Built motion from commit 6a09e18b.|2.6.11

[motion2.git] / legacy-libs / grpc-cloned / deps / grpc / src / core / ext / filters / client_channel / resolving_lb_policy.h

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+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVING_LB_POLICY_H
+#define GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVING_LB_POLICY_H
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/ext/filters/client_channel/lb_policy.h"
+#include "src/core/ext/filters/client_channel/lb_policy_factory.h"
+#include "src/core/ext/filters/client_channel/resolver.h"
+#include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/channel/channel_stack.h"
+#include "src/core/lib/debug/trace.h"
+#include "src/core/lib/gprpp/inlined_vector.h"
+#include "src/core/lib/gprpp/orphanable.h"
+#include "src/core/lib/iomgr/call_combiner.h"
+#include "src/core/lib/iomgr/closure.h"
+#include "src/core/lib/iomgr/polling_entity.h"
+#include "src/core/lib/iomgr/pollset_set.h"
+#include "src/core/lib/transport/connectivity_state.h"
+#include "src/core/lib/transport/metadata_batch.h"
+
+namespace grpc_core {
+
+// An LB policy that wraps a resolver and a child LB policy to make use
+// of the addresses returned by the resolver.
+//
+// When used in the client_channel code, the resolver will attempt to
+// fetch the service config, and the child LB policy name and config
+// will be determined based on the service config.
+//
+// When used in an LB policy implementation that needs to do another
+// round of resolution before creating a child policy, the resolver does
+// not fetch the service config, and the caller must pre-determine the
+// child LB policy and config to use.
+class ResolvingLoadBalancingPolicy : public LoadBalancingPolicy {
+ public:
+  // Synchronous callback that takes the resolver result and sets
+  // lb_policy_name and lb_policy_config to point to the right data.
+  // Returns true if the service config has changed since the last result.
+  // If the returned service_config_error is not none and lb_policy_name is
+  // empty, it means that we don't have a valid service config to use, and we
+  // should set the channel to be in TRANSIENT_FAILURE.
+  typedef bool (*ProcessResolverResultCallback)(
+      void* user_data, const Resolver::Result& result,
+      const char** lb_policy_name,
+      RefCountedPtr<LoadBalancingPolicy::Config>* lb_policy_config,
+      grpc_error** service_config_error);
+  // If error is set when this returns, then construction failed, and
+  // the caller may not use the new object.
+  ResolvingLoadBalancingPolicy(
+      Args args, TraceFlag* tracer, UniquePtr<char> target_uri,
+      ProcessResolverResultCallback process_resolver_result,
+      void* process_resolver_result_user_data);
+
+  virtual const char* name() const override { return "resolving_lb"; }
+
+  // No-op -- should never get updates from the channel.
+  // TODO(roth): Need to support updating child LB policy's config for xds
+  // use case.
+  void UpdateLocked(UpdateArgs args) override {}
+
+  void ExitIdleLocked() override;
+
+  void ResetBackoffLocked() override;
+
+ private:
+  using TraceStringVector = InlinedVector<char*, 3>;
+
+  class ResolverResultHandler;
+  class ResolvingControlHelper;
+
+  ~ResolvingLoadBalancingPolicy();
+
+  void ShutdownLocked() override;
+
+  void OnResolverError(grpc_error* error);
+  void CreateOrUpdateLbPolicyLocked(
+      const char* lb_policy_name,
+      RefCountedPtr<LoadBalancingPolicy::Config> lb_policy_config,
+      Resolver::Result result, TraceStringVector* trace_strings);
+  OrphanablePtr<LoadBalancingPolicy> CreateLbPolicyLocked(
+      const char* lb_policy_name, const grpc_channel_args& args,
+      TraceStringVector* trace_strings);
+  void MaybeAddTraceMessagesForAddressChangesLocked(
+      bool resolution_contains_addresses, TraceStringVector* trace_strings);
+  void ConcatenateAndAddChannelTraceLocked(
+      TraceStringVector* trace_strings) const;
+  void OnResolverResultChangedLocked(Resolver::Result result);
+
+  // Passed in from caller at construction time.
+  TraceFlag* tracer_;
+  UniquePtr<char> target_uri_;
+  ProcessResolverResultCallback process_resolver_result_ = nullptr;
+  void* process_resolver_result_user_data_ = nullptr;
+  UniquePtr<char> child_policy_name_;
+  RefCountedPtr<LoadBalancingPolicy::Config> child_lb_config_;
+
+  // Resolver and associated state.
+  OrphanablePtr<Resolver> resolver_;
+  bool previous_resolution_contained_addresses_ = false;
+
+  // Child LB policy.
+  OrphanablePtr<LoadBalancingPolicy> lb_policy_;
+  OrphanablePtr<LoadBalancingPolicy> pending_lb_policy_;
+};
+
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVING_LB_POLICY_H */