Constraints operator "is not", "not" and "!=" doesn't work as expected with missing meta tags

[mclate]

Nomad version

Nomad v0.4.0

Operating system and Environment details

Ubuntu 140.4, docker 1.11.2

Issue

Consider having some nodes with meta "router" = true and some that doesn't have that tag.

Having constraints that look like this:

        "Constraints": [
            {
                "LTarget": "${meta.router}",
                "Operand": "is not",
                "RTarget": "1"
            }
        ]

won't start task on any node, while it is expected to be started on nodes that don't have router = true meta tag.

Here is nomad task output (i'm having 2 nodes with that tag set and 10 without it and want to start two instances in task group):

Task Group "admin":
  * Constraint "${meta.router} is not 1" filtered 8 nodes
  * Constraint "computed class ineligible" filtered 4 nodes

Expected behavior

Nomad should handle missing meta tags and do matching for is not, not and != against None (or undefined)

[mclate]

Any word on this one?

BTW, in documentation it says Operator (json, hcl), while nomad actually expects Operand to be passed.

[diptanu]

@mclate I believe we fixed the documentation bug.

[mclate]

* Constraint "${meta.router} == ${meta.other}" filtered 7 nodes
And no allocations were created.

I'm not quite follow what "undefined behavior" this would lead to. Wouldn't it be the same behaviour as running task with no constraints only for nodes that don't have meta tag i've mentioned?

So, right now, if i don't provide any constraints, task will run on any node. I'm able to say "run only on these nodes", but how would i say "run on any nodes other than these" (without requirement to specify all possible tags on all nodes)?

Also it's not quite clear what's the difference between is and == as well as is not and !=. Looks like they do pretty much the same.

Wonder if it would make sense to use ==/!= for strict matching (where ${meta.key} != 2 would only match nodes that do have key and key doesn't equal to 2) and is/is not to be used for scenario i've described (where for is not we don't care about key presence)

[dadgar]

Yeah I understand now. Reopening

[mclate]

Guys, am i right assuming that this issue didn't appear in latest release (v.0.5.0)?

[dadgar]

@mclate Correct it still hasn't been resolved. I am tentatively going to mark this for 0.6.0

[marcosnils]

@dadgar @mclate this hasn't been resolved yet I assume?. Just hit the same issue and I'm force to add a tag to all my nodes so nomad doesn't exclude all of them when using a != operator.

[dadgar]

@marcosnils Sorry still hasn't been resolved.

[github-actions]

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