Merge pull request #19936 from AspirinSJL/const_param

Change xds args to const

src/core/ext/filters/client_channel/lb_policy/xds/xds.cc

@@ -575,7 +575,7 @@ class XdsLb : public LoadBalancingPolicy {
   OrphanablePtr<LbChannelState> pending_lb_chand_;
 
   // Timeout in milliseconds for the LB call. 0 means no deadline.
-  int lb_call_timeout_ms_ = 0;
+  const grpc_millis lb_call_timeout_ms_;
 
   // Whether the checks for fallback at startup are ALL pending. There are
   // several cases where this can be reset:
@@ -587,7 +587,7 @@ class XdsLb : public LoadBalancingPolicy {
   bool fallback_at_startup_checks_pending_ = false;
   // Timeout in milliseconds for before using fallback backend addresses.
   // 0 means not using fallback.
-  int lb_fallback_timeout_ms_ = 0;
+  const grpc_millis lb_fallback_timeout_ms_;
   // The backend addresses from the resolver.
   ServerAddressList fallback_backend_addresses_;
   // Fallback timer.
@@ -1705,7 +1705,13 @@ grpc_channel_args* BuildBalancerChannelArgs(const grpc_channel_args* args) {
 //
 
 XdsLb::XdsLb(Args args)
-    : LoadBalancingPolicy(std::move(args)), locality_map_(this) {
+    : LoadBalancingPolicy(std::move(args)),
+      lb_call_timeout_ms_(grpc_channel_args_find_integer(
+          args.args, GRPC_ARG_GRPCLB_CALL_TIMEOUT_MS, {0, 0, INT_MAX})),
+      lb_fallback_timeout_ms_(grpc_channel_args_find_integer(
+          args.args, GRPC_ARG_XDS_FALLBACK_TIMEOUT_MS,
+          {GRPC_XDS_DEFAULT_FALLBACK_TIMEOUT_MS, 0, INT_MAX})),
+      locality_map_(this) {
   // Record server name.
   const grpc_arg* arg = grpc_channel_args_find(args.args, GRPC_ARG_SERVER_URI);
   const char* server_uri = grpc_channel_arg_get_string(arg);
@@ -1719,13 +1725,6 @@ XdsLb::XdsLb(Args args)
             server_name_);
   }
   grpc_uri_destroy(uri);
-  // Record LB call timeout.
-  arg = grpc_channel_args_find(args.args, GRPC_ARG_GRPCLB_CALL_TIMEOUT_MS);
-  lb_call_timeout_ms_ = grpc_channel_arg_get_integer(arg, {0, 0, INT_MAX});
-  // Record fallback timeout.
-  arg = grpc_channel_args_find(args.args, GRPC_ARG_XDS_FALLBACK_TIMEOUT_MS);
-  lb_fallback_timeout_ms_ = grpc_channel_arg_get_integer(
-      arg, {GRPC_XDS_DEFAULT_FALLBACK_TIMEOUT_MS, 0, INT_MAX});
 }
 
 XdsLb::~XdsLb() {

src/core/lib/channel/channel_args.cc

@@ -257,6 +257,13 @@ int grpc_channel_arg_get_integer(const grpc_arg* arg,
   return arg->value.integer;
 }
 
+int grpc_channel_args_find_integer(const grpc_channel_args* args,
+                                   const char* name,
+                                   const grpc_integer_options options) {
+  const grpc_arg* arg = grpc_channel_args_find(args, name);
+  return grpc_channel_arg_get_integer(arg, options);
+}
+
 char* grpc_channel_arg_get_string(const grpc_arg* arg) {
   if (arg == nullptr) return nullptr;
   if (arg->type != GRPC_ARG_STRING) {
@@ -266,6 +273,12 @@ char* grpc_channel_arg_get_string(const grpc_arg* arg) {
   return arg->value.string;
 }
 
+char* grpc_channel_args_find_string(const grpc_channel_args* args,
+                                    const char* name) {
+  const grpc_arg* arg = grpc_channel_args_find(args, name);
+  return grpc_channel_arg_get_string(arg);
+}
+
 bool grpc_channel_arg_get_bool(const grpc_arg* arg, bool default_value) {
   if (arg == nullptr) return default_value;
   if (arg->type != GRPC_ARG_INTEGER) {
@@ -284,6 +297,12 @@ bool grpc_channel_arg_get_bool(const grpc_arg* arg, bool default_value) {
   }
 }
 
+bool grpc_channel_args_find_bool(const grpc_channel_args* args,
+                                 const char* name, bool default_value) {
+  const grpc_arg* arg = grpc_channel_args_find(args, name);
+  return grpc_channel_arg_get_bool(arg, default_value);
+}
+
 bool grpc_channel_args_want_minimal_stack(const grpc_channel_args* args) {
   return grpc_channel_arg_get_bool(
       grpc_channel_args_find(args, GRPC_ARG_MINIMAL_STACK), false);

src/core/lib/channel/channel_args.h

@@ -73,16 +73,30 @@ typedef struct grpc_integer_options {
   int max_value;
 } grpc_integer_options;
 
-/** Returns the value of \a arg, subject to the contraints in \a options. */
+/** Returns the value of \a arg, subject to the constraints in \a options. */
 int grpc_channel_arg_get_integer(const grpc_arg* arg,
                                  const grpc_integer_options options);
+/** Similar to the above, but needs to find the arg from \a args by the name
+ * first. */
+int grpc_channel_args_find_integer(const grpc_channel_args* args,
+                                   const char* name,
+                                   const grpc_integer_options options);
 
 /** Returns the value of \a arg if \a arg is of type GRPC_ARG_STRING.
     Otherwise, emits a warning log, and returns nullptr.
     If arg is nullptr, returns nullptr, and does not emit a warning. */
 char* grpc_channel_arg_get_string(const grpc_arg* arg);
-
+/** Similar to the above, but needs to find the arg from \a args by the name
+ * first. */
+char* grpc_channel_args_find_string(const grpc_channel_args* args,
+                                    const char* name);
+/** If \a arg is of type GRPC_ARG_INTEGER, returns true if it's non-zero.
+ * Returns \a default_value if \a arg is of other types. */
 bool grpc_channel_arg_get_bool(const grpc_arg* arg, bool default_value);
+/** Similar to the above, but needs to find the arg from \a args by the name
+ * first. */
+bool grpc_channel_args_find_bool(const grpc_channel_args* args,
+                                 const char* name, bool default_value);
 
 // Helpers for creating channel args.
 grpc_arg grpc_channel_arg_string_create(char* name, char* value);