Newbie having trouble with regex escaping in blackbox exporter

[TommyG]

(repost because I made a mess of the formatting last time)

Hi folks

New to Prometheus but liking it so far.

I'm trying to use the blackbox exporter to test an API. I want to check the contents of the response body but I'm having trouble with regex that may or may not be related to escaping the | character.

I'm sending in HL7 messages and getting a HL7 response, they make extensive use of the pipe character.

My blackbox.yaml 

  http_post_2xx:
    prober: http
    http:
      preferred_ip_protocol: "ip4"
      method: POST
  http_post_json:
    prober: http
    timeout: 5s
    http:
      method: POST
      preferred_ip_protocol: "ip4"
      headers:
        Content-Type: application/json
      body: "MSH|^~\\&|MLEMS|TEST|MLEMS|TEST|20200102101206||ADT^A31|123456|P|2.4\n <deletia>"
      fail_if_body_not_matches_regexp:
        - .*MSA|AE|123456$

The actual response body is plaintext as shown below

 

MSH|^~\&|EMS|RA9|PAS|RA9|20200307152450.723+0000||ACK^A31|3352|P|2.4
MSA|AA|123456

I'm only interested in the last line, specifically MSA|AA|123456

My problem is that this regex passes (which is fine) but if I change the |AA| to |AE| i.e. 

fail_if_body_not_matches_regexp:
        - .*MSA|AE|123456$

A successful response i.e. one ending MSA|AA|123456 still passes????

I've tried escaping the | characters i.e. 

fail_if_body_not_matches_regexp:
        - .*MSA\|AE\|123456$

But then all messages fail.

I've tried various combinations of using double and single quotes but haven't had any success although there's a fair chance I missed the right combo.

 

Any help much appreciated

[Harald Koch]

On Sat, Mar 7, 2020, at 11:49, TommyG wrote:

fail_if_body_not_matches_regexp:
        - .*MSA|AE|123456$

This matches anything containing "MSA" or "AE" or "123456", which is why it's matching the AA response also.

fail_if_body_not_matches_regexp:
        - .*MSA\|AE\|123456$

My first suspicion would be that CR is used by most systems as a segment terminator, so there's a CR at the end of the MSA segment. Either remove the $ or add a ".*" before it?

(Also it's a tiny thing, but in your headers the Content-Type: should be x-application/hl7-v2+er7 :)

hth,

--

Harald

c...@pobox.com

[TommyG]

That was exactly what it was.

Many thanks for the answer and the explanation.

On Saturday, 7 March 2020 17:02:51 UTC, Harald Koch wrote:

fail_if_body_not_matches_regexp:
        - .*MSA\|AE\|123456$

[Harald Koch]

On Sat, Mar 7, 2020, at 12:48, TommyG wrote:

That was exactly what it was.

Many thanks for the answer and the explanation.

Your timing was perfect - I've spent the last couple of weeks replacing the ACK generator in our engine, so it's all fresh in my brain!

--

Harald