Add version metric (#533)

* Add version metric.

* Update documentation. Metric's name style fix.

server/README_METRICS.md

@@ -25,4 +25,5 @@ Below is the table with metrics description that collected inside application. T
 |extender.service.sdk.get.download|Counter|Unit|How many times Defold sdk was downloaded|
 |extender.service.sdk.get.duration|Timer|Milliseconds|How long Defold sdk was downloading|
 |extender.service.gradle.unpack|Timer|Milliseconds|How long Gradle was unpacking dependencies|
-|extender.service.gradle.get|Timer|Milliseconds|How long Gradle dependencies step was going|
+|extender.service.gradle.get|Timer|Milliseconds|How long Gradle dependencies step was going|
+|extender.versionInfo|Gauge|Unit|Always return 1. Labels contains git tag and git commit sha with current version|

server/build.gradle

@@ -106,16 +106,18 @@ task createVersionFile() {
         }
     }
     def build_time = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date ())
+    def app_version = project.ext.extenderVersion
     def text = """
 // Auto generated by gradle
 
 package com.defold.extender;
 public class Version {
     public static final String gitVersion = "${sha}";
     public static final String buildTime = "${build_time}";
+    public static final String appVersion = "${app_version}";
 }
 """
-    def binding = ["sha" : sha, "build_time" : build_time]
+    def binding = []
 
     def engine = new groovy.text.SimpleTemplateEngine()
     def template = engine.createTemplate(text).make(binding)

server/src/main/java/com/defold/extender/ExtenderController.java

@@ -29,6 +29,8 @@
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
+
+import io.micrometer.core.instrument.Gauge;
 import io.micrometer.core.instrument.MeterRegistry;
 
 import jakarta.servlet.http.HttpServletRequest;
@@ -44,6 +46,7 @@
 import java.nio.file.StandardCopyOption;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Supplier;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -123,7 +126,10 @@ public ExtenderController(DefoldSdkService defoldSdkService,
         this.jobResultLocation = new File(jobResultLocation);
         this.jobResultLocation.mkdirs();
 
-        this.asyncBuilder = asyncBuilder;            
+        this.asyncBuilder = asyncBuilder;
+
+        Supplier<Number> staticValue = () -> 1;
+        Gauge.builder("extender.versionInfo", staticValue).tags("version", Version.appVersion, "commit_sha", Version.gitVersion).register(meterRegistry);
     }
 
     @ExceptionHandler({ExtenderException.class})