cron (360 Bench fork)

Part of 360 Bench, tested fixes for abandoned packages.

This is a fork of robfig/cron by Rob Figueiredo and its contributors, published so that programs which parse user-supplied schedules stop crashing. Upstream has not tagged a release since v3.0.1 (January 2020), and the panic below has four unmerged fix PRs. All credit for the original library goes to its author and contributors; it remains available under the same MIT license.

What's fixed in this fork

Based on the upstream v3.0.1 tag (January 2020). The API is unchanged, and wherever v3.0.1 didn't panic it behaves exactly the same: every schedule that parsed before parses to the same thing.

• No more panic: runtime error: slice bounds out of range [:-1] when a schedule is only a timezone prefix. cron.ParseStandard("TZ=0"), "TZ=UTC", "CRON_TZ=Asia/Tokyo", "TZ=" or "TZ=TZ=TZ=", passed to any parser or to Cron.AddFunc / AddJob, used to crash the whole process, which matters when schedules come from users or config. They now return the error missing schedule after timezone: <spec>. Upstream issues: #554, #470. Same fix proposed in unmerged PRs #555, #566, #567 and #574 (and the earlier, closed #365).

Not included, on purpose: #574 also rejects steps larger than the field range (such as */90 * * * *, issue #543). Those specs parse without panicking today, so rejecting them would change behaviour for existing users.

A fuzz test (FuzzParse) runs every parser over the seed corpus on each go test; longer fuzzing runs found no other parser panics.

Not included: upstream's unreleased master commits

Upstream merged four commits after v3.0.1 but never tagged them. They are deliberately not in this fork, so that v3.0.2 is v3.0.1 plus the panic fix only (360 Bench rule: same behaviour wherever the original didn't crash):

• bc59245 SkipIfStillRunning: return the run token even if the job panics. This changes runtime behaviour, so it is left to upstream.
• e7da914, 208b4f7, 6a8421b: README and code-comment fixes.

How to switch

Either change your imports to the fork:

go get github.com/fitzyracing1/cron/v3@v3.0.2
# then replace github.com/robfig/cron/v3 with github.com/fitzyracing1/cron/v3 in your imports

import "github.com/fitzyracing1/cron/v3"

Or keep your imports (and fix it for dependencies that import robfig/cron too) with a replace directive in your go.mod:

replace github.com/robfig/cron/v3 => github.com/fitzyracing1/cron/v3 v3.0.2

It requires Go 1.11 or later due to usage of Go Modules.

Refer to the documentation here: https://pkg.go.dev/github.com/fitzyracing1/cron/v3

Tests

go test ./... -race
go vet ./...
go test -run='^$' -fuzz=FuzzParse -fuzztime=60s   # optional, Go 1.18+

The regression tests are in parser_tz_test.go and parser_fuzz_test.go; they panic on upstream v3.0.1 and pass here.

License

MIT, copyright (C) 2012 Rob Figueiredo. See LICENSE. Fork changes by Joshua Almeida are under the same license.

---

The rest of this README is upstream's.

The rest of this document describes the the advances in v3 and a list of breaking changes for users that wish to upgrade from an earlier version.

Upgrading to v3 (June 2019)

cron v3 is a major upgrade to the library that addresses all outstanding bugs, feature requests, and rough edges. It is based on a merge of master which contains various fixes to issues found over the years and the v2 branch which contains some backwards-incompatible features like the ability to remove cron jobs. In addition, v3 adds support for Go Modules, cleans up rough edges like the timezone support, and fixes a number of bugs.

New features:

• Support for Go modules. Callers must now import this library as github.com/robfig/cron/v3, instead of gopkg.in/...

• Fixed bugs:

  • 0f01e6b parser: fix combining of Dow and Dom (#70)
  • dbf3220 adjust times when rolling the clock forward to handle non-existent midnight (#157)
  • eeecf15 spec_test.go: ensure an error is returned on 0 increment (#144)
  • 70971dc cron.Entries(): update request for snapshot to include a reply channel (#97)
  • 1cba5e6 cron: fix: removing a job causes the next scheduled job to run too late (#206)

• Standard cron spec parsing by default (first field is "minute"), with an easy way to opt into the seconds field (quartz-compatible). Although, note that the year field (optional in Quartz) is not supported.

• Extensible, key/value logging via an interface that complies with the https://github.com/go-logr/logr project.

• The new Chain & JobWrapper types allow you to install "interceptors" to add cross-cutting behavior like the following:

  • Recover any panics from jobs
  • Delay a job's execution if the previous run hasn't completed yet
  • Skip a job's execution if the previous run hasn't completed yet
  • Log each job's invocations
  • Notification when jobs are completed

It is backwards incompatible with both v1 and v2. These updates are required:

• The v1 branch accepted an optional seconds field at the beginning of the cron spec. This is non-standard and has led to a lot of confusion. The new default parser conforms to the standard as described by the Cron wikipedia page.

  UPDATING: To retain the old behavior, construct your Cron with a custom parser:

  // Seconds field, required
  cron.New(cron.WithSeconds())
  
  // Seconds field, optional
  cron.New(
      cron.WithParser(
          cron.SecondOptional | cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow | cron.Descriptor))
  

• The Cron type now accepts functional options on construction rather than the previous ad-hoc behavior modification mechanisms (setting a field, calling a setter).

  UPDATING: Code that sets Cron.ErrorLogger or calls Cron.SetLocation must be updated to provide those values on construction.

• CRON_TZ is now the recommended way to specify the timezone of a single schedule, which is sanctioned by the specification. The legacy "TZ=" prefix will continue to be supported since it is unambiguous and easy to do so.

  UPDATING: No update is required.

• By default, cron will no longer recover panics in jobs that it runs. Recovering can be surprising (see issue #192) and seems to be at odds with typical behavior of libraries. Relatedly, the cron.WithPanicLogger option has been removed to accommodate the more general JobWrapper type.

  UPDATING: To opt into panic recovery and configure the panic logger:

  cron.New(cron.WithChain(
      cron.Recover(logger),  // or use cron.DefaultLogger
  ))
  

• In adding support for https://github.com/go-logr/logr, cron.WithVerboseLogger was removed, since it is duplicative with the leveled logging.

  UPDATING: Callers should use WithLogger and specify a logger that does not discard Info logs. For convenience, one is provided that wraps *log.Logger:

  cron.New(
      cron.WithLogger(cron.VerbosePrintfLogger(logger)))
  

Background - Cron spec format

There are two cron spec formats in common usage:

• The "standard" cron format, described on the Cron wikipedia page and used by the cron Linux system utility.

• The cron format used by the Quartz Scheduler, commonly used for scheduled jobs in Java software

The original version of this package included an optional "seconds" field, which made it incompatible with both of these formats. Now, the "standard" format is the default format accepted, and the Quartz format is opt-in.

Documentation

• In-repo docs: docs/
• Wiki: https://github.com/fitzyracing1/cron/wiki