fix: record previous value of sampler counter metrics so they report …

…correctly (#1281)

## Which problem is this PR solving?

- Fixes #1279 

## Short description of the changes

- Update the previous values 
- Fix a test that was sensitive to existing standard envvar

config/config_test.go

@@ -614,13 +614,17 @@ func TestHoneycombLoggerConfig(t *testing.T) {
 	config, rules := createTempConfigs(t, cm, rm)
 	defer os.Remove(rules)
 	defer os.Remove(config)
+	// Set the environment variable to test that it overrides the config
+	oldenv := os.Getenv("REFINERY_HONEYCOMB_API_KEY")
+	os.Setenv("REFINERY_HONEYCOMB_API_KEY", "321cba")
+	defer os.Setenv("REFINERY_HONEYCOMB_API_KEY", oldenv)
 	c, err := getConfig([]string{"--no-validate", "--config", config, "--rules_config", rules})
 	assert.NoError(t, err)
 
 	loggerConfig := c.GetHoneycombLoggerConfig()
 
 	assert.Equal(t, "http://honeycomb.io", loggerConfig.APIHost)
-	assert.Equal(t, "1234", loggerConfig.APIKey)
+	assert.Equal(t, "321cba", loggerConfig.APIKey)
 	assert.Equal(t, "loggerDataset", loggerConfig.Dataset)
 	assert.Equal(t, true, loggerConfig.GetSamplerEnabled())
 	assert.Equal(t, 5, loggerConfig.SamplerThroughput)

sample/dynamic.go

@@ -89,6 +89,7 @@ func (d *DynamicSampler) GetSampleRate(trace *types.Trace) (rate uint, keep bool
 		case "counter":
 			delta := val - d.lastMetrics[name]
 			d.Metrics.Count(name, delta)
+			d.lastMetrics[name] = val
 		case "gauge":
 			d.Metrics.Gauge(name, val)
 		}

sample/dynamic_ema.go

@@ -97,6 +97,7 @@ func (d *EMADynamicSampler) GetSampleRate(trace *types.Trace) (rate uint, keep b
 		case "counter":
 			delta := val - d.lastMetrics[name]
 			d.Metrics.Count(name, delta)
+			d.lastMetrics[name] = val
 		case "gauge":
 			d.Metrics.Gauge(name, val)
 		}

sample/ema_throughput.go

@@ -114,6 +114,7 @@ func (d *EMAThroughputSampler) GetSampleRate(trace *types.Trace) (rate uint, kee
 		case "counter":
 			delta := val - d.lastMetrics[name]
 			d.Metrics.Count(name, delta)
+			d.lastMetrics[name] = val
 		case "gauge":
 			d.Metrics.Gauge(name, val)
 		}

sample/totalthroughput.go

@@ -106,6 +106,7 @@ func (d *TotalThroughputSampler) GetSampleRate(trace *types.Trace) (rate uint, k
 		case "counter":
 			delta := val - d.lastMetrics[name]
 			d.Metrics.Count(name, delta)
+			d.lastMetrics[name] = val
 		case "gauge":
 			d.Metrics.Gauge(name, val)
 		}

sample/windowed_throughput.go

@@ -102,6 +102,7 @@ func (d *WindowedThroughputSampler) GetSampleRate(trace *types.Trace) (rate uint
 		case "counter":
 			delta := val - d.lastMetrics[name]
 			d.Metrics.Count(name, delta)
+			d.lastMetrics[name] = val
 		case "gauge":
 			d.Metrics.Gauge(name, val)
 		}