extensions: add retry host predicate for attempted hosts (#4452)

Adds a simple RetryHostPredicate that keeps track of hosts that have
already been attempted, triggering a new host to be selected if an
already attempted host is selected.

Signed-off-by: Snow Pettersen snowp@squareup.com

Risk Level: Low
Testing: Unit test
Docs Changes: n/a
Release Notes: n/a
Part of #3958

Signed-off-by: Snow Pettersen <snowp@squareup.com>

include/envoy/upstream/retry.h

@@ -119,7 +119,7 @@ class RetryHostPredicateFactory {
   virtual ~RetryHostPredicateFactory() {}
 
   virtual void createHostPredicate(RetryHostPredicateFactoryCallbacks& callbacks,
-                                   const ProtobufWkt::Struct& config) PURE;
+                                   const Protobuf::Message& config) PURE;
 
   /**
    * @return name name of this factory.

source/extensions/extensions_build_config.bzl

@@ -108,6 +108,9 @@ EXTENSIONS = {
     # TODO(lizan): switch to config target once a transport socket exists
     "envoy.transport_sockets.alts":                     "//source/extensions/transport_sockets/alts:tsi_handshaker",
     "envoy.transport_sockets.capture":                  "//source/extensions/transport_sockets/capture:config",
+
+    # Retry host predicates
+    "envoy.retry_host_predicates.other_hosts":          "//source/extensions/retry/host/other_hosts:config",
 }
 
 WINDOWS_EXTENSIONS = {

source/extensions/retry/host/BUILD

@@ -0,0 +1,17 @@
+licenses(["notice"])  # Apache 2
+
+load(
+    "//bazel:envoy_build_system.bzl",
+    "envoy_cc_library",
+    "envoy_package",
+)
+
+envoy_package()
+
+envoy_cc_library(
+    name = "well_known_names",
+    hdrs = ["well_known_names.h"],
+    deps = [
+        "//source/common/singleton:const_singleton",
+    ],
+)

source/extensions/retry/host/other_hosts/BUILD

@@ -0,0 +1,29 @@
+licenses(["notice"])  # Apache 2
+
+load(
+    "//bazel:envoy_build_system.bzl",
+    "envoy_cc_library",
+    "envoy_package",
+)
+
+envoy_package()
+
+envoy_cc_library(
+    name = "other_hosts_predicate_lib",
+    hdrs = ["other_hosts.h"],
+    deps = [
+        "//include/envoy/upstream:retry_interface",
+    ],
+)
+
+envoy_cc_library(
+    name = "config",
+    srcs = ["config.cc"],
+    hdrs = ["config.h"],
+    deps = [
+        ":other_hosts_predicate_lib",
+        "//include/envoy/registry",
+        "//include/envoy/upstream:retry_interface",
+        "//source/extensions/retry/host:well_known_names",
+    ],
+)

source/extensions/retry/host/other_hosts/config.cc

@@ -0,0 +1,17 @@
+#include "extensions/retry/host/other_hosts/config.h"
+
+#include "envoy/registry/registry.h"
+#include "envoy/upstream/retry.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace Retry {
+namespace Host {
+
+static Registry::RegisterFactory<OtherHostsRetryPredicateFactory,
+                                 Upstream::RetryHostPredicateFactory>
+    register_;
+}
+} // namespace Retry
+} // namespace Extensions
+} // namespace Envoy

source/extensions/retry/host/other_hosts/config.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include "envoy/upstream/retry.h"
+
+#include "extensions/retry/host/other_hosts/other_hosts.h"
+#include "extensions/retry/host/well_known_names.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace Retry {
+namespace Host {
+
+class OtherHostsRetryPredicateFactory : public Upstream::RetryHostPredicateFactory {
+public:
+  void createHostPredicate(Upstream::RetryHostPredicateFactoryCallbacks& callbacks,
+                           const Protobuf::Message&) override {
+    callbacks.addHostPredicate(std::make_shared<OtherHostsRetryPredicate>());
+  }
+
+  std::string name() override { return RetryHostPredicateValues::get().PreviousHostsPredicate; }
+};
+
+} // namespace Host
+} // namespace Retry
+} // namespace Extensions
+} // namespace Envoy

source/extensions/retry/host/other_hosts/other_hosts.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "envoy/upstream/retry.h"
+#include "envoy/upstream/upstream.h"
+
+namespace Envoy {
+class OtherHostsRetryPredicate : public Upstream::RetryHostPredicate {
+public:
+  bool shouldSelectAnotherHost(const Upstream::Host& candidate_host) override {
+    return attempted_hosts_.find(candidate_host.address()->asString()) != attempted_hosts_.end();
+  }
+  void onHostAttempted(Upstream::HostDescriptionConstSharedPtr attempted_host) override {
+    attempted_hosts_.insert(attempted_host->address()->asString());
+  }
+
+private:
+  std::unordered_set<std::string> attempted_hosts_;
+};
+} // namespace Envoy

