filter_lua: support enable_flb_null

Signed-off-by: Takahiro Yamashita <[email protected]>

plugins/filter_lua/lua.c

@@ -61,6 +61,10 @@ static int cb_lua_init(struct flb_filter_instance *f_ins,
     }
     ctx->lua = lj;
 
+    if (ctx->enable_flb_null) {
+        flb_lua_enable_flb_null(lj->state);
+    }
+
     /* Lua script source code */
     if (ctx->code) {
         ret = flb_luajit_load_buffer(ctx->lua,
@@ -683,6 +687,13 @@ static struct flb_config_map config_map[] = {
      "If enabled, Fluent-bit will pass the timestamp as a Lua table "
      "with keys \"sec\" for seconds since epoch and \"nsec\" for nanoseconds."
     },
+    {
+     FLB_CONFIG_MAP_BOOL, "enable_flb_null", "false",
+     0, FLB_TRUE, offsetof(struct lua_filter, enable_flb_null),
+     "If enabled, null will be converted to flb_null in Lua. "
+     "It is useful to prevent removing key/value "
+     "since nil is a special value to remove key value from map in Lua."
+    },
 
     {0}
 };

plugins/filter_lua/lua_config.h

@@ -35,6 +35,7 @@ struct lua_filter {
     flb_sds_t buffer;                 /* json dec buffer */
     int    protected_mode;            /* exec lua function in protected mode */
     int    time_as_table;             /* timestamp as a Lua table */
+    int    enable_flb_null;           /* Use flb_null in Lua */
     struct flb_lua_l2c_config l2cc;   /* lua -> C config */
     struct flb_luajit *lua;           /* state context   */
     struct flb_filter_instance *ins;  /* filter instance */