Make sbws generate bandwidth files atomically, and document

changed milestone to %sbws: 1.0.x-final

added component::core tor/sbws milestone::sbws: 1.0.x-final owner::teor parent::26851 priority::medium resolution::fixed sbws-1.0-must-closed-moved-20181128 severity::normal status::closed type::defect labels

Trac:
Status: assigned to needs_review

https://github.com/pastly/simple-bw-scanner/pull/231

Please link to the PR once there is one to help me/us move between Trac and GitHub.

I completed #26702 (moved) and I am about to complete #26694 (moved).

While I was writing these tickets, I realised that we only need to avoid the following periods:

• HH:45-HH:55, because the bandwidth file is read at HH:50
• HH:15-HH:25, because the bandwidth file is read at HH:20 during a consensus failure

I also suggest that add these times to the sbws generate documentation.

Trac:
Status: needs_review to needs_revision

Trac:
Parent: N/A to #25925 (moved)

Documented: https://github.com/pastly/simple-bw-scanner/pull/235

Crontab file will be created in system packages

Changed title and description

Trac:
Summary: Add crontab file to generate bandwidth files at valid times to Document at which times should bandwidth files be generated
Description: Related to #26702 (moved), it would be easier for authority operators to remember at which times they should generate and transfer files if a sbws system package setup a default crontab. Because different system distributions can use the same crontab format, let's distribute it with sbws.

to

N/A

Trac:
Status: needs_revision to needs_review

Replying to juga:

Documented: https://github.com/pastly/simple-bw-scanner/pull/235

I don't think we need all those words, please see my comment on the pull request.

Looks good to me, let's merge it.

Trac:
Status: needs_review to merge_ready

Merged as b42a77f8b239071986ff0ef94757cdca901328af..b4bfea6e16a05608a077de6067c058c732800936

Trac:
Status: merge_ready to closed
Resolution: N/A to implemented

Trac:
Status: closed to reopened
Parent: #25925 (moved) to #26851 (moved)
Resolution: implemented to N/A
Summary: Document at which times should bandwidth files be generated to Document that bandwidth files should be generated atomically

Trac:
Status: reopened to assigned
Owner: juga to teor

sbws was deleting the symlink after generating the file. When the symlink is deleted, reading the path is not atomic, because it can fail with a file not found error.

This change is based on nickm's feedback at: https://trac.torproject.org/projects/tor/ticket/26702#comment:12

Please see my pull request: https://github.com/pastly/simple-bw-scanner/pull/237

Trac:
Status: assigned to needs_review
Summary: Document that bandwidth files should be generated atomically to Make sbws generate bandwidth files atomically, and document
Milestone: sbws 1.0 (MVP nice) to sbws 1.0 (MVP must)

merged!

Trac:
Status: needs_review to closed
Resolution: N/A to fixed

Move all closed sbws 1.0 must tickets to sbws 1.0.x-final

Trac:
Milestone: sbws 1.0 (MVP must) to sbws: 1.0.x-final
Keywords: N/A deleted, sbws-1.0-must-closed-moved-20181128 added

closed

moved to tpo/network-health/sbws#26740 (closed)