aos: add dynamic logging on an opt-in basis

Applications including this can have vlog changed with:

aos_send /aos aos.logging.DynamicLogCommand '{"name": "app", "vlog_level": 1}'

Change-Id: Id387cdb501ad84ed3e266a2077ea93478b480afa
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/logging/dynamic_logging_test.cc b/aos/logging/dynamic_logging_test.cc
new file mode 100644
index 0000000..216193c
--- /dev/null
+++ b/aos/logging/dynamic_logging_test.cc
@@ -0,0 +1,93 @@
+#include <sys/stat.h>
+
+#include "aos/events/event_loop.h"
+#include "aos/events/simulated_event_loop.h"
+#include "aos/logging/dynamic_logging.h"
+#include "aos/testing/path.h"
+#include "glog/logging.h"
+#include "gtest/gtest.h"
+
+using aos::testing::ArtifactPath;
+
+namespace aos {
+namespace logging {
+namespace testing {
+
+namespace chrono = std::chrono;
+
+class DynamicLoggingTest : public ::testing::Test {
+ public:
+  DynamicLoggingTest()
+      : config_(aos::configuration::ReadConfig(
+            ArtifactPath("aos/events/pingpong_config.json"))),
+        event_loop_factory_(&config_.message()),
+        event_loop_send_(event_loop_factory_.MakeEventLoop("send")),
+        event_loop_main_(event_loop_factory_.MakeEventLoop("main")) {}
+
+  aos::FlatbufferDetachedBuffer<aos::Configuration> config_;
+  SimulatedEventLoopFactory event_loop_factory_;
+
+  std::unique_ptr<EventLoop> event_loop_send_;
+  std::unique_ptr<EventLoop> event_loop_main_;
+};
+
+TEST_F(DynamicLoggingTest, TestVLog) {
+  aos::Sender<DynamicLogCommand> dynamic_log_command_sender =
+      event_loop_send_->MakeSender<DynamicLogCommand>("/aos");
+
+  // Set VLOG level to 1 at t=50us and then back to 0 at t=150us.
+  int log_level = 1;
+  aos::TimerHandler *timer_handler = event_loop_send_->AddTimer(
+      [this, &dynamic_log_command_sender, &log_level, &timer_handler]() {
+        aos::Sender<DynamicLogCommand>::Builder message =
+            dynamic_log_command_sender.MakeBuilder();
+        const auto name_str = message.fbb()->CreateString("main");
+
+        DynamicLogCommand::Builder builder =
+            message.MakeBuilder<DynamicLogCommand>();
+        builder.add_name(name_str);
+        builder.add_vlog_level(log_level);
+        CHECK_EQ(message.Send(builder.Finish()), RawSender::Error::kOk);
+        --log_level;
+        if (log_level >= 0) {
+          timer_handler->Setup(event_loop_send_->monotonic_now() +
+                               chrono::microseconds(100));
+        }
+      });
+  timer_handler->Setup(event_loop_send_->monotonic_now() +
+                       chrono::microseconds(50));
+
+  // VLOG(1) at t=0us, t=100us, t=200us
+  aos::TimerHandler *vlog_timer_handler =
+      event_loop_main_->AddTimer([]() { VLOG(1) << "VLOG 1"; });
+  vlog_timer_handler->Setup(event_loop_main_->monotonic_now(),
+                            chrono::microseconds(100));
+
+  DynamicLogging dynamic_logging(event_loop_main_.get());
+
+  {
+    // Validate no log message in first 50us.
+    ::testing::internal::CaptureStderr();
+    event_loop_factory_.RunFor(chrono::microseconds(50));
+    std::string output = ::testing::internal::GetCapturedStderr();
+    EXPECT_EQ(output.find("VLOG 1"), std::string::npos);
+  }
+  {
+    // Validate 1 log message between 50us to 150us
+    ::testing::internal::CaptureStderr();
+    event_loop_factory_.RunFor(chrono::microseconds(100));
+    std::string output = ::testing::internal::GetCapturedStderr();
+    EXPECT_NE(output.find("VLOG 1"), std::string::npos);
+  }
+  {
+    // Validate no log message between 150us to 250us
+    ::testing::internal::CaptureStderr();
+    event_loop_factory_.RunFor(chrono::microseconds(100));
+    std::string output = ::testing::internal::GetCapturedStderr();
+    EXPECT_EQ(output.find("VLOG 1"), std::string::npos);
+  }
+}
+
+}  // namespace testing
+}  // namespace logging
+}  // namespace aos