* Fixed int64 overflow for timestamp in v1/api parseDuration and parseTime
This led to unexpected results on wrong query with "(...)&start=148966367200.372&end=1489667272.372"
That query is wrong because of `start > end` but actually internal int64 overflow caused start to be something around MinInt64 (huge negative value) and was passing validation.
BTW: Not sure if negative timestamp makes sense even.. But model.Earliest is actually MinInt64, can someone explain me why?
Signed-off-by: Bartek Plotka <bwplotka@gmail.com>
* Added missing trailing periods on comments.
Signed-off-by: Bartek Plotka <bwplotka@gmail.com>
* MOved to only `<` and `>`. Removed equal.
Signed-off-by: Bartek Plotka <bwplotka@gmail.com>
Expose buildQueryUrl, refactor dispatch to use
buildQueryUrl will allow users to execute queries over the range of an
existing graph. This will be helpful to select data series they wish to
annotate the graph with, for example.
The fuzzy library didn't try to find a "best match", but settled on the
first fuzzy match that exists. This patch includes a modified version of
the fuzzy library, which recursivley tries on the rest of the search
string to find a better match. If found, returns that one.
Another small modification is that if a pattern fully matches, it
skips the lookup entirley and returns the highest score possible for
that match.
For some of the queries, the fuzzy lookup was not filtering properly.
The problem is due to the "replace" beind made on the query itself. It
accidently removes only the first underscore. This patch changes it so
that it removes all of the whitespaces, letting the fuzzy algorithm do
its magic, also fixing this problem.
Originally, the underscore were replaced by a space for this specific
reason, to let the user type a space and have the lookup treat it as the
word break.
Fixes#2380
retreival.Target contains a mutex. It was copied in the Targets()
call. This potentially can wreak a lot of havoc.
It might even have caused the issues reported as #2266 and #2262 .
Right now the /alerts page of Prometheus sorts alerts by severity
(firing, pending, inactive). Once multiple alerts have the same
severity, their order seems to correlate to how they are placed in the
configuration files, but not always. Looking at the code, we make use of
sort.Sort(), which is documented not to provide a stable sort. The
Less() function also only takes the alert state into account.
This change extends the Less() function to provide a lexicographic order
on both the alert state and the name. This means I can finally find the
alerts I'm looking for without using my browser's search feature.
We are writing federation responses streaming. So after
the first byte we wrote, the status header is fixed. We cannot
return an HTTP error for intermediate error but should just abort
and log instead.
Adds also the moment.js library, which is a dependency of it.
Following conventions in the web/ui directory, I am not including the original
sources or LICENSE files.
If an existing request is aborted due to a new request, ignore the completion of the initial request.
Example:
1. Chrome dev tools: enable 5 second network latency
2. Execute query
3. A second later, execute the query again
4. Currently, the spinner will hide, and the stats will immediately display, as if the request had completed. Instead, the spinner and stats should wait until the 2nd execution finishes.
* Add fuzzy search to /graph textarea
We have a few thousands different metrics and looking up some of them
can be quite annoying with the simple string matching.
This patch adds a fuzzy search to the textarea lookup box on the /graph
page. It uses a small neat library from github.com/mattyork/fuzzy.
* Add fuzzy lib to NOTICE and re-build assets
Previously built assets changed the mode.
This extracts Querier as an instantiateable and closeable object
rather than just defining extending methods of the storage interface.
This improves composability and allows abstracting query transactions,
which can be useful for transaction-level caches, consistent data views,
and encapsulating teardown.
If an existing request is aborted due to a new request, ignore the completion of the initial request.
Example:
1. Chrome dev tools: enable 5 second network latency
2. Execute query
3. A second later, execute the query again
4. Currently, the spinner will hide, and the stats will immediately display, as if the request had completed. Instead, the spinner and stats should wait until the 2nd execution finishes.
This is based on https://github.com/prometheus/prometheus/pull/1997.
This adds contexts to the relevant Storage methods and already passes
PromQL's new per-query context into the storage's query methods.
The immediate motivation supporting multi-tenancy in Frankenstein, but
this could also be used by Prometheus's normal local storage to support
cancellations and timeouts at some point.
For Weaveworks' Frankenstein, we need to support multitenancy. In
Frankenstein, we initially solved this without modifying the promql
package at all: we constructed a new promql.Engine for every
query and injected a storage implementation into that engine which would
be primed to only collect data for a given user.
