customers");
     print_opt("-Y, --enable-hot-reload", "enable for hot reloading");
+    print_opt("-W, --disable-thread-safety-on-hot-reloading", "disable thread safety on hot reloading");
     print_opt("-V, --version", "show version number");
     print_opt("-h, --help", "print this help");
 
@@ -804,6 +805,7 @@ int flb_main(int argc, char **argv)
 #ifdef FLB_HAVE_CHUNK_TRACE
         { "enable-chunk-trace",    no_argument, NULL, 'Z' },
 #endif
+        { "disable-thread-safety-on-hot-reload", no_argument, NULL, 'W' },
         { NULL, 0, NULL, 0 }
     };
 
@@ -830,7 +832,7 @@ int flb_main(int argc, char **argv)
     /* Parse the command line options */
     while ((opt = getopt_long(argc, argv,
                               "b:c:dDf:C:i:m:o:R:F:p:e:"
-                              "t:T:l:vw:qVhJL:HP:s:SYZ",
+                              "t:T:l:vw:qVhJL:HP:s:SWYZ",
                               long_opts, NULL)) != -1) {
 
         switch (opt) {
@@ -988,6 +990,10 @@ int flb_main(int argc, char **argv)
         case 'Y':
             flb_cf_section_property_add(cf_opts, service->properties, FLB_CONF_STR_HOT_RELOAD, 0, "on", 0);
             break;
+        case 'W':
+            flb_cf_section_property_add(cf_opts, service->properties,
+                                        FLB_CONF_STR_HOT_RELOAD_ENSURE_THREAD_SAFETY, 0, "off", 0);
+            break;
 #ifdef FLB_HAVE_CHUNK_TRACE
         case 'Z':
             flb_cf_section_property_add(cf_opts, service->properties, FLB_CONF_STR_ENABLE_CHUNK_TRACE, 0, "on", 0);