Reimplement platform-independent metrics printing (#220)

Author: russgold

wls-exporter-core/src/main/java/com/oracle/wls/exporter/MetricsStream.java

@@ -3,12 +3,12 @@
 
 package com.oracle.wls.exporter;
 
-import javax.management.MBeanServerConnection;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.io.PrintStream;
 import java.lang.management.ManagementFactory;
 import java.util.Locale;
+import javax.management.MBeanServerConnection;
 
 import com.sun.management.OperatingSystemMXBean;
 
@@ -19,6 +19,7 @@
  * @author Russell Gold
  */
 class MetricsStream extends PrintStream {
+    private static final String PROMETHEUS_LINE_SEPARATOR = "\n"; // This is not dependent on the platform running the exporter.
     private static final double NANOSEC_PER_SECONDS = 1000000000;
 
     private final PerformanceProbe performanceProbe;
@@ -58,18 +59,18 @@ class MetricsStream extends PrintStream {
      * @param value the metric value
      */
     void printMetric(String name, Object value) {
-        print(name + " " + value + System.lineSeparator());
+        print(name + " " + value + PROMETHEUS_LINE_SEPARATOR);
         scrapeCount++;
     }
 
     /**
      * Prints the summary performance metrics
      */
     void printPlatformMetrics() {
-        printf( "%s %d%n", getCountName(), scrapeCount);
-        printf(Locale.US, "%s %.2f%n", getDurationName(), toSeconds(getElapsedTime()));
-        printf(Locale.US, "%s %.2f%n", getCpuUsageName(), toSeconds(getCpuUsed()));
-        printf("%s %d%n", getExporterVersionName(), 1);
+        printMetric(getCountName(), scrapeCount);
+        printMetric(getDurationName(), toSecondsString(getElapsedTime()));
+        printMetric(getCpuUsageName(), toSecondsString(getCpuUsed()));
+        printMetric(getExporterVersionName(), 1);
     }
 
     private String getDurationName() {
@@ -107,8 +108,8 @@ private long getElapsedTime() {
         return performanceProbe.getCurrentTime() - startTime;
     }
 
-    private double toSeconds(long nanoSeconds) {
-        return nanoSeconds / NANOSEC_PER_SECONDS;
+    private String toSecondsString(long nanoSeconds) {
+        return String.format(Locale.US, "%.2f", nanoSeconds / NANOSEC_PER_SECONDS);
     }
 
     private long getCpuUsed() {

wls-exporter-core/src/test/java/com/oracle/wls/exporter/MetricsStreamTest.java

@@ -18,7 +18,6 @@
 import com.meterware.simplestub.Memento;
 import com.meterware.simplestub.StaticStubSupport;
 import com.meterware.simplestub.SystemPropertySupport;
-import com.oracle.wls.exporter.matchers.PrometheusMetricsMatcher;
 import com.oracle.wls.exporter.webapp.HttpServletRequestStub;
 import com.oracle.wls.exporter.webapp.ServletUtils;
 import org.junit.jupiter.api.AfterEach;
@@ -35,6 +34,7 @@
  * @author Russell Gold
  */
 class MetricsStreamTest {
+    private static final String Linux_LINE_SEPARATOR = "\n";
     private static final long NANOSEC_PER_SECONDS = 1000000000;
     private static final String LINE_SEPARATOR = "line.separator";
     private static final String WINDOWS_LINE_SEPARATOR = "\r\n";
@@ -79,7 +79,7 @@ private String getPrintedMetrics() {
     }
 
     @Test
-    void whenMetricsPrinted_eachHasItsOwnLineSeparatedByCarriageReturns() {
+    void whenMetricsPrinted_eachHasItsOwnLineSeparatedByLinuxLineSeparators() {
         metrics.printMetric("a", 12);
         metrics.printMetric("b", 120);
         metrics.printMetric("c", 0);
@@ -88,7 +88,7 @@ void whenMetricsPrinted_eachHasItsOwnLineSeparatedByCarriageReturns() {
     }
 
     @Test
-    void whenMetricsPrintedOnWindows_eachHasItsOwnLineSeparatedByCarriageReturns() throws NoSuchFieldException {
+    void whenMetricsPrintedOnWindows_eachHasItsOwnLineSeparatedByLinuxLineSeparators() throws NoSuchFieldException {
         simulateWindows();
 
         metrics.printMetric("a", 12);
@@ -106,11 +106,15 @@ private void simulateWindows() throws NoSuchFieldException {
 
     private List<String> getPrintedMetricValues() {
         return Arrays.stream(getPrintedMetrics()
-              .split(System.lineSeparator()))
-              .map(PrometheusMetricsMatcher::getMetricValue)
+              .split(Linux_LINE_SEPARATOR))
+              .map(this::getMetricValue)
               .collect(Collectors.toList());
     }
 
+    private String getMetricValue(String metricLine) {
+        return metricLine.substring(metricLine.lastIndexOf(' ') + 1);
+    }
+
     @Test
     void afterMetricsScraped_reportScrapedCount() {
         metrics.printMetric("a", 12);

wls-exporter-core/src/test/java/com/oracle/wls/exporter/matchers/PrometheusMetricsMatcher.java

@@ -20,14 +20,6 @@ public static PrometheusMetricsMatcher followsPrometheusRules() {
         return new PrometheusMetricsMatcher();
     }
 
-    /**
-     * Given a line with a described metric, returns the actual metric string.
-     * @param metric a line containing a qualified name and a Prometheus metric
-     */
-    public static String getMetricValue(String metric) {
-        return metric.substring(metric.lastIndexOf(' ')).trim();
-    }
-
     @Override
     protected boolean matchesSafely(String metricsList, Description description) {
         String[] metrics = Arrays.stream(metricsList.split("\n"))
@@ -69,6 +61,10 @@ private boolean hasNonNumericValue(String metric) {
         }
     }
 
+    private static String getMetricValue(String metric) {
+        return metric.substring(metric.lastIndexOf(' ')).trim();
+    }
+
     private boolean metricsInOrder(Description description, String[] metrics) {
         String outOfOrderMetric = getOutOfOrderMetric(metrics);
         if (outOfOrderMetric == null) return true;