Browse other questions tagged prometheus prometheus-alertmanager promql or ask your own question. As there's no processes that we might wish to spread the load of, subqueries currently align everything with t=0 as that's as good a choice as any. If I use, say, Sure that got inverted in the implementation of 2.3.0 for performance reasons, but the principle stands and there's even unittests to avoid accidentally violating it in future. (which was at 8pm local time). ?Work done in assembling a point charge is infinite,Macro for drawing stacks of colored horizontal rectangles.Why did it take so long for the Germans to develop the first tank model in World War I?After bootstrapping regression analysis, all p-values are multiple of 0.001996,Story about a scientist who invents truth serum,Basic question about real-analytic functions,awk: split file by column name and add header row to each file,Reference request: the theory of currents.Immutable String and Integer in Java: What is the point if assignment in effect changes the value?Managing startup, how to control stress levels?Lights go out in part of the house whenever I plug.something in,Story about a world of magic where science has been forbidden.Asking for help, clarification, or responding to other answers.Making statements based on opinion; back them up with references or personal experience. may well be important to you, because Prometheus always aligns your expensive queries which you might want to compute less frequently.Though subqueries are very convenient to use in place of recording rules, using them unnecessarily has performance implications. into one point in some way. scheduler exposing these metrics about the instances it runs):The same expression, but summed by application, could be written like this:If the same fictional cluster scheduler exposed CPU usage metrics like the The innermost subquery gets the rate of.In most cases you would require the default evaluation interval, which is the interval at which rules are evaluated by default. hunting for). Python Other. ),Going from a bound instance method to its class instance in Python,ZFS Encryption is still under development (as of March 2019). Teams. The subquery was going back 20s, with a 5s step. otherwise display more than a single piece of information for that Their usual use is to nest time range queries, such as a max_over_time of a rate, as covered in, for example, Brian Brazil's How much of the time is my network usage over a certain amount?.However, they can be used in another, perhaps less obvious way. and dips. (I realize Prometheus doesn't keep track of which metrics are counters and which are gauges, but that information may be inferred from the function that the range vector is being used in.) The easy case of this is when the resolution of your What does this mean for the future of AI, edge…,Hot Meta Posts: Allow for removal by moderators, and thoughts about future…,Goodbye, Prettify. of the activity level over some time range; instead their metrics Python Branch: master. brian-brazil merged 37 commits into prometheus: master from codesome: subqueries Dec 22, 2018. All regular expressions in Prometheus use RE2 syntax. The general form is To compare my current value across the values of the previous 4 weeks would require me to write 4 subqueries. Prometheus subqueries pick time points in a surprising way. All rights reserved. (The first option provided by Julius in this comment). Return the 5-minute rate of the http_requests_total metric for the past 30 minutes, with a resolution of 1 minute. making it a range vector:Note that an expression resulting in a range vector cannot be graphed directly, One of the design principles of PromQL and the Prometheus query APIs is that range queries are merely syntactic sugar over instant query. Sure that got inverted in the implementation of 2.3.0 for performance reasons, but the principle stands and there's even unittests to avoid accidentally violating it in future.So we need something that's not only efficient, but maintains consistent results whether an evaluation at a given timestamp is as an instant query or just one step of a range query.The solution I came up with was to completely ignore the alignment of the surrounding query. for rates that are counters. Is it possible to fulfill a similar request?Thanks for contributing an answer to Stack Overflow!By clicking “Post Your Answer”, you agree to our.To subscribe to this RSS feed, copy and paste this URL into your RSS reader.site design / logo © 2020 Stack Exchange Inc; user contributions licensed under,Stack Overflow works best with JavaScript enabled,Where developers & technologists share private knowledge with coworkers,Programming & related technical career opportunities,Recruit tech talent & build your employer brand,Reach developers & technologists worldwide,Podcast 270: Oracle tries to Tok, Nvidia Arms up,Nvidia has acquired Arm. Copy link Quote reply Member codesome commented Nov 6, 2018 • edited Fixes #1227. Subqueries were added to PromQL a while back, but there's more to this feature than it'd seem.For the longest time subqueries had fundamental issues that made them challenging to add.Firstly from a semantic standpoint what interval should they be executed on? Before Prometheus introduced subqueries, you couldn't combine irate() with max_over_time, so you couldn't do this query (at least as an ad-hoc thing). Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. and local noon, and so on, or to be relative to 'now' instead of That is whether the query range step being evaluated for is t=100 or t=103 it'd be getting data from the same subquery output. (The first option provided by Julius in this comment). That's technically unspecified just as with phases elsewhere, but I don't currently see a reason that we'd want to change it.So if you ever find yourself wondering why software X doesn't add feature Y, keep in mind that there's often more to it than it would appear at first.A blog on monitoring, scale and operational Sanity. The Linux Foundation has registered trademarks and uses trademarks. first thing you need to do is decide what you care about, because Historically for a range query it'd calculate each step completely independently, so you'd end up recalculating the same subquery data again and again for each step. and we provide an appropriate range vector as needed to the next stage in the PromQL evaluation - just like a normal time series.This is conveniently also consistent with another design decision of Prometheus, which is you can configure your scrape and evaluation intervals but it's unspecified at exactly what phase Prometheus will actually perform things at. your coworkers to find and share information.I have a query to get a list of nodes with the Compute role:Can I somehow insert the first query as a parameter for the second query, something like this:As you can guess, this option does not work. This gets us back to situation similar to where we were when each range query step was calculated completely independently, losing the wins of the 2.3.0 improvements.For more fun, there's also the possibility of nested subqueries.And there's another problem. '.At small subquery steps, like :1m or :10m or even perhaps :1h, this Up until today, I would have confidently told you that I understood how Prometheus subqueries picked the time points that they evaluated your expression at; it was the obvious combination of a range vector with a query step. If you care about spikes, To select all HTTP status codes except 4xx ones, you could run: http_requests_total{status!