in plugins allow 'null' name to clear txn strategy

Author: traeak

doc/admin-guide/plugins/header_rewrite.en.rst

@@ -1093,7 +1093,7 @@ set-next-hop-strategy
 Replaces/Sets the current next hop parent selection strategy with
 the matching strategy specified in `strategies.yaml`
 
-Setting to "" removes the current strategy which will fall back
+Setting to "null" removes the current strategy which will fall back
 to other methods (ie: parent.config or remap to url).
 
 set-redirect

doc/admin-guide/plugins/lua.en.rst

@@ -1958,8 +1958,8 @@ ts.http.set_next_hop_strategy
 **description** Looks for the named strategy and sets the current
 transaction to use that strategy.
 
-Use empty string to clear the strategy and fall back to parent.config
-or the remap to url.
+Use empty string or "null" to clear the strategy and fall back to
+parent.config or the remap to url.
 
 Here is an example:
 

doc/admin-guide/plugins/regex_remap.en.rst

@@ -143,7 +143,7 @@ remap.config. The following options are available ::
 
     @caseless                   - Make regular expressions case insensitive
     @lowercase_substitutions    - Turn on (enable) lower case substitutions
-		@strategy                   - Specify a strategy from strategies.yaml
+		@strategy                   - Specify a strategy from strategies.yaml. "null" or "" will clear the strategy.
 
 
 This can be useful to force a particular response for some URLs, e.g. ::

plugins/header_rewrite/operators.cc

@@ -1658,7 +1658,7 @@ OperatorSetNextHopStrategy::exec(const Resources &res) const
   _value.append_value(value, res);
 
   // Setting an empty strategy clears it for either parent.config or remap to
-  if (value.empty()) {
+  if ("null" == value || value.empty()) {
     Dbg(pi_dbg_ctl, "Clearing strategy");
     TSHttpTxnNextHopStrategySet(txnp, nullptr);
     return true;

plugins/lua/ts_lua_http.cc

@@ -565,7 +565,7 @@ ts_lua_http_set_next_hop_strategy(lua_State *L)
     size_t      name_len;
 
     name = luaL_checklstring(L, 1, &name_len);
-    if (0 == name_len) {
+    if (0 == name_len || "null" == std::string_view(name)) {
       Dbg(dbg_ctl, "Clearning strategy (use parent.config)");
       TSHttpTxnNextHopStrategySet(http_ctx->txnp, nullptr);
     } else {

plugins/regex_remap/regex_remap.cc

@@ -981,7 +981,7 @@ TSRemapDoRemap(void *ih, TSHttpTxn txnp, TSRemapRequestInfo *rri)
         TSHttpTxnDNSTimeoutSet(txnp, re->dns_timeout_option());
       }
       auto const &strat = re->strategy();
-      if (strat.empty()) {
+      if (strat.empty() || "null" == strat) {
         Dbg(dbg_ctl, "Clearing strategy (use parent.config)");
         TSHttpTxnNextHopStrategySet(txnp, nullptr);
       } else {

tests/gold_tests/pluginTest/strategies/strategies_plugins.test.py

@@ -106,7 +106,7 @@
         '/nh1 http://origin/path @strategy=',
         "/nh2 http://origin/path @strategy=nh0",
     ])
-ts.Disk.MakeConfigFile("strat.lua").AddLines(
+ts.Disk.MakeConfigFile("strategies.lua").AddLines(
     [
         'function do_remap()',
         ' local uri = ts.client_request.get_uri()',
@@ -168,9 +168,9 @@
         "map http://nh0_rr http://origin @strategy=nh0 @plugin=regex_remap.so @pparam=regex_remap.config",
         "map http://nh1_rr http://origin @strategy=nh1 @plugin=regex_remap.so @pparam=regex_remap.config",
         "map http://nh2_rr http://origin @plugin=regex_remap.so @pparam=regex_remap.config",
-        "map http://nh0_lua http://origin @strategy=nh0 @plugin=tslua.so @pparam=strat.lua",
-        "map http://nh1_lua http://origin @strategy=nh1 @plugin=tslua.so @pparam=strat.lua",
-        "map http://nh2_lua http://origin @plugin=tslua.so @pparam=strat.lua",
+        "map http://nh0_lua http://origin @strategy=nh0 @plugin=tslua.so @pparam=strategies.lua",
+        "map http://nh1_lua http://origin @strategy=nh1 @plugin=tslua.so @pparam=strategies.lua",
+        "map http://nh2_lua http://origin @plugin=tslua.so @pparam=strategies.lua",
     ])
 
 # Tests