trace_processor: add initial support for running metrics using shell

Context: go/perfetto-metrics
Bug: 129747127
Change-Id: Id07ddae420f00b376085142fd3b08e44467a0acb

src/trace_processor/trace_processor_shell.cc

diff --git a/src/trace_processor/trace_processor_shell.cc b/src/trace_processor/trace_processor_shell.cc
index ce8c481..d868d29 100644
--- a/src/trace_processor/trace_processor_shell.cc
+++ b/src/trace_processor/trace_processor_shell.cc
@@ -22,13 +22,16 @@
 
 #include <functional>
 #include <iostream>
+#include <vector>
 
 #include "perfetto/base/build_config.h"
 #include "perfetto/base/logging.h"
 #include "perfetto/base/scoped_file.h"
+#include "perfetto/base/string_splitter.h"
 #include "perfetto/base/time.h"
 #include "perfetto/trace_processor/trace_processor.h"
 
+#include "perfetto/metrics/metrics.pb.h"
 #include "perfetto/trace_processor/raw_query.pb.h"
 
 #if PERFETTO_BUILDFLAG(PERFETTO_OS_LINUX) ||   \
@@ -200,6 +203,15 @@
   return 0;
 }
 
+int RunMetrics(const std::vector<std::string>& metric_names) {
+  protos::TraceMetrics metrics_proto;
+  for (const auto& metric : metric_names) {
+    perfetto::base::ignore_result(metric);
+  }
+  perfetto::base::ignore_result(metrics_proto);
+  return 0;
+}
+
 void PrintQueryResultInteractively(base::TimeNanos t_start,
                                    const protos::RawQueryResult& res) {
   if (res.has_error()) {
@@ -417,11 +429,13 @@
       "Interactive trace processor shell.\n"
       "Usage: %s [OPTIONS] trace_file.pb\n\n"
       "Options:\n"
-      " -d        Enable virtual table debugging.\n"
-      " -s FILE   Read and execute contents of file before launching an "
-      "interactive shell.\n"
-      " -q FILE   Read and execute an SQL query from a file.\n"
-      " -e FILE   Export the trace into a SQLite database.\n",
+      " -d                   Enable virtual table debugging.\n"
+      " -s FILE              Read and execute contents of file before "
+      "launching an interactive shell.\n"
+      " -q FILE              Read and execute an SQL query from a file.\n"
+      " -e FILE              Export the trace into a SQLite database.\n"
+      " --run-metrics x,y,z   Runs a comma separated list of metrics and "
+      "prints the result as a TraceMetrics proto to stdout.\n",
       argv[0]);
 }
 
@@ -433,6 +447,7 @@
   const char* trace_file_path = nullptr;
   const char* query_file_path = nullptr;
   const char* sqlite_file_path = nullptr;
+  const char* metric_names = nullptr;
   bool launch_shell = true;
   for (int i = 1; i < argc; i++) {
     if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--version") == 0) {
@@ -458,6 +473,13 @@
       }
       sqlite_file_path = argv[i];
       continue;
+    } else if (strcmp(argv[i], "--run-metrics") == 0) {
+      if (++i == argc) {
+        PrintUsage(argv);
+        return 1;
+      }
+      metric_names = argv[i];
+      continue;
     } else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) {
       PrintUsage(argv);
       return 0;
@@ -532,6 +554,16 @@
   signal(SIGINT, [](int) { g_tp->InterruptQuery(); });
 #endif
 
+  // First, see if we have some metrics to run. If we do, just run them and
+  // return.
+  if (metric_names) {
+    std::vector<std::string> metrics;
+    for (base::StringSplitter ss(metric_names, ','); ss.Next();) {
+      metrics.emplace_back(ss.cur_token());
+    }
+    return RunMetrics(std::move(metrics));
+  }
+
   // If we were given a query file, load contents
   std::vector<std::string> queries;
   if (query_file_path) {