Add http client/server example (#632)

Author: lalitb

examples/CMakeLists.txt

@@ -6,3 +6,4 @@ add_subdirectory(simple)
 add_subdirectory(batch)
 add_subdirectory(metrics_simple)
 add_subdirectory(multithreaded)
+add_subdirectory(http)

examples/http/CMakeLists.txt

@@ -0,0 +1,24 @@
+find_package(CURL)
+
+if(NOT CURL_FOUND)
+  message(WARNING "Skipping http client/server example build: CURL not found")
+else()
+  include_directories(${CMAKE_SOURCE_DIR}/exporters/ostream/include
+                      ${CMAKE_SOURCE_DIR}/ext/include ${CMAKE_SOURCE_DIR/})
+
+  add_executable(http_client client.cc)
+  add_executable(http_server server.cc)
+
+  target_link_libraries(
+    http_client
+    ${CMAKE_THREAD_LIBS_INIT}
+    ${CORE_RUNTIME_LIBS}
+    opentelemetry_trace
+    http_client_curl
+    opentelemetry_exporter_ostream_span
+    ${CURL_LIBRARIES})
+
+  target_link_libraries(
+    http_server ${CMAKE_THREAD_LIBS_INIT} ${CORE_RUNTIME_LIBS}
+    opentelemetry_trace http_client_curl opentelemetry_exporter_ostream_span)
+endif()

examples/http/README.md

@@ -0,0 +1,87 @@
+# OpenTelemetry C++  Example
+
+## HTTP
+
+This is a simple example that demonstrates tracing an HTTP request from client to server. The example shows several aspects of tracing such as:
+
+* Using the `TracerProvider`
+* Span Attributes
+* Span Events
+* Using the ostream exporter
+* Nested spans (TBD)
+* W3c Trace Context Propagation (TBD)
+
+### Running the example
+
+1. The example uses HTTP server and client provided as part of this repo:
+    * [HTTP Client](https://github.com/open-telemetry/opentelemetry-cpp/tree/main/ext/include/opentelemetry/ext/http/client)
+    * [HTTP Server](https://github.com/open-telemetry/opentelemetry-cpp/tree/main/ext/include/opentelemetry/ext/http/server)
+
+2. Build and Deploy the opentelementry-cpp as described in [INSTALL.md](../../INSTALL.md)
+
+3. Start the server from the `examples/http` directory
+
+   ```console
+   $ http_server 8800
+    Server is running..Press ctrl-c to exit...
+   ```
+
+4. In a separate terminal window, run the client to make a single request:
+
+    ```console
+    $ ./http_client 8800
+    ...
+    ...
+    ```
+
+5. You should see console exporter output for both the client and server sessions.
+   * Client console
+
+   ```console
+   {
+     name          : /helloworld
+     trace_id      : 15c7ca1993b536085f4097f2818a7be4
+     span_id       : 7d9136e4eb4cb59d
+     parent_span_id: 0000000000000000
+     start         : 1617075613395810300
+     duration      : 1901100
+     description   :
+     span kind     : Client
+     status        : Unset
+     attributes    :
+           http.header.Date: Tue, 30 Mar 2021 03:40:13 GMT
+           http.header.Content-Length: 0
+           http.status_code: 200
+           http.method: GET
+           http.header.Host: localhost
+           http.header.Content-Type: text/plain
+           http.header.Connection: keep-alive
+           http.scheme: http
+           http.url: h**p://localhost:8800/helloworld
+   }
+   ```
+
+   * Server console
+
+   ```console
+   {
+     name          : /helloworld
+     trace_id      : bfa611a4bbb8b1871ef6a222d6a0f4dd
+     span_id       : 19e3cda7df63c9b9
+     parent_span_id: 0000000000000000
+     start         : 1617075522491536300
+     duration      : 50700
+     description   :
+     span kind     : Server
+     status        : Unset
+     attributes    :
+           http.header.Accept: */*
+           http.request_content_length: 0
+           http.header.Host: localhost:8800
+           http.scheme: http
+           http.client_ip: 127.0.0.1:44616
+           http.method: GET
+           net.host.port: 8800
+           http.server_name: localhost
+   }
+   ```

