This fixes https://github.com/prometheus/prometheus/issues/1059 , but
not in the obvious way (simply not updating the persist watermark,
because that's actually not that simple - we don't really know what
has gone wrong exactly). As any errors relevant here are most likely
caused by severe and unrecoverable problems with the series file,
Using the now quarantine feature is the right step. We don't really
have to be worried about any inconsistent state of the series because
it will be removed for good ASAP. Another plus is that we don't have
to declare the whole storage dirty anymore.
This requires all the panic calls upon unexpected data to be converted
into errors returned. This pollute the function signatures quite
lot. Well, this is Go...
The ideas behind this are the following:
- panic only if it's a programming error. Data corruptions happen, and
they are not programming errors.
- If we detect a data corruption, we "quarantine" the series,
essentially removing it from the database and putting its data into
a separate directory for forensics.
- Failure during writing to a series file is not considered corruption
automatically. It will call setDirty, though, so that a
crashrecovery upon the next restart will commence and check for
that.
- Series quarantining and setDirty calls are logged and counted in
metrics, but are hidden from the user of the interfaces in
interface.go, whith the notable exception of Append(). The reasoning
is that we treat corruption by removing the corrupted series, i.e. a
query for it will return no results on its next call anyway, so
return no results right now. In the case of Append(), we want to
tell the user that no data has been appended, though.
Minor side effects:
- Now consistently using filepath.* instead of path.*.
- Introduced structured logging where I touched it. This makes things
less consistent, but a complete change to structured logging would
be out of scope for this PR.
This considers static labels in the equality of alerts to
avoid falsely copying state from a different alert definition with
the same name across reloads.
To be safe, it also copies the state map rather than just its pointer
so that remaining collisions disappear after one evaluation interval.
This commit simplifies the TargetHealth type and moves the target
status into the target itself. This also removes a race where error
and last scrape time could have been out of sync.
This commit removes the scrapeConfig entirely from Target.
All identity defining parameters are thus immutable now and the mutex
can be removed..
Target identity is now correctly defined by the labels and the full URL.
This in particular includes URL parameters that are not specified in the
label set.
Fingerprint is also removed from hash to remove an unnecessary tight coupling
to the common/model package.
With this commit the scrape pool deduplicates incoming
targets before scraping them. This way multiple target providers
can produce the same target but it will be scraped only once.
This commit updates a target set's scrape configuration
on reload. This will cause all running scrape loops to be
stopped and started again with new parameters.
This commit changes the scraper interface to accept a timestamp
so the reported timestamp by the caller and the timestamp
attached to samples does not differ.
This commit moves Scraper handling into a separate scrapePool type.
TargetSets only manage TargetProvider lifecycles and sync the
retrieved updates to the scrapePool.
TargetProviders are now expected to send a full initial target set
within 5 seconds. The scrapePools preserve target state across reloads
and only drop targets after the initial set was synced.
We group providers by their scrape configuration. Each provider produces
target groups with an unique identifier.
On stopping a set of target providers we cancel the target providers,
stop scraping the targets and wait for the scrapers to finish.
On configuration reload all provider sets are stopped and new ones
are created. This will make targets disappear briefly on configuration
reload. Potentially scrapes are missed but due to the consistent
scrape intervals implemented recently, the impact is minor.
