Add trace propagation and linking

src/bk_download.cpp

@@ -276,11 +276,11 @@ bool BkDownload::download_blob() {
     return true;
 }
 
-void bk_download_proc(std::list<BKDL::BkDownload *> &dl_list, uint64_t delay_sec, int &running) {
+void bk_download_proc(std::list<BKDL::BkDownload *> &dl_list, uint64_t delay_sec, int &running, opentelemetry::trace::SpanContext linkContext) {
     auto tracer = overlaybd_otel::GetTracer();
     auto span = tracer->StartSpan("background_download_process");
+    span->AddLink(linkContext, {});
     auto scope = tracer->WithActiveSpan(span);
-
     span->SetAttribute("delay_seconds", delay_sec);
     span->SetAttribute("initial_queue_size", dl_list.size());
 

src/bk_download.h

@@ -67,6 +67,6 @@ class BkDownload {
     bool force_download = false;
 };
 
-void bk_download_proc(std::list<BKDL::BkDownload *> &, uint64_t, int &);
+void bk_download_proc(std::list<BKDL::BkDownload *> &, uint64_t, int &, opentelemetry::trace::SpanContext);
 
 } // namespace BKDL

src/config.h

@@ -65,6 +65,7 @@ struct ImageConfig : public ConfigUtils::Config {
     APPCFG_PARA(download, DownloadConfig);
     APPCFG_PARA(accelerationLayer, bool, false);
     APPCFG_PARA(recordTracePath, std::string, "");
+    APPCFG_PARA(traceContext, ConfigUtils::Document);
 };
 
 struct P2PConfig : public ConfigUtils::Config {

src/image_file.cpp

@@ -35,6 +35,7 @@
 #include "switch_file.h"
 #include "overlaybd/gzip/gz.h"
 #include "overlaybd/gzindex/gzfile.h"
+#include "overlaybd/otel/tracer_common.h"
 #include "overlaybd/tar/tar_file.h"
 
 #define PARALLEL_LOAD_INDEX 32
@@ -217,8 +218,10 @@ void ImageFile::start_bk_dl_thread() {
     uint64_t delay_sec = (rand() % extra_range) + conf.download().delay();
     LOG_INFO("background download is enabled, delay `, maxMBps `, tryCnt `, blockSize `", delay_sec,
              conf.download().maxMBps(), conf.download().tryCnt(), conf.download().blockSize());
+    opentelemetry::trace::SpanContext linkContext = overlaybd_otel::GetTracer()->GetCurrentSpan()->GetContext();
     dl_thread_jh = photon::thread_enable_join(
-        photon::thread_create11(&BKDL::bk_download_proc, dl_list, delay_sec, m_status));
+        photon::thread_create11(
+            BKDL::bk_download_proc, dl_list, delay_sec, m_status, std::move(linkContext)));
 }
 
 struct ParallelOpenTask {
@@ -437,6 +440,15 @@ LSMT::IFileRW *ImageFile::open_upper(ImageConfigNS::UpperConfig &upper) {
 }
 
 int ImageFile::init_image_file() {
+    // Extracts the trace context from the image config as a parent context.
+    // This allows us to link activity associated with overlaybd-snapshotter.
+    auto parent_context = overlaybd_otel::ExtractTraceContext(conf.traceContext());
+    auto tracer = overlaybd_otel::GetTracer();
+    opentelemetry::trace::StartSpanOptions opts;
+    opts.parent = parent_context;
+    auto span = tracer->StartSpan("ImageFile::init_image_file", opts);
+    auto scope = tracer->WithActiveSpan(span);
+
     LSMT::IFileRO *lower_file = nullptr;
     LSMT::IFileRW *upper_file = nullptr;
     LSMT::IFileRW *stack_ret = nullptr;

src/overlaybd/otel/CMakeLists.txt

@@ -26,6 +26,7 @@ set_target_properties(otel_lib PROPERTIES LINKER_LANGUAGE CXX)
 target_include_directories(otel_lib PUBLIC 
     ${CMAKE_CURRENT_SOURCE_DIR}
     ${PHOTON_INCLUDE_DIR}
+    ${rapidjson_SOURCE_DIR}/include
     ${opentelemetry-cpp_SOURCE_DIR}/api/include
     ${opentelemetry-cpp_SOURCE_DIR}/sdk/include
     ${opentelemetry-cpp_SOURCE_DIR}/exporters/otlp/include

