Make phase condition reasons part of the API

TaskRuns and PipelineRuns use the "Reason" field to complement the
value of the "Succeeded" condition. Those values are not part of
the API and are even owned by the underlying resource (pod) in
case of TaskRuns. This makes it difficult to rely on them to
understand that the state of the resource is.

In case of corev1.ConditionTrue, the reason can be used to
distinguish between:
- Successful
- Successful, some parts were skipped (pipelinerun only)

In case of corev1.ConditionFalse, the reason can be used to
distinguish between:
- Failed
- Failed because of timeout
- Failed because of cancelled by the user

In case of corev1.ConditionUnknown, the reason can be used to
distinguish between:
- Just started reconciling
- Validation done, running (or still running)
- Cancellation requested

This is implemented through the following changes:
- Bubble up reasons for taskrun and pipelinerun to the
  v1beta1 API, except for reason that are defined by the
  underlying resource
- Enforce the start reason to be set during condition init

This allows for an additional change in the eventing module: the
condition before and after can be used to decide whether to send
an event at all. If they are different, the after condition now
contains enough information to send the event.

The cloudevent module is extended with ability to send the correct
event based on both status and reason.

docs/pipelineruns.md

@@ -18,6 +18,7 @@ weight: 4
   - [Specifying `Workspaces`](#specifying-workspaces)
   - [Specifying `LimitRange` values](#specifying-limitrange-values)
   - [Configuring a failure timeout](#configuring-a-failure-timeout)
+- [Monitoring execution status](#monitoring-execution-status)
 - [Cancelling a `PipelineRun`](#cancelling-a-pipelinerun)
 - [Events](events.md#pipelineruns)
 
@@ -337,6 +338,70 @@ The `timeout` value is a `duration` conforming to Go's
 values are `1h30m`, `1h`, `1m`, and `60s`. If you set the global timeout to 0, all `PipelineRuns`
 that do not have an idividual timeout set will fail immediately upon encountering an error.
 
+## Monitoring execution status
+
+As your `PipelineRun` executes, its `status` field accumulates information on the execution of each `TaskRun`
+as well as the `PipelineRun` as a whole. This information includes the name of the pipeline `Task` associated
+to a `TaskRun`, the complete [status of the `TaskrRun`](taskruns.md#monitoring-execution-status) and details
+about `Conditions` that may be associated to a `TaskRun`.
+
+The following example shows an extract from tje `status` field of a `PipelineRun` that has executed successfully:
+
+```yaml
+completionTime: "2020-05-04T02:19:14Z"
+conditions:
+- lastTransitionTime: "2020-05-04T02:19:14Z"
+  message: 'Tasks Completed: 4, Skipped: 0'
+  reason: Succeeded
+  status: "True"
+  type: Succeeded
+startTime: "2020-05-04T02:00:11Z"
+taskRuns:
+  triggers-release-nightly-frwmw-build-ng2qk:
+    pipelineTaskName: build
+    status:
+      completionTime: "2020-05-04T02:10:49Z"
+      conditions:
+      - lastTransitionTime: "2020-05-04T02:10:49Z"
+        message: All Steps have completed executing
+        reason: Succeeded
+        status: "True"
+        type: Succeeded
+      podName: triggers-release-nightly-frwmw-build-ng2qk-pod-8vj99
+      resourcesResult:
+      - key: commit
+        resourceRef:
+          name: git-source-triggers-frwmw
+        value: 9ab5a1234166a89db352afa28f499d596ebb48db
+      startTime: "2020-05-04T02:05:07Z"
+      steps:
+      - container: step-build
+        imageID: docker-pullable://golang@sha256:a90f2671330831830e229c3554ce118009681ef88af659cd98bfafd13d5594f9
+        name: build
+        terminated:
+          containerID: docker://6b6471f501f59dbb7849f5cdde200f4eeb64302b862a27af68821a7fb2c25860
+          exitCode: 0
+          finishedAt: "2020-05-04T02:10:45Z"
+          reason: Completed
+          startedAt: "2020-05-04T02:06:24Z"
+  ```
+
+The following tables shows how to read the overall status of a `PipelineRun`:
+
+`status`|`reason`|`completionTime` is set|PipelineRun status
+:-------|:-------|:---------------------:|--------------:
+Unknown|Started|No|The `PipelineRun` has just been picked up by the controller.
+Unknown|Running|No|The `PipelineRun` has been validate and started to perform its work.
+Unknown|PipelineRunCancelled|No|The user requested the PipelineRun to be cancelled. Cancellation has not be done yet.
+True|Succeeded|Yes|The `PipelineRun` completed successfully.
+False|Failed|Yes|The `PipelineRun` failed because one of the `TaskRuns` failed.
+False|\[Error message\]|Yes|The `PipelineRun` failed with a permanent error (usually validation).
+False|PipelineRunCancelled|Yes|The `PipelineRun` was cancelled successfully.
+False|PipelineRunTimeout|Yes|The `PipelineRun` timed out.
+False|\[Error message\]|No|The `PipelineRun` encountered an error, but it's still running.
+
+When a `PipelineRun` changes status, [events](events.md#pipelineruns) are triggered accordingly.
+
 ## Cancelling a `PipelineRun`
 
 To cancel a `PipelineRun` that's currently executing, update its definition

docs/taskruns.md

@@ -155,7 +155,7 @@ point for the `Pod` in which the container images specified in your `Task` will
 customize the `Pod` configuration specifically for that `TaskRun`.
 
 In the following example, the `Task` specifies a `volumeMount` (`my-cache`) object, also provided by the `TaskRun`,
-using a `PersistentVolumeClaim` volume. A specific scheduler is also configured in the  `SchedulerName` field. 
+using a `PersistentVolumeClaim` volume. A specific scheduler is also configured in the  `SchedulerName` field.
 The `Pod` executes with regular (non-root) user permissions.
 
