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#include <memory>
#include <string>
#include <thread>
#include <utility>
#include <vector>

#include <gflags/gflags.h>
#include <grpc++/create_channel.h>
#include <grpc++/grpc++.h>
#include <grpc++/impl/thd.h>
#include <grpc/support/time.h>

#include "test/cpp/interop/interop_client.h"
#include "test/cpp/interop/stress_interop_client.h"
#include "test/cpp/util/metrics_server.h"
#include "test/cpp/util/test_config.h"
#include "test/proto/metrics.grpc.pb.h"
#include "test/proto/metrics.pb.h"

DEFINE_int32(metrics_port, 8081, "The metrics server port.");

DEFINE_int32(metrics_collection_interval_secs, 5,
             "How often (in seconds) should metrics be recorded.");

DEFINE_int32(sleep_duration_ms, 0,
             "The duration (in millisec) between two"
             " consecutive test calls (per server) issued by the server.");

DEFINE_int32(test_duration_secs, -1,
             "The length of time (in seconds) to run"
             " the test. Enter -1 if the test should run continuously until"
             " forcefully terminated.");

DEFINE_string(server_addresses, "localhost:8080",
              "The list of server"
              " addresses in the format:\n"
              " \"<name_1>:<port_1>,<name_2>:<port_1>...<name_N>:<port_N>\"\n"
              " Note: <name> can be servername or IP address.");

DEFINE_int32(num_channels_per_server, 1, "Number of channels for each server");

DEFINE_int32(num_stubs_per_channel, 1,
             "Number of stubs per each channels to server. This number also "
             "indicates the max number of parallel RPC calls on each channel "
             "at any given time.");

// TODO(sreek): Add more test cases here in future
DEFINE_string(test_cases, "",
              "List of test cases to call along with the"
              " relative weights in the following format:\n"
              " \"<testcase_1:w_1>,<testcase_2:w_2>...<testcase_n:w_n>\"\n"
              " The following testcases are currently supported:\n"
              "   empty_unary\n"
              "   large_unary\n"
              "   large_compressed_unary\n"
              "   client_streaming\n"
              "   server_streaming\n"
              "   empty_stream\n"
              " Example: \"empty_unary:20,large_unary:10,empty_stream:70\"\n"
              " The above will execute 'empty_unary', 20% of the time,"
              " 'large_unary', 10% of the time and 'empty_stream' the remaining"
              " 70% of the time");

using grpc::testing::kTestCaseList;
using grpc::testing::MetricsService;
using grpc::testing::MetricsServiceImpl;
using grpc::testing::StressTestInteropClient;
using grpc::testing::TestCaseType;
using grpc::testing::UNKNOWN_TEST;
using grpc::testing::WeightedRandomTestSelector;

TestCaseType GetTestTypeFromName(const grpc::string& test_name) {
  TestCaseType test_case = UNKNOWN_TEST;

  for (auto it = kTestCaseList.begin(); it != kTestCaseList.end(); it++) {
    if (test_name == it->second) {
      test_case = it->first;
      break;
    }
  }

  return test_case;
}

// Converts a string of comma delimited tokens to a vector of tokens
bool ParseCommaDelimitedString(const grpc::string& comma_delimited_str,
                               std::vector<grpc::string>& tokens) {
  size_t bpos = 0;
  size_t epos = grpc::string::npos;

  while ((epos = comma_delimited_str.find(',', bpos)) != grpc::string::npos) {
    tokens.emplace_back(comma_delimited_str.substr(bpos, epos - bpos));
    bpos = epos + 1;
  }

  tokens.emplace_back(comma_delimited_str.substr(bpos));  // Last token
  return true;
}

// Input: Test case string "<testcase_name:weight>,<testcase_name:weight>...."
// Output:
//   - Whether parsing was successful (return value)
//   - Vector of (test_type_enum, weight) pairs returned via 'tests' parameter
bool ParseTestCasesString(const grpc::string& test_cases,
                          std::vector<std::pair<TestCaseType, int>>& tests) {
  bool is_success = true;

  std::vector<grpc::string> tokens;
  ParseCommaDelimitedString(test_cases, tokens);

  for (auto it = tokens.begin(); it != tokens.end(); it++) {
    // Token is in the form <test_name>:<test_weight>
    size_t colon_pos = it->find(':');
    if (colon_pos == grpc::string::npos) {
      gpr_log(GPR_ERROR, "Error in parsing test case string: %s", it->c_str());
      is_success = false;
      break;
    }