This is problematic to upstream, however. Prometheus assumes that there
is only one engine: the query concurrency gate is part of the engine,
and the engine contains one central cancellable context to shut down all
queries. Also, creating a new engine for every query seems like overkill.
Thus, we want to be able to pass per-query contexts into a single engine.
This change gets rid of the promql.Engine's built-in base context and
allows passing in a per-query context instead. Central cancellation of
all queries is still possible by deriving all passed-in contexts from
one central one, but this is now the responsibility of the caller. The
central query context is now created in main() and passed into the
relevant components (web handler / API, rule manager).
In a next step, the per-query context would have to be passed to the
storage implementation, so that the storage can implement multi-tenancy
or other features based on the contextual information.
This will avoid duplicate MetricFamilies, thereby shrinking the size
of the federation payload and also creating legal text format.
Also, add unit tests for federation. They were also needed for the
previous state of the code, but were missing.
This reverts commit aa43d34a86.
This brings back the /graph changes so that @grandbora can continue to
work on the redirect for backwards compatibility. And other changes
can already take the new /graph parameters into account.
This revert will be reverted once v1.1 is released and has its own
release branch. Since we had already change on top of this, there was
no cleaner way of cutting those changes out.
This commit reverts the following commits:
Revert "Update backend helpers and templates to new url schema"
This reverts commit fc6cdd0611.
Revert "Refactor graph.js"
This reverts commit 445fac56e0.
Revert "Use query parameters in the url"
This reverts commit 3e18d86d8a.
Revert "Point to correct place for GraphLinkForExpression"
This reverts commit 3da825fc76.
Assets are also updated.
There's no corresponding table column for this table header. The
placeholder link for silences was removed in e8800730.
Accordingly, regenerate `web/ui/bindata.go` by running:
make assets format
See discussion in
https://groups.google.com/forum/#!topic/prometheus-developers/bkuGbVlvQ9g
The main idea is that the user of a storage shouldn't have to deal with
fingerprints anymore, and should not need to do an individual preload
call for each metric. The storage interface needs to be made more
high-level to not expose these details.
This also makes it easier to reuse the same storage interface for remote
storages later, as fewer roundtrips are required and the fingerprint
concept doesn't work well across the network.
NOTE: this deliberately gets rid of a small optimization in the old
query Analyzer, where we dedupe instants and ranges for the same series.
This should have a minor impact, as most queries do not have multiple
selectors loading the same series (and at the same offset).
I got feedback from different sources about rules and targets being
too heavy in the status tab if their are lots of them.
This change also allows for more fine-granular locking.
Prometheus is Apache 2 licensed, and most source files have the
appropriate copyright license header, but some were missing it without
apparent reason. Correct that by adding it.
The chunk encoding was hardcoded there because it mostly doesn't
matter what encoding is chosen in that test. Since type 1 is
battle-hardened enough, I'm switching to type 2 here so that we can
catch unexpected problems as a byproduct. My expectation is that the
chunk encoding doesn't matter anyway, as said, but then "unexpected
problems" contains the word "unexpected".
WIP: This needs more tests.
It now gets a from and through value, which it may opportunistically
use to optimize the retrieval. With possible future range indices,
this could be used in a very efficient way. This change merely applies
some easy checks, which should nevertheless solve the use case of
heavy rule evaluations on servers with a lot of series churn.
Idea is the following:
- Only archive series that are at least as old as the headChunkTimeout
(which was already extremely unlikely to happen).
- Then maintain a high watermark for the last archival, i.e. no
archived series has a sample more recent than that watermark.
- Any query that doesn't reach to a time before that watermark doesn't
have to touch the archive index at all. (A production server at
Soundcloud with the aforementioned series churn and heavy rule
evaluations spends 50% of its CPU time in archive index
lookups. Since rule evaluations usually only touch very recent
values, most of those lookup should disappear with this change.)
- Federation with a very broad label matcher will profit from this,
too.
As a byproduct, the un-needed MetricForFingerprint method was removed
from the Storage interface.
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.
Formalize ZeroSamplePair as return value for non-existing samples.
Change LastSamplePairForFingerprint to return a SamplePair (and not a
pointer to it), which saves allocations in a potentially extremely
frequent call.
It's actually happening in several places (and for flags, we use the
standard Go time.Duration...). This at least reduces all our
home-grown parsing to one place (in model).
This enables metric name autocompletion for every word in an expression,
not just the very first one. It would be great to also support all
language keywords during autocompletion in the future.
This adapts some functionality from the Go standard library for string
literal lexing and unquoting/unescaping.
