Make exporters/trace/stackdriver more consistent with the stats one. (#105)

- This simplifies the public API.
- Remove stackdriver_exporter_test for now, it wasn't testing anything.
- Add README pointing at the stats/ README.

Author: g-easy

opencensus/exporters/stats/stackdriver/README.md

@@ -19,18 +19,24 @@ In order to be able to push your stats to [Stackdriver Monitoring](stackdriver-m
 These steps enable the API but don't require that your app is hosted on Google Cloud Platform.
 
 ### Setup authentication
+
 The Stackdriver exporter uses gRPC, which requires a certificate
 (`etc/roots.pem` in the gRPC repository) copied to
 to `/usr/share/grpc/roots.pem`.
 
 If your application runs on Google Cloud Platform, it can automatically
 determine credentials to authenticate to Stackdriver from the VM environment.
+
 Otherwise, create a
-[Google Cloud service account](https://cloud.google.com/iam/docs/creating-managing-service-accounts)
-with the "Monitoring Editor" role, create and download a service account key,
+[Google Cloud service account](https://cloud.google.com/iam/docs/creating-managing-service-accounts),
+create and download a service account key,
 and set the environment variable `GOOGLE_APPLICATION_CREDENTIALS` to the path to
 that key.
 
+Please refer to the [Stats access controls](https://cloud.google.com/monitoring/access-control)
+and [Trace access controls](https://cloud.google.com/trace/docs/iam)
+documentation for configuring roles.
+
 ### Register the exporter
 
 `#include opencensus/exporters/stats/stackdriver/stackdriver_exporter.h` (if

opencensus/exporters/trace/stackdriver/BUILD

@@ -16,7 +16,7 @@ load("//opencensus:copts.bzl", "DEFAULT_COPTS", "TEST_COPTS")
 
 licenses(["notice"])  # Apache License 2.0
 
-package(default_visibility = ["//visibility:public"])
+package(default_visibility = ["//visibility:private"])
 
 # Libraries
 # ========================================================================= #
@@ -26,27 +26,12 @@ cc_library(
     srcs = ["internal/stackdriver_exporter.cc"],
     hdrs = ["stackdriver_exporter.h"],
     copts = DEFAULT_COPTS,
+    visibility = ["//visibility:public"],
     deps = [
         "//google/devtools/cloudtrace/v2:tracing_proto",
         "//opencensus/trace",
         "@com_github_grpc_grpc//:grpc++",
-        "@com_google_absl//absl/base:core_headers",
         "@com_google_absl//absl/memory",
         "@com_google_absl//absl/strings",
     ],
 )
-
-# Tests
-# ========================================================================= #
-
-cc_test(
-    name = "stackdriver_exporter_test",
-    srcs = ["internal/stackdriver_exporter_test.cc"],
-    copts = TEST_COPTS,
-    deps = [
-        ":stackdriver_exporter",
-        "//opencensus/trace",
-        "@com_github_grpc_grpc//test/core/util:gpr_test_util",
-        "@com_google_googletest//:gtest_main",
-    ],
-)

opencensus/exporters/trace/stackdriver/README.md

@@ -0,0 +1,3 @@
+Please refer to the
+[Stackdriver Stats Exporter instructions](../../stats/stackdriver/README.md) for
+setup.

opencensus/exporters/trace/stackdriver/internal/stackdriver_exporter.cc

@@ -21,25 +21,32 @@
 #include "absl/memory/memory.h"
 #include "absl/strings/str_cat.h"
 #include "absl/time/clock.h"
+#include "google/devtools/cloudtrace/v2/tracing.grpc.pb.h"
+#include "include/grpc++/grpc++.h"
+#include "opencensus/trace/exporter/span_data.h"
+#include "opencensus/trace/exporter/span_exporter.h"
 
 using grpc::ClientContext;
 using grpc::Status;
 
 namespace opencensus {
 namespace exporters {
 namespace trace {
-
-static constexpr size_t kAttributeStringLen = 256;
-static constexpr size_t kAnnotationStringLen = 256;
-static constexpr size_t kDisplayNameStringLen = 128;
-static constexpr char kGoogleStackDriverTraceAddress[] =
-    "cloudtrace.googleapis.com";
-
 namespace {
 
