Merge pull request #2266 from HubSpot/allow_empty_instance_requests

Mutate request instances based on existing request

Author: rosalind210

SingularityService/src/main/java/com/hubspot/singularity/config/SingularityConfiguration.java

@@ -455,6 +455,8 @@ public class SingularityConfiguration extends Configuration {
 
   private boolean skipPersistingTooLongTaskIds = false;
 
+  private boolean allowEmptyRequestInstances = false;
+
   public long getAskDriverToKillTasksAgainAfterMillis() {
     return askDriverToKillTasksAgainAfterMillis;
   }
@@ -2129,4 +2131,12 @@ public boolean skipPersistingTooLongTaskIds() {
   public void setSkipPersistingTooLongTaskIds(boolean skipPersistingTooLongTaskIds) {
     this.skipPersistingTooLongTaskIds = skipPersistingTooLongTaskIds;
   }
+
+  public boolean allowEmptyRequestInstances() {
+    return allowEmptyRequestInstances;
+  }
+
+  public void setAllowEmptyRequestInstances(boolean allowEmptyRequestInstances) {
+    this.allowEmptyRequestInstances = allowEmptyRequestInstances;
+  }
 }

SingularityService/src/main/java/com/hubspot/singularity/data/SingularityValidator.java

@@ -230,11 +230,26 @@ public SingularityRequest checkSingularityRequest(
       request.getId().length(),
       request.getId()
     );
+
     checkBadRequest(
       !request.getInstances().isPresent() || request.getInstances().get() > 0,
       "Instances must be greater than 0"
     );
 
+    if (singularityConfiguration.allowEmptyRequestInstances()) {
+      if (
+        (
+          request.getRequestType().equals(RequestType.SERVICE) ||
+          request.getRequestType().equals(RequestType.WORKER)
+        ) &&
+        existingRequest.flatMap(SingularityRequest::getInstances).isPresent() &&
+        !request.getInstances().isPresent()
+      ) {
+        request =
+          request.toBuilder().setInstances(existingRequest.get().getInstances()).build();
+      }
+    }
+
     checkBadRequest(
       request.getInstancesSafe() <= maxInstancesPerRequest,
       "Instances (%s) be greater than %s (maxInstancesPerRequest in mesos configuration)",

SingularityService/src/test/java/com/hubspot/singularity/data/ValidatorTest.java

@@ -562,4 +562,30 @@ public void itDoesNotAllowOtherRequestTypesToChange() {
         )
     );
   }
+
+  @Test
+  public void itKeepPreviousInstancesCountWhenEmpty() {
+    singularityConfiguration.setAllowEmptyRequestInstances(true);
+    SingularityRequest request = new SingularityRequestBuilder("test", RequestType.WORKER)
+      .setInstances(Optional.of(5))
+      .build();
+    SingularityRequest newRequest = new SingularityRequestBuilder(
+      "test",
+      RequestType.WORKER
+    )
+    .build();
+
+    SingularityRequest returnedRequest = validator.checkSingularityRequest(
+      newRequest,
+      Optional.of(request),
+      Optional.empty(),
+      Optional.empty()
+    );
+
+    Assertions.assertTrue(returnedRequest.getInstances().isPresent());
+    Assertions.assertSame(
+      returnedRequest.getInstances().get(),
+      request.getInstances().get()
+    );
+  }
 }