 ```yaml
@@ -281,7 +281,7 @@ For more information, see [`ServiceAccount`](auth.md).
 ## Monitoring execution status
 
 As your `TaskRun` executes, its `status` field accumulates information on the execution of each `Step`
-as well as the `TaskRun` as a whole. This information includes start and stop times, exit codes, the 
+as well as the `TaskRun` as a whole. This information includes start and stop times, exit codes, the
 fully-qualified name of the container image, and the corresponding digest.
 
 **Note:** If any `Pods` have been [`OOMKilled`](https://kubernetes.io/docs/tasks/administer-cluster/out-of-resource/)
@@ -311,6 +311,22 @@ steps:
     startedAt: "2019-08-12T18:22:54Z"
   ```
 
+The following tables shows how to read the overall status of a `TaskRun`:
+
+`status`|`reason`|`completionTime` is set|TaskRun status
+:-------|:-------|:---------------------:|--------------:
+Unknown|Started|No|The TaskRun has just been picked up by the controller.
+Unknown|Running|No|The TaskRun has been validate and started to perform its work.
+Unknown|TaskRunCancelled|No|The user requested the TaskRun to be cancelled. Cancellation has not be done yet.
+True|Succeeded|Yes|The TaskRun completed successfully.
+False|Failed|Yes|The TaskRun failed because one of the steps failed.
+False|\[Error message\]|Yes|The TaskRun failed with a permanent error (usually validation).
+False|TaskRunCancelled|Yes|The TaskRun was cancelled successfully.
+False|TaskRunTimeout|Yes|The TaskRun timed out.
+False|\[Error message\]|No|The TaskRun encountered an error, but it's still running.
+
+When a `TaskRun` changes status, [events](events.md#taskruns) are triggered accordingly.
+
 ### Monitoring `Steps`
 
 If multiple `Steps` are defined in the `Task` invoked by the `TaskRun`, you can monitor their execution

pkg/apis/pipeline/v1beta1/pipelinerun_types.go

@@ -220,6 +220,32 @@ type PipelineRunStatus struct {
 	PipelineRunStatusFields `json:",inline"`
 }
 
+// PipelineRunSucceededReason represents a reason for the pipeline run "Succeeded" condition
+type PipelineRunSucceededReason string
+
+const (
+	// PipelineRunSucceededReasonStarted is the reason set when the PipelineRun has just started
+	PipelineRunSucceededReasonStarted PipelineRunSucceededReason = "Started"
+	// PipelineRunSucceededReasonRunning is the reason set when the PipelineRun is running
+	PipelineRunSucceededReasonRunning PipelineRunSucceededReason = "Running"
+	// PipelineRunSucceededReasonSuccessful is the reason set when the PipelineRun completed successfully
+	PipelineRunSucceededReasonSuccessful PipelineRunSucceededReason = "Succeeded"
+	// PipelineRunSucceededReasonCompleted is the reason set when the PipelineRun completed successfully with one or more skipped Tasks
+	PipelineRunSucceededReasonCompleted PipelineRunSucceededReason = "Completed"
+	// PipelineRunSucceededReasonFailed is the reason set when the PipelineRun completed with a failure
+	PipelineRunSucceededReasonFailed PipelineRunSucceededReason = "Failed"
+	// PipelineRunSucceededReasonCancelled is the reason set when the PipelineRun cancelled by the user
+	// This reason may be found with a corev1.ConditionFalse status, if the cancellation was processed successfully
