Fix units in metrics, stop using cached time (elastic#133456)

Author: nicktindall

server/src/main/java/org/elasticsearch/repositories/SnapshotMetrics.java

@@ -71,8 +71,8 @@ public SnapshotMetrics(MeterRegistry meterRegistry) {
             meterRegistry.registerLongCounter(SNAPSHOT_BYTES_UPLOADED, "snapshot bytes uploaded", "bytes"),
             meterRegistry.registerLongCounter(SNAPSHOT_UPLOAD_DURATION, "snapshot upload duration", "ms"),
             meterRegistry.registerLongCounter(SNAPSHOT_UPLOAD_READ_DURATION, "time spent in read() calls when snapshotting", "ms"),
-            meterRegistry.registerLongCounter(SNAPSHOT_CREATE_THROTTLE_DURATION, "time throttled in snapshot create", "bytes"),
-            meterRegistry.registerLongCounter(SNAPSHOT_RESTORE_THROTTLE_DURATION, "time throttled in snapshot restore", "bytes"),
+            meterRegistry.registerLongCounter(SNAPSHOT_CREATE_THROTTLE_DURATION, "time throttled in snapshot create", "ns"),
+            meterRegistry.registerLongCounter(SNAPSHOT_RESTORE_THROTTLE_DURATION, "time throttled in snapshot restore", "ns"),
             meterRegistry
         );
     }

server/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreRepository.java

@@ -4156,9 +4156,9 @@ private void checkAborted() {
                 };
                 final String partName = fileInfo.partName(i);
                 logger.trace("[{}] Writing [{}] to [{}]", metadata.name(), partName, shardContainer.path());
-                final long startMillis = threadPool.relativeTimeInMillis();
+                final long startMillis = threadPool.rawRelativeTimeInMillis();
                 shardContainer.writeBlob(OperationPurpose.SNAPSHOT_DATA, partName, inputStream, partBytes, false);
-                final long uploadTimeInMillis = threadPool.relativeTimeInMillis() - startMillis;
+                final long uploadTimeInMillis = threadPool.rawRelativeTimeInMillis() - startMillis;
                 blobStoreSnapshotMetrics.incrementCountersForPartUpload(partBytes, uploadTimeInMillis);
                 logger.trace(
                     "[{}] Writing [{}] of size [{}b] to [{}] took [{}ms]",