src/overlaybd/otel/tracer_common.cpp

@@ -1,13 +1,19 @@
-#include "opentelemetry/context/runtime_context.h"
 #include "tracer_common.h"
+
 #include "context_storage.h"
+#include "opentelemetry/context/runtime_context.h"
+
+using opentelemetry::nostd::unique_ptr;
+using opentelemetry::nostd::shared_ptr;
+using opentelemetry::nostd::string_view;
+using opentelemetry::nostd::function_ref;
 
 namespace overlaybd_otel {
 
 void InitTracer() {
     // Install a libphoton coroutine-aware context storage implementation, which uses libphoton's thread-local implementation.
     opentelemetry::context::RuntimeContext::SetRuntimeContextStorage(
-        opentelemetry::nostd::unique_ptr<opentelemetry::context::RuntimeContextStorage>(
+        unique_ptr<opentelemetry::context::RuntimeContextStorage>(
             new LibPhotonContextStorage()));
 
     // Create OTLP/HTTP exporter using the factory
@@ -26,12 +32,44 @@ void InitTracer() {
 }
 
 void CleanupTracer() {
-    std::shared_ptr<opentelemetry::trace::TracerProvider> none;
-    opentelemetry::sdk::trace::Provider::SetTracerProvider(none);
+    opentelemetry::sdk::trace::Provider::SetTracerProvider({});
 }
 
 opentelemetry::nostd::shared_ptr<opentelemetry::trace::Tracer> GetTracer(opentelemetry::nostd::string_view tracer_name) {
     return opentelemetry::trace::Provider::GetTracerProvider()->GetTracer(tracer_name);
 }
 
+class JsonTextMapCarrier : public opentelemetry::context::propagation::TextMapCarrier {
+public:
+    JsonTextMapCarrier(const rapidjson::Document& traceContext): m_traceContext(traceContext) {}
+
+    string_view Get(string_view key) const noexcept override {
+        for (auto iter = m_traceContext.MemberBegin(); iter != m_traceContext.MemberEnd(); ++iter) {
+            if (key == iter->name.GetString() && iter->value.IsString()) {
+                return iter->value.GetString();
+            }
+        }
+        return {};
+    }
+
+    void Set(string_view key, string_view value) noexcept override {
+        // not implemented
+    }
+
+private:
+    const rapidjson::Document& m_traceContext;
+};
+
+opentelemetry::context::Context ExtractTraceContext(const rapidjson::Document& document) {
+    if (!document.IsObject()) {
+        return {};
+    }
+
+    // Extract the traceContext if it exists.
+    opentelemetry::context::Context context;
+    auto carrier = JsonTextMapCarrier(document);
+    auto propagator = opentelemetry::trace::propagation::HttpTraceContext();
+    return propagator.Extract(carrier, context);
+}
+
 } // namespace overlaybd_otel

src/overlaybd/otel/tracer_common.h

@@ -1,7 +1,7 @@
-// Copyright The OpenTelemetry Authors
-// SPDX-License-Identifier: Apache-2.0
-
 #pragma once
+
+#define OPENTELEMETRY_ABI_VERSION_NO 2
+
 #include "opentelemetry/exporters/otlp/otlp_http_exporter_factory.h"
 #include "opentelemetry/exporters/otlp/otlp_http_exporter_options.h"
 #include "opentelemetry/nostd/shared_ptr.h"
@@ -20,11 +20,16 @@
 #include <iostream>
 #include <vector>
 
-namespace overlaybd_otel {
+#include <rapidjson/document.h>
 
+namespace overlaybd_otel {
 
 void InitTracer();
+
 void CleanupTracer();
+
 opentelemetry::nostd::shared_ptr<opentelemetry::trace::Tracer> GetTracer(opentelemetry::nostd::string_view tracer_name = "overlaybd");
 
+opentelemetry::context::Context ExtractTraceContext(const rapidjson::Document& config);
+
 } // namespace overlaybd_otel