xds: reimplement EDS LB policy with downstream LB config generations …

…that migrate to hierarchical LB tree codepath (#7391)

Implemented the new EDS LB policy, which generates a LB config for instantiating a hierarchical load balancing subtree. The subtree includes downstream LB policies: 

- priority LB policy, which load balances individual priorities separately
- weighted-target LB policy, which load balances individual localities within the same priority separately
- lrs LB policy, which applies load recording that aggregates load stats for each locality
- leaf LB policy (round_robin)

The EDS LB policy is the place that receives endpoint information from traffic director and organizes the data into a model for hierarchical load balancing for the cluster.

xds/src/main/java/io/grpc/xds/EdsLoadBalancerProvider.java

@@ -17,23 +17,17 @@
 package io.grpc.xds;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static io.grpc.xds.XdsLbPolicies.WEIGHTED_TARGET_POLICY_NAME;
 
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Objects;
-import com.google.common.collect.ImmutableMap;
 import io.grpc.Internal;
 import io.grpc.LoadBalancer;
 import io.grpc.LoadBalancer.Helper;
 import io.grpc.LoadBalancerProvider;
 import io.grpc.LoadBalancerRegistry;
 import io.grpc.NameResolver.ConfigOrError;
-import io.grpc.Status;
-import io.grpc.internal.JsonUtil;
-import io.grpc.internal.ServiceConfigUtil;
-import io.grpc.internal.ServiceConfigUtil.LbConfig;
 import io.grpc.internal.ServiceConfigUtil.PolicySelection;
-import java.util.Collections;
-import java.util.List;
 import java.util.Map;
 import javax.annotation.Nullable;
 
@@ -68,60 +62,43 @@ public LoadBalancer newLoadBalancer(Helper helper) {
   @Override
   public ConfigOrError parseLoadBalancingPolicyConfig(
       Map<String, ?> rawLoadBalancingPolicyConfig) {
-    LoadBalancerRegistry registry = LoadBalancerRegistry.getDefaultRegistry();
-    try {
-      String cluster = JsonUtil.getString(rawLoadBalancingPolicyConfig, "cluster");
-      if (cluster == null) {
-        return ConfigOrError.fromError(Status.INTERNAL.withDescription("Cluster name required"));
-      }
-      String edsServiceName = JsonUtil.getString(rawLoadBalancingPolicyConfig, "edsServiceName");
-      String lrsServerName =
-          JsonUtil.getString(rawLoadBalancingPolicyConfig, "lrsLoadReportingServerName");
-
-      // TODO(chengyuanzhang): figure out locality_picking_policy parsing and its default value.
-
-      LbConfig roundRobinConfig = new LbConfig("round_robin", ImmutableMap.<String, Object>of());
-      List<LbConfig> endpointPickingPolicy =
-          ServiceConfigUtil
-              .unwrapLoadBalancingConfigList(
-                  JsonUtil.getListOfObjects(
-                      rawLoadBalancingPolicyConfig, "endpointPickingPolicy"));
-      if (endpointPickingPolicy == null || endpointPickingPolicy.isEmpty()) {
-        endpointPickingPolicy = Collections.singletonList(roundRobinConfig);
-      }
-      ConfigOrError endpointPickingConfigOrError =
-          ServiceConfigUtil.selectLbPolicyFromList(endpointPickingPolicy, registry);
-      if (endpointPickingConfigOrError.getError() != null) {
-        return endpointPickingConfigOrError;
-      }
-      PolicySelection endpointPickingSelection =
-          (PolicySelection) endpointPickingConfigOrError.getConfig();
-      return ConfigOrError.fromConfig(
-          new EdsConfig(cluster, edsServiceName, lrsServerName, endpointPickingSelection));
-    } catch (RuntimeException e) {
-      return ConfigOrError.fromError(
-          Status.fromThrowable(e).withDescription(
-              "Failed to parse EDS LB config: " + rawLoadBalancingPolicyConfig));
-    }
+    throw new UnsupportedOperationException("not supported as top-level LB policy");
   }
 
   static final class EdsConfig {
-
     final String clusterName;
     @Nullable
     final String edsServiceName;
     @Nullable
     final String lrsServerName;
+    final PolicySelection localityPickingPolicy;
     final PolicySelection endpointPickingPolicy;
 