examples/http/client.cc

@@ -0,0 +1,78 @@
+#include "opentelemetry/ext/http/client/http_client_factory.h"
+#include "opentelemetry/ext/http/common/url_parser.h"
+#include "tracer_common.hpp"
+
+namespace
+{
+
+void sendRequest(const std::string &url)
+{
+  auto http_client = opentelemetry::ext::http::client::HttpClientFactory::CreateSync();
+
+  // start active span
+  opentelemetry::trace::StartSpanOptions options;
+  options.kind = opentelemetry::trace::SpanKind::kClient;  // client
+  opentelemetry::ext::http::common::UrlParser url_parser(url);
+
+  std::string span_name = url_parser.path_;
+  auto span             = get_tracer("http-client")
+                  ->StartSpan(span_name,
+                              {{"http.url", url_parser.url_},
+                               {"http.scheme", url_parser.scheme_},
+                               {"http.method", "GET"}},
+                              options);
+  auto scope = get_tracer("http-client")->WithActiveSpan(span);
+
+  opentelemetry::ext::http::client::Result result = http_client->Get(url);
+  if (result)
+  {
+    // set span attributes
+    auto status_code = result.GetResponse().GetStatusCode();
+    span->SetAttribute("http.status_code", status_code);
+    result.GetResponse().ForEachHeader([&span](opentelemetry::nostd::string_view header_name,
+                                               opentelemetry::nostd::string_view header_value) {
+      span->SetAttribute("http.header." + std::string(header_name.data()), header_value);
+      return true;
+    });
+
+    if (status_code >= 400)
+    {
+      span->SetStatus(opentelemetry::trace::StatusCode::kError);
+    }
+  }
+  else
+  {
+    span->SetStatus(opentelemetry::trace::StatusCode::kError,
+                    "Response Status :" +
+                        std::to_string(static_cast<typename std::underlying_type<
+                                           opentelemetry::ext::http::client::SessionState>::type>(
+                            result.GetSessionState())));
+  }
+  // end span and export data
+  span->End();
+}
+
+}  // namespace
+
+int main(int argc, char *argv[])
+{
+  initTracer();
+  constexpr char default_host[]   = "localhost";
+  constexpr char default_path[]   = "/helloworld";
+  constexpr uint16_t default_port = 8800;
+  uint16_t port;
+
+  // The port the validation service listens to can be specified via the command line.
+  if (argc > 1)
+  {
+    port = atoi(argv[1]);
+  }
+  else
+  {
+    port = default_port;
+  }
+
+  std::string url = "http://" + std::string(default_host) + ":" + std::to_string(port) +
+                    std::string(default_path);
+  sendRequest(url);
+}

examples/http/server.cc

@@ -0,0 +1,75 @@
+#include "server.hpp"
+#include "tracer_common.hpp"
+
+#include <iostream>
+#include <thread>
+
+namespace
+{
+uint16_t server_port         = 8800;
+constexpr char server_name[] = "localhost";
+
+class RequestHandler : public HTTP_SERVER_NS::HttpRequestCallback
+{
+public:
+  virtual int onHttpRequest(HTTP_SERVER_NS::HttpRequest const &request,
+                            HTTP_SERVER_NS::HttpResponse &response) override
+  {
+    opentelemetry::trace::StartSpanOptions options;
+    options.kind          = opentelemetry::trace::SpanKind::kServer;  // server
+    std::string span_name = request.uri;
+
+    auto span = get_tracer("http-server")
+                    ->StartSpan(span_name,
+                                {{"http.server_name", server_name},
+                                 {"net.host.port", server_port},
+                                 {"http.method", request.method},
+                                 {"http.scheme", "http"},
+                                 {"http.request_content_length", request.content.length()},
+                                 {"http.client_ip", request.client}},
+                                options);
+
+    auto scope = get_tracer("http_server")->WithActiveSpan(span);
+    for (auto &kv : request.headers)
+    {
+      span->SetAttribute("http.header." + std::string(kv.first.data()), kv.second);
+    }
+    if (request.uri == "/helloworld")
+    {
+      span->AddEvent("Processing request");
+      response.headers[HTTP_SERVER_NS::CONTENT_TYPE] = HTTP_SERVER_NS::CONTENT_TYPE_TEXT;
+      span->End();
+      return 200;
+    }
+    span->End();
+    return 404;
+  }
+};
+}  // namespace
+
+int main(int argc, char *argv[])
+{
+  initTracer();
+  uint16_t port;
+
+  // The port the validation service listens to can be specified via the command line.
+  if (argc > 1)
+  {
+    server_port = atoi(argv[1]);
+  }
+
+  HttpServer http_server(server_name, server_port);
+  RequestHandler req_handler;
+  http_server.AddHandler("/helloworld", &req_handler);
+  auto root_span = get_tracer("http_server")->StartSpan(__func__);
+  opentelemetry::trace::Scope scope(root_span);
+  http_server.Start();
+  std::cout << "Server is running..Press ctrl-c to exit...\n";
+  while (1)
+  {
+    std::this_thread::sleep_for(std::chrono::seconds(100));
+  }
+  http_server.Stop();
+  root_span->End();
+  return 0;
+}