The following string types are now supported:
Double- or single-quoted strings:
These support all escape sequences that Go supports in double-quoted
string literals. The difference is that Prometheus also has
single-quoted strings (instead of single-quoted runes in Go). Raw
newlines are not allowed.
Backtick-quoted raw strings:
Strings quoted in backticks are treated as raw strings just like in Go
and may contain raw newlines and other special characters directly.
Fixes https://github.com/prometheus/prometheus/issues/1122
Fixes https://github.com/prometheus/prometheus/issues/1121
This is with `golint -min_confidence=0.5`.
I left several lint warnings untouched because they were either
incorrect or I felt it was better not to change them at the moment.
Let's remove the silencing links until we actually have support for that.
A silencing link shouldn't only redirect to Alertmanager, but also open a
silencing dialog for the respective alert name or active alert element.
This got broken in
78047326b4
since it stopped using the DefaultServeMux.
This approach will defer pprof requests to the DefaultServeMux, which
may or may not have pprof enabled (in Prometheus, it gets it included in
main.go). An alternative approach would be to duplicate the four lines in
https://golang.org/src/net/http/pprof/pprof.go#L62. When choosing that
approach though, we would not automatically gain any new endpoints added
by net/http/pprof or other /debug endpoints in the future.
Besides fixing https://github.com/prometheus/prometheus/issues/805 by
making the entire externally reachable server URL configurable, this
adds tests for the "globalURL" template function and makes it easier to
test other such functions in the future.
This breaks the `web.Hostname` flag (and introduces `web.external-url`).
This flag is likely only used by few users, so I hope that's
justifiable.
Fixes https://github.com/prometheus/prometheus/issues/805
Also remove hidden input fields that are not used anymore, because the
query params are now passed as JSON to the AJAX function. This also has
the wonderful side effect that we're no longer sending all the other
non-hidden fields along to the query endpoints anymore.
Changes to the UI:
- "Active Since" timestamps are now human-readable.
- Alerting rules are now pretty-printed better.
- Labels are no longer just strings, but alert bubbles (like we do on
the status page for base labels).
- Alert states and target health states are now capitalized in the
presentation layer rather than at the source.
This commit adds a federation handler on /federate. It accepts `match[]`
query parameters containing vector selectors. Their intersection determines
the in-memory metrics that are returned in the same way as the
/metrics endpoint does (modulo sorting).
Version information is determined at build-time and thus there is
no need to pass it down from main. In its own package it can
be used from various other packages.
Also, rearrange and clean up some things to make this work.
The textarea starts as a single line, but auto-expands when entering
multiple lines (e.g. via Shift+Enter). Pressing just "Enter" still
executes the expression.
Main changes:
- Switched to using `go-bindata` in place of `scripts/embed-static.sh`.
- Support for building Prometheus without a `Makefile`.
- Minor typo fix to make Prometheus build on Windows (without Makefiles).
Please note that this does not mean that prometheus will work on Windows.
There are still failing tests!
Figuring out what's going on with the new service discovery
and labels is difficult. Add a popover with the labels
to the target table to make things simpler, and help
discovery of potentially useful labels.
Previously we redirected any non-existent path to the root (or path
prefix).
The new behavior:
With no path prefix:
- "" -> "/"
- "/biz" -> 404
With path prefix of "/foo/bar":
- "" -> "/foo/bar/"
- "/" -> "/foo/bar/"
- "/foo/bar" -> "/foo/bar/"
- "/biz" -> /foo/bar/biz"
(anything not starting with the path prefix gets the prefix prepended)
- "/foo/bar/biz" -> 404
This change is conceptually very simple, although the diff is large. It
switches logging from "github.com/golang/glog" to
"github.com/prometheus/log", while not actually changing any log
messages. V(1)-style logging has been changed to be log.Debug*().
Appending to the storage can block for a long time. Timing out
scrapes can also cause longer blocks. This commit avoids that those
blocks affect other compnents than the target itself.
Also the Target interface was removed.
The target implementation and interface contain methods only serving a
specific purpose of the templates. They were moved to the template
as they operate on more fundamental target data.
With this commit, sending SIGHUP to the Prometheus process will reload
and apply the configuration file. The different components attempt
to handle failing changes gracefully.
This commits renames the RuleManager to Manager as the package
name is 'rules' now. The unused layer of abstraction of the
RuleManager interface is removed.
This commit shifts responsibility for maintaining targets from providers and
pools to the target manager. Target groups have a source name that identifies
them for updates.
