GCP: Add option to configure minimum number of instances

google-cloud-server-base/src/main/java/jetbrains/buildServer/clouds/base/AbstractCloudClient.java

@@ -87,6 +87,11 @@ public void terminateInstance(@NotNull final CloudInstance baseInstance) {
     instance.getImage().terminateInstance(instance);
   }
 
+  public boolean canDeleteExistingInstance(@NotNull final CloudImage baseImage) {
+    final T image = (T) baseImage;
+    return image.canDeleteExistingInstance();
+  }
+
   public boolean canStartNewInstance(@NotNull final CloudImage baseImage) {
     final T image = (T) baseImage;
     return image.canStartNewInstance();

google-cloud-server-base/src/main/java/jetbrains/buildServer/clouds/base/AbstractCloudImage.java

@@ -87,6 +87,8 @@ public void addInstance(@NotNull final T instance) {
     myInstances.put(instance.getInstanceId(), instance);
   }
 
+  public abstract boolean canDeleteExistingInstance();
+
   public abstract boolean canStartNewInstance();
 
   public abstract void terminateInstance(@NotNull final T instance);

google-cloud-server-base/src/main/java/jetbrains/buildServer/clouds/base/beans/CloudImageDetails.java

@@ -27,6 +27,7 @@ public interface CloudImageDetails {
 
   CloneBehaviour getBehaviour();
 
+  int getMinInstances();
   int getMaxInstances();
 
   String getSourceId();

google-cloud-server-base/src/test/java/jetbrains/buildServer/clouds/models/FakeCloudImageDetails.java

@@ -39,6 +39,11 @@ public CloneBehaviour getBehaviour() {
         return null;
     }
 
+    @Override
+    public int getMinInstances() {
+        return 0;
+    }
+
     @Override
     public int getMaxInstances() {
         return 0;

google-cloud-server/src/main/kotlin/jetbrains/buildServer/clouds/google/GoogleCloudClientFactory.kt

@@ -97,6 +97,7 @@ class GoogleCloudClientFactory(cloudRegistrar: CloudRegistrar,
                     it.getParameter(GoogleConstants.MACHINE_CORES),
                     it.getParameter(GoogleConstants.MACHINE_MEMORY),
                     (it.getParameter(GoogleConstants.MACHINE_MEMORY_EXT) ?: "").toBoolean(),
+                    (it.getParameter(GoogleConstants.MIN_INSTANCES_COUNT) ?: "0").toInt(),
                     (it.getParameter(GoogleConstants.MAX_INSTANCES_COUNT) ?: "1").toInt(),
                     it.agentPoolId,
                     it.getParameter(GoogleConstants.PROFILE_ID)!!,

google-cloud-server/src/main/kotlin/jetbrains/buildServer/clouds/google/GoogleCloudImage.kt

@@ -65,13 +65,19 @@ DisposableHandle, CoroutineScope {
         }
     }
 
+    override fun canDeleteExistingInstance(): Boolean {
+        return activeInstances.size > myImageDetails.getMinInstances()
+    }
+
     override fun canStartNewInstance(): Boolean {
-        return activeInstances.size < myImageDetails.maxInstances
+        return activeInstances.size < myImageDetails.getMaxInstances()
     }
 
     override fun startNewInstance(userData: CloudInstanceUserData): GoogleCloudInstance = runBlocking {
         if (!canStartNewInstance()) {
-            throw QuotaException("Unable to start more instances. Limit has reached")
+            throw QuotaException(
+                "Unable to start more instances. Configured maximum limit has reached (max: ${myImageDetails.getMaxInstances()})"
+            )
         }
 
         createInstance(userData)
@@ -133,8 +139,14 @@ DisposableHandle, CoroutineScope {
     }
 
     override fun terminateInstance(instance: GoogleCloudInstance) {
-        instance.status = InstanceStatus.SCHEDULED_TO_STOP
+        if (!canDeleteExistingInstance()) {
+            LOG.info(
+                "Unable to terminate anymore instances. Configured minimum limit has reached (min: ${myImageDetails.getMinInstances()})"
+            )
+            return
+        }
 
+        instance.status = InstanceStatus.SCHEDULED_TO_STOP
         launch {
             try {
                 if (myImageDetails.behaviour.isDeleteAfterStop) {

google-cloud-server/src/main/kotlin/jetbrains/buildServer/clouds/google/GoogleCloudImageDetails.kt

@@ -49,6 +49,8 @@ class GoogleCloudImageDetails(
         val machineMemory: String?,
         @SerializedName(GoogleConstants.MACHINE_MEMORY_EXT)
         val machineMemoryExt: Boolean = false,
+        @SerializedName(GoogleConstants.MIN_INSTANCES_COUNT)
+        private val minInstances: Int,
         @SerializedName(GoogleConstants.MAX_INSTANCES_COUNT)
         private val maxInstances: Int,
         @SerializedName(CloudImageParameters.AGENT_POOL_ID_FIELD)
@@ -72,6 +74,10 @@ class GoogleCloudImageDetails(
         return sourceId
     }
 
