Add Ostream log exporter and tests (open-telemetry#430)

exporters/ostream/BUILD

@@ -1,5 +1,28 @@
 package(default_visibility = ["//visibility:public"])
 
+cc_library(
+    name = "ostream_log_exporter",
+    srcs = [
+        "src/log_exporter.cc",
+    ],
+    hdrs = [
+        "include/opentelemetry/exporters/ostream/log_exporter.h",
+    ],
+    strip_include_prefix = "include",
+    deps = [
+        "//sdk/src/logs",
+    ],
+)
+
+cc_test(
+    name = "ostream_log_test",
+    srcs = ["test/ostream_log_test.cc"],
+    deps = [
+        ":ostream_log_exporter",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_library(
     name = "ostream_metrics_exporter",
     srcs = [

exporters/ostream/CMakeLists.txt

@@ -1,11 +1,13 @@
 include_directories(include)
 
+add_library(opentelemetry_exporter_ostream_logs src/log_exporter.cc)
 add_library(opentelemetry_exporter_ostream_metrics src/metrics_exporter.cc)
 add_library(opentelemetry_exporter_ostream_span src/span_exporter.cc)
 
 if(BUILD_TESTING)
   add_executable(ostream_metrics_test test/ostream_metrics_test.cc)
   add_executable(ostream_span_test test/ostream_span_test.cc)
+  add_executable(ostream_log_test test/ostream_log_test.cc)
 
   target_link_libraries(
     ostream_span_test ${GTEST_BOTH_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT}
@@ -15,12 +17,23 @@ if(BUILD_TESTING)
     ostream_metrics_test ${GTEST_BOTH_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT}
     opentelemetry_exporter_ostream_metrics)
 
+  target_link_libraries(
+    ostream_log_test ${GTEST_BOTH_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT}
+    opentelemetry_exporter_ostream_logs opentelemetry_logs)
+
+  gtest_add_tests(
+    TARGET ostream_log_test
+    TEST_PREFIX exporter.
+    TEST_LIST ostream_log_test)
+
   gtest_add_tests(
     TARGET ostream_metrics_test
     TEST_PREFIX exporter.
     TEST_LIST ostream_metrics_test)
+
   gtest_add_tests(
     TARGET ostream_span_test
     TEST_PREFIX exporter.
     TEST_LIST ostream_span_test)
+
 endif() # BUILD_TESTING

exporters/ostream/include/opentelemetry/exporters/ostream/log_exporter.h

@@ -0,0 +1,67 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * 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 "opentelemetry/nostd/type_traits.h"
+#include "opentelemetry/sdk/logs/exporter.h"
+#include "opentelemetry/sdk/logs/log_record.h"
+#include "opentelemetry/version.h"
+
+#include <iostream>
+#include <sstream>
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace logs
+{
+/**
+ * The OStreamLogExporter exports logs through an ostream (default set to std::cout)
+ */
+class OStreamLogExporter final : public opentelemetry::sdk::logs::LogExporter
+{
+public:
+  /**
+   * Create an OStreamLogExporter. This constructor takes in a reference to an ostream that the
+   * Export() method will send log data into. The default ostream is set to stdout.
+   */
+  explicit OStreamLogExporter(std::ostream &sout = std::cout) noexcept;
+
+  std::unique_ptr<sdk::logs::Recordable> MakeRecordable() noexcept override;
+
+  /**
+   * Exports a span of logs sent from the processor.
+   */
+  opentelemetry::sdk::logs::ExportResult Export(
+      const opentelemetry::nostd::span<std::unique_ptr<sdk::logs::Recordable>>
+          &records) noexcept override;
+
+  /**
+   * Marks the OStream Log Exporter as shut down.
+   */
+  bool Shutdown(
+      std::chrono::microseconds timeout = std::chrono::microseconds::max()) noexcept override;
+
+private:
+  // The OStream to send the logs to
+  std::ostream &sout_;
+  // Whether this exporter has been shut down
+  bool is_shutdown_ = false;
+};
+}  // namespace logs
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE

