Update the queue length metric after trimming, not before.

[nageru] / metrics.cpp

diff --git a/metrics.cpp b/metrics.cpp
index f44ced2c15a66715977b352736122442c9ba4541..5079acb2064e5515a1a549af00c35924edcc57dd 100644 (file)
--- a/metrics.cpp
+++ b/metrics.cpp
@@ -63,10 +63,11 @@ void Metrics::add(const string &name, const vector<pair<string, string>> &labels
        types[name] = type;
 }
 
-void Metrics::add(const string &name, const vector<pair<string, string>> &labels, Histogram *location)
+void Metrics::add(const string &name, const vector<pair<string, string>> &labels, Histogram *location, Laziness laziness)
 {
        Metric metric;
        metric.data_type = DATA_TYPE_HISTOGRAM;
+       metric.laziness = laziness;
        metric.location_histogram = location;
 
        lock_guard<mutex> lock(mu);
@@ -118,9 +119,15 @@ string Metrics::serialize() const
                if (metric.data_type == DATA_TYPE_INT64) {
                        ss << name << " " << metric.location_int64->load() << "\n";
                } else if (metric.data_type == DATA_TYPE_DOUBLE) {
-                       ss << name << " " << metric.location_double->load() << "\n";
+                       double val = metric.location_double->load();
+                       if (isnan(val)) {
+                               // Prometheus can't handle “-nan”.
+                               ss << name << " NaN\n";
+                       } else {
+                               ss << name << " " << val << "\n";
+                       }
                } else {
-                       ss << metric.location_histogram->serialize(key_and_metric.first.name, key_and_metric.first.labels);
+                       ss << metric.location_histogram->serialize(metric.laziness, key_and_metric.first.name, key_and_metric.first.labels);
                }
        }
 
@@ -169,8 +176,22 @@ void Histogram::count_event(double val)
        sum = sum + val;
 }
 
-string Histogram::serialize(const string &name, const vector<pair<string, string>> &labels) const
+string Histogram::serialize(Metrics::Laziness laziness, const string &name, const vector<pair<string, string>> &labels) const
 {
+       // Check if the histogram is empty and should not be serialized.
+       if (laziness == Metrics::PRINT_WHEN_NONEMPTY && count_after_last_bucket.load() == 0) {
+               bool empty = true;
+               for (size_t bucket_idx = 0; bucket_idx < num_buckets; ++bucket_idx) {
+                       if (buckets[bucket_idx].count.load() != 0) {
+                               empty = false;
+                               break;
+                       }
+               }
+               if (empty) {
+                       return "";
+               }
+       }
+
        stringstream ss;
        ss.imbue(locale("C"));
        ss.precision(20);