This change fixes the variable names holding the tsdb_head_max_time and
tsdb_head_min_time metrics. It is a cosmetic change to improve the
code readability as the metric values are taken from the correct
variables.
The timer semantics is really hard. The simple pattern as given in the
godoc for the time package assumes we are not elsewhere consuming from
the timer's channel. However, exactly that can happen here with the
right sequence of events. Thus, we have to drain the channel only if
it has something to drain.
This allows to insert IDs to postings out of order until
a trigger function is called. This avoids the insertion sort we usually
do which can be very costly since WAL entries are more out of order than
regular adds.
This means that if there is no stale marker, only the usual staleness
delta (5m) applies.
It has occured to me that there is an oddity in the heurestic. It works
fine as long as you have 2 points within the last 5m, but breaks down
when the time window advances to the point where you have just 1 point.
Consider you had points at t=0 and t=10. With the heurestic it goes stale
at t=51, up until t=300. However from t=301 until t=310 we only
see the t=10 point and the series comes back to life. That is not
desirable.
I don't see a way to keep this form of heurestic working given this
issue, so thus I'm removing it.
* Re-add contexts to storage.Storage.Querier()
These are needed when replacing the storage by a multi-tenant
implementation where the tenant is stored in the context.
The 1.x query interfaces already had contexts, but they got lost in 2.x.
* Convert promql.Engine to use native contexts
The usage of govalidator is redundant with the call to url.Parse for
url validation. Removing it has the following benefits:
- The explicit error message is displayed instead of just a generic
valid/invalid message
- Slightly smaller code with one fewer external dependency
- Speed improvement by removing duplicate call to url.Parse (inside
govalidator.IsURL()
- Resolves issue #2717
The only potential drawback of removing govalidator is that certain
URLs will be considered valid which were previously invalid. For example:
- URLs with hostnames that start and/or end with an underscore (http://_example.com_)
- URLs with hostnames that contain some special characters (http://foo&*bar.org)
These are valid URIs according to RFC 3986 and valid domain names per RFC 2181,
however they are not valid hostnames per RFC 952.
