docs: add an example how to check connection credentials

[bednar]

Closes #131

Proposed Changes

Added an example how to check if the credentials has sufficient permission to query/write.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• pytest tests completes successfully
• Commit messages are in semantic format
• Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

Merging #269 (d56fb02) into master (12ab822) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #269   +/-   ##
=======================================
  Coverage   90.52%   90.52%           
=======================================
  Files          39       39           
  Lines        3355     3355           
=======================================
  Hits         3037     3037           
  Misses        318      318           

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[rhajek]

In the current InfluxDB API is no possibility to ask for write / read rights for a given bucket… Workaround with an empty lineprotocol and empty query can be a temporary solution. InfluxDB API should be improved.

[powersj]

In the current InfluxDB API is no possibility to ask for write / read rights for a given bucket… Workaround with an empty lineprotocol and empty query can be a temporary solution. InfluxDB API should be improved.

Agreed that this should be given at the API level. However, having an example seems like a good workaround for now. Was there a bug report against influxdb make the API changes or an official response regarding adding this feature?

[bednar]

@powersj We have discussed this issue with Ryan but with no clear outcome https://influxdata.slack.com/archives/C5BSZ026L/p1594730843212900.

[powersj]

It looks like the Authorizaitons API pointed about in the slack comment only works when the user has at least read access to the authorizations service, which I expect most users will not have. In fact, in most cases, I would expect a user to have a read or read-write token specifically for a bucket only, so this will not work.

@rhajek, was there a concern with the include the example for now?

[rhajek]

Is this tested on both OSS and Cloud2 ? I can imagine that the can be different order of 400 and 404 checks.

[rhajek]

I tested the latest version of InfluxDB v2.3.0+SNAPSHOT.090f681737 and InfluxDB Cloud 2. There is little inconsistency between query check that always fail with 404 (could not find bucket) but the write can fail with 403 or 404.

403 - bucket exists but you don't have a write permission

Reason: Forbidden
HTTP response body: {"code":"forbidden","message":"insufficient permissions for write"}

404 - bucket does not exists

Reason: Not Found
HTTP response body: {"code":"not found","message":"bucket "xxx" not found"}