+	// This reason may be found with a corev1.ConditionUnknown status, if the cancellation is being processed or failed
+	PipelineRunSucceededReasonCancelled PipelineRunSucceededReason = "Cancelled"
+	// PipelineRunSucceededReasonTimedOut is the reason set when the PipelineRun has timed out
+	PipelineRunSucceededReasonTimedOut PipelineRunSucceededReason = "PipelineRunTimeout"
+)
+
+func (t PipelineRunSucceededReason) String() string {
+	return string(t)
+}
+
 var pipelineRunCondSet = apis.NewBatchConditionSet()
 
 // GetCondition returns the Condition matching the given type.
@@ -236,7 +262,12 @@ func (pr *PipelineRunStatus) InitializeConditions() {
 	if pr.StartTime.IsZero() {
 		pr.StartTime = &metav1.Time{Time: time.Now()}
 	}
-	pipelineRunCondSet.Manage(pr).InitializeConditions()
+	conditionManager := pipelineRunCondSet.Manage(pr)
+	conditionManager.InitializeConditions()
+	// Ensure the started reason is set for the "Succeeded" condition
+	initialCondition := conditionManager.GetCondition(apis.ConditionSucceeded)
+	initialCondition.Reason = TaskRunSucceededReasonStarted.String()
+	conditionManager.SetCondition(*initialCondition)
 }
 
 // SetCondition sets the condition, unsetting previous conditions with the same

pkg/apis/pipeline/v1beta1/run_interface.go

@@ -23,20 +23,48 @@ import (
 
 // RunsToCompletionStatus is implemented by TaskRun.Status and PipelineRun.Status
 type RunsToCompletionStatus interface {
+
+	// GetCondition returns the Condition for the specified ConditionType
 	GetCondition(t apis.ConditionType) *apis.Condition
+
+	// InitializeConditions is used to set up the initial conditions for the
+	// RunsToCompletion  when it's initially started
 	InitializeConditions()
+
+	// SetCondition is used to set up a conditions for the specified ConditionType
 	SetCondition(newCond *apis.Condition)
 }
 
 // RunsToCompletion is implemented by TaskRun and PipelineRun
 type RunsToCompletion interface {
+
+	// GetTypeMeta returns the TypeMeta
 	GetTypeMeta() *metav1.TypeMeta
+
+	// GetObjectMeta returns the ObjectMeta
 	GetObjectMeta() *metav1.ObjectMeta
+
+	// GetOwnerReference returns the RunsToCompletion as owner reference for any related object
 	GetOwnerReference() metav1.OwnerReference
+
+	// GetStatus returns the status as RunsToCompletionStatus
 	GetStatus() RunsToCompletionStatus
+
+	// IsDone returns true once the reconcile work on the resource is complete
+	// except for postrun actions (stop timeout timer, emit events, record metrics)
 	IsDone() bool
+
+	// HasStarted returns true after the RunsToCompletion has been reconciled for
+	// the first time. It must be true after InitializeConditions has been invoked
+	// on the associated RunsToCompletionStatus
 	HasStarted() bool
+
+	// IsCancelled returns true if the user marked the RunsToCompletion for cancellation
 	IsCancelled() bool
+
+	// HasTimedOut returns true once the RunsToCompletion has passed its maximum run time
 	HasTimedOut() bool
+
+	// GetRunKey returns the RunsToCompletion keuy which is equeued in the controller queue
 	GetRunKey() string
 }

pkg/apis/pipeline/v1beta1/taskrun_types.go

@@ -72,10 +72,6 @@ const (