+    override fun getMinInstances(): Int {
+        return minInstances
+    }
+
     override fun getMaxInstances(): Int {
         return maxInstances
     }

google-cloud-server/src/main/kotlin/jetbrains/buildServer/clouds/google/GoogleConstants.kt

@@ -48,6 +48,9 @@ class GoogleConstants {
     val zone: String
         get() = ZONE
 
+    val minInstancesCount: String
+        get() = MIN_INSTANCES_COUNT
+
     val maxInstancesCount: String
         get() = MAX_INSTANCES_COUNT
 
@@ -111,6 +114,7 @@ class GoogleConstants {
         const val REGION = "region"
         const val NETWORK_ID = "network"
         const val SUBNET_ID = "subnet"
+        const val MIN_INSTANCES_COUNT = "minInstances"
         const val MAX_INSTANCES_COUNT = "maxInstances"
         const val MACHINE_CUSTOM = "machineCustom"
         const val MACHINE_TYPE = "machineType"

google-cloud-server/src/main/resources/buildServerResources/images.vm.js

@@ -110,6 +110,7 @@ function GoogleImagesViewModel($, ko, dialog, config) {
             }
         }),
         subnet: ko.observable(),
+        minInstances: ko.observable(0).extend({required: true, min: 0}),
         maxInstances: ko.observable(1).extend({required: true, min: 0}),
         preemptible: ko.observable(false),
         machineCustom: self.machineCustom,
@@ -251,6 +252,7 @@ function GoogleImagesViewModel($, ko, dialog, config) {
     self.images_data.subscribe(function (data) {
         var images = ko.utils.parseJson(data || "[]");
         images.forEach(function (image) {
+            image.minInstances = image.minInstances || 0;
             image.imageType = image.imageType || imageTypes.image;
             image.preemptible = getBoolean(image.preemptible);
             image.machineCustom = getBoolean(image.machineCustom);
@@ -264,11 +266,12 @@ function GoogleImagesViewModel($, ko, dialog, config) {
     self.originalImage = null;
 
     self.showDialog = function (data) {
+        var model = self.image();
         self.originalImage = data;
 
-        var model = self.image();
         var image = data || {
             imageType: imageTypes.image,
+            minInstances: 0,
             maxInstances: 1,
             preemptible: false,
             machineCustom: false,
@@ -324,6 +327,7 @@ function GoogleImagesViewModel($, ko, dialog, config) {
         model.machineMemory(image.machineMemory);
         model.machineMemoryExt(image.machineMemoryExt);
         model.diskType(diskType);
+        model.minInstances(image.minInstances);
         model.maxInstances(image.maxInstances);
         model.preemptible(image.preemptible);
         model.vmNamePrefix(image['source-id']);
@@ -357,6 +361,7 @@ function GoogleImagesViewModel($, ko, dialog, config) {
             zone: model.zone(),
             network: model.network(),
             subnet: model.subnet(),
+            minInstances: model.minInstances(),
             maxInstances: model.maxInstances(),
             preemptible: model.preemptible(),
             'source-id': model.vmNamePrefix(),

google-cloud-server/src/main/resources/buildServerResources/settings.jsp

@@ -144,9 +144,13 @@
             <tr>
                 <th><label for="${cons.maxInstancesCount}">Instances limit: <l:star/></label></th>
                 <td>
-                    <input type="text" name="${cons.maxInstancesCount}" class="longField ignoreModified"
+                    <input type="text" name="${cons.minInstancesCount}" class="shortField ignoreModified"
+                           data-bind="textInput: image().minInstances"/>
+                    <span class="smallNote">Minimum number of instances that are kept alive at all times</span>
+                    <span class="error option-error" data-bind="validationMessage: image().minInstances"></span><br>
+                    <input type="text" name="${cons.maxInstancesCount}" class="shortField ignoreModified"
                            data-bind="textInput: image().maxInstances"/>
-                    <span class="smallNote">Maximum number of instances which can be started</span>
+                    <span class="smallNote">Maximum number of instances that can be started</span>
                     <span class="error option-error" data-bind="validationMessage: image().maxInstances"></span>
                 </td>
             </tr>
@@ -304,7 +308,7 @@
                 <tr>
                     <th class="name">Agent name prefix</th>
                     <th class="name">Cloud image</th>
-                    <th class="name center" title="Maximum number of instances">Limit</th>
+                    <th class="name center" title="Minimum/Maximum number of instances" colspan="2">Instance limits (min/max)</th>
                     <th class="name center" colspan="2">Actions</th>
                 </tr>
                 </thead>
@@ -319,6 +323,7 @@
                         <span data-bind="text: instanceTemplate.slice(-80), attr: {title: instanceTemplate}"></span>
                         <!-- /ko -->
                     </td>
+                    <td class="center edit" data-bind="text: minInstances"></td>
                     <td class="center edit" data-bind="text: maxInstances"></td>
                     <td class="edit">
                         <a href="#" data-bind="click: $parent.showDialog,