Fix NaN value for gauge version

Author: thewhitewizard

CHANGELOG.md

@@ -8,7 +8,7 @@ All notable changes to this project will be documented in this file.
 
 - Share code between transaction types in `IexecHubService`. (#556)
 - Expose Pre, App & Post-Compute durations. (#559, #560, #561, #562, #563, #565)
-- Expose version through prometheus endpoint and through VersionController. (#569)
+- Expose version through prometheus endpoint and through VersionController. (#569 #570)
 
 ### Quality
 

src/main/java/com/iexec/worker/version/VersionController.java

@@ -32,7 +32,8 @@ public class VersionController {
     public static final String METRIC_INFO_GAUGE_DESC = "A metric to expose version and application name.";
     public static final String METRIC_INFO_LABEL_APP_NAME = "iexecAppName";
     public static final String METRIC_INFO_LABEL_APP_VERSION = "iexecAppVersion";
-
+    // Must be static final to avoid garbage collect and side effect on gauge
+    public static final int METRIC_VALUE = 1;
     private final BuildProperties buildProperties;
 
     public VersionController(BuildProperties buildProperties) {
@@ -41,7 +42,7 @@ public VersionController(BuildProperties buildProperties) {
 
     @PostConstruct
     void initializeGaugeVersion() {
-        Gauge.builder(METRIC_INFO_GAUGE_NAME, 1.0, n -> n)
+        Gauge.builder(METRIC_INFO_GAUGE_NAME, METRIC_VALUE, n -> METRIC_VALUE)
                 .description(METRIC_INFO_GAUGE_DESC)
                 .tags(METRIC_INFO_LABEL_APP_VERSION, buildProperties.getVersion(),
                         METRIC_INFO_LABEL_APP_NAME, buildProperties.getName())

src/test/java/com/iexec/worker/version/VersionControllerTests.java

@@ -75,6 +75,7 @@ void shouldReturnInfoGauge() {
                         id -> id.getTag(VersionController.METRIC_INFO_LABEL_APP_VERSION)
                 )
                 .containsExactly(buildProperties.getName(), buildProperties.getVersion());
+        assertThat(info.value()).isEqualTo(VersionController.METRIC_VALUE);
     }
 }