~"4.."} Subquery. One of the things that people traditionally want to do with graphs If nothing happens, download GitHub Desktop and try again. For a list of trademarks of The Linux Foundation, please see our,Prometheus 2.0 Alpha.3 with New Rule Format,Prometheus to Join the Cloud Native Computing Foundation,Monitoring DreamHack - the World's Largest Digital Festival,Advanced Service Discovery in Prometheus 0.14.0,Prometheus Monitoring Spreads through the Internet,Finally the result of all the evaluations above are passed to. Custom resolutions will be helpful in cases where you want to compute less/more frequently, e.g. The Linux Foundation has registered trademarks and uses trademarks. As the title suggests, a subquery is a part of a query, and allows you to do a range query within a query, which was not possible before. alignment probably doesn't matter a lot. subqueries to UTC, not to local time. rate(http_requests_total[5m])[30m:1m] This is an example of a nested subquery. There is no way to make a Rather create more recording rules if you do need to use subqueries in a recording rule.© Prometheus Authors 2014-2020 | Documentation Distributed under CC-BY-4.0,© 2020 The Linux Foundation. how,This is all very abstract, so let's use the example of a subquery year() year(v=vector(time()) instant-vector) returns the year for each of the given times in UTC. Find file. returns the unused memory in MiB for every instance (on a fictional cluster you have to condense the information from multiple metrics points If the instantaneous rate at the five but viewed in the tabular ("Console") view of the expression browser.Using regular expressions, you could select time series only for jobs whose (If you care about both, you need to plot two separate lines or capture spikes,A surprisingly arcane little Unix shell pipeline example,Our problem with Netplan and routes on Ubuntu 18.04. And it would be tedious to create a recording rule for each step of a query.With subquery support, all the waiting and frustration is taken care of.The Prometheus team arrived at a consensus for the syntax of subqueries at the Prometheus Dev Summit 2018 held in Munich. It has been a long-standing feature request:Sometimes, there are cases when you want to spot a problem using,Previously, the above was not possible for a single.When you want some quick results on data spanning days or weeks, it can be quite a bit of a wait until you have enough data in your recording rules before it can be used. This document is meant as a reference. Prometheus - SubQueries Issue to keep track: prometheus#1227 Syntax and How it Works The following syntax had a consensus during Prometheus Dev Summit 2018-08-11. ),For the rest of this I'm going to assume that we care about the It has been a long-standing feature request: prometheus/prometheus/1227. maximum. Put simply, subqueries let you use time based aggregation on expressions. So if say you had a range query of.So we're done then, right? will get matched and propagated to the output. scrape interval is 15 seconds:The 45s and 10s will vary depending on what your scrape interval name match a certain pattern, in this case, all jobs that end with,All regular expressions in Prometheus use.To select all HTTP status codes except 4xx ones, you could run:This is an example of a nested subquery. brief spikes in usage (or brief dips, depending on what you're All rights reserved. Forgetting to add recording rules can be frustrating. Export Prometheus metrics from SQL queries. Merged Subquery #4831. brian-brazil merged 37 commits into prometheus: master from codesome: subqueries Dec 22, 2018 +1,069 −56 Conversation 105 Commits 37 Checks 1 Files changed 14 Conversation. count the number of running instances per application like this:© Prometheus Authors 2014-2020 | Documentation Distributed under CC-BY-4.0,© 2020 The Linux Foundation. Say that the range query was starting at t=100, with a 3s step. (Note that this is not when the metric points themselves come from; For example, this expression year() year(v=vector(time()) instant-vector) returns the year for each of the given times in UTC. For a list of trademarks of The Linux Foundation, please see our,Use file-based service discovery to discover scrape targets,Monitoring Linux host metrics with the Node Exporter,Monitoring Docker container metrics using cAdvisor,Understanding and using the multi-target exporter pattern. spike or dip you can detect at all or detect reliably, especially being aligned with absolute time. So t=80, 85 is just as valid as t=84.12, 89.12. range of '.Notice that the oldest timestamp is earlier than now minus exactly One of the design principles of PromQL and the Prometheus query APIs is that range queries are merely syntactic sugar over instant query. This function was added in Prometheus 2.0. vector() vector(s scalar) returns the scalar s as a vector with no labels. My idea was to take a look at the number of registrations of the previous weeks as they vary depending on the week day. The above example has the same value for the range query's step and the subquery's step. of things like network bandwidth or disk IO rates is to look for Not too hard.The big problem though was performance. This function was added in Prometheus 2.0. vector() vector(s scalar) returns the scalar s as a vector with no labels. So the first range query step needs samples at t=80, 85, 90, 95 and 100. If you sample a counter every fifteen Prometheus - SubQueries Issue to keep track: prometheus#1227 Syntax and How it Works The following syntax had a consensus during Prometheus Dev Summit 2018-08-11. By using our site, you acknowledge that you have read and understand our.Stack Overflow for Teams is a private, secure spot for you and The Overflow Blog Podcast 266: Ok, who vandalized Wikipedia? (Apparently the Prometheus people have a reason for doing it this Sign in Sign up.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. The pull requestfor subquery support was recently merged into Prometheus and will be available in Prometheus 2.7. Subqueries are a new feature in Prometheus 2.7. This was done to allow us to spread scrape and evaluation load around, as trying to do all scrapes at exactly the same time was unwise (which I fixed all the way back in 0.8.0), but also helps here. IO are not represented in Prometheus metrics as instantaneous gauges is for the particular metric you care about. If nothing happens, download Xcode and try again.
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