+constexpr size_t kAttributeStringLen = 256;
+constexpr size_t kAnnotationStringLen = 256;
+constexpr size_t kDisplayNameStringLen = 128;
+constexpr char kGoogleStackDriverTraceAddress[] = "cloudtrace.googleapis.com";
+
 constexpr char kAgentKey[] = "g.co/agent";
 constexpr char kAgentValue[] = "opencensus-cpp";
 
+std::string ToString(const grpc::Status& status) {
+  return absl::StrCat("status code ", status.error_code(), " details \"",
+                      status.error_message(), "\"");
+}
+
 gpr_timespec ConvertToTimespec(absl::Time time) {
   gpr_timespec g_time;
   int64_t secs = absl::ToUnixSeconds(time);
@@ -243,64 +250,44 @@ void ConvertSpans(
   }
 }
 
-}  // namespace
+class Handler : public ::opencensus::trace::exporter::SpanExporter::Handler {
+ public:
+  Handler(absl::string_view project_id,
+          const std::shared_ptr<grpc::Channel>& channel)
+      : project_id_(project_id),
+        stub_(::google::devtools::cloudtrace::v2::TraceService::NewStub(
+            channel)) {}
 
-Status StackdriverExporter::TraceClient::BatchWriteSpans(
-    const ::google::devtools::cloudtrace::v2::BatchWriteSpansRequest& request) {
-  ::google::protobuf::Empty response;
+  void Export(const std::vector<::opencensus::trace::exporter::SpanData>& spans)
+      override;
 
-  // Context for the client. It could be used to convey extra information to
-  // the server and/or tweak certain RPC behaviors. Deadline set for 3000
-  // milliseconds.
-  ClientContext context;
-  context.set_deadline(
-      ConvertToTimespec(absl::Now() + absl::Milliseconds(3000)));
-
-  // The actual RPC that sends the span information to Stackdriver.
-  return stub_->BatchWriteSpans(&context, request, &response);
-}
-
-void StackdriverExporter::Register(absl::string_view project_id) {
-  StackdriverExporter* exporter = new StackdriverExporter(project_id);
-  auto creds = grpc::GoogleDefaultCredentials();
-  auto channel = ::grpc::CreateChannel(kGoogleStackDriverTraceAddress, creds);
-  exporter->trace_client_ = absl::make_unique<TraceClient>(channel);
-  ::opencensus::trace::exporter::SpanExporter::RegisterHandler(
-      absl::WrapUnique<::opencensus::trace::exporter::SpanExporter::Handler>(
-          exporter));
-}
+ private:
+  const std::string project_id_;
+  std::unique_ptr<google::devtools::cloudtrace::v2::TraceService::Stub> stub_;
+};
 
-void StackdriverExporter::Export(
+void Handler::Export(
     const std::vector<::opencensus::trace::exporter::SpanData>& spans) {
   ::google::devtools::cloudtrace::v2::BatchWriteSpansRequest request;
   request.set_name(absl::StrCat("projects/", project_id_));
   ConvertSpans(spans, project_id_, &request);
-
-  Status status = trace_client_->BatchWriteSpans(request);
-  // Act upon its status.
+  ::google::protobuf::Empty response;
+  ClientContext context;
+  context.set_deadline(
+      ConvertToTimespec(absl::Now() + absl::Milliseconds(3000)));
+  Status status = stub_->BatchWriteSpans(&context, request, &response);
   if (!status.ok()) {
-    // TODO: log error.
+    std::cerr << "BatchWriteSpans failed: " << ToString(status) << "\n";
   }
 }
 
