Ring hash implementation (grpc#26356)

* Ring hash implementation

* Fixing an error caught during import:
ipv6 addresses need small modifications when creating the ring entry.

* fixing an error

* removing debugs

* Remove unnecssary hashing

* small cleanup

BUILD

@@ -1116,6 +1116,7 @@ grpc_cc_library(
         "grpc_client_authority_filter",
         "grpc_lb_policy_pick_first",
         "grpc_lb_policy_priority",
+        "grpc_lb_policy_ring_hash",
         "grpc_lb_policy_round_robin",
         "grpc_lb_policy_weighted_target",
         "grpc_client_idle_filter",
@@ -1555,6 +1556,7 @@ grpc_cc_library(
         "grpc_base",
         "grpc_client_channel",
         "grpc_lb_address_filtering",
+        "grpc_lb_policy_ring_hash",
         "grpc_lb_xds_channel_args",
         "grpc_lb_xds_common",
         "grpc_resolver_fake",
@@ -1647,6 +1649,10 @@ grpc_cc_library(
     hdrs = [
         "src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.h",
     ],
+    external_deps = [
+        "absl/strings",
+        "xxhash",
+    ],
     language = "c++",
     deps = [
         "grpc_base",

CMakeLists.txt

@@ -2327,6 +2327,7 @@ add_library(grpc_unsecure
   src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc
   src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
   src/core/ext/filters/client_channel/lb_policy/priority/priority.cc
+  src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc
   src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
   src/core/ext/filters/client_channel/lb_policy/weighted_target/weighted_target.cc
   src/core/ext/filters/client_channel/lb_policy_registry.cc

Makefile

@@ -1735,6 +1735,7 @@ LIBGRPC_UNSECURE_SRC = \
     src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc \
     src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc \
     src/core/ext/filters/client_channel/lb_policy/priority/priority.cc \
+    src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc \
     src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc \
     src/core/ext/filters/client_channel/lb_policy/weighted_target/weighted_target.cc \
     src/core/ext/filters/client_channel/lb_policy_registry.cc \
@@ -2669,7 +2670,6 @@ ifneq ($(OPENSSL_DEP),)
 # installing headers to their final destination on the drive. We need this
 # otherwise parallel compilation will fail if a source is compiled first.
 src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel_secure.cc: $(OPENSSL_DEP)
-src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc: $(OPENSSL_DEP)
 src/core/ext/filters/client_channel/lb_policy/xds/cds.cc: $(OPENSSL_DEP)
 src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_impl.cc: $(OPENSSL_DEP)
 src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc: $(OPENSSL_DEP)

build_autogenerated.yaml

@@ -1618,6 +1618,7 @@ libs:
   - src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h
   - src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.h
   - src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.h
+  - src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.h
   - src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
   - src/core/ext/filters/client_channel/lb_policy_factory.h
   - src/core/ext/filters/client_channel/lb_policy_registry.h
@@ -1828,6 +1829,7 @@ libs:
   - src/core/lib/transport/transport.h
   - src/core/lib/transport/transport_impl.h
   - src/core/lib/uri/uri_parser.h
+  - third_party/xxhash/xxhash.h
   src:
   - src/core/ext/filters/census/grpc_context.cc
   - src/core/ext/filters/client_channel/backend_metric.cc
@@ -1854,6 +1856,7 @@ libs:
   - src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc
   - src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
   - src/core/ext/filters/client_channel/lb_policy/priority/priority.cc
+  - src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc
   - src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
   - src/core/ext/filters/client_channel/lb_policy/weighted_target/weighted_target.cc
   - src/core/ext/filters/client_channel/lb_policy_registry.cc

doc/environment_variables.md

@@ -75,6 +75,7 @@ some configuration as environment variables that can be set.
     in DEBUG)
   - priority_lb - traces priority LB policy
   - resource_quota - trace resource quota objects internals
+  - ring_hash_lb - traces the ring hash load balancing policy
   - round_robin - traces the round_robin load balancing policy
   - queue_pluck
   - server_channel - lightweight trace of significant server channel events

grpc.gyp

@@ -1122,6 +1122,7 @@
         'src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc',
         'src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc',
         'src/core/ext/filters/client_channel/lb_policy/priority/priority.cc',
+        'src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc',
         'src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc',
         'src/core/ext/filters/client_channel/lb_policy/weighted_target/weighted_target.cc',
         'src/core/ext/filters/client_channel/lb_policy_registry.cc',