Merge pull request #25214 from markdroth/xds_bootstrap_env_var

Add ability to read xDS bootstrap config from an env var.

src/core/ext/xds/xds_bootstrap.cc

@@ -157,19 +157,13 @@ std::unique_ptr<XdsBootstrap> ParseJsonAndCreate(
 
 }  // namespace
 
-std::unique_ptr<XdsBootstrap> XdsBootstrap::ReadFromFile(
-    XdsClient* client, TraceFlag* tracer, const char* fallback_config,
+std::unique_ptr<XdsBootstrap> XdsBootstrap::Create(XdsClient* client,
+                                                   TraceFlag* tracer,
+                                                   const char* fallback_config,
                                                    grpc_error** error) {
+  // First, try GRPC_XDS_BOOTSTRAP env var.
   grpc_core::UniquePtr<char> path(gpr_getenv("GRPC_XDS_BOOTSTRAP"));
-  if (path == nullptr) {
-    if (fallback_config != nullptr) {
-      return ParseJsonAndCreate(client, tracer, fallback_config,
-                                "fallback config", error);
-    }
-    *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-        "Environment variable GRPC_XDS_BOOTSTRAP not defined");
-    return nullptr;
-  }
+  if (path != nullptr) {
     if (GRPC_TRACE_FLAG_ENABLED(*tracer)) {
       gpr_log(GPR_INFO,
               "[xds_client %p] Got bootstrap file location from "
@@ -177,7 +171,8 @@ std::unique_ptr<XdsBootstrap> XdsBootstrap::ReadFromFile(
               client, path.get());
     }
     grpc_slice contents;
-  *error = grpc_load_file(path.get(), /*add_null_terminator=*/true, &contents);
+    *error =
+        grpc_load_file(path.get(), /*add_null_terminator=*/true, &contents);
     if (*error != GRPC_ERROR_NONE) return nullptr;
     absl::string_view contents_str_view = StringViewFromSlice(contents);
     if (GRPC_TRACE_FLAG_ENABLED(*tracer)) {
@@ -189,6 +184,24 @@ std::unique_ptr<XdsBootstrap> XdsBootstrap::ReadFromFile(
                                      bootstrap_source, error);
     grpc_slice_unref_internal(contents);
     return result;
+  }
+  // Next, try GRPC_XDS_BOOTSTRAP_CONFIG env var.
+  grpc_core::UniquePtr<char> env_config(
+      gpr_getenv("GRPC_XDS_BOOTSTRAP_CONFIG"));
+  if (env_config != nullptr) {
+    return ParseJsonAndCreate(client, tracer, env_config.get(),
+                              "GRPC_XDS_BOOTSTRAP_CONFIG env var", error);
+  }
+  // Finally, try fallback config.
+  if (fallback_config != nullptr) {
+    return ParseJsonAndCreate(client, tracer, fallback_config,
+                              "fallback config", error);
+  }
+  // No bootstrap config found.
+  *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+      "Environment variables GRPC_XDS_BOOTSTRAP or GRPC_XDS_BOOTSTRAP_CONFIG "
+      "not defined");
+  return nullptr;
 }
 
 XdsBootstrap::XdsBootstrap(Json json, grpc_error** error) {

src/core/ext/xds/xds_bootstrap.h

@@ -67,11 +67,16 @@ class XdsBootstrap {
     bool ShouldUseV3() const;
   };
 
-  // Normally locates the bootstrap file via an env var.  If no env var
-  // is set, fallback_config will be used instead (if non-null).
+  // Creates bootstrap object, obtaining the bootstrap JSON as appropriate
+  // for the environment:
+  // - If the GRPC_XDS_BOOTSTRAP env var is set, reads the file it specifies
+  //   to obtain the bootstrap JSON.
+  // - Otherwise, if the GRPC_XDS_BOOTSTRAP_CONFIG env var is set, reads the
+  //   content of that env var to obtain the bootstrap JSON.
+  // - Otherwise, the JSON will be read from fallback_config (if non-null).
   // If *error is not GRPC_ERROR_NONE after returning, then there was an
-  // error reading the file.
-  static std::unique_ptr<XdsBootstrap> ReadFromFile(XdsClient* client,
+  // error (e.g., no config found or error reading the file).
+  static std::unique_ptr<XdsBootstrap> Create(XdsClient* client,
                                               TraceFlag* tracer,
                                               const char* fallback_config,
                                               grpc_error** error);

