Make OTLPMetricsIndexingRestIT.testIngestMetricDataViaMetricExporter more resilient (#134435)

Author: felixbarny

muted-tests.yml

@@ -513,9 +513,6 @@ tests:
 - class: org.elasticsearch.xpack.logsdb.qa.BulkDynamicMappingChallengeRestIT
   method: testDateHistogramAggregation
   issue: https://github.com/elastic/elasticsearch/issues/134389
-- class: org.elasticsearch.xpack.oteldata.otlp.OTLPMetricsIndexingRestIT
-  method: testIngestMetricDataViaMetricExporter
-  issue: https://github.com/elastic/elasticsearch/issues/134426
 
 # Examples:
 #

x-pack/plugin/otel-data/src/javaRestTest/java/org/elasticsearch/xpack/oteldata/otlp/OTLPMetricsIndexingRestIT.java

@@ -157,8 +157,8 @@ public void testIngestMetricDataViaMetricExporter() throws Exception {
         ObjectPath search = search("metrics-generic.otel-default");
         assertThat(search.toString(), search.evaluate("hits.total.value"), equalTo(1));
         var source = search.evaluate("hits.hits.0._source");
-        assertThat(evaluate(source, "@timestamp"), equalTo(timestampAsString(now)));
-        assertThat(evaluate(source, "start_timestamp"), equalTo(timestampAsString(now)));
+        assertThat(Instant.parse(evaluate(source, "@timestamp")), equalTo(Instant.ofEpochMilli(TimeUnit.NANOSECONDS.toMillis(now))));
+        assertThat(Instant.parse(evaluate(source, "start_timestamp")), equalTo(Instant.ofEpochMilli(TimeUnit.NANOSECONDS.toMillis(now))));
         assertThat(evaluate(source, "_metric_names_hash"), isA(String.class));
         assertThat(ObjectPath.<Number>evaluate(source, "metrics.jvm\\.memory\\.total").longValue(), equalTo(totalMemory));
         assertThat(evaluate(source, "unit"), equalTo("By"));
@@ -413,10 +413,6 @@ private static Map<String, Object> getMapping(String target) throws IOException
         return mapping;
     }
 
-    private static String timestampAsString(long now) {
-        return Instant.ofEpochMilli(TimeUnit.NANOSECONDS.toMillis(now)).toString();
-    }
-
     private void export(List<MetricData> metrics) throws Exception {
         CompletableResultCode result = exporter.export(metrics).join(10, TimeUnit.SECONDS);
         Throwable failure = result.getFailureThrowable();