This PR adds a Prometheus counter called
`zrepl_zfs_list_unmatched_user_specified_dataset_count`.
Monitor for increases of the counter to detect filesystem filter rules that
have no effect because they don't match any local filesystem.
An example use case for this is the following story:
1. Someone sets up zrepl with `filesystems` filter for `zroot/pg14<`.
2. During the upgrade to Postgres 15, they rename the dataset to `zroot/pg15`,
but forget to update the zrepl `filesystems` filter.
3. zrepl will not snapshot / replicate the `zroot/pg15<` datasets.
Since `filesystems` rules are always evaluated on the side that has the datasets,
we can smuggle this functionality into the `zfs` module's `ZFSList` function that
is used by all jobs with a `filesystems` filter.
Dashboard changes:
- histogram with increase in $__interval, one row per job
- table with increase in $__range
- explainer text box, so, people know what the previous two are about
We had to re-arrange some panels, hence the Git diff isn't great.
closes https://github.com/zrepl/zrepl/pull/653
Co-authored-by: Christian Schwarz <me@cschwarz.com>
Co-authored-by: Goran Mekić <meka@tilda.center>
They are useful, not least to debug issues with debugging
SIGSYS caused by overly restrictive settings in the unit file.
(See previous commit for an example.)
Go 1.19 uses it during startup.
From the Go changelog:
> On Unix operating systems, Go programs that import package os now
> automatically increase the open file limit (RLIMIT_NOFILE) to the
> maximum allowed value; that is, they change the soft limit to match the
> hard limit. This corrects artificially low limits set on some systems
> for compatibility with very old C programs using the select system call.
> Go programs are not helped by that limit, and instead even simple
> programs like gofmt often ran out of file descriptors on such systems
> when processing many files in parallel. One impact of this change is
> that Go programs that in turn execute very old C programs in child
> processes may run those programs with too high a limit. This can be
> corrected by setting the hard limit before invoking the Go program.
- uses version metric for 'instances up'
- displays active task count
- displays send abstractions cache entry count
- in general, graphs have a shorter y axis for better overview
fixes#332
