amtool --duration implementation wrong

[ulikl]

What did you do?

I want to create a silence for 2h in the future via

amtool silence add --start=2021-10-31T10:00:00.000-02:00 --duration=2h ...

What did you expect to see?

According to amtool --help-long the

--duration=DURATION  Duration of silence

I expected a silence starting at 2021-10-31T12:00:00.000Z and ending at 2021-10-31T14:00:00.000Z

Remark: In the Alertmanager GUI the endtime is already calculated from the duration in the browser.
Endtime is here mandatory for submit action. So here we do not face this problem. I haven't check the alertmanager API.

What did you see instead? Under which circumstances?

Abort with error
amtool: error: silence cannot start after it ends

When execution + duration > start timestamp, a silence is created ending at 20d from now.

Environment

• System information:

  insert output of uname -srm here

Alertmanager:
Linux 3.10.0-1127.19.1.el7.x86_64 x86_64
amtool:

Linux 4.18.0-338.el8.x86_64 x86_64

• Alertmanager version:

Alertmanager from status GUI:

Branch: HEAD
BuildDate: 20210602-07:50:37
BuildUser: root@b595c7f32520
GoVersion: go1.16.4
Revision: 44f8adc06af5101ad64bd8b9c8b18273f2922051
Version: 0.22.2

 amtool --version
amtool, version 0.22.2 (branch: HEAD, revision: 44f8adc06af5101ad64bd8b9c8b18273f2922051)
  build user:       root@b595c7f32520
  build date:       20210602-07:50:37
  go version:       go1.16.4
  platform:         linux/amd64

• Prometheus version:

not relevant

• Alertmanager configuration file:

not relevant

• Prometheus configuration file:

not relevant

• Logs:
  no log entries created for these amtool calls.

[nekketsuuu]

This issue is dup of #2490.

I think we can say this is a bug of amtool. If we pass --duration to amtool silence add, it calculates endsAt not as startsAt + duration, but as time.Now() + duration.

alertmanager/cli/silence_add.go

Line 125 in 523c932

endsAt = time.Now().UTC().Add(time.Duration(d))

When the --duration option was impelmented, amtool silence update was implemented to calculate endsAt as startsAt + duration (ref), but amtool silence add was not.

I'll send a patch to change this behavior.

I haven't check the alertmanager API.

Alertmanager API v2 does not prepare the duration option.

alertmanager/api/v2/openapi.yaml

Lines 327 to 339 in 523c932

	properties:
	matchers:
	$ref: '#/definitions/matchers'
	startsAt:
	type: string
	format: date-time
	endsAt:
	type: string
	format: date-time
	createdBy:
	type: string
	comment:
	type: string