implement log and trace integration (#79)

README.md

@@ -158,6 +158,31 @@ After setup configurations, try to put values with
 curl --request PUT --data-binary "@./config.yaml" http://localhost:8500/v1/kv/configuration-discovery.default.agentConfigurations
 ```
 
+## Trace and Log integration
+
+cpp2sky implements to output logs which is the key to integrate with actual tracing context.
+
+#### Supported Logger
+
+- [spdlog](https://github.com/gabime/spdlog)
+
+```cpp
+#include <spdlog/spdlog.h>
+#include <cpp2sky/trace_log.h>
+
+int main() {
+  auto logger = spdlog::default_logger();
+  // set_pattern must be called.
+  logger->set_pattern(logFormat<decltype(logger)::element_type>());
+
+  // It will generate log message as follows.
+  //
+  // {"level": "warning", "msg": "sample", "SW_CTX": ["service","instance","trace_id","segment_id","span_id"]}
+  //
+  logger->warn(tracing_context->logMessage("sample"));
+}
+```
+
 ## Security
 
 If you've found any security issues, please read [Security Reporting Process](https://github.com/SkyAPM/cpp2sky/blob/main/SECURITY.md) and take described steps.

cpp2sky/BUILD

@@ -23,6 +23,8 @@ cc_library(
     "well_known_names.h",
     "exception.h",
     "time.h",
+    "assert.h",
+    "trace_log.h",
   ],
   deps = [
     ":config_cc_proto",
@@ -38,6 +40,7 @@ cc_library(
     "well_known_names.h",
     "exception.h",
     "time.h",
+    "assert.h",
   ],
   deps = [
     ":config_cc_proto",

cpp2sky/assert.h

@@ -0,0 +1,24 @@
+// Copyright 2020 SkyAPM
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+namespace cpp2sky {
+
+template <class T>
+static constexpr bool false_v = false;
+
+#define CPP2SKY_STATIC_ASSERT(T, m) static_assert(false_v<T>, m)
+
+}  // namespace cpp2sky

cpp2sky/time.h

@@ -16,17 +16,16 @@
 
 #include <chrono>
 
+#include "cpp2sky/assert.h"
+
 namespace cpp2sky {
 
 using SystemTime = std::chrono::system_clock::time_point;
 using SteadyTime = std::chrono::steady_clock::time_point;
 
-template <class T>
-static constexpr bool false_v = false;
-
 template <class T>
 class TimePoint {
-  static_assert(false_v<T>, "Invalid time type");
+  CPP2SKY_STATIC_ASSERT(T, "Invalid time type");
 };
 
 template <>

cpp2sky/trace_log.h

@@ -0,0 +1,38 @@
+// Copyright 2021 SkyAPM
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <spdlog/logger.h>
+
+#include <string_view>
+#include <type_traits>
+
+#include "cpp2sky/assert.h"
+
+namespace cpp2sky {
+
+static constexpr std::string_view SPDLOG_LOG_FORMAT =
+    "{\"level\": \"%^%l%$\", \"msg\": \"%v";
+
+template <class T>
+std::string logFormat() {
+  if constexpr (std::is_same_v<T, spdlog::logger>) {
+    return SPDLOG_LOG_FORMAT.data();
+  } else {
+    CPP2SKY_STATIC_ASSERT(T, "non-supported logger type");
+  }
+}
+
+}  // namespace cpp2sky

cpp2sky/tracing_context.h

@@ -264,6 +264,13 @@ class TracingContext {
    * Determine whether to send this segment or not.
    */
   virtual bool readyToSend() = 0;
+
+  /**
+   * Get log message. Output value of this function is based on default cpp2sky
+   * logging format following with any format extracted with
+   * cpp2sky::logFormat().
+   */
+  virtual std::string logMessage(std::string_view message) const = 0;
 };
 
 using TracingContextPtr = std::shared_ptr<TracingContext>;

source/BUILD

@@ -8,7 +8,7 @@ cc_library(
     "grpc_async_client_impl.h",
     "tracer_impl.h",
     "cds_impl.h",
-    "dynamic_config.h"
+    "dynamic_config.h",
   ],
   srcs = [
     "propagation_impl.cc",

source/tracing_context_impl.cc

@@ -267,6 +267,23 @@ bool TracingContextImpl::readyToSend() {
   return true;
 }
 
+std::string TracingContextImpl::logMessage(std::string_view message) const {
+  std::string output = message.data();
+  output += "\", \"SW_CTX\": [";
+  output += "\"" + service_ + "\",";
+  output += "\"" + service_instance_ + "\",";
+  output += "\"" + trace_id_ + "\",";
+  output += "\"" + trace_segment_id_ + "\",";
+
+  if (!spans_.empty()) {
+    output += "\"" + std::to_string(spans_.back()->spanId()) + "\"]}";
+  } else {
+    output += "\"-1\"]}";
+  }
+
+  return output;
+}
+
 TracingContextFactory::TracingContextFactory(const TracerConfig& config)
     : service_name_(config.service_name()),
       instance_name_(config.instance_name()) {}

source/tracing_context_impl.h

@@ -155,6 +155,7 @@ class TracingContextImpl : public TracingContext {
   void setSkipAnalysis() override { should_skip_analysis_ = true; }
   bool skipAnalysis() override { return should_skip_analysis_; }
   bool readyToSend() override;
+  std::string logMessage(std::string_view message) const override;
 
  private:
   std::string encodeSpan(TracingSpanPtr parent_span,

test/tracing_context_test.cc

@@ -372,4 +372,12 @@ TEST_F(TracingContextTest, ReadyToSendTest) {
   EXPECT_FALSE(sc->readyToSend());
 }
 
+TEST_F(TracingContextTest, TraceLogTest) {
+  TracingContextImpl sc(config_.service_name(), config_.instance_name(),
+                        span_ctx_, span_ext_ctx_, random_);
+  EXPECT_EQ(
+      "test\", \"SW_CTX\": [\"mesh\",\"service_0\",\"1\",\"uuid\",\"-1\"]}",
+      sc.logMessage("test"));
+}
+
 }  // namespace cpp2sky