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Add HTTP example server. (#314)
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‎examples/http/BUILD‎

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# Copyright 2019, OpenCensus Authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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load("//opencensus:copts.bzl", "DEFAULT_COPTS", "TEST_COPTS")
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licenses(["notice"]) # Apache License 2.0
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package(default_visibility = ["//visibility:private"])
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cc_binary(
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name = "server",
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srcs = ["server.cc"],
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copts = DEFAULT_COPTS,
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deps = [
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"//opencensus/exporters/stats/prometheus:prometheus_exporter",
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"//opencensus/exporters/stats/stackdriver:stackdriver_exporter",
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"//opencensus/exporters/stats/stdout:stdout_exporter",
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"//opencensus/exporters/trace/stackdriver:stackdriver_exporter",
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"//opencensus/exporters/trace/stdout:stdout_exporter",
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"//opencensus/exporters/trace/zipkin:zipkin_exporter",
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"//opencensus/trace",
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"@civetweb",
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"@com_github_jupp0r_prometheus_cpp//pull",
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"@com_google_absl//absl/strings",
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],
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)

‎examples/http/README.md‎

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# Example HTTP server
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This example uses OpenCensus to instrument an HTTP server.
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Usage:
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```shell
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bazel run examples/http:server -- 9001
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curl -i -H "traceparent: 00-404142434445464748494a4b4c4d4e4f-6162636465666768-01" 127.0.0.1:9001
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```
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Prometheus metrics can be seen at http://127.0.0.1:8080/metrics
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and running Zipkin will show traces, e.g.:
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```shell
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docker run -p 9411:9411 openzipkin/zipkin
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```

‎examples/http/server.cc‎

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// Copyright 2019, OpenCensus Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Example HTTP server with OpenCensus instrumentation.
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#include <cstdlib>
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#include <iostream>
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#include <memory>
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#include <string>
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#include "CivetServer.h"
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#include "absl/strings/escaping.h"
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#include "absl/strings/numbers.h"
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#include "absl/strings/str_cat.h"
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#include "absl/time/clock.h"
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#include "absl/time/time.h"
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#include "opencensus/exporters/stats/prometheus/prometheus_exporter.h"
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#include "opencensus/exporters/stats/stackdriver/stackdriver_exporter.h"
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#include "opencensus/exporters/stats/stdout/stdout_exporter.h"
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#include "opencensus/exporters/trace/stackdriver/stackdriver_exporter.h"
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#include "opencensus/exporters/trace/stdout/stdout_exporter.h"
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#include "opencensus/exporters/trace/zipkin/zipkin_exporter.h"
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#include "opencensus/stats/stats.h"
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#include "opencensus/trace/propagation/trace_context.h"
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#include "opencensus/trace/sampler.h"
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#include "opencensus/trace/span.h"
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#include "opencensus/trace/trace_config.h"
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#include "prometheus/exposer.h"
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namespace {
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using opencensus::exporters::trace::ZipkinExporter;
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using opencensus::exporters::trace::ZipkinExporterOptions;
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opencensus::stats::MeasureInt64 HitsMeasure() {
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static const opencensus::stats::MeasureInt64 measure =
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opencensus::stats::MeasureInt64::Register(
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"hits", "Number of hits to the webserver.", "1");
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return measure;
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}
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class CounterHandler : public CivetHandler {
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public:
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bool handleGet(CivetServer *server, struct mg_connection *conn) {
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// Handle incoming trace context.
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::opencensus::trace::SpanContext parent;
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const char *traceparent = server->getHeader(conn, "traceparent");
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if (traceparent != nullptr) {
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parent =
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opencensus::trace::propagation::FromTraceParentHeader(traceparent);
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}
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std::cerr << "parent is " << parent.ToString() << "\n";
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auto span = parent.IsValid()
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? ::opencensus::trace::Span::StartSpanWithRemoteParent(
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"Counter", parent)
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: ::opencensus::trace::Span::StartSpan("Counter");
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const mg_request_info *req = mg_get_request_info(conn);
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printf("Got %d headers:\n", req->num_headers);
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for (int i = 0; i < req->num_headers; ++i) {
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printf(" %s: %s\n", req->http_headers[i].name,
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req->http_headers[i].value);
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}
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// Perform work.
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counter_++;
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span.AddAnnotation("Incremented counter.", {{"counter_value", counter_}});
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mg_printf(conn,
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"HTTP/1.1 200 OK\r\nContent-Type: text/html\r\nConnection: "
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"close\r\n\r\n");
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mg_printf(conn, "<!DOCTYPE html>\n");
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mg_printf(conn, "<html><body>There have been %d hits.</body></html>\n",
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counter_);
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span.AddAnnotation("Built response.");
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opencensus::stats::Record({{HitsMeasure(), 1}});
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span.End();
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return true;
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}
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private:
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int counter_ = 0;
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};
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} // namespace
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int main(int argc, char **argv) {
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// Handle port argument.
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int port = 0;
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if (argc == 2) {
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if (!absl::SimpleAtoi(argv[1], &port)) {
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std::cerr << "Invalid port number: \"" << argv[1] << "\"";
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return 1;
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}
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}
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// For debugging, register exporters that just write to stdout.
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opencensus::exporters::stats::StdoutExporter::Register();
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opencensus::exporters::trace::StdoutExporter::Register();
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// Use the Prometheus exporter for stats.
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auto exporter =
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std::make_shared<opencensus::exporters::stats::PrometheusExporter>();
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prometheus::Exposer exposer("127.0.0.1:8080");
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exposer.RegisterCollectable(exporter);
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// Use the Zipkin exporter for tracing.
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ZipkinExporterOptions options("http://127.0.0.1:9411/api/v2/spans");
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options.service_name = "counter_server";
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ZipkinExporter::Register(options);
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// Add a View for hits.
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HitsMeasure();
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const auto hits_view =
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opencensus::stats::ViewDescriptor()
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.set_name("hits_view")
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.set_description("number of hits to the server over time")
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.set_measure("hits")
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.set_aggregation(opencensus::stats::Aggregation::Sum());
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opencensus::stats::View view(hits_view);
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assert(view.IsValid());
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hits_view.RegisterForExport();
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// Start the webserver.
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CivetServer server{
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{"listening_ports", absl::StrCat(port), "num_threads", "2"}};
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CounterHandler handler;
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server.addHandler("/", handler);
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std::cout << "Server listening on port " << port << "\n";
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for (;;) {
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absl::SleepFor(absl::Seconds(1));
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}
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}

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