This commit fixes a data race that exists when the metric used in any
`promhttp` middleware doesn't collect the `code` and `method` but uses
`WithLabelFromCtx` to collect values from context.
The problem happens because when no `code` and `method` tags are
collected, the `labels` function returns a pre-initialized map
`emptyLabels` for every request.
When one or multipe `WithLabelFromCtx` options are configured, the
returned map from the `labels` function call is used to collect the
metrics from context which creates a multi-write data race.
Signed-off-by: Tiago Silva <tiago.silva@goteleport.com>
* fix assorted oddities found by golangci-lint
Signed-off-by: Christoph Mewes <christoph@kubermatic.com>
* permanently enable the linters
Signed-off-by: Christoph Mewes <christoph@kubermatic.com>
* post-rebase blues
Signed-off-by: Christoph Mewes <christoph@kubermatic.com>
* Check validity of method and code label values
Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>
* Use more flexibly functional option pattern for configuration
Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>
* Update documentation
Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>
* Simplify
Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>
* Fix inconsistent method naming
Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>
Without this fix, the `InstrumentHandler...` middlewares get locked in
an endless loop in case of an invalid Collector, eating all the memory.
Signed-off-by: beorn7 <beorn@grafana.com>
In principle, we needed to iterate through all permutations, mirroring
the same that is happening in the code. For lack of time, I only
picked one of the cases currently buggy.
As said, this really needs code generation, should we ever find
ourselves touching this again.
The idea behind it is described in detail in
https://github.com/prometheus/client_golang/issues/320 .
This commit also updates the example given in
promhttp/instrument_server_test.go , which nicely illustrates the
benefit of this change.
So far, currying could be emulated by creating different metric vec's
with different values in their ConstLabels. This was quite difficult
to grasp - which is essentially what was done in the example mentioned
above. Now that this use case can be solved without ConstLabels, we
can safely declare ConstLabels as rarely used. (Perhaps we can
deprecate them entirely one day, but I'll take a raincheck on that
when the changes of v0.10 have materialized.) This commit thus also
updates the ConstLabel doc comments in the various Opts. (It contained
fairly outdated stuff anyway.)
As it turned out, it's not that esay to guess "common" combination of
interface upgrades. So I decided to just implement all 32 possible
combination of interface upgrades. (Only 16 with Go 1.7 and earlier.)
Clearly, this calls for code generation. But right now, we still need
to find out what's the best form of the code. For later additions,
implementing code generation might be useful.
Note that newDelegator is called for each HTTP request. Thus, this
commit aims to make the upgrade selection quick. (After the type
checks, it's just directly accessing an element in a slice.)
Tiago Silva