Use Nomad jobs as runners instead of allocations

As we can't control which allocations are destroyed when downscaling a job, we decided
to use Nomad jobs as our runners. Thus for each runner we prewarm for an environment,
a corresponding job is created in Nomad. We create a default job that serves as a template
for the runners. Using this, already existing execution environments can easily be restored,
once Poseidon is restarted.

runner/nomad_environment_storage_test.go

@@ -0,0 +1,76 @@
+package runner
+
+import (
+	nomadApi "github.com/hashicorp/nomad/api"
+	"github.com/stretchr/testify/suite"
+	"testing"
+)
+
+func TestJobStoreTestSuite(t *testing.T) {
+	suite.Run(t, new(JobStoreTestSuite))
+}
+
+type JobStoreTestSuite struct {
+	suite.Suite
+	jobStorage *localNomadJobStorage
+	job        *NomadEnvironment
+}
+
+func (suite *JobStoreTestSuite) SetupTest() {
+	suite.jobStorage = NewLocalNomadJobStorage()
+	suite.job = &NomadEnvironment{environmentID: defaultEnvironmentId}
+}
+
+func (s *JobStoreTestSuite) TestAddedJobCanBeRetrieved() {
+	s.jobStorage.Add(s.job)
+	retrievedJob, ok := s.jobStorage.Get(s.job.ID())
+	s.True(ok, "A saved runner should be retrievable")
+	s.Equal(s.job, retrievedJob)
+}
+
+func (suite *JobStoreTestSuite) TestJobWithSameIdOverwritesOldOne() {
+	otherJobWithSameID := &NomadEnvironment{environmentID: defaultEnvironmentId}
+	otherJobWithSameID.templateJob = &nomadApi.Job{}
+	suite.NotEqual(suite.job, otherJobWithSameID)
+
+	s.jobStorage.Add(s.job)
+	s.jobStorage.Add(otherJobWithSameID)
+	retrievedJob, _ := s.jobStorage.Get(s.job.ID())
+	s.NotEqual(s.job, retrievedJob)
+	s.Equal(otherJobWithSameID, retrievedJob)
+}
+
+func (s *JobStoreTestSuite) TestDeletedJobIsNotAccessible() {
+	s.jobStorage.Add(s.job)
+	s.jobStorage.Delete(s.job.ID())
+	retrievedRunner, ok := s.jobStorage.Get(s.job.ID())
+	s.Nil(retrievedRunner)
+	s.False(ok, "A deleted runner should not be accessible")
+}
+
+func (s *JobStoreTestSuite) TestLenOfEmptyPoolIsZero() {
+	s.Equal(0, s.jobStorage.Length())
+}
+
+func (s *JobStoreTestSuite) TestLenChangesOnStoreContentChange() {
+	s.Run("len increases when job is added", func() {
+		s.jobStorage.Add(s.job)
+		s.Equal(1, s.jobStorage.Length())
+	})
+
+	s.Run("len does not increase when job with same id is added", func() {
+		s.jobStorage.Add(s.job)
+		s.Equal(1, s.jobStorage.Length())
+	})
+
+	s.Run("len increases again when different job is added", func() {
+		anotherJob := &NomadEnvironment{environmentID: anotherEnvironmentID}
+		s.jobStorage.Add(anotherJob)
+		s.Equal(2, s.jobStorage.Length())
+	})
+
+	s.Run("len decreases when job is deleted", func() {
+		s.jobStorage.Delete(s.job.ID())
+		s.Equal(1, s.jobStorage.Length())
+	})
+}