    grpc::string test_name = it->substr(0, colon_pos);
    int weight = std::stoi(it->substr(colon_pos + 1));
    TestCaseType test_case = GetTestTypeFromName(test_name);
    if (test_case == UNKNOWN_TEST) {
      gpr_log(GPR_ERROR, "Unknown test case: %s", test_name.c_str());
      is_success = false;
      break;
    }

    tests.emplace_back(std::make_pair(test_case, weight));
  }

  return is_success;
}

// For debugging purposes
void LogParameterInfo(const std::vector<grpc::string>& addresses,
                      const std::vector<std::pair<TestCaseType, int>>& tests) {
  gpr_log(GPR_INFO, "server_addresses: %s", FLAGS_server_addresses.c_str());
  gpr_log(GPR_INFO, "test_cases : %s", FLAGS_test_cases.c_str());
  gpr_log(GPR_INFO, "sleep_duration_ms: %d", FLAGS_sleep_duration_ms);
  gpr_log(GPR_INFO, "test_duration_secs: %d", FLAGS_test_duration_secs);

  int num = 0;
  for (auto it = addresses.begin(); it != addresses.end(); it++) {
    gpr_log(GPR_INFO, "%d:%s", ++num, it->c_str());
  }

  num = 0;
  for (auto it = tests.begin(); it != tests.end(); it++) {
    TestCaseType test_case = it->first;
    int weight = it->second;
    gpr_log(GPR_INFO, "%d. TestCaseType: %d, Weight: %d", ++num, test_case,
            weight);
  }
}

int main(int argc, char** argv) {
  grpc::testing::InitTest(&argc, &argv, true);

  srand(time(NULL));

  // Parse the server addresses
  std::vector<grpc::string> server_addresses;
  ParseCommaDelimitedString(FLAGS_server_addresses, server_addresses);

  // Parse test cases and weights
  if (FLAGS_test_cases.length() == 0) {
    gpr_log(GPR_INFO, "Not running tests. The 'test_cases' string is empty");
    return 1;
  }

  std::vector<std::pair<TestCaseType, int>> tests;
  if (!ParseTestCasesString(FLAGS_test_cases, tests)) {
    gpr_log(GPR_ERROR, "Error in parsing test cases string %s ",
            FLAGS_test_cases.c_str());
    return 1;
  }

  LogParameterInfo(server_addresses, tests);

  WeightedRandomTestSelector test_selector(tests);
  MetricsServiceImpl metrics_service;

  gpr_log(GPR_INFO, "Starting test(s)..");

  std::vector<grpc::thread> test_threads;

  // Create and start the test threads.
  // Note that:
  // - Each server can have multiple channels (as configured by
  // FLAGS_num_channels_per_server).
  //
  // - Each channel can have multiple stubs (as configured by
  // FLAGS_num_stubs_per_channel). This is to test calling multiple RPCs in
  // parallel on the same channel.
  int thread_idx = 0;
  int server_idx = -1;
  char buffer[256];
  for (auto it = server_addresses.begin(); it != server_addresses.end(); it++) {
    ++server_idx;
    // Create channel(s) for each server
    for (int channel_idx = 0; channel_idx < FLAGS_num_channels_per_server;
         channel_idx++) {
      // TODO (sreek). This won't work for tests that require Authentication
      std::shared_ptr<grpc::Channel> channel(
          grpc::CreateChannel(*it, grpc::InsecureChannelCredentials()));

      // Create stub(s) for each channel
      for (int stub_idx = 0; stub_idx < FLAGS_num_stubs_per_channel;
           stub_idx++) {
        StressTestInteropClient* client = new StressTestInteropClient(
            ++thread_idx, *it, channel, test_selector, FLAGS_test_duration_secs,
            FLAGS_sleep_duration_ms, FLAGS_metrics_collection_interval_secs);

        bool is_already_created;
        // Gauge name
        std::snprintf(buffer, sizeof(buffer),
                      "/stress_test/server_%d/channel_%d/stub_%d/qps",
                      server_idx, channel_idx, stub_idx);

        test_threads.emplace_back(grpc::thread(
            &StressTestInteropClient::MainLoop, client,
            metrics_service.CreateGauge(buffer, &is_already_created)));

        // The Gauge should not have been already created
        GPR_ASSERT(!is_already_created);
      }
    }
  }

  // Start metrics server before waiting for the stress test threads
  std::unique_ptr<grpc::Server> metrics_server =
      metrics_service.StartServer(FLAGS_metrics_port);

  // Wait for the stress test threads to complete
  for (auto it = test_threads.begin(); it != test_threads.end(); it++) {
    it->join();
  }

  metrics_server->Wait();
  return 0;
}