CPP-885 Fix filtering load balancing policies (#16)

Also, the load balancing policy chains were being duplicated in
`RequestProcessor` initialization code.

Author: mpenick

CHANGELOG.md

@@ -18,6 +18,7 @@ Features
 
 Bug Fixes
 --------
+* [CPP-885] Fix filtering load balancing policies (and remove duplicated load balancing policy chain)
 * [CPP-884] Deprecate pending request timeouts metric and remove unused internal logic
 * [CPP-871] Fix SSL cleanup on error conditions in mockssandra
 * [CPP-855] Fix C\*/DSE protocol lowering attempts when `cass_cluster_set_use_beta_protocol_version()` is true

src/execution_profile.hpp

@@ -44,9 +44,7 @@ class ExecutionProfile : public Allocated {
       , serial_consistency_(CASS_CONSISTENCY_UNKNOWN)
       , latency_aware_routing_(false)
       , token_aware_routing_(true)
-      , token_aware_routing_shuffle_replicas_(true)
-      , load_balancing_policy_(NULL)
-      , retry_policy_(NULL) {}
+      , token_aware_routing_shuffle_replicas_(true) {}
 
   uint64_t request_timeout_ms() const { return request_timeout_ms_; }
 
@@ -102,13 +100,27 @@ class ExecutionProfile : public Allocated {
 
   const LoadBalancingPolicy::Ptr& load_balancing_policy() const { return load_balancing_policy_; }
 
-  void set_load_balancing_policy(LoadBalancingPolicy* lbp) { load_balancing_policy_.reset(lbp); }
+  void set_load_balancing_policy(LoadBalancingPolicy* lbp) {
+    base_load_balancing_policy_.reset(lbp);
+  }
+
+  /**
+   * Use another profile's load balancing policy. This is used to override profiles that don't have
+   * policies of their own with the default profile's load balancing policy.
+   *
+   * @param lbp The other profile's load balancing policy chain.
+   */
+  void use_load_balancing_policy(const LoadBalancingPolicy::Ptr& lbp) {
+    assert(!base_load_balancing_policy_ &&
+           "The profile should have a no base load balancing policy");
+    load_balancing_policy_ = lbp;
+  }
 
   void build_load_balancing_policy() {
     // The base LBP can be augmented by special wrappers (whitelist,
     // token aware, latency aware)
-    if (load_balancing_policy_) {
-      LoadBalancingPolicy* chain = load_balancing_policy_->new_instance();
+    if (base_load_balancing_policy_) {
+      LoadBalancingPolicy* chain = base_load_balancing_policy_->new_instance();
 
       if (!blacklist_.empty()) {
         chain = new BlacklistPolicy(chain, blacklist_);
@@ -159,6 +171,7 @@ class ExecutionProfile : public Allocated {
   ContactPointList whitelist_;
   DcList whitelist_dc_;
   LoadBalancingPolicy::Ptr load_balancing_policy_;
+  LoadBalancingPolicy::Ptr base_load_balancing_policy_;
   RetryPolicy::Ptr retry_policy_;
   SpeculativeExecutionPolicy::Ptr speculative_execution_policy_;
 };

src/list_policy.cpp

@@ -57,8 +57,8 @@ void ListPolicy::on_host_added(const Host::Ptr& host) {
   }
 }
 
-void ListPolicy::on_host_removed(const Host::Ptr& host) {
+void ListPolicy::on_host_up(const Host::Ptr& host) {
   if (is_valid_host(host)) {
-    child_policy_->on_host_removed(host);
+    child_policy_->on_host_up(host);
   }
 }

src/list_policy.hpp

@@ -39,7 +39,7 @@ class ListPolicy : public ChainedLoadBalancingPolicy {
                                     const TokenMap* token_map);
 
   virtual void on_host_added(const Host::Ptr& host);
-  virtual void on_host_removed(const Host::Ptr& host);
+  virtual void on_host_up(const Host::Ptr& host);
 
   virtual ListPolicy* new_instance() = 0;
 

src/request_processor.cpp

@@ -204,7 +204,7 @@ RequestProcessor::RequestProcessor(RequestProcessorListener* listener, EventLoop
       LOG_TRACE("Built load balancing policy for '%s' execution profile", it->first.c_str());
       load_balancing_policies_.push_back(load_balancing_policy);
     } else {
-      it->second.set_load_balancing_policy(default_profile_.load_balancing_policy().get());
+      it->second.use_load_balancing_policy(default_profile_.load_balancing_policy());
     }
   }