Add metric with number of checkpoints

Author: lalinsky

src/Index.zig

@@ -222,6 +222,8 @@ fn doCheckpoint(self: *Self) !bool {
     self.memory_segments.commitUpdate(&memory_segments_update);
     self.file_segments.commitUpdate(&file_segments_update);
 
+    metrics.checkpoint();
+
     self.maybeScheduleFileSegmentMerge();
 
     return true;
@@ -266,7 +268,7 @@ fn maybeMergeFileSegments(self: *Self) !bool {
     defer self.segments_lock.unlock();
 
     self.file_segments.commitUpdate(&upd);
-    // log.debug("committed file segments merge", .{});
+
     metrics.fileSegmentMerge();
 
     return true;
@@ -294,7 +296,7 @@ fn maybeMergeMemorySegments(self: *Self) !bool {
     defer self.segments_lock.unlock();
 
     self.memory_segments.commitUpdate(&upd);
-    // log.debug("committed memory segments merge", .{});
+
     metrics.memorySegmentMerge();
 
     self.maybeScheduleCheckpoint();

src/metrics.zig

@@ -5,6 +5,7 @@ var metrics = m.initializeNoop(Metrics);
 const Metrics = struct {
     searches: m.Counter(u64),
     updates: m.Counter(u64),
+    checkpoints: m.Counter(u64),
     memory_segment_merges: m.Counter(u64),
     file_segment_merges: m.Counter(u64),
 };
@@ -17,6 +18,10 @@ pub fn update(count: usize) void {
     metrics.updates.incrBy(@intCast(count));
 }
 
+pub fn checkpoint() void {
+    metrics.checkpoints.incr();
+}
+
 pub fn memorySegmentMerge() void {
     metrics.memory_segment_merges.incr();
 }
@@ -29,6 +34,7 @@ pub fn initializeMetrics(comptime opts: m.RegistryOpts) !void {
     metrics = .{
         .searches = m.Counter(u64).init("searches_total", .{}, opts),
         .updates = m.Counter(u64).init("updates_total", .{}, opts),
+        .checkpoints = m.Counter(u64).init("checkpoints_total", .{}, opts),
         .memory_segment_merges = m.Counter(u64).init("memory_segment_merges_total", .{}, opts),
         .file_segment_merges = m.Counter(u64).init("file_segment_merges_total", .{}, opts),
     };