If there is only one admin role member, the member cannot be deleted.

servers/zms/src/main/java/com/yahoo/athenz/zms/ZMSImpl.java

@@ -2201,6 +2201,19 @@ public void deleteDomainRoleMember(ResourceContext ctx, String domainName, Strin
         setRequestDomain(ctx, domainName);
         memberName = memberName.toLowerCase();
 
+        // if this is the admin role then we need to make sure
+        // the admin is not himself who happens to be the last
+        // member in the role
+        AthenzDomain domain = getAthenzDomain(domainName, false);
+        Role adminRole = getRoleFromDomain(ZMSConsts.ADMIN_ROLE_NAME, domain);
+        if (adminRole == null) {
+            throw ZMSUtils.notFoundError("Invalid domain name specified", caller);
+        }
+        List<RoleMember> members = adminRole.getRoleMembers();
+        if (members.size() == 1 && members.get(0).getMemberName().equals(memberName)) {
+            throw ZMSUtils.forbiddenError("deleteDomainRoleMember: Cannot delete last member of 'admin' role", caller);
+        }
+
         // verify that request is properly authenticated for this request
 
         verifyAuthorizedServiceOperation(((RsrcCtxWrapper) ctx).principal().getAuthorizedService(), caller);

servers/zms/src/test/java/com/yahoo/athenz/zms/ZMSDeleteDomainTest.java

@@ -860,6 +860,39 @@ public void testDeleteDomainRoleMember() {
         zmsImpl.deleteTopLevelDomain(ctx, domainName, auditRef, null);
     }
 
+    @Test
+    public void testDeleteDomainRoleMemberWhenSingleAdmin() {
+
+        String domainName = "deletedomainrolemember3";
+        ZMSImpl zmsImpl = zmsTestInitializer.getZms();
+        RsrcCtxWrapper ctx = zmsTestInitializer.getMockDomRsrcCtx();
+        final String auditRef = zmsTestInitializer.getAuditRef();
+
+        TopLevelDomain dom1 = zmsTestInitializer.createTopLevelDomainObject(domainName,
+                "Test Domain1", "testOrg", zmsTestInitializer.getAdminUser());
+        zmsImpl.postTopLevelDomain(ctx, auditRef, null, dom1);
+
+        Role adminRole = zmsTestInitializer.createRoleObject(domainName, "admin", null,
+                "user.jack", null);
+        zmsImpl.putRole(ctx, domainName, "admin", auditRef, false, null, adminRole);
+
+        DomainRoleMembers domainRoleMembers = zmsImpl.getDomainRoleMembers(ctx, domainName);
+        assertEquals(domainName, domainRoleMembers.getDomainName());
+
+        List<DomainRoleMember> members = domainRoleMembers.getMembers();
+        assertNotNull(members);
+        assertEquals(members.size(), 1);
+        ZMSTestUtils.verifyDomainRoleMember(members, "user.jack", "admin");
+
+        try {
+            zmsImpl.deleteDomainRoleMember(ctx, domainName, "user.jack", auditRef);
+            fail();
+        } catch (ResourceException ex) {
+            assertEquals(ex.getCode(), ResourceException.FORBIDDEN);
+        }
+        zmsImpl.deleteTopLevelDomain(ctx, domainName, auditRef, null);
+    }
+
     @Test
     public void testDeleteUserDomainNull() {
         Authority userAuthority = new com.yahoo.athenz.common.server.debug.DebugUserAuthority();