 	// TaskRunSpecStatusCancelled indicates that the user wants to cancel the task,
 	// if not already cancelled or terminated
 	TaskRunSpecStatusCancelled = "TaskRunCancelled"
-
-	// TaskRunReasonCancelled indicates that the TaskRun has been cancelled
-	// because it was requested so by the user
-	TaskRunReasonCancelled = "TaskRunCancelled"
 )
 
 // TaskRunInputs holds the input values that this task was invoked with.
@@ -102,6 +98,43 @@ type TaskRunStatus struct {
 	TaskRunStatusFields `json:",inline"`
 }
 
+// TaskRunSucceededReason is an enum used to store all TaskRun reason for
+// the Succeeded condition that are controlled by the TaskRun itself. Failure
+// reasons that emerge from underlying resources are not included here
+type TaskRunSucceededReason string
+
+const (
+	// TaskRunSucceededReasonStarted is the reason set when the TaskRun has just started
+	TaskRunSucceededReasonStarted TaskRunSucceededReason = "Started"
+	// TaskRunSucceededReasonRunning is the reason set when the TaskRun is running
+	TaskRunSucceededReasonRunning TaskRunSucceededReason = "Running"
+	// TaskRunSucceededReasonSuccessful is the reason set when the TaskRun completed successfully
+	TaskRunSucceededReasonSuccessful TaskRunSucceededReason = "Succeeded"
+	// TaskRunSucceededReasonFailed is the reason set when the TaskRun completed with a failure
+	TaskRunSucceededReasonFailed TaskRunSucceededReason = "Failed"
+	// TaskRunSucceededReasonCancelled is the reason set when the Taskrun is cancelled by the user
+	TaskRunSucceededReasonCancelled TaskRunSucceededReason = "TaskRunCancelled"
+	// TaskRunSucceededReasonTimedOut is the reason set when the Taskrun has timed out
+	TaskRunSucceededReasonTimedOut TaskRunSucceededReason = "TaskRunTimeout"
+)
+
+func (t TaskRunSucceededReason) String() string {
+	return string(t)
+}
+
+// GetStartedReason returns the reason set to the "Succeeded" condition when
+// InitializeConditions is invoked
+func (trs *TaskRunStatus) GetStartedReason() string {
+	return TaskRunSucceededReasonStarted.String()
+}
+
+// GetRunningReason returns the reason set to the "Succeeded" condition when
+// the RunsToCompletion starts running. This is used indicate that the resource
+// could be validated is starting to perform its job.
+func (trs *TaskRunStatus) GetRunningReason() string {
+	return TaskRunSucceededReasonRunning.String()
+}
+
 // MarkResourceNotConvertible adds a Warning-severity condition to the resource noting
 // that it cannot be converted to a higher version.
 func (trs *TaskRunStatus) MarkResourceNotConvertible(err *CannotConvertError) {
@@ -116,11 +149,11 @@ func (trs *TaskRunStatus) MarkResourceNotConvertible(err *CannotConvertError) {
 
 // MarkResourceFailed sets the ConditionSucceeded condition to ConditionFalse
 // based on an error that occurred and a reason
-func (trs *TaskRunStatus) MarkResourceFailed(reason string, err error) {
+func (trs *TaskRunStatus) MarkResourceFailed(reason TaskRunSucceededReason, err error) {
 	taskRunCondSet.Manage(trs).SetCondition(apis.Condition{
 		Type:    apis.ConditionSucceeded,
 		Status:  corev1.ConditionFalse,
-		Reason:  reason,
+		Reason:  reason.String(),
 		Message: err.Error(),
