hugo/lazy/init.go
Michael Lynch fe60b7d9e4 Add diagnostic hints to init timeout message
Expand the text in the init timeout message to give the reader more hints as to what may be causing the issue.

The current error sent me on a wild goose chase trying to debug my shortcodes, but it turned out that the issue was just that I wasn't caching my resources/ directory on my build server. Once I found this blog post, I solved the issue in minutes:

https://www.henriksommerfeld.se/hugo-timeout-not-a-circular-loop-in-shortcode/

Googling the error message yields several additional posts from users who focus on loops in their shortcode when the problem seems to be overly-expensive builds.
2020-04-27 13:23:35 +02:00

198 lines
4.4 KiB
Go

// Copyright 2019 The Hugo Authors. All rights reserved.
//
// 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 lazy
import (
"context"
"sync"
"time"
"github.com/pkg/errors"
)
// New creates a new empty Init.
func New() *Init {
return &Init{}
}
// Init holds a graph of lazily initialized dependencies.
type Init struct {
mu sync.Mutex
prev *Init
children []*Init
init onceMore
out interface{}
err error
f func() (interface{}, error)
}
// Add adds a func as a new child dependency.
func (ini *Init) Add(initFn func() (interface{}, error)) *Init {
if ini == nil {
ini = New()
}
return ini.add(false, initFn)
}
// AddWithTimeout is same as Add, but with a timeout that aborts initialization.
func (ini *Init) AddWithTimeout(timeout time.Duration, f func(ctx context.Context) (interface{}, error)) *Init {
return ini.Add(func() (interface{}, error) {
return ini.withTimeout(timeout, f)
})
}
// Branch creates a new dependency branch based on an existing and adds
// the given dependency as a child.
func (ini *Init) Branch(initFn func() (interface{}, error)) *Init {
if ini == nil {
ini = New()
}
return ini.add(true, initFn)
}
// BranchdWithTimeout is same as Branch, but with a timeout.
func (ini *Init) BranchWithTimeout(timeout time.Duration, f func(ctx context.Context) (interface{}, error)) *Init {
return ini.Branch(func() (interface{}, error) {
return ini.withTimeout(timeout, f)
})
}
// Do initializes the entire dependency graph.
func (ini *Init) Do() (interface{}, error) {
if ini == nil {
panic("init is nil")
}
ini.init.Do(func() {
prev := ini.prev
if prev != nil {
// A branch. Initialize the ancestors.
if prev.shouldInitialize() {
_, err := prev.Do()
if err != nil {
ini.err = err
return
}
} else if prev.inProgress() {
// Concurrent initialization. The following init func
// may depend on earlier state, so wait.
prev.wait()
}
}
if ini.f != nil {
ini.out, ini.err = ini.f()
}
for _, child := range ini.children {
if child.shouldInitialize() {
_, err := child.Do()
if err != nil {
ini.err = err
return
}
}
}
})
ini.wait()
return ini.out, ini.err
}
// TODO(bep) investigate if we can use sync.Cond for this.
func (ini *Init) wait() {
var counter time.Duration
for !ini.init.Done() {
counter += 10
if counter > 600000000 {
panic("BUG: timed out in lazy init")
}
time.Sleep(counter * time.Microsecond)
}
}
func (ini *Init) inProgress() bool {
return ini != nil && ini.init.InProgress()
}
func (ini *Init) shouldInitialize() bool {
return !(ini == nil || ini.init.Done() || ini.init.InProgress())
}
// Reset resets the current and all its dependencies.
func (ini *Init) Reset() {
mu := ini.init.ResetWithLock()
defer mu.Unlock()
for _, d := range ini.children {
d.Reset()
}
}
func (ini *Init) add(branch bool, initFn func() (interface{}, error)) *Init {
ini.mu.Lock()
defer ini.mu.Unlock()
if branch {
return &Init{
f: initFn,
prev: ini,
}
}
ini.checkDone()
ini.children = append(ini.children, &Init{
f: initFn,
})
return ini
}
func (ini *Init) checkDone() {
if ini.init.Done() {
panic("init cannot be added to after it has run")
}
}
func (ini *Init) withTimeout(timeout time.Duration, f func(ctx context.Context) (interface{}, error)) (interface{}, error) {
ctx, cancel := context.WithTimeout(context.Background(), timeout)
defer cancel()
c := make(chan verr, 1)
go func() {
v, err := f(ctx)
select {
case <-ctx.Done():
return
default:
c <- verr{v: v, err: err}
}
}()
select {
case <-ctx.Done():
return nil, errors.New("timed out initializing value. You may have a circular loop in a shortcode, or your site may have resources that take longer to build than the `timeout` limit in your Hugo config file.")
case ve := <-c:
return ve.v, ve.err
}
}
type verr struct {
v interface{}
err error
}