prometheus static factory method

flatmap-core/src/main/java/com/onthegomap/flatmap/config/Arguments.java

@@ -1,7 +1,6 @@
 package com.onthegomap.flatmap.config;
 
 import com.onthegomap.flatmap.geo.GeoUtils;
-import com.onthegomap.flatmap.stats.PrometheusStats;
 import com.onthegomap.flatmap.stats.Stats;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -130,7 +129,7 @@ public class Arguments {
       LOGGER.info("Using prometheus push gateway stats");
       String job = get("pushgateway.job", "prometheus pushgateway job ID", "flatmap");
       Duration interval = duration("pushgateway.interval", "how often to send stats to prometheus push gateway", "15s");
-      return new PrometheusStats(prometheus, job, interval);
+      return Stats.prometheusPushGateway(prometheus, job, interval);
     } else {
       LOGGER.info("Using in-memory stats");
       return Stats.inMemory();

flatmap-core/src/main/java/com/onthegomap/flatmap/stats/PrometheusStats.java

@@ -47,7 +47,7 @@ public class PrometheusStats implements Stats {
   private final Map<String, MemoryEstimator.HasEstimate> heapObjectsToMonitor = Collections
     .synchronizedMap(new LinkedHashMap<>());
 
-  public PrometheusStats(String job) {
+  PrometheusStats(String job) {
     this.job = job;
     DefaultExports.register(registry);
     new ThreadDetailsExports().register(registry);
@@ -57,7 +57,7 @@ public class PrometheusStats implements Stats {
     new PostGcMemoryCollector().register(registry);
   }
 
-  public PrometheusStats(String destination, String job, Duration interval) {
+  PrometheusStats(String destination, String job, Duration interval) {
     this(job);
     try {
       URL url = new URL(destination);

flatmap-core/src/main/java/com/onthegomap/flatmap/stats/Stats.java

@@ -4,6 +4,7 @@ import static io.prometheus.client.Collector.NANOSECONDS_PER_SECOND;
 
 import com.onthegomap.flatmap.util.MemoryEstimator;
 import java.nio.file.Path;
+import java.time.Duration;
 import java.util.Map;
 import java.util.function.Supplier;
 
@@ -55,6 +56,10 @@ public interface Stats extends AutoCloseable {
     return new InMemory();
   }
 
+  static Stats prometheusPushGateway(String destination, String job, Duration interval) {
+    return new PrometheusStats(destination, job, interval);
+  }
+
   class InMemory implements Stats {
 
     private final Timers timers = new Timers();