This adds the population standard deviation and
variance as aggregation functions, useful for
spotting how many standard deviations some samples
are from the mean.
Don't handle `0` as a special timestamp value for "now" anymore, except
in the `QueryRange()` case, where existing API consumers still expect
`0` to mean "now".
Also, properly return errors now for malformed timestamp/duration
float values.
/api/targets was undocumented and never used and also broken.
Showing instance and job labels on the status page (next to targets)
does not make sense as those labels are set in an obvious way.
Also add a doc comment to TargetStateToClass.
The one central sample ingestion channel has caused a variety of
trouble. This commit removes it. Targets and rule evaluation call an
Append method directly now. To incorporate multiple storage backends
(like OpenTSDB), storage.Tee forks the Append into two different
appenders.
Note that the tsdb queue manager had its own queue anyway. It was a
queue after a queue... Much queue, so overhead...
Targets have their own little buffer (implemented as a channel) to
avoid stalling during an http scrape. But a new scrape will only be
started once the old one is fully ingested.
The contraption of three pipelined ingesters was removed. A Target is
an ingester itself now. Despite more logic in Target, things should be
less confusing now.
Also, remove lint and vet warnings in ast.go.
- original series data is saved so it can be re-transformed after
Rickshaw's stacking modified the series data
- always reconstruct graphs from scratch instead of updating the
settings of an existing one (simplification)
- always wipe and recreate all graph-related DOM elements completely so
that no left-over event handlers cause background event handlers
This is related to #454. Queries now timeout after a duration set by
the -query.timeout flag. The TotalEvalTimer is now started/stopped
inside any of the ast.Eval* functions.
When Rickshaw was updated to 1.5.1 in
fd43daf82e,
the Rickshaw upstream package now contained 3 different D3 files:
d3.min.js
d3.v2.js
d3.v3.js
For details on why that is, see
https://groups.google.com/forum/#!topic/d3-js/lXQgKA7mtEw
For the 1.5.1 Rickshaw to work properly (being able to format dates with
D3 without causing a JS error), it needs d3.v2.js or d3.v3.js, not the
d3.min.js one. I chose to update us to d3.v3.js now, since that is the
most recent and minified version, and I didn't see any problems with it
(also, the current Rickshaw examples are using that D3 version).
Currently, displaying graphs with a range >14d is broken. This fixes
that.
While the recent commit 7e5745f solved the issue of having an
independent blob-stamp file, which was possible to become out of
sync with the necessary web/blob/files.go file, this change further
simplifies the setup by merging the two Makefile.
The only purpose of web/Makefile was to call targets in
web/blob/Makefile. As all dependencies for blob/files.go are
outside of the blob/ directory, the separation isn't logically
necessary.
- Use only the minified versions of bootstrap.
- Do not embed non-minified bootstrap files and bootstrap map files.
- Simplify the 'blob-stamp' Makefile contraption.
- Move CONTRIBUTORS.md to the more common AUTHORS.
- Added the required NOTICE file.
- Changed "Prometheus Team" to "The Prometheus Authors".
- Reverted the erroneous changes to the Apache License.
This provides the basic js, css and console template
templates required to build dashboards.
Included as an example are consoles for the node_exporter.
Change-Id: I4cfeea5e9691a9413f74ae98ca32a908df8e4a59
The "Address" is actually a URL which may contain username and
password. Calling this Address is misleading so we rename it.
Change-Id: I441c7ab9dfa2ceedc67cde7a47e6843a65f60511
This doesn't make the import order consistend everywhere, just where
it was touched by the previous commit.
Change-Id: I82fc75f8691da9901c7ceb808e6f6fe8e5d62c0e
Essentially:
- Remove unused code.
- Make it 'go vet' clean. The only remaining warnings are in generated code.
- Make it 'golint' clean. The only remaining warnings are in gerenated code.
- Smoothed out same minor things.
Change-Id: I3fe5c1fbead27b0e7a9c247fee2f5a45bc2d42c6
After many transformations, it doesn't make sense to keep the metric
names, since the result of the transformation is no longer that metric.
This drops the metric name after such transformations and makes the web
UI deal well with missing metric names.
This depends on the current branch on the following things:
- prometheus/client_golang needs to be at
e237cf15c6
in branch "julius/int-fingerprints" (to be merged with new storage)
- prometheus/promdash needs to be at
dd7691c9c2
Change-Id: Ib3c8cad8d647d9854e8c653c424b8c235ccc231d
This removes the dependancy on C leveldb and snappy.
It also takes care of fewer dependencies as they would
anyway not work on any non-Debian, non-Brew system.
