fix get gauge (#114)

Author: ecbadeaux

spectator/registry.h

@@ -69,6 +69,10 @@ struct single_table_state {
     return get_or_create<typename types::gauge_t>(std::move(id));
   }
 
+  auto get_gauge_ttl(IdPtr id, unsigned int ttl_seconds) {
+    return get_or_create<typename types::gauge_t>(std::move(id), ttl_seconds);
+  }
+
   auto get_max_gauge(IdPtr id) {
     return get_or_create<typename types::max_gauge_t>(std::move(id));
   }
@@ -168,6 +172,14 @@ class base_registry {
   auto GetGauge(absl::string_view name, Tags tags = {}) {
     return GetGauge(Id::of(name, std::move(tags)));
   }
+  
+  auto GetGaugeTTL(const IdPtr& id, unsigned int ttl_seconds) {
+    return state_.get_gauge_ttl(final_id(id), ttl_seconds);
+  }
+
+  auto GetGaugeTTL(absl::string_view name, unsigned int ttl_seconds, Tags tags = {}) {
+    return GetGaugeTTL(Id::of(name, std::move(tags)), ttl_seconds);
+  }
 
   auto GetMaxGauge(const IdPtr& id) {
     return state_.get_max_gauge(final_id(id));
@@ -284,6 +296,10 @@ struct stateless {
     return std::make_shared<typename types::gauge_t>(std::move(id), publisher.get());
   }
 
+  auto get_gauge_ttl(IdPtr id, unsigned int ttl_seconds) {
+    return std::make_shared<typename types::gauge_t>(std::move(id), publisher.get(), ttl_seconds);
+  }
+
   auto get_max_gauge(IdPtr id) {
     return std::make_shared<typename types::max_gauge_t>(std::move(id), publisher.get());
   }

spectator/stateless_meters.h

@@ -137,10 +137,10 @@ class DistributionSummary : public StatelessMeter<Pub> {
 template <typename Pub>
 class Gauge : public StatelessMeter<Pub> {
  public:
-  Gauge(IdPtr id, Pub* publisher, unsigned int ttl = 0)
+  Gauge(IdPtr id, Pub* publisher, unsigned int ttl_seconds = 0)
       : StatelessMeter<Pub>(std::move(id), publisher) {
-    if (ttl > 0) {
-      type_str_ = "g," + std::to_string(ttl);
+    if (ttl_seconds > 0) {
+      type_str_ = "g," + std::to_string(ttl_seconds);
     }
   }
   void Set(double value) noexcept { this->send(value); }

spectator/statelessregistry_test.cc

@@ -61,9 +61,14 @@ TEST(StatelessRegistry, Gauge) {
   TestStatelessRegistry r;
   auto g = r.GetGauge("foo");
   auto g2 = r.GetGauge("bar", {{"id", "2"}});
+  auto g3 = r.GetGaugeTTL("baz", 1);
+  auto g4 = r.GetGaugeTTL("quux", 2, {{"id", "2"}});
   g->Set(100);
   g2->Set(101);
-  std::vector<std::string> expected = {"g:foo:100", "g:bar,id=2:101"};
+  g3->Set(102);
+  g4->Set(103);
+  std::vector<std::string> expected = {"g:foo:100", "g:bar,id=2:101",
+                                       "g,1:baz:102", "g,2:quux,id=2:103"};
   EXPECT_EQ(r.SentMessages(), expected);
 }