examples/http/server.hpp

@@ -0,0 +1,47 @@
+#pragma once
+#include "opentelemetry/ext/http/server/http_server.h"
+#include<string>
+#include<atomic>
+
+
+namespace {
+
+class HttpServer : public HTTP_SERVER_NS::HttpRequestCallback
+{
+
+protected:
+    HTTP_SERVER_NS::HttpServer server_;
+    std::string server_url_ ;
+    uint16_t port_ ;
+    std::atomic<bool> is_running_{false};
+
+public:
+
+    HttpServer(std::string server_name = "test_server",uint16_t port = 8800): port_(port){
+        server_.setServerName(server_name);
+        server_.setKeepalive(false);
+    }
+
+    void AddHandler(std::string path, HTTP_SERVER_NS::HttpRequestCallback *request_handler){
+        server_.addHandler(path, *request_handler);
+    }
+
+    void Start() {
+        if (!is_running_.exchange(true)) {
+            server_.addListeningPort(port_);
+            server_.start();
+        }
+    }
+
+    void Stop() {
+        if (is_running_.exchange(false)){
+            server_.stop();
+        }
+    }
+
+    ~HttpServer(){
+        Stop();
+    }
+};
+
+}

examples/http/tracer_common.hpp

@@ -0,0 +1,29 @@
+#pragma once
+#include "opentelemetry/exporters/ostream/span_exporter.h"
+#include "opentelemetry/sdk/trace/simple_processor.h"
+#include "opentelemetry/sdk/trace/tracer_provider.h"
+#include "opentelemetry/trace/provider.h"
+
+#include <iostream>
+
+namespace {
+
+void initTracer() {
+  auto exporter = std::unique_ptr<sdktrace::SpanExporter>(
+      new opentelemetry::exporter::trace::OStreamSpanExporter);
+  auto processor = std::shared_ptr<sdktrace::SpanProcessor>(
+      new sdktrace::SimpleSpanProcessor(std::move(exporter)));
+  auto provider = nostd::shared_ptr<opentelemetry::trace::TracerProvider>(
+      new sdktrace::TracerProvider(processor, opentelemetry::sdk::resource::Resource::Create({}),
+                                   std::make_shared<opentelemetry::sdk::trace::AlwaysOnSampler>()));
+  // Set the global trace provider
+  opentelemetry::trace::Provider::SetTracerProvider(provider);
+}
+
+nostd::shared_ptr<opentelemetry::trace::Tracer> get_tracer(std::string tracer_name)
+{
+  auto provider = opentelemetry::trace::Provider::GetTracerProvider();
+  return provider->GetTracer(tracer_name);
+}
+
+}

exporters/ostream/include/opentelemetry/exporters/ostream/span_exporter.h

@@ -107,15 +107,12 @@ class OStreamSpanExporter final : public sdktrace::SpanExporter
   void printAttributes(std::unordered_map<std::string, sdkcommon::OwnedAttributeValue> map)
   {
     size_t size = map.size();
-    size_t i    = 1;
+    // size_t i    = 1;
     for (auto kv : map)
     {
-      sout_ << kv.first << ": ";
+      sout_ << "\t" << kv.first << ": ";
       print_value(kv.second);
-
-      if (i != size)
-        sout_ << ", ";
-      i++;
+      sout_ << std::endl;
     }
   }
 };

exporters/ostream/src/span_exporter.cc

@@ -69,10 +69,10 @@ sdktrace::ExportResult OStreamSpanExporter::Export(
             << "\n  duration      : " << span->GetDuration().count()
             << "\n  description   : " << span->GetDescription()
             << "\n  span kind     : " << span->GetSpanKind()
-            << "\n  status        : " << statusMap[int(span->GetStatus())]
-            << "\n  attributes    : ";
+            << "\n  status        : " << statusMap[int(span->GetStatus())] << "\n  attributes    : "
+            << "\n";
       printAttributes(span->GetAttributes());
-      sout_ << "\n}\n";
+      sout_ << "}\n";
     }
   }