source/extensions/retry/host/well_known_names.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include "common/singleton/const_singleton.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace Retry {
+namespace Host {
+
+/**
+ * Well-known retry host predicate names.
+ */
+class RetryHostPredicatesNameValues {
+public:
+  // Previous host predicate. Rejects hosts that have already been tried.
+  const std::string PreviousHostsPredicate = "envoy.retry_host_predicates.previous_hosts";
+};
+
+typedef ConstSingleton<RetryHostPredicatesNameValues> RetryHostPredicateValues;
+
+} // namespace Host
+} // namespace Retry
+} // namespace Extensions
+} // namespace Envoy

test/extensions/retry/host/other_hosts/BUILD

@@ -0,0 +1,22 @@
+licenses(["notice"])  # Apache 2
+
+load(
+    "//bazel:envoy_build_system.bzl",
+    "envoy_package",
+)
+load(
+    "//test/extensions:extensions_build_system.bzl",
+    "envoy_extension_cc_test",
+)
+
+envoy_package()
+
+envoy_extension_cc_test(
+    name = "config_test",
+    srcs = ["config_test.cc"],
+    extension_name = "envoy.retry_host_predicates.other_hosts",
+    deps = [
+        "//source/extensions/retry/host/other_hosts:config",
+        "//test/mocks/upstream:upstream_mocks",
+    ],
+)

test/extensions/retry/host/other_hosts/config_test.cc

@@ -0,0 +1,65 @@
+#include "envoy/registry/registry.h"
+#include "envoy/upstream/retry.h"
+
+#include "extensions/retry/host/other_hosts/config.h"
+#include "extensions/retry/host/well_known_names.h"
+
+#include "test/mocks/upstream/mocks.h"
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+using namespace testing;
+
+namespace Envoy {
+namespace Extensions {
+namespace Retry {
+namespace Host {
+
+struct TestHostPredicateFactoryCallback : public Upstream::RetryHostPredicateFactoryCallbacks {
+
+  void addHostPredicate(Upstream::RetryHostPredicateSharedPtr host_predicate) {
+    host_predicate_ = host_predicate;
+  }
+
+  Upstream::RetryHostPredicateSharedPtr host_predicate_;
+};
+
+TEST(OtherHostsRetryPredicateConfigTest, PredicateTest) {
+  auto factory = Registry::FactoryRegistry<Upstream::RetryHostPredicateFactory>::getFactory(
+      RetryHostPredicateValues::get().PreviousHostsPredicate);
+
+  ASSERT_NE(nullptr, factory);
+
+  TestHostPredicateFactoryCallback callback;
+  ProtobufWkt::Struct config;
+  factory->createHostPredicate(callback, config);
+
+  auto predicate = callback.host_predicate_;
+
+  auto host1 = std::make_shared<NiceMock<Upstream::MockHost>>();
+  auto host1_address = std::make_shared<Network::Address::Ipv4Instance>("127.0.0.1", 123);
+  ON_CALL(*host1, address()).WillByDefault(Return(host1_address));
+
+  auto host2 = std::make_shared<NiceMock<Upstream::MockHost>>();
+  auto host2_address = std::make_shared<Network::Address::Ipv4Instance>("127.0.0.1", 456);
+  ON_CALL(*host2, address()).WillByDefault(Return(host2_address));
+
+  ASSERT_FALSE(predicate->shouldSelectAnotherHost(*host1));
+  ASSERT_FALSE(predicate->shouldSelectAnotherHost(*host2));
+
+  predicate->onHostAttempted(host1);
+
+  ASSERT_TRUE(predicate->shouldSelectAnotherHost(*host1));
+  ASSERT_FALSE(predicate->shouldSelectAnotherHost(*host2));
+
+  predicate->onHostAttempted(host2);
+
+  ASSERT_TRUE(predicate->shouldSelectAnotherHost(*host1));
+  ASSERT_TRUE(predicate->shouldSelectAnotherHost(*host2));
+}
+
+} // namespace Host
+} // namespace Retry
+} // namespace Extensions
+} // namespace Envoy

test/integration/test_host_predicate_config.h

@@ -10,7 +10,7 @@ class TestHostPredicateFactory : public Upstream::RetryHostPredicateFactory {
   std::string name() override { return "envoy.test_host_predicate"; }
 
   void createHostPredicate(Upstream::RetryHostPredicateFactoryCallbacks& callbacks,
-                           const ProtobufWkt::Struct&) override {
+                           const Protobuf::Message&) override {
     callbacks.addHostPredicate(std::make_shared<TestHostPredicate>());
   }
 };