yb_stats snapshot results
Directory yb_stats.snapshots
When yb_stats is run with the --snapshot mode switch, it will try to find a directory in the current working directory by the name of yb_stats.snaphots.
If it can't find the directory, it will try to create it. If opening the directory in the case of existence, or creating in the case of non-existence fails, execution will stop with an error indicating the issue.
The yb_stats.snapshots/snapshot.index file
Inside the yb_stats.snapshots directory the first snapshot will create a CSV file called snapshot.index. This file lists the snapshots taken, comma separated with the following fields:
- snapshot number
- snapshot timestamp
- snapshot comments
Using this file, yb_stats can understand the snapshot numbers, and add one to the highest number for a new snapshot.
Another use of this file is to obtain the first snapshot timestamp for use with snapshot diffs: if a second snapshot inserts a metric that is not present in the first snapshot, it can safely assume the first snapshot value of that metric to be 0. However, it must make a guess about the approximate first snapshot time; which is where the timestamp is used.
A last use of this file is when yb_stats is run with the --snapshot-list switch: yb_stats will list this information, and quit.
Example
This is how a typical snapshot is performed:
% yb_stats --snapshot
snapshot number 0
Error
If the current working directory is not writable, it will provide the following error:
[2022-11-30T10:59:18Z ERROR yb_stats::snapshot] Fatal: error creating directory /Users/fritshoogland/Downloads/t/yb_stats.snapshots: Permission denied (os error 13)