+    // TODO(chengyuanzhang): delete me.
+    EdsConfig(
+        String clusterName,
+        @Nullable String edsServiceName,
+        @Nullable String lrsServerName,
+        PolicySelection endpointPickingPolicy) {
+      this.clusterName = checkNotNull(clusterName, "clusterName");
+      this.edsServiceName = edsServiceName;
+      this.lrsServerName = lrsServerName;
+      this.endpointPickingPolicy = checkNotNull(endpointPickingPolicy, "endpointPickingPolicy");
+      LoadBalancerProvider provider =
+          LoadBalancerRegistry.getDefaultRegistry().getProvider(WEIGHTED_TARGET_POLICY_NAME);
+      localityPickingPolicy = new PolicySelection(provider, null, null);
+    }
+
     EdsConfig(
         String clusterName,
         @Nullable String edsServiceName,
         @Nullable String lrsServerName,
+        PolicySelection localityPickingPolicy,
         PolicySelection endpointPickingPolicy) {
       this.clusterName = checkNotNull(clusterName, "clusterName");
       this.edsServiceName = edsServiceName;
       this.lrsServerName = lrsServerName;
+      this.localityPickingPolicy = checkNotNull(localityPickingPolicy, "localityPickingPolicy");
       this.endpointPickingPolicy = checkNotNull(endpointPickingPolicy, "endpointPickingPolicy");
     }
 
@@ -131,6 +108,7 @@ public String toString() {
           .add("clusterName", clusterName)
           .add("edsServiceName", edsServiceName)
           .add("lrsServerName", lrsServerName)
+          .add("localityPickingPolicy", localityPickingPolicy)
           .add("endpointPickingPolicy", endpointPickingPolicy)
           .toString();
     }
@@ -144,6 +122,7 @@ public boolean equals(Object obj) {
       return Objects.equal(this.clusterName, that.clusterName)
           && Objects.equal(this.edsServiceName, that.edsServiceName)
           && Objects.equal(this.lrsServerName, that.lrsServerName)
+          && Objects.equal(this.localityPickingPolicy, that.localityPickingPolicy)
           && Objects.equal(this.endpointPickingPolicy, that.endpointPickingPolicy);
     }
 
@@ -154,6 +133,7 @@ public int hashCode() {
               clusterName,
               edsServiceName,
               lrsServerName,
+              localityPickingPolicy,
               endpointPickingPolicy);
     }
   }

xds/src/main/java/io/grpc/xds/PriorityLoadBalancerProvider.java

@@ -20,6 +20,7 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.common.base.MoreObjects;
+import io.grpc.Internal;
 import io.grpc.LoadBalancer;
 import io.grpc.LoadBalancer.Helper;
 import io.grpc.LoadBalancerProvider;
@@ -31,7 +32,8 @@
 import java.util.Map;
 
 /** Provider for priority load balancing policy. */
-final class PriorityLoadBalancerProvider extends LoadBalancerProvider {
+@Internal
+public final class PriorityLoadBalancerProvider extends LoadBalancerProvider {
 
   @Override
   public boolean isAvailable() {

xds/src/main/java/io/grpc/xds/WeightedTargetLoadBalancerProvider.java

@@ -127,7 +127,6 @@ static final class WeightedPolicySelection {
     final int weight;
     final PolicySelection policySelection;
 
-    @VisibleForTesting
     WeightedPolicySelection(int weight, PolicySelection policySelection) {
       this.weight = weight;
       this.policySelection = policySelection;

xds/src/main/java/io/grpc/xds/XdsLbPolicies.java

@@ -20,7 +20,10 @@ final class XdsLbPolicies {
   static final String CLUSTER_MANAGER_POLICY_NAME = "cluster_manager_experimental";
   static final String CDS_POLICY_NAME = "cds_experimental";
   static final String EDS_POLICY_NAME = "eds_experimental";
+  static final String PRIORITY_POLICY_NAME = "priority_experimental";
   static final String WEIGHTED_TARGET_POLICY_NAME = "weighted_target_experimental";
+  static final String LRS_POLICY_NAME = "lrs_experimental";
+  // TODO(chengyuanzhang): delete routing policy.
   static final String XDS_ROUTING_POLICY_NAME = "xds_routing_experimental";
 
   private XdsLbPolicies() {}

xds/src/main/resources/META-INF/services/io.grpc.LoadBalancerProvider

@@ -1,5 +1,7 @@
 io.grpc.xds.CdsLoadBalancerProvider
 io.grpc.xds.EdsLoadBalancerProvider
+io.grpc.xds.PriorityLoadBalancerProvider
 io.grpc.xds.WeightedTargetLoadBalancerProvider
+io.grpc.xds.LrsLoadBalancerProvider
 io.grpc.xds.XdsRoutingLoadBalancerProvider
 io.grpc.xds.ClusterManagerLoadBalancerProvider