-void StackdriverExporter::ExportForTesting(
-    absl::string_view project_id,
-    const std::vector<::opencensus::trace::exporter::SpanData>& spans) {
+}  // namespace
+
+void StackdriverExporter::Register(absl::string_view project_id) {
   auto creds = grpc::GoogleDefaultCredentials();
   auto channel = ::grpc::CreateChannel(kGoogleStackDriverTraceAddress, creds);
-  std::unique_ptr<StackdriverExporter::TraceClient> trace_client =
-      absl::make_unique<TraceClient>(channel);
-
-  ::google::devtools::cloudtrace::v2::BatchWriteSpansRequest request;
-  request.set_name(absl::StrCat("projects/", project_id));
-  ConvertSpans(spans, project_id, &request);
-
-  Status status = trace_client->BatchWriteSpans(request);
-  // Act upon its status.
-  if (!status.ok()) {
-    std::cerr << "BatchWriteSpans failed with code " << status.error_code()
-              << ": " << status.error_message() << "\n";
-  }
+  ::opencensus::trace::exporter::SpanExporter::RegisterHandler(
+      absl::make_unique<Handler>(project_id, channel));
 }
 
 }  // namespace trace

opencensus/exporters/trace/stackdriver/internal/stackdriver_exporter_test.cc

@@ -15,62 +15,19 @@
 #ifndef OPENCENSUS_EXPORTERS_TRACE_STACKDRIVER_STACKDRIVER_EXPORTER_H_
 #define OPENCENSUS_EXPORTERS_TRACE_STACKDRIVER_STACKDRIVER_EXPORTER_H_
 
-#include <memory>
-#include <string>
-#include <vector>
-
-#include "google/devtools/cloudtrace/v2/tracing.grpc.pb.h"
-#include "include/grpc++/grpc++.h"
-#include "opencensus/trace/exporter/span_data.h"
-#include "opencensus/trace/exporter/span_exporter.h"
+#include "absl/strings/string_view.h"
 
 namespace opencensus {
 namespace exporters {
 namespace trace {
 
-class StackdriverExporter
-    : public ::opencensus::trace::exporter::SpanExporter::Handler {
+class StackdriverExporter {
  public:
-  StackdriverExporter(absl::string_view project_id) : project_id_(project_id) {}
-  void Export(const std::vector<::opencensus::trace::exporter::SpanData>& spans)
-      override;
-
-  // Registers the exporter and sets the project Id. The following are required
-  // to communicate with stackdriver: a valid project Id, a valid authentication
-  // key which has been generated for that project, and the server security
-  // credentials. An authentication key can be generated for your project in the
-  // gcp/stackdriver settings for your account. Grpc will look for the key using
-  // the path defined by GOOGLE_APPLICATION_CREDENTIALS environment variable
-  // (export GOOGLE_APPLICATION_CREDENTIALS=<path_to_key>). The server security
-  // credentials located in <grpc_path>/etc/roots.pem needs to be copied to
-  // /usr/share/grpc/roots.pem
+  // Registers the exporter and sets the project ID.
   static void Register(absl::string_view project_id);
 
  private:
-  class TraceClient {
-   public:
-    TraceClient(const std::shared_ptr<grpc::Channel>& channel)
-        : stub_(google::devtools::cloudtrace::v2::TraceService::NewStub(
-              channel)) {}
-
-    // Packages a batch of spans into a single request and writes it to
-    // stackdriver. Returns the status of the operation.
-    grpc::Status BatchWriteSpans(
-        const ::google::devtools::cloudtrace::v2::BatchWriteSpansRequest&
-            request);
-
-   private:
-    std::unique_ptr<google::devtools::cloudtrace::v2::TraceService::Stub> stub_;
-  };
-
-  friend class StackdriverExporterTestPeer;
-
-  static void ExportForTesting(
-      absl::string_view project_id,
-      const std::vector<::opencensus::trace::exporter::SpanData>& spans);
-
-  const std::string project_id_;
-  std::unique_ptr<TraceClient> trace_client_;
+  StackdriverExporter() = delete;
 };
 
 }  // namespace trace