filter_lua: support nil_str to replace null value

Signed-off-by: Takahiro Yamashita <[email protected]>
fluent · Aug 6, 2023 · 88ed925 · 88ed925
1 parent 410fbac
commit 88ed925
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Showing 3 changed files with 18 additions and 1 deletion.
diff --git a/plugins/filter_lua/lua.c b/plugins/filter_lua/lua.c
@@ -503,7 +503,7 @@ static int cb_lua_filter(const void *data, size_t bytes,
             lua_pushnumber(ctx->lua->state, ts);
         }
 
-        flb_lua_pushmsgpack(ctx->lua->state, log_event.body);
+        flb_lua_pushmsgpack(ctx->lua->state, log_event.body, ctx->l2cc.l2c_nil_str);
         if (ctx->protected_mode) {
             ret = lua_pcall(ctx->lua->state, 3, 3, 0);
             if (ret != 0) {
@@ -671,6 +671,13 @@ static struct flb_config_map config_map[] = {
      "If these keys are matched, the fields are converted to array. "
      "If more than one key, delimit by space."
     },
+    {
+     FLB_CONFIG_MAP_STR, "nil_str", NULL,
+     0, FLB_TRUE, offsetof(struct lua_filter, nil_str),
+     "If set, nil value will be replaced by this string in Lua. "
+     "It is to prevent remove nil value from record "
+     "since nil value is to delete key/value from associative array in Lua."
+    },
     {
      FLB_CONFIG_MAP_BOOL, "protected_mode", "true",
      0, FLB_TRUE, offsetof(struct lua_filter, protected_mode),

diff --git a/plugins/filter_lua/lua_config.c b/plugins/filter_lua/lua_config.c
@@ -127,6 +127,12 @@ struct lua_filter *lua_config_create(struct flb_filter_instance *ins,
     }
 
     lf->l2cc.l2c_types_num = 0;
+    if (lf->nil_str) {
+        lf->l2cc.l2c_nil_str = flb_sds_create(lf->nil_str);
+    }
+    else {
+        lf->l2cc.l2c_nil_str = NULL;
+    }
     tmp = flb_filter_get_property("type_int_key", ins);
     if (tmp) {
         split = flb_utils_split(tmp, ' ', FLB_LUA_L2C_TYPES_NUM_MAX);
@@ -189,6 +195,9 @@ void lua_config_destroy(struct lua_filter *lf)
     if (lf->buffer) {
         flb_sds_destroy(lf->buffer);
     }
+    if (lf->l2cc.l2c_nil_str) {
+        flb_sds_destroy(lf->l2cc.l2c_nil_str);
+    }
 
     mk_list_foreach_safe(head, tmp_list, &lf->l2cc.l2c_types) {
         l2c = mk_list_entry(head, struct flb_lua_l2c_type, _head);

diff --git a/plugins/filter_lua/lua_config.h b/plugins/filter_lua/lua_config.h
@@ -33,6 +33,7 @@ struct lua_filter {
     flb_sds_t script;                 /* lua script path */
     flb_sds_t call;                   /* function name   */
     flb_sds_t buffer;                 /* json dec buffer */
+    flb_sds_t nil_str;                /* The string to represent nil value in Lua */
     int    protected_mode;            /* exec lua function in protected mode */
     int    time_as_table;             /* timestamp as a Lua table */
     struct flb_lua_l2c_config l2cc;   /* lua -> C config */