exporters/ostream/src/log_exporter.cc

@@ -0,0 +1,189 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * 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.
+ */
+
+#include "opentelemetry/exporters/ostream/log_exporter.h"
+
+#include <iostream>
+
+namespace nostd   = opentelemetry::nostd;
+namespace sdklogs = opentelemetry::sdk::logs;
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace logs
+{
+/*********************** Helper functions ************************/
+
+/*
+  print_value is used to print out the value of an attribute within a vector.
+  These values are held in a variant which makes the process of printing them much more
+  complicated.
+*/
+
+template <typename T>
+void print_value(const T &item, std::ostream &sout)
+{
+  sout << item;
+}
+
+template <typename T>
+void print_value(const std::vector<T> &vec, std::ostream &sout)
+{
+  sout << '[';
+  size_t i  = 1;
+  size_t sz = vec.size();
+  for (auto v : vec)
+  {
+    sout << v;
+    if (i != sz)
+      sout << ',' << ' ';
+    i++;
+  };
+  sout << ']';
+}
+
+// Prior to C++14, generic lambda is not available so fallback to functor.
+#if __cplusplus < 201402L
+
+class OwnedAttributeValueVisitor
+{
+public:
+  OwnedAttributeValueVisitor(std::ostream &sout) : sout_(sout) {}
+
+  template <typename T>
+  void operator()(T &&arg)
+  {
+    print_value(arg, sout_);
+  }
+
+private:
+  // The OStream to send the logs to
+  std::ostream &sout_;
+};
+
+#endif
+
+void print_value(sdk::common::OwnedAttributeValue &value, std::ostream &sout)
+{
+#if __cplusplus < 201402L
+  nostd::visit(OwnedAttributeValueVisitor(sout), value);
+#else
+  nostd::visit([&sout](auto &&arg) { print_value(arg, sout); }, value);
+#endif
+}
+
+void printMap(std::unordered_map<std::string, sdk::common::OwnedAttributeValue> map,
+              std::ostream &sout)
+{
+  sout << "{";
+  size_t size = map.size();
+  size_t i    = 1;
+  for (auto kv : map)
+  {
+    sout << "{" << kv.first << ": ";
+    print_value(kv.second, sout);
+    sout << "}";
+
+    if (i != size)
+      sout << ", ";
+    i++;
+  }
+  sout << "}";
+}
+
+/*********************** Constructor ***********************/
+
+OStreamLogExporter::OStreamLogExporter(std::ostream &sout) noexcept : sout_(sout) {}
+
+/*********************** Exporter methods ***********************/
+
+std::unique_ptr<sdklogs::Recordable> OStreamLogExporter::MakeRecordable() noexcept
+{
+  return std::unique_ptr<sdklogs::Recordable>(new sdklogs::LogRecord());
+}
+
+sdklogs::ExportResult OStreamLogExporter::Export(
+    const nostd::span<std::unique_ptr<sdklogs::Recordable>> &records) noexcept
+{
+  if (is_shutdown_)
+  {
+    return sdklogs::ExportResult::kFailure;
+  }
+
+  for (auto &record : records)
+  {
+    // Convert recordable to a LogRecord so that the getters of the LogRecord can be used
+    auto log_record =
+        std::unique_ptr<sdklogs::LogRecord>(static_cast<sdklogs::LogRecord *>(record.release()));
+
+    if (log_record == nullptr)
+    {
+      // TODO: Log Internal SDK error "recordable data was lost"
+      continue;
+    }
+
+    // Convert trace, spanid, traceflags into exportable representation
+    constexpr int trace_id_len    = 32;
+    constexpr int span_id__len    = 16;
+    constexpr int trace_flags_len = 2;
+
+    char trace_id[trace_id_len]       = {0};
+    char span_id[span_id__len]        = {0};
+    char trace_flags[trace_flags_len] = {0};
+
+    log_record->GetTraceId().ToLowerBase16(trace_id);
+    log_record->GetSpanId().ToLowerBase16(span_id);
+    log_record->GetTraceFlags().ToLowerBase16(trace_flags);
+
+    // Print out each field of the log record, noting that severity is separated
+    // into severity_num and severity_text
+    sout_ << "{\n"
+          << "  timestamp     : " << log_record->GetTimestamp().time_since_epoch().count() << "\n"
+          << "  severity_num  : " << static_cast<int>(log_record->GetSeverity()) << "\n"
+          << "  severity_text : "
+          << opentelemetry::logs::SeverityNumToText[static_cast<int>(log_record->GetSeverity())]
+          << "\n"
+          << "  name          : " << log_record->GetName() << "\n"
+          << "  body          : " << log_record->GetBody() << "\n"
+          << "  resource      : ";
+
+    printMap(log_record->GetResource(), sout_);
+
+    sout_ << "\n"
+          << "  attributes    : ";
+
+    printMap(log_record->GetAttributes(), sout_);
+
+    sout_ << "\n"
+          << "  trace_id      : " << std::string(trace_id, trace_id_len) << "\n"
+          << "  span_id       : " << std::string(span_id, span_id__len) << "\n"
+          << "  trace_flags   : " << std::string(trace_flags, trace_flags_len) << "\n"
+          << "}\n";
+  }
+
+  return sdklogs::ExportResult::kSuccess;
+}
+
+bool OStreamLogExporter::Shutdown(std::chrono::microseconds timeout) noexcept
+{
+  is_shutdown_ = true;
+  return true;
+}
+
+}  // namespace logs
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE