Merge pull request grpc#9184 from jtattermusch/qps_driver_cmdline

Better qps_json_driver message when QPS_WORKERS env is missing

test/cpp/qps/driver.cc

@@ -44,6 +44,7 @@
 #include <grpc/support/alloc.h>
 #include <grpc/support/host_port.h>
 #include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
 
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/env.h"
@@ -99,23 +100,36 @@ static std::unordered_map<string, std::deque<int>> get_hosts_and_cores(
  return hosts;
 }
 
-static deque<string> get_workers(const string& name) {
- char* env = gpr_getenv(name.c_str());
- if (!env || strlen(env) == 0) return deque<string>();
-
+static deque<string> get_workers(const string& env_name) {
+ char* env = gpr_getenv(env_name.c_str());
+ if (!env) {
+ env = gpr_strdup("");
+ }
  deque<string> out;
  char* p = env;
- for (;;) {
- char* comma = strchr(p, ',');
- if (comma) {
- out.emplace_back(p, comma);
- p = comma + 1;
- } else {
- out.emplace_back(p);
- gpr_free(env);
- return out;
+ if (strlen(env) != 0) {
+ for (;;) {
+ char* comma = strchr(p, ',');
+ if (comma) {
+ out.emplace_back(p, comma);
+ p = comma + 1;
+ } else {
+ out.emplace_back(p);
+ break;
+ }
  }
  }
+ if (out.size() == 0) {
+ gpr_log(GPR_ERROR,
+ "Environment variable \"%s\" does not contain a list of QPS "
+ "workers to use. Set it to a comma-separated list of "
+ "hostname:port pairs, starting with hosts that should act as "
+ "servers. E.g. export "
+ "%s=\"serverhost1:1234,clienthost1:1234,clienthost2:1234\"",
+ env_name.c_str(), env_name.c_str());
+ }
+ gpr_free(env);
+ return out;
 }
 
 // helpers for postprocess_scenario_result
@@ -241,6 +255,7 @@ std::unique_ptr<ScenarioResult> RunScenario(
  workers.push_back(addr);
  }
  }
+ GPR_ASSERT(workers.size() != 0);
 
  // if num_clients is set to <=0, do dynamic sizing: all workers
  // except for servers are clients
@@ -560,6 +575,9 @@ bool RunQuit() {
  // Get client, server lists
  bool result = true;
  auto workers = get_workers("QPS_WORKERS");
+ if (workers.size() == 0) {
+ return false;
+ }
  for (size_t i = 0; i < workers.size(); i++) {
  auto stub = WorkerService::NewStub(
  CreateChannel(workers[i], InsecureChannelCredentials()));