[CSM O11y] Example logs (#37823)

Closes #37823

PiperOrigin-RevId: 681149244

examples/cpp/csm/observability/BUILD

@@ -44,6 +44,8 @@ cc_binary(
         "@com_google_absl//absl/flags:flag",
         "@com_google_absl//absl/flags:parse",
         "@com_google_absl//absl/log",
+        "@com_google_absl//absl/log:globals",
+        "@com_google_absl//absl/log:initialize",
         "@io_opentelemetry_cpp//exporters/prometheus:prometheus_exporter",
         "@io_opentelemetry_cpp//sdk/src/metrics",
     ],

examples/cpp/csm/observability/Dockerfile.server

@@ -27,6 +27,8 @@ RUN cp -rL /workdir/bazel-bin/examples/cpp/csm/observability/csm_greeter_server
 
 FROM python:3.9-slim-bookworm
 
+ENV GRPC_TRACE="xds_client,xds_resolver,xds_cluster_manager_lb,cds_lb,xds_cluster_resolver_lb,priority_lb,xds_cluster_impl_lb,weighted_target_lb,xds_server_config_fetcher,ring_hash_lb,outlier_detection_lb,xds_wrr_locality_lb,xds_override_host_lb"
+
 RUN apt-get update \
     && apt-get -y upgrade \
     && apt-get -y autoremove \

examples/cpp/csm/observability/csm_greeter_server.cc

@@ -22,6 +22,8 @@
 
 #include "absl/flags/flag.h"
 #include "absl/flags/parse.h"
+#include "absl/log/globals.h"
+#include "absl/log/initialize.h"
 #include "absl/log/log.h"
 #include "absl/strings/str_cat.h"
 #include "examples/cpp/otel/util.h"
@@ -42,6 +44,9 @@ ABSL_FLAG(std::string, prometheus_endpoint, "localhost:9464",
 
 int main(int argc, char** argv) {
   absl::ParseCommandLine(argc, argv);
+  absl::SetStderrThreshold(absl::LogSeverityAtLeast::kInfo);
+  absl::SetGlobalVLogLevel(2);
+  absl::InitializeLog();
   opentelemetry::exporter::metrics::PrometheusExporterOptions opts;
   // default was "localhost:9464" which causes connection issue across GKE pods
   opts.url = "0.0.0.0:9464";

examples/cpp/otel/util.cc

@@ -169,10 +169,10 @@ void RunClient(const std::string& target_str) {
   // are created. This channel models a connection to an endpoint specified by
   // the argument "--target=" which is the only expected argument.
   grpc::ChannelArguments args;
+  GreeterClient greeter(grpc::CreateCustomChannel(
+      target_str, grpc::InsecureChannelCredentials(), args));
   // Continuously send RPCs every second.
   while (true) {
-    GreeterClient greeter(grpc::CreateCustomChannel(
-        target_str, grpc::InsecureChannelCredentials(), args));
     std::string user("world");
     std::string reply = greeter.SayHello(user);
     std::cout << "Greeter received: " << reply << std::endl;