Add option to use the kubernetes scheduler for workflow pods (#111)

* Add option to use kube scheduler

This should only be used when rwx volumes are supported or when using a single node cluster.

* Add option to set timeout for prepare job

If the kube scheduler is used to hold jobs until sufficient resources are available,
then prepare job needs to wait for a longer period until the workflow pod is running.
This timeout will mostly need an increase in cases where many jobs are triggered
which together exceed the resources available in the cluster.
The workflows can then be gracefully handled later when sufficient resources become available again.

* Skip name override warning when names match or job extension

* Add guard for positive timeouts with a warning

* Write out ReadWriteMany in full

packages/k8s/tests/prepare-job-test.ts

@@ -5,6 +5,7 @@ import { createContainerSpec, prepareJob } from '../src/hooks/prepare-job'
 import { TestHelper } from './test-setup'
 import {
   ENV_HOOK_TEMPLATE_PATH,
+  ENV_USE_KUBE_SCHEDULER,
   generateContainerName,
   readExtensionFromFile
 } from '../src/k8s/utils'
@@ -130,6 +131,17 @@ describe('Prepare job', () => {
     expect(got.spec?.containers[2].args).toEqual(['-c', 'sleep 60'])
   })
 
+  it('should not throw exception using kube scheduler', async () => {
+    // only for ReadWriteMany volumes or single node cluster
+    process.env[ENV_USE_KUBE_SCHEDULER] = 'true'
+
+    await expect(
+      prepareJob(prepareJobData.args, prepareJobOutputFilePath)
+    ).resolves.not.toThrow()
+
+    delete process.env[ENV_USE_KUBE_SCHEDULER]
+  })
+
   test.each([undefined, null, []])(
     'should not throw exception when portMapping=%p',
     async pm => {