Better, non-static approach to handling the queue

merlin-worker/src/main/java/gov/nasa/jpl/aerie/merlin/worker/postgres/PostgresProfileStreamer.java

@@ -1,7 +1,6 @@
 package gov.nasa.jpl.aerie.merlin.worker.postgres;
 
 import gov.nasa.jpl.aerie.merlin.driver.resources.ResourceProfiles;
-import gov.nasa.jpl.aerie.merlin.driver.resources.TaskQueue;
 import gov.nasa.jpl.aerie.merlin.server.remotes.postgres.DatabaseException;
 
 import javax.sql.DataSource;
@@ -11,16 +10,17 @@
 public class PostgresProfileStreamer implements Consumer<ResourceProfiles>, AutoCloseable {
   private final DataSource dataSource;
   private long datasetId;
+  private PostgresQueryQueue queryQueue;
 
   public PostgresProfileStreamer(DataSource dataSource, long datasetId) throws SQLException {
     this.dataSource = dataSource;
     this.datasetId = datasetId;
-
+    this.queryQueue = new PostgresQueryQueue();
   }
 
   @Override
   public void accept(final ResourceProfiles resourceProfiles) {
-    TaskQueue.addToQueue(() -> {
+    queryQueue.addToQueue(() -> {
       try (var transaction = new PostgresProfileQueryHandler(dataSource, datasetId)) {
           transaction.uploadResourceProfiles(resourceProfiles);
       } catch (SQLException e) {
@@ -31,8 +31,7 @@ public void accept(final ResourceProfiles resourceProfiles) {
 
   @Override
   public void close() {
-    // This class should conform to the AutoCloseable interface, but member variables that could be closed have
-    // been abstracted out to PostgresProfileQueryHandler, which auto-closes in the above accept method.
+    queryQueue.shutdown();
   }
 
 }

merlin-worker/src/main/java/gov/nasa/jpl/aerie/merlin/worker/postgres/PostgresQueryQueue.java

@@ -0,0 +1,17 @@
+package gov.nasa.jpl.aerie.merlin.worker.postgres;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class PostgresQueryQueue {
+  private final ExecutorService executor = Executors.newSingleThreadExecutor();
+
+  public void addToQueue(Runnable task) {
+    executor.submit(task);
+  }
+
+  /** Gracefully shut down the ExecutorService */
+  public void shutdown() {
+    executor.shutdown();
+  }
+}