 	})
 }
@@ -211,7 +244,12 @@ func (trs *TaskRunStatus) InitializeConditions() {
 	if trs.StartTime.IsZero() {
 		trs.StartTime = &metav1.Time{Time: time.Now()}
 	}
-	taskRunCondSet.Manage(trs).InitializeConditions()
+	conditionManager := taskRunCondSet.Manage(trs)
+	conditionManager.InitializeConditions()
+	// Ensure the started reason is set for the "Succeeded" condition
+	initialCondition := conditionManager.GetCondition(apis.ConditionSucceeded)
+	initialCondition.Reason = TaskRunSucceededReasonStarted.String()
+	conditionManager.SetCondition(*initialCondition)
 }
 
 // SetCondition sets the condition, unsetting previous conditions with the same

pkg/pod/status.go

@@ -45,13 +45,6 @@ const (
 	// that taskrun failed runtime validation
 	ReasonFailedValidation = "TaskRunValidationFailed"
 
-	// ReasonRunning indicates that the reason for the inprogress status is that the TaskRun
-	// is just starting to be reconciled
-	ReasonRunning = "Running"
-
-	// ReasonTimedOut indicates that the TaskRun has taken longer than its configured timeout
-	ReasonTimedOut = "TaskRunTimeout"
-
 	// ReasonExceededResourceQuota indicates that the TaskRun failed to create a pod due to
 	// a ResourceQuota in the namespace
 	ReasonExceededResourceQuota = "ExceededResourceQuota"
@@ -68,13 +61,6 @@ const (
 	// is that the creation of the pod backing the TaskRun failed
 	ReasonPodCreationFailed = "PodCreationFailed"
 
-	// ReasonSucceeded indicates that the reason for the finished status is that all of the steps
-	// completed successfully
-	ReasonSucceeded = "Succeeded"
-
-	// ReasonFailed indicates that the reason for the failure status is unknown or that one of the steps failed
-	ReasonFailed = "Failed"
-
 	//timeFormat is RFC3339 with millisecond
 	timeFormat = "2006-01-02T15:04:05.000Z07:00"
 )
@@ -114,7 +100,7 @@ func MakeTaskRunStatus(logger *zap.SugaredLogger, tr v1beta1.TaskRun, pod *corev
 		trs.SetCondition(&apis.Condition{
 			Type:    apis.ConditionSucceeded,
 			Status:  corev1.ConditionUnknown,
-			Reason:  ReasonRunning,
+			Reason:  v1beta1.TaskRunSucceededReasonRunning.String(),
 			Message: "Not all Steps in the Task have finished executing",
 		})
 	}
@@ -197,14 +183,14 @@ func updateCompletedTaskRun(trs *v1beta1.TaskRunStatus, pod *corev1.Pod) {
 		trs.SetCondition(&apis.Condition{
 			Type:    apis.ConditionSucceeded,
 			Status:  corev1.ConditionFalse,
-			Reason:  ReasonFailed,
+			Reason:  v1beta1.TaskRunSucceededReasonFailed.String(),
 			Message: msg,
 		})
 	} else {
 		trs.SetCondition(&apis.Condition{
 			Type:    apis.ConditionSucceeded,
 			Status:  corev1.ConditionTrue,
-			Reason:  ReasonSucceeded,
+			Reason:  v1beta1.TaskRunSucceededReasonSuccessful.String(),
 			Message: "All Steps have completed executing",
 		})
 	}
@@ -219,7 +205,7 @@ func updateIncompleteTaskRun(trs *v1beta1.TaskRunStatus, pod *corev1.Pod) {
 		trs.SetCondition(&apis.Condition{
 			Type:    apis.ConditionSucceeded,
 			Status:  corev1.ConditionUnknown,
-			Reason:  ReasonRunning,
+			Reason:  v1beta1.TaskRunSucceededReasonRunning.String(),
 			Message: "Not all Steps in the Task have finished executing",
 		})
 	case corev1.PodPending: