Merge "rometheus API with grafana uses labels" from Amnon

"
This series address issues from the grafana over prometheus integration.

The grafana dashboard uses labels for displaying hostname, and sum metrics from different shards.

After this series, the grafana dashboard (when removing the collectd_ prefix from the metrics definitions) works as expected."

* 'amnon/grafana_metrics_v5' of github.com:cloudius-systems/seastar-dev:
  prometheus: Use labels for metrics
  collectd: expose the hostname

core/prometheus.cc

@@ -25,6 +25,7 @@
 #include "proto/metrics2.pb.h"
 
 #include "scollectd_api.hh"
+#include "scollectd-impl.hh"
 #include "http/function_handlers.hh"
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/range/algorithm_ext/erase.hpp>
@@ -64,27 +65,50 @@ static std::string safe_name(const sstring& name) {
 }
 
 static sstring collectd_name(const scollectd::type_instance_id & id, uint32_t cpu) {
-    return safe_name(id.plugin()) + ":" + safe_name(id.type()) + ":" + safe_name(id.type_instance()) + ":" + std::to_string(cpu);
+    return safe_name(id.plugin());
 }
 
+static pm::Metric* add_label(pm::Metric* mt, const scollectd::type_instance_id & id, uint32_t cpu) {
+    auto label = mt->add_label();
+    label->set_name("shard");
+    label->set_value(std::to_string(cpu));
+    label = mt->add_label();
+    label->set_name("type");
+    label->set_value(id.type());
 
-static void fill_metric(pm::MetricFamily& mf, const std::vector<scollectd::collectd_value>& vals) {
+    if (id.type_instance() != "") {
+        label = mt->add_label();
+        label->set_name("metric");
+        label->set_value(id.type_instance());
+    }
+    const sstring& host = scollectd::get_impl().host();
+    if (host != "") {
+        label = mt->add_label();
+        label->set_name("instance");
+        label->set_value(host);
+    }
+    return mt;
+}
+
+static void fill_metric(pm::MetricFamily& mf, const std::vector<scollectd::collectd_value>& vals,
+        const scollectd::type_instance_id & id, uint32_t cpu) {
     for (const scollectd::collectd_value& c : vals) {
         switch (c.type()) {
         case scollectd::data_type::DERIVE:
-            mf.add_metric()->mutable_counter()->set_value(c.i());
+            add_label(mf.add_metric(), id, cpu)->mutable_counter()->set_value(c.i());
             mf.set_type(pm::MetricType::COUNTER);
             break;
         case scollectd::data_type::GAUGE:
-            mf.add_metric()->mutable_gauge()->set_value(c.d());
+            add_label(mf.add_metric(), id, cpu)->mutable_gauge()->set_value(c.d());
             mf.set_type(pm::MetricType::GAUGE);
             break;
         default:
-            mf.add_metric()->mutable_counter()->set_value(c.ui());
+            add_label(mf.add_metric(), id, cpu)->mutable_counter()->set_value(c.ui());
             mf.set_type(pm::MetricType::COUNTER);
             break;
         }
     }
+
 }
 
 future<> start(httpd::http_server_control& http_server, const config& ctx) {
@@ -105,9 +129,9 @@ future<> start(httpd::http_server_control& http_server, const config& ctx) {
                             pm::MetricFamily mtf;
                             std::string s;
                             google::protobuf::io::StringOutputStream os(&s);
-                            mtf.set_name(collectd_name(i.first, cpu));
+                            mtf.set_name(ctx.prefix + "_" + collectd_name(i.first, cpu));
                             mtf.set_help(ctx.metric_help);
-                            fill_metric(mtf, i.second);
+                            fill_metric(mtf, i.second, i.first, cpu);
                             if (mtf.metric_size() > 0) {
                                 std::stringstream ss;
                                 if (!write_delimited_to(mtf, &os)) {

core/prometheus.hh

@@ -30,6 +30,7 @@ namespace prometheus {
  */
 struct config {
     sstring metric_help; //!< Default help message for the returned metrics
+    sstring prefix = "seastar"; //!< a prefix that will be added to metric names
 };
 
 future<> start(httpd::http_server_control& http_server, const config& ctx);

core/scollectd-impl.hh

@@ -61,6 +61,9 @@ public:
     void stop();
 
     value_list_map& get_value_list_map();
+    const sstring& host() const {
+        return _host;
+    }
 
 private:
     void arm();