Fix Dynatrace Exported to Generate DELTA Temporality (#174)

The Dynatrace OTel metrics API requires DELTA temporality,
since CUMULATIVE is currently unsupported. This change will
allow configuration of the temporality via

`otel.exporter.dynatrace.metrics.temporality.preference`

This config now defaults to "delta" instead to the hard-coded
"cumulative" before. Usually, no configuration is required.

Signed-off-by: Karsten Schnitter <k.schnitter@sap.com>
Co-authored-by: Anika Solanka <anika.solanka@sap.com>

cf-java-logging-support-opentelemetry-agent-extension/src/main/java/com/sap/hcf/cf/logging/opentelemetry/agent/ext/exporter/DynatraceMetricsExporterProvider.java

@@ -16,6 +16,7 @@
 import io.pivotal.cfenv.core.CfService;
 
 import java.time.Duration;
+import java.util.Locale;
 import java.util.function.Function;
 import java.util.logging.Logger;
 
@@ -46,20 +47,39 @@ private static Duration getTimeOut(ConfigProperties config) {
         return timeout != null ? timeout : config.getDuration("otel.exporter.dynatrace.timeout");
     }
 
+    private static AggregationTemporalitySelector getAggregationTemporalitySelector(ConfigProperties config) {
+        String temporalityStr = config.getString("otel.exporter.dynatrace.metrics.temporality.preference");
+        if (temporalityStr == null) {
+            return AggregationTemporalitySelector.deltaPreferred();
+        }
+        AggregationTemporalitySelector temporalitySelector;
+        switch (temporalityStr.toLowerCase(Locale.ROOT)) {
+        case "cumulative":
+            return AggregationTemporalitySelector.alwaysCumulative();
+        case "delta":
+            return AggregationTemporalitySelector.deltaPreferred();
+        case "lowmemory":
+            return AggregationTemporalitySelector.lowMemory();
+        default:
+            throw new ConfigurationException("Unrecognized aggregation temporality: " + temporalityStr);
+        }
+    }
+
     private static DefaultAggregationSelector getDefaultAggregationSelector(ConfigProperties config) {
         String defaultHistogramAggregation =
                 config.getString("otel.exporter.dynatrace.metrics.default.histogram.aggregation");
         if (defaultHistogramAggregation == null) {
-            return DefaultAggregationSelector.getDefault().with(InstrumentType.HISTOGRAM, Aggregation.defaultAggregation());
+            return DefaultAggregationSelector.getDefault()
+                                             .with(InstrumentType.HISTOGRAM, Aggregation.defaultAggregation());
         }
         if (AggregationUtil.aggregationName(Aggregation.base2ExponentialBucketHistogram())
-                .equalsIgnoreCase(defaultHistogramAggregation)) {
-            return
-                    DefaultAggregationSelector.getDefault()
-                            .with(InstrumentType.HISTOGRAM, Aggregation.base2ExponentialBucketHistogram());
+                           .equalsIgnoreCase(defaultHistogramAggregation)) {
+            return DefaultAggregationSelector.getDefault().with(InstrumentType.HISTOGRAM,
+                                                                Aggregation.base2ExponentialBucketHistogram());
         } else if (AggregationUtil.aggregationName(explicitBucketHistogram())
-                .equalsIgnoreCase(defaultHistogramAggregation)) {
-            return DefaultAggregationSelector.getDefault().with(InstrumentType.HISTOGRAM, Aggregation.explicitBucketHistogram());
+                                  .equalsIgnoreCase(defaultHistogramAggregation)) {
+            return DefaultAggregationSelector.getDefault()
+                                             .with(InstrumentType.HISTOGRAM, Aggregation.explicitBucketHistogram());
         } else {
             throw new ConfigurationException(
                     "Unrecognized default histogram aggregation: " + defaultHistogramAggregation);
@@ -83,16 +103,19 @@ public MetricExporter createExporter(ConfigProperties config) {
             return NoopMetricExporter.getInstance();
         }
 
-        LOG.info("Creating metrics exporter for service binding " + cfService.getName() + " (" + cfService.getLabel() + ")");
+        LOG.info(
+                "Creating metrics exporter for service binding " + cfService.getName() + " (" + cfService.getLabel() + ")");
 
         String apiUrl = cfService.getCredentials().getString(CRED_DYNATRACE_APIURL);
         if (isBlank(apiUrl)) {
-            LOG.warning("Credential \"" + CRED_DYNATRACE_APIURL + "\" not found. Skipping dynatrace exporter configuration");
+            LOG.warning(
+                    "Credential \"" + CRED_DYNATRACE_APIURL + "\" not found. Skipping dynatrace exporter configuration");
             return NoopMetricExporter.getInstance();
         }
         String tokenName = config.getString("otel.javaagent.extension.sap.cf.binding.dynatrace.metrics.token-name");
         if (isBlank(tokenName)) {
-            LOG.warning("Configuration \"otel.javaagent.extension.sap.cf.binding.dynatrace.metrics.token-name\" not found. Skipping dynatrace exporter configuration");
+            LOG.warning(
+                    "Configuration \"otel.javaagent.extension.sap.cf.binding.dynatrace.metrics.token-name\" not found. Skipping dynatrace exporter configuration");
             return NoopMetricExporter.getInstance();
         }
         String apiToken = cfService.getCredentials().getString(tokenName);
@@ -102,19 +125,18 @@ public MetricExporter createExporter(ConfigProperties config) {
         }
 
         OtlpHttpMetricExporterBuilder builder = OtlpHttpMetricExporter.builder();
-        builder.setEndpoint(apiUrl + DT_APIURL_METRICS_SUFFIX)
-                .setCompression(getCompression(config))
-                .addHeader("Authorization", "Api-Token " + apiToken)
-                .setRetryPolicy(RetryPolicy.getDefault())
-                .setAggregationTemporalitySelector(AggregationTemporalitySelector.alwaysCumulative())
-                .setDefaultAggregationSelector(getDefaultAggregationSelector(config));
+        builder.setEndpoint(apiUrl + DT_APIURL_METRICS_SUFFIX).setCompression(getCompression(config))
+               .addHeader("Authorization", "Api-Token " + apiToken).setRetryPolicy(RetryPolicy.getDefault())
+               .setAggregationTemporalitySelector(getAggregationTemporalitySelector(config))
+               .setDefaultAggregationSelector(getDefaultAggregationSelector(config));
 
         Duration timeOut = getTimeOut(config);
         if (timeOut != null) {
             builder.setTimeout(timeOut);
         }
 
-        LOG.info("Created metrics exporter for service binding " + cfService.getName() + " (" + cfService.getLabel() + ")");
+        LOG.info(
+                "Created metrics exporter for service binding " + cfService.getName() + " (" + cfService.getLabel() + ")");
         return builder.build();
     }