Change-Id: Ia70dce1ba8a816a003587927e0b3a3f8ad2fd28c
Gracefully handle decimal values, by truncating them.
Limit amount of steps, to avoid accidentally pulling too much data.
This limit returns up to ~500kB per timeseries, and allows
for 60s granularity for a week and 1h granularity for a year.
Change-Id: Ie549fc24deb2eecbc6c5d1b6088a548a6b02e849
Having metrics with variable timestamps inconsistently
spaced when things fail will make it harder to write correct rules.
Update status page, requires some refactoring to insert a function.
Change-Id: Ie1c586cca53b8f3b318af8c21c418873063738a8
This fixes the problem where samples become temporarily unavailable for
queries while they are being flushed to disk. Although the entire
flushing code could use some major refactoring, I'm explicitly trying to
do the minimal change to fix the problem since there's a whole new
storage implementation in the pipeline.
Change-Id: I0f5393a30b88654c73567456aeaea62f8b3756d9
Due to the lack of a </a>, this makes the entire header render badly.
Accordingly it's safe to assume noone is using it, so remove it.
With the new console template support, we'll need to something a bit
more nuanced later.
Change-Id: I3424bed6aea18cbd4c63ad48f98808098dadc3ad
Add a function to bypass the new auto-escaping.
Add a function to workaround go's templates only allowing passing in one argument.
Change-Id: Id7aa3f95e7c227692dc22108388b1d9b1e2eec99
This is consistent with alertmanager, and more intiutive for users.
The graphs page just has graphs, so remove mention of consoles.
Change-Id: I87780a4ade33697a6095423e1a7de47d341d2838
Move rulemanager to it's own package to break cicrular dependency.
Make NewTestTieredStorage available to tests, remove duplication.
Change-Id: I33b321245a44aa727bfc3614a7c9ae5005b34e03
This was initially motivated by wanting to distribute the rule checker
tool under `tools/rule_checker`. However, this was not possible without
also distributing the LevelDB dynamic libraries because the tool
transitively depended on Levigo:
rule checker -> query layer -> tiered storage layer -> leveldb
This change separates external storage interfaces from the
implementation (tiered storage, leveldb storage, memory storage) by
putting them into separate packages:
- storage/metric: public, implementation-agnostic interfaces
- storage/metric/tiered: tiered storage implementation, including memory
and LevelDB storage.
I initially also considered splitting up the implementation into
separate packages for tiered storage, memory storage, and LevelDB
storage, but these are currently so intertwined that it would be another
major project in itself.
The query layers and most other parts of Prometheus now have notion of
the storage implementation anymore and just use whatever implementation
they get passed in via interfaces.
The rule_checker is now a static binary :)
Change-Id: I793bbf631a8648ca31790e7e772ecf9c2b92f7a0
The closing of Prometheus now using a sync.Once wrapper to prevent
any accidental multiple invocations of it, which could trigger
corruption or a race condition. The shutdown process is made more
verbose through logging.
A not-enabled by default web handler has been provided to trigger a
remote shutdown if requested for debugging purposes.
Change-Id: If4fee75196bbff1fb1e4a4ef7e1cfa53fef88f2e
This also fixes the compaction test, which before worked only because
the input sample sorting was accidentally equal to the resulting on-disk
sample sorting.
Change-Id: I2a21c4b46ba562424b27058fc02eba84fa6a6006
So far we've been using Go's native time.Time for anything related to sample
timestamps. Since the range of time.Time is much bigger than what we need, this
has created two problems:
- there could be time.Time values which were out of the range/precision of the
time type that we persist to disk, therefore causing incorrectly ordered keys.
One bug caused by this was:
https://github.com/prometheus/prometheus/issues/367
It would be good to use a timestamp type that's more closely aligned with
what the underlying storage supports.
- sizeof(time.Time) is 192, while Prometheus should be ok with a single 64-bit
Unix timestamp (possibly even a 32-bit one). Since we store samples in large
numbers, this seriously affects memory usage. Furthermore, copying/working
with the data will be faster if it's smaller.
*MEMORY USAGE RESULTS*
Initial memory usage comparisons for a running Prometheus with 1 timeseries and
100,000 samples show roughly a 13% decrease in total (VIRT) memory usage. In my
tests, this advantage for some reason decreased a bit the more samples the
timeseries had (to 5-7% for millions of samples). This I can't fully explain,
but perhaps garbage collection issues were involved.
