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// Demonstrates how to load a tracer library in at runtime and how to use it
// to construct spans. To run it using the mocktracer, invoke with
//
// TRACER_CONFIG=`mktemp`
// echo '{ "output_file": "/dev/stdout" }' > $TRACER_CONFIG
// dynamic_load-example /path/to/libopentracing_mocktracer.so $TRACER_CONFIG
#include <opentracing/dynamic_load.h>
#include <cassert>
#include <cerrno>
#include <fstream>
#include <iostream>
#include <iterator>
#include <string>
#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable : 4996)
#endif
int main(int argc, char* argv[]) {
if (argc != 3) {
std::cerr << "Usage: <tracer_library> <tracer_config_file>\n";
return -1;
}
// Load the tracer library.
std::string error_message;
auto handle_maybe =
opentracing::DynamicallyLoadTracingLibrary(argv[1], error_message);
if (!handle_maybe) {
std::cerr << "Failed to load tracer library " << error_message << "\n";
return -1;
}
// Read in the tracer's configuration.
std::ifstream istream{argv[2]};
if (!istream.good()) {
std::cerr << "Failed to open tracer config file " << argv[2] << ": "
<< std::strerror(errno) << "\n";
return -1;
}
std::string tracer_config{std::istreambuf_iterator<char>{istream},
std::istreambuf_iterator<char>{}};
// Construct a tracer.
auto& tracer_factory = handle_maybe->tracer_factory();
auto tracer_maybe =
tracer_factory.MakeTracer(tracer_config.c_str(), error_message);
if (!tracer_maybe) {
std::cerr << "Failed to create tracer " << error_message << "\n";
return -1;
}
auto& tracer = *tracer_maybe;
// Use the tracer to create some spans.
{
auto span_a = tracer->StartSpan("A");
assert(span_a != nullptr);
span_a->SetTag("abc", 123);
auto span_b =
tracer->StartSpan("B", {opentracing::ChildOf(&span_a->context())});
assert(span_b != nullptr);
span_b->SetTag("xyz", 987);
}
tracer->Close();
return 0;
}
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