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// Copyright 2020 CUE Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package flow
// This file contains functionality for identifying tasks in the configuration
// and annotating the dependencies between them.
import (
"cuelang.org/go/cue"
"cuelang.org/go/cue/errors"
"cuelang.org/go/internal"
"cuelang.org/go/internal/core/adt"
"cuelang.org/go/internal/core/dep"
)
// initTasks takes the current configuration and adds tasks to the list of
// tasks. It can be run multiple times on increasingly more concrete
// configurations to add more tasks, whereby the task pointers of previously
// found tasks are preserved.
func (c *Controller) initTasks() {
// Clear previous cache.
c.nodes = map[*adt.Vertex]*Task{}
v := c.inst.LookupPath(c.cfg.Root)
if err := v.Err(); err != nil {
c.addErr(err, "invalid root")
c.cancel()
return
}
// Mark any task that is located under the root.
c.findRootTasks(v)
// Mark any tasks that are implied by dependencies.
// Note that the list of tasks may grow as this loop progresses.
for i := 0; i < len(c.tasks); i++ {
t := c.tasks[i]
c.markTaskDependencies(t, t.vertex())
}
// Check if there are cycles in the task dependencies.
if err := checkCycle(c.tasks); err != nil {
c.addErr(err, "cyclic task")
}
if c.errs != nil {
c.cancel()
}
}
// findRootTasks finds tasks under the root.
func (c *Controller) findRootTasks(v cue.Value) {
t := c.getTask(nil, v)
if t != nil {
return
}
for iter, _ := v.Fields(); iter.Next(); {
c.findRootTasks(iter.Value())
}
}
// This file contains the functionality to locate and record the tasks of
// a configuration. It:
// - create Task struct for each node that is a task
// - associate nodes in a configuration with a Task, if applicable.
// The node-to-task map is used to determine task dependencies.
// getTask finds and marks tasks that are descendents of v.
func (c *Controller) getTask(scope *Task, v cue.Value) *Task {
// Look up cached node.
_, n := internal.CoreValue(v)
w := n.(*adt.Vertex)
if t, ok := c.nodes[w]; ok {
return t
}
// Look up cached task from previous evaluation.
p := v.Path()
key := p.String()
t := c.keys[key]
if t == nil {
r, err := c.isTask(v)
var errs errors.Error
if err != nil {
if !c.inRoot(w) {
// Must be in InferTask mode. In this case we ignore the error.
r = nil
} else {
c.addErr(err, "invalid task")
errs = errors.Promote(err, "create task")
}
}
if r != nil {
index := len(c.tasks)
t = &Task{
v: v,
c: c,
r: r,
path: p,
labels: w.Path(),
key: key,
index: index,
err: errs,
}
c.tasks = append(c.tasks, t)
c.keys[key] = t
}
}
// Process nodes of task for this evaluation.
if t != nil {
scope = t
if t.state <= Ready {
// Don't set the value if the task is currently running as this may
// result in all kinds of inconsistency issues.
t.v = v
}
c.tagChildren(w, t)
}
c.nodes[w] = scope
return t
}
func (c *Controller) tagChildren(n *adt.Vertex, t *Task) {
for _, a := range n.Arcs {
c.nodes[a] = t
c.tagChildren(a, t)
}
}
// findImpliedTask determines the task of corresponding to node n, if any. If n
// is not already associated with a task, it tries to determine whether n is
// part of a task by checking if any of the parent nodes is a task.
//
// TODO: it is actually more accurate to check for tasks from top down. TODO:
// What should be done if a subtasks is referenced that is embedded in another
// task. Should the surrounding tasks be added as well?
func (c *Controller) findImpliedTask(d dep.Dependency) *Task {
// Ignore references into packages. Fill will fundamentally not work for
// packages, and packages cannot point back to the main package as cycles
// are not allowed.
if d.Import() != nil {
return nil
}
n := d.Node
for ; n != nil; n = n.Parent {
if c.cfg.IgnoreConcrete && n.IsConcrete() {
if k := n.BaseValue.Kind(); k != adt.StructKind && k != adt.ListKind {
return nil
}
}
t, ok := c.nodes[n]
if ok || !c.cfg.InferTasks {
return t
}
if !d.IsRoot() {
v := cue.MakeValue(c.opCtx, n)
if t := c.getTask(nil, v); t != nil {
return t
}
}
}
return nil
}
// markTaskDependencies traces through all conjuncts of a Task and marks
// any dependencies on other tasks.
//
// The dependencies for a node by traversing the nodes of a task and then
// traversing the dependencies of the conjuncts.
//
// This terminates because:
//
// - traversing all nodes of all tasks is guaranteed finite (CUE does not
// evaluate to infinite structure).
//
// - traversing conjuncts of all nodes is finite, as the input syntax is
// inherently finite.
//
// - as regular nodes are traversed recursively they are marked with a cycle
// marker to detect cycles, ensuring a finite traversal as well.
//
func (c *Controller) markTaskDependencies(t *Task, n *adt.Vertex) {
dep.VisitFields(c.opCtx, n, func(d dep.Dependency) error {
depTask := c.findImpliedTask(d)
if depTask != nil {
if depTask != cycleMarker {
t.addDep(depTask)
}
return nil
}
// If this points to a non-task node, it may itself point to a task.
// Handling this allows for dynamic references. For instance, such a
// value may reference the result value of a task, or even create
// new tasks based on the result of another task.
if d.Import() == nil {
c.nodes[d.Node] = cycleMarker
c.markTaskDependencies(t, d.Node)
c.nodes[d.Node] = nil
}
return nil
})
}
func (c *Controller) inRoot(n *adt.Vertex) bool {
path := cue.MakeValue(c.opCtx, n).Path().Selectors()
root := c.cfg.Root.Selectors()
if len(path) < len(root) {
return false
}
for i, sel := range root {
if path[i] != sel {
return false
}
}
return true
}
var cycleMarker = &Task{}