From 1a9150fd8435914eec35a0dbdff3a9a2266d9e97 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Mon, 24 Dec 2018 11:07:19 +0100
Subject: [PATCH] Add metrics for reading frames from disk.

---
 futatabi/frame_on_disk.cpp | 46 ++++++++++++++++++++++++++++++++++++++
 futatabi/frame_on_disk.h   |  1 +
 2 files changed, 47 insertions(+)

diff --git a/futatabi/frame_on_disk.cpp b/futatabi/frame_on_disk.cpp
index b496b3d..34fcd38 100644
--- a/futatabi/frame_on_disk.cpp
+++ b/futatabi/frame_on_disk.cpp
@@ -1,22 +1,60 @@
 #include <fcntl.h>
 #include <unistd.h>
 
+#include <atomic>
+#include <chrono>
+#include <mutex>
+
 #include "frame_on_disk.h"
+#include "shared/metrics.h"
 
 using namespace std;
+using namespace std::chrono;
+
+namespace {
+
+// There can be multiple FrameReader classes, so make all the metrics static.
+once_flag frame_metrics_inited;
+
+atomic<int64_t> metric_frame_opened_files{0};
+atomic<int64_t> metric_frame_closed_files{0};
+atomic<int64_t> metric_frame_read_bytes{0};
+atomic<int64_t> metric_frame_read_frames{0};
+
+Summary metric_frame_read_time_seconds;
+
+}  // namespace
+
+FrameReader::FrameReader()
+{
+	call_once(frame_metrics_inited, []{
+		global_metrics.add("frame_opened_files", &metric_frame_opened_files);
+		global_metrics.add("frame_closed_files", &metric_frame_closed_files);
+		global_metrics.add("frame_read_bytes", &metric_frame_read_bytes);
+		global_metrics.add("frame_read_frames", &metric_frame_read_frames);
+
+		vector<double> quantiles{0.01, 0.1, 0.25, 0.5, 0.75, 0.9, 0.99};
+		metric_frame_read_time_seconds.init(quantiles, 60.0);
+		global_metrics.add("frame_read_time_seconds", &metric_frame_read_time_seconds);
+	});
+}
 
 FrameReader::~FrameReader()
 {
 	if (fd != -1) {
 		close(fd);
+		++metric_frame_closed_files;
 	}
 }
 
 string FrameReader::read_frame(FrameOnDisk frame)
 {
+	steady_clock::time_point start = steady_clock::now();
+
 	if (int(frame.filename_idx) != last_filename_idx) {
 		if (fd != -1) {
 			close(fd);  // Ignore errors.
+			++metric_frame_closed_files;
 		}
 
 		string filename;
@@ -35,6 +73,7 @@ string FrameReader::read_frame(FrameOnDisk frame)
 		posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);
 
 		last_filename_idx = frame.filename_idx;
+		++metric_frame_opened_files;
 	}
 
 	string str;
@@ -49,5 +88,12 @@ string FrameReader::read_frame(FrameOnDisk frame)
 
 		offset += ret;
 	}
+
+	steady_clock::time_point stop = steady_clock::now();
+	metric_frame_read_time_seconds.count_event(duration<double>(stop - start).count());
+
+	metric_frame_read_bytes += frame.size;
+	++metric_frame_read_frames;
+
 	return str;
 }
diff --git a/futatabi/frame_on_disk.h b/futatabi/frame_on_disk.h
index 47fcb32..2ac86fc 100644
--- a/futatabi/frame_on_disk.h
+++ b/futatabi/frame_on_disk.h
@@ -27,6 +27,7 @@ extern std::vector<std::string> frame_filenames;  // Under frame_mu.
 // for a single .frames file.)
 class FrameReader {
 public:
+	FrameReader();
 	~FrameReader();
 	std::string read_frame(FrameOnDisk frame);
 
-- 
2.39.2