src/core/ext/xds/xds_client.cc

@@ -1734,8 +1734,8 @@ XdsClient::XdsClient(grpc_error** error)
                                                                   : nullptr),
       request_timeout_(GetRequestTimeout()),
       interested_parties_(grpc_pollset_set_create()),
-      bootstrap_(XdsBootstrap::ReadFromFile(
-          this, &grpc_xds_client_trace, g_fallback_bootstrap_config, error)),
+      bootstrap_(XdsBootstrap::Create(this, &grpc_xds_client_trace,
+                                      g_fallback_bootstrap_config, error)),
       certificate_provider_store_(MakeOrphanable<CertificateProviderStore>(
           bootstrap_ == nullptr
               ? CertificateProviderStore::PluginDefinitionMap()

test/cpp/end2end/xds_end2end_test.cc

@@ -1506,17 +1506,25 @@ class XdsEnd2endTest : public ::testing::TestWithParam<TestType> {
  protected:
   XdsEnd2endTest(size_t num_backends, size_t num_balancers,
                  int client_load_reporting_interval_seconds = 100,
-                 bool use_xds_enabled_server = false)
+                 bool use_xds_enabled_server = false,
+                 bool bootstrap_contents_from_env_var = false)
       : num_backends_(num_backends),
         num_balancers_(num_balancers),
         client_load_reporting_interval_seconds_(
             client_load_reporting_interval_seconds),
-        use_xds_enabled_server_(use_xds_enabled_server) {}
+        use_xds_enabled_server_(use_xds_enabled_server),
+        bootstrap_contents_from_env_var_(bootstrap_contents_from_env_var) {}
 
   void SetUp() override {
     gpr_setenv("GRPC_XDS_EXPERIMENTAL_V3_SUPPORT", "true");
-    gpr_setenv("GRPC_XDS_BOOTSTRAP",
-               GetParam().use_v2() ? g_bootstrap_file_v2 : g_bootstrap_file_v3);
+    if (bootstrap_contents_from_env_var_) {
+      gpr_setenv("GRPC_XDS_BOOTSTRAP_CONFIG",
+                 GetParam().use_v2() ? kBootstrapFileV2 : kBootstrapFileV3);
+    } else {
+      gpr_setenv("GRPC_XDS_BOOTSTRAP", GetParam().use_v2()
+                                           ? g_bootstrap_file_v2
+                                           : g_bootstrap_file_v3);
+    }
     g_port_saver->Reset();
     bool localhost_resolves_to_ipv4 = false;
     bool localhost_resolves_to_ipv6 = false;
@@ -1597,6 +1605,8 @@ class XdsEnd2endTest : public ::testing::TestWithParam<TestType> {
     // Clear global xDS channel args, since they will go out of scope
     // when this test object is destroyed.
     grpc_core::internal::SetXdsChannelArgsForTest(nullptr);
+    gpr_unsetenv("GRPC_XDS_BOOTSTRAP");
+    gpr_unsetenv("GRPC_XDS_BOOTSTRAP_CONFIG");
   }
 
   void StartAllBackends() {
@@ -2272,6 +2282,7 @@ class XdsEnd2endTest : public ::testing::TestWithParam<TestType> {
   RouteConfiguration default_route_config_;
   Cluster default_cluster_;
   bool use_xds_enabled_server_;
+  bool bootstrap_contents_from_env_var_;
 };
 
 class BasicTest : public XdsEnd2endTest {
@@ -7833,6 +7844,22 @@ TEST_P(ClientLoadReportingWithDropTest, Vanilla) {
                                 kDropRateForThrottle * (1 + kErrorTolerance))));
 }
 
+class BootstrapContentsFromEnvVarTest : public XdsEnd2endTest {
+ public:
+  BootstrapContentsFromEnvVarTest() : XdsEnd2endTest(4, 1, 100, false, true) {}
+};
+
+TEST_P(BootstrapContentsFromEnvVarTest, Vanilla) {
+  SetNextResolution({});
+  SetNextResolutionForLbChannelAllBalancers();
+  AdsServiceImpl::EdsResourceArgs args({
+      {"locality0", GetBackendPorts()},
+  });
+  balancers_[0]->ads_service()->SetEdsResource(
+      BuildEdsResource(args, DefaultEdsServiceName()));
+  WaitForAllBackends();
+}
+
 std::string TestTypeName(const ::testing::TestParamInfo<TestType>& info) {
   return info.param.AsString();
 }
@@ -7967,6 +7994,10 @@ INSTANTIATE_TEST_SUITE_P(XdsTest, ClientLoadReportingWithDropTest,
                                            TestType(true, true)),
                          &TestTypeName);
 
+INSTANTIATE_TEST_SUITE_P(XdsTest, BootstrapContentsFromEnvVarTest,
+                         ::testing::Values(TestType(true, false)),
+                         &TestTypeName);
+
 }  // namespace
 }  // namespace testing
 }  // namespace grpc