Logical bit-wise AND of two boolean instant vectors on PromQL

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Samuel Alfageme

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Dec 4, 2019, 9:24:18 AM12/4/19
to Prometheus Users
(I'm cross-posting this one from StackOverflow - https://stackoverflow.com/questions/59153907)

I'm trying to define an E2E access availability of a service from a user perspective as the result of applying the bit-wise AND operation between two (Boolean) instant vectors representing individual service availability (e.g. S1 and S2).

I'm fetching the probe_success results of pinging these two services from a "user node" with a blackbox_exporter preinstalled:

            +-------+     +---------------------+     +-------+
            |S1     |     |                     |     |     S2|
            |       |     |   User node with    |     |       |
            |       +<----+  blackbox_exporter  +---->+       |
            |       | icmp|                     |icmp6|       |
            +-------+     +---------------------+     +-------+

+-------------------------------------+-----+---+---+---+---+
| probe_success{user="foo", job="S1"} | ... | 0 | 0 | 1 | 1 |
+-------------------------------------+-----+---+---+---+---+
| probe_success{user="foo", job="S2"} | ... | 0 | 1 | 0 | 1 |
+-------------------------------------+-----+---+---+---+---+
|                     E2E{user="foo"} | ... | 0 | 0 | 0 | 1 |
+-------------------------------------+-----+---+---+---+---+

Since the targets are probed using different modules (icmp and icmp6) I'm using two jobs and therefore getting two instant vectors:

probe_success{job="S1", user="foo"}
# AND
probe_success{job="S2", user="foo"}

As I read on Prometheus' (querying) logical operators docs(https://prometheus.io/docs/prometheus/latest/querying/operators/#logical-set-binary-operators), that logical and is not exactly what I'm looking for. ¿Is there an easy way to perform these kind of "bit-wise" operations in PromQL?

A user on SO suggested trying a recording rule to generate a new instant vector that does the trick: 

  (scalar(probe_success{job="S1", user="foo"}) + scalar(probe_success{job="S2", user="foo"})) == bool(2)

But, since scalar() drops the matching labels of the original metrics (i.e. 'user') I cannot use the rule applied to different users; being forced to use one per user. As this does not scale at all, I ask you guys; do you know a better way to use this kind of logic with PromQL? Is my reasoning flawed?

Brian Brazil

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Dec 4, 2019, 9:37:26 AM12/4/19
to Samuel Alfageme, Prometheus Users
On Wed, 4 Dec 2019 at 14:24, Samuel Alfageme <samuel....@gmail.com> wrote:
(I'm cross-posting this one from StackOverflow - https://stackoverflow.com/questions/59153907)

I'm trying to define an E2E access availability of a service from a user perspective as the result of applying the bit-wise AND operation between two (Boolean) instant vectors representing individual service availability (e.g. S1 and S2).

I'm fetching the probe_success results of pinging these two services from a "user node" with a blackbox_exporter preinstalled:

            +-------+     +---------------------+     +-------+
            |S1     |     |                     |     |     S2|
            |       |     |   User node with    |     |       |
            |       +<----+  blackbox_exporter  +---->+       |
            |       | icmp|                     |icmp6|       |
            +-------+     +---------------------+     +-------+

+-------------------------------------+-----+---+---+---+---+
| probe_success{user="foo", job="S1"} | ... | 0 | 0 | 1 | 1 |
+-------------------------------------+-----+---+---+---+---+
| probe_success{user="foo", job="S2"} | ... | 0 | 1 | 0 | 1 |
+-------------------------------------+-----+---+---+---+---+
|                     E2E{user="foo"} | ... | 0 | 0 | 0 | 1 |
+-------------------------------------+-----+---+---+---+---+

Since the targets are probed using different modules (icmp and icmp6) I'm using two jobs and therefore getting two instant vectors:

probe_success{job="S1", user="foo"}
# AND
probe_success{job="S2", user="foo"}

As I read on Prometheus' (querying) logical operators docs(https://prometheus.io/docs/prometheus/latest/querying/operators/#logical-set-binary-operators), that logical and is not exactly what I'm looking for. ¿Is there an easy way to perform these kind of "bit-wise" operations in PromQL?

PromQL has no bitwise operators, however you don't need them in this case. See https://www.robustperception.io/booleans-logic-and-math a min ignoring(job)(probe_success) should cover you here.

Brian



A user on SO suggested trying a recording rule to generate a new instant vector that does the trick: 

  (scalar(probe_success{job="S1", user="foo"}) + scalar(probe_success{job="S2", user="foo"})) == bool(2)

But, since scalar() drops the matching labels of the original metrics (i.e. 'user') I cannot use the rule applied to different users; being forced to use one per user. As this does not scale at all, I ask you guys; do you know a better way to use this kind of logic with PromQL? Is my reasoning flawed?

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Julien Pivotto

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Dec 4, 2019, 9:44:46 AM12/4/19
to Brian Brazil, Samuel Alfageme, Prometheus Users
On 04 Dec 14:37, Brian Brazil wrote:
> On Wed, 4 Dec 2019 at 14:24, Samuel Alfageme <samuel....@gmail.com>
> wrote:
>
> >
> > *(I'm cross-posting this one from StackOverflow -
> > https://stackoverflow.com/questions/59153907
> > <https://stackoverflow.com/questions/59153907>)*
> >
> > I'm trying to define an E2E access availability of a service from a user
> > perspective as the result of applying the *bit-wise AND operation*
it is without(), not ignoring():

min without(job) probe_success

>
> --
> Brian Brazil
> www.robustperception.io
>
> --
> You received this message because you are subscribed to the Google Groups "Prometheus Users" group.
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--
(o- Julien Pivotto
//\ Open-Source Consultant
V_/_ Inuits - https://www.inuits.eu
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Samuel Alfageme

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Dec 5, 2019, 6:12:45 AM12/5/19
to Prometheus Users
Awesome; Brian, Julien. Thank you so much for your help.

In order to get the desired metric; I ended up querying:

min by (user)(probe_success{job=~"S1|S2"})

Since I do have more blackbox_exporter jobs reporting with the same users involved the without(job) would mix up those.

Now I can simply aggregate with an avg() those to get a rough overview of the platform's SLA. Great!

Best,
Samuel
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