impl(pubsub): add MaxOtelLinkCountOption (#13024)

googleapis · Nov 3, 2023 · 4110eeb · 4110eeb
1 parent ce762e1
commit 4110eeb
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Showing 3 changed files with 59 additions and 2 deletions.
diff --git a/google/cloud/pubsub/internal/defaults.cc b/google/cloud/pubsub/internal/defaults.cc
@@ -22,6 +22,7 @@
 #include "google/cloud/internal/populate_grpc_options.h"
 #include "google/cloud/internal/user_agent_prefix.h"
 #include "google/cloud/options.h"
+#include "absl/strings/numbers.h"
 #include <chrono>
 #include <limits>
 #include <thread>
@@ -105,6 +106,13 @@ Options DefaultPublisherOptionsOnly(Options opts) {
   if (!opts.has<pubsub::CompressionAlgorithmOption>()) {
     opts.set<pubsub::CompressionAlgorithmOption>(GRPC_COMPRESS_DEFLATE);
   }
+  auto e = internal::GetEnv("OTEL_SPAN_LINK_COUNT_LIMIT");
+  size_t link_count;
+  if (e && absl::SimpleAtoi(e.value(), &link_count)) {
+    opts.set<pubsub::MaxOtelLinkCountOption>(link_count);
+  } else if (!opts.has<pubsub::MaxOtelLinkCountOption>()) {
+    opts.set<pubsub::MaxOtelLinkCountOption>(128);
+  }
 
   return opts;
 }

diff --git a/google/cloud/pubsub/internal/defaults_test.cc b/google/cloud/pubsub/internal/defaults_test.cc
@@ -121,6 +121,26 @@ TEST(OptionsTest, UserSetCommonOptions) {
   EXPECT_THAT(*s, HasSubstr("test-prefix"));
 }
 
+TEST(OptionsTest, SetOtelLinkLimitEnvOverrides) {
+  ScopedEnvironment env("OTEL_SPAN_LINK_COUNT_LIMIT", "5");
+  auto opts =
+      DefaultPublisherOptions(Options{}.set<pubsub::MaxOtelLinkCountOption>(1));
+  EXPECT_EQ(5U, opts.get<pubsub::MaxOtelLinkCountOption>());
+}
+
+TEST(OptionsTest, UnsetOtelLinkLimitEnv) {
+  ScopedEnvironment env("OTEL_SPAN_LINK_COUNT_LIMIT", absl::nullopt);
+  auto opts =
+      DefaultPublisherOptions(Options{}.set<pubsub::MaxOtelLinkCountOption>(1));
+  EXPECT_EQ(1U, opts.get<pubsub::MaxOtelLinkCountOption>());
+}
+
+TEST(OptionsTest, UnsetOtelLinkLimitEnvNoUserOption) {
+  ScopedEnvironment env("OTEL_SPAN_LINK_COUNT_LIMIT", absl::nullopt);
+  auto opts = DefaultPublisherOptions(Options{});
+  EXPECT_EQ(128U, opts.get<pubsub::MaxOtelLinkCountOption>());
+}
+
 TEST(OptionsTest, PublisherDefaults) {
   auto opts = DefaultPublisherOptions(Options{});
   EXPECT_EQ(ms(10), opts.get<pubsub::MaxHoldTimeOption>());
@@ -136,6 +156,7 @@ TEST(OptionsTest, PublisherDefaults) {
   EXPECT_EQ(GRPC_COMPRESS_DEFLATE,
             opts.get<pubsub::CompressionAlgorithmOption>());
   EXPECT_FALSE(opts.has<pubsub::CompressionThresholdOption>());
+  EXPECT_EQ(128, opts.get<pubsub::MaxOtelLinkCountOption>());
 }
 
 TEST(OptionsTest, UserSetPublisherOptions) {
@@ -148,7 +169,8 @@ TEST(OptionsTest, UserSetPublisherOptions) {
                                   .set<pubsub::MaxPendingMessagesOption>(4)
                                   .set<pubsub::MessageOrderingOption>(true)
                                   .set<pubsub::FullPublisherActionOption>(
-                                      pubsub::FullPublisherAction::kIgnored));
+                                      pubsub::FullPublisherAction::kIgnored)
+                                  .set<pubsub::MaxOtelLinkCountOption>(1));
 
   EXPECT_EQ(ms(100), opts.get<pubsub::MaxHoldTimeOption>());
   EXPECT_EQ(1U, opts.get<pubsub::MaxBatchMessagesOption>());
@@ -158,6 +180,7 @@ TEST(OptionsTest, UserSetPublisherOptions) {
   EXPECT_TRUE(opts.get<pubsub::MessageOrderingOption>());
   EXPECT_EQ(pubsub::FullPublisherAction::kIgnored,
             opts.get<pubsub::FullPublisherActionOption>());
+  EXPECT_EQ(1U, opts.get<pubsub::MaxOtelLinkCountOption>());
 }
 
 TEST(OptionsTest, SubscriberDefaults) {

diff --git a/google/cloud/pubsub/options.h b/google/cloud/pubsub/options.h
@@ -220,12 +220,38 @@ struct CompressionAlgorithmOption {
   using Type = int;
 };
 
+/**
+ * The maximum number of Open Telemetry span links.
+ *
+ * This option controls the number of links contained in a single publish span.
+ *
+ * @note Application developers should keep in mind that Cloud Trace
+ *    sets [limits][cloud-trace-quota-link] on the number of links per span
+ *    (128). Additionally, Open Telemetry sets the default
+ *    [limit][otel-quota-link] to 128.
+ *
+ * @ingroup pubsub-options
+ *
+ * @par Environment variable
+ *    This option is controlled by the `OTEL_SPAN_LINK_COUNT_LIMIT`
+ *    environment variable. If the environment variable is unset or unparsable,
+ *    it uses the user provided value, and then the default of 128.
+ *
+ * [otel-quota-link]:
+ * https://opentelemetry.io/docs/specs/otel/configuration/sdk-environment-variables/#span-limits
+ * [cloud-trace-quota-link]:
+ * https://github.com/googleapis/googleapis/blob/52180f8ba240022dd8ce756ee69fe5a3c429ad4d/google/devtools/cloudtrace/v2/trace.proto#L266
+ */
+struct MaxOtelLinkCountOption {
+  using Type = std::size_t;
+};
+
 /// The list of options specific to publishers.
 using PublisherOptionList =
     OptionList<MaxHoldTimeOption, MaxBatchMessagesOption, MaxBatchBytesOption,
                MaxPendingMessagesOption, MaxPendingBytesOption,
                MessageOrderingOption, FullPublisherActionOption,
-               CompressionThresholdOption>;
+               CompressionThresholdOption, MaxOtelLinkCountOption>;
 
 /**
  * The maximum deadline for each incoming message.