[pgbouncer] Fixed newest versions failing checks due to extra field #735
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@ISauve, thanks for your PR! By analyzing the history of the files in this pull request, we identified @olivielpeau, @gmmeyer and @degemer to be potential reviewers. |
truthbk
requested changes
Oct 13, 2017
pgbouncer/check.py
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| @@ -50,7 +50,7 @@ class PgBouncer(AgentCheck): | |||
| ('database', 'db'), | |||
| ('user', 'user'), | |||
| ], | |||
| 'metrics': [ | |||
| 'metrics': [ | |||
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nit: can we remove this extra space?
| row = row[:-1] | ||
| elif len(row) == len(cols) + len(desc) + 2: |
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As we discussed in person, we cannot be 100% sure if we'll get all extra columns in other versions, but since we can't really get the column titles without resorting to some crazy VIEW trickery (http://peter.eisentraut.org/blog/2015/03/25/retrieving-pgbouncer-statistics-via-dblink/) - this sensible assumption is probably the best we can do. Tests seem to confirm this now works on newer pgbouncers.
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A customer reported that the newest version of pgbouncer was failing our check because the 'SHOW POOLS' query returned an extra column (issue #555). This query already returned a variable number of columns (either 10 or 11 depending on which version of pgbouncer was being run), and the newest update means that this number can now vary from 10-12.
A brief description of the change being made with this pull request.
Added a small fix so that if there is 1 or 2 extra columns returned, check.py will now just ignore them.
Also added checks to travis.yml for the different versions of pgbouncer currently available on docker.
Versioning
manifest.jsonCHANGELOG.md. Please useUnreleasedas the date in the titlefor the new section.
Additional Notes
The issue with this approach is that our check simply verifies if we have at least 10 columns returned (and no more than 12), but it does not check which columns. So, were there to be a case where an extra column is returned but a main metric is not (due to some other issue), the test would still pass.
The best solution I could see would be to check for the existence of these extra fields (version 1.7.2 introduced pool_mode and the newest versions will now also have maxwait_us) and then adjusting the number of expected columns accordingly - however, the only information accessible through the connection to the PostgreSQL db is the return value of the query, not the accompanying keys identifying which value belonged to what. Thus this may not be possible.
Another possible solutions could be to check which version of pgbouncer is being run, and have a set number of columns that should be returned for that version - but again, this information is not accessible.