*WHEN TO USE THE NEW TIMESTAMP TYPE*
The new clientmodel.Timestamp type should be used whenever time
calculations are either directly or indirectly related to sample
timestamps.
For example:
- the timestamp of a sample itself
- all kinds of watermarks
- anything that may become or is compared to a sample timestamp (like the timestamp
passed into Target.Scrape()).
When to still use time.Time:
- for measuring durations/times not related to sample timestamps, like duration
telemetry exporting, timers that indicate how frequently to execute some
action, etc.
*NOTE ON OPERATOR OPTIMIZATION TESTS*
We don't use operator optimization code anymore, but it still lives in
the code as dead code. It still has tests, but I couldn't get all of them to
pass with the new timestamp format. I commented out the failing cases for now,
but we should probably remove the dead code soon. I just didn't want to do that
in the same change as this.
Change-Id: I821787414b0debe85c9fffaeb57abd453727af0f
Due to on going issues, we've decided to remove gorest. It started with gorest
not being thread-safe (it does introspection to create a new handler which is
an easy process to mess up with multiple threads of execution):
https://code.google.com/p/gorest/issues/detail?id=15
While the issue has been marked fixed, it looks like the patch has introduced
more problems than the original issue and simply doesn't work properly.
I'm not sure the behaviour was thought through properly. If a new instance is
needed every request then a handler-factory is needed or the library needs to
set expectations about how the new objects should interact with their
constructor state.
While it was tempting to try out another routing library, I think for now
it's better to use dumb vanilla Go routing. At least until we decide which
URL format we intend to standardize on.
Change-Id: Ica3da135d05f8ab8fc206f51eeca4f684f8efa0e
This commit fixes a critique of the old storage API design, whereby
the input parameters were always as raw bytes and never Protocol
Buffer messages that encapsulated the data, meaning every place a
read or mutation was conducted needed to manually perform said
translations on its own. This is taxing.
Change-Id: I4786938d0d207cefb7782bd2bd96a517eead186f
An design question was open for me in the beginning was whether to
serialize other types to disk, but Protocol Buffers quickly won out,
which allows us to drop support for other types. This is a good
start to cleaning up a lot of cruft in the storage stack and
can let us eventually decouple the various moving parts into
separate subsystems for easier reasoning.
This commit is not strictly required, but it is a start to making
the rest a lot more enjoyable to interact with.
This adds timers around several query-relevant code blocks. For now, the
query timer stats are only logged for queries initiated through the UI.
In other cases (rule evaluations), the stats are simply thrown away.
My hope is that this helps us understand where queries spend time,
especially in cases where they sometimes hang for unusual amounts of
time.
In order to help corroborate whether a Prometheus instance has
flapped until meta-monitoring is in-place, we ought to provide the
instance's start time in the console to aid in diagnostics.
This commit simplifies the way that compactions across a database's
keyspace occur due to reading the LevelDB internals. Secondarily it
introduces the database size estimation mechanisms.
Include database health and help interfaces.
Add database statistics; remove status goroutines.
This commit kills the use of Go routines to expose status throughout
the web components of Prometheus. It also dumps raw LevelDB status
on a separate /databases endpoint.
This commit introduces three background compactors, which compact
sparse samples together.
1. Older than five minutes is grouped together into chunks of 50 every 30
minutes.
2. Older than 60 minutes is grouped together into chunks of 250 every 50
minutes.
3. Older than one day is grouped together into chunks of 5000 every 70
minutes.
Unfortunately ``cp`` on Darwin regards some flags as positional and
requires them to be in a specific place. The new Protocol Buffer
descriptor bundling fails on Mac OS.
The Protocol Buffer compiler supports generating a machine-readable
descriptor file encoded as a provided Protocol Buffer message type,
which can be used to decode messages that have been encoded with it
after-the-fact. The generated descriptor also bundles in dependent
message types.
We can use this to perform forensics on old Prometheus clients, if
necessary.
Go's time.Time represents time as UTC in its fundamental data type.
That said, when using ``time.Unix(...)``, it sets the zone for the
time representation to the local. Unfortunately with diagnosis and
our tests, it is a PITA to jump between various zones, even though
the serialized version remains the same.
To keep things easy, all places where times are generated or read
are converted into UTC. These conversions are cheap, for
``Time.In`` merely changes a pointer reference in the struct,
nothing more. This enables me to diagnose test failures with fixture
data very easily.
By setting Access-Control headers, the Prometheus metrics API can be
accessed by cross-origin javascript applications (e.g., an external
dashboard pulling Prometheus metrics).
