prometheus query return 0 if no data

You signed in with another tab or window. promql - Prometheus query check if value exist - Stack Overflow But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. If the time series already exists inside TSDB then we allow the append to continue. For example, /api/v1/query?query=http_response_ok [24h]&time=t would return raw samples on the time range (t-24h . metric name, as measured over the last 5 minutes: Assuming that the http_requests_total time series all have the labels job Its also worth mentioning that without our TSDB total limit patch we could keep adding new scrapes to Prometheus and that alone could lead to exhausting all available capacity, even if each scrape had sample_limit set and scraped fewer time series than this limit allows. Thats why what our application exports isnt really metrics or time series - its samples. Prometheus allows us to measure health & performance over time and, if theres anything wrong with any service, let our team know before it becomes a problem. Select the query and do + 0. Do new devs get fired if they can't solve a certain bug? These are the sane defaults that 99% of application exporting metrics would never exceed. We know that each time series will be kept in memory. or something like that. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. I then hide the original query. Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. rev2023.3.3.43278. Finally you will want to create a dashboard to visualize all your metrics and be able to spot trends. Of course there are many types of queries you can write, and other useful queries are freely available. Youve learned about the main components of Prometheus, and its query language, PromQL. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This is the standard flow with a scrape that doesnt set any sample_limit: With our patch we tell TSDB that its allowed to store up to N time series in total, from all scrapes, at any time. I am interested in creating a summary of each deployment, where that summary is based on the number of alerts that are present for each deployment. You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana. Prometheus - exclude 0 values from query result - Stack Overflow TSDB used in Prometheus is a special kind of database that was highly optimized for a very specific workload: This means that Prometheus is most efficient when continuously scraping the same time series over and over again. @rich-youngkin Yeah, what I originally meant with "exposing" a metric is whether it appears in your /metrics endpoint at all (for a given set of labels). PromQL / How to return 0 instead of ' no data' - Medium To get a better idea of this problem lets adjust our example metric to track HTTP requests. So lets start by looking at what cardinality means from Prometheus' perspective, when it can be a problem and some of the ways to deal with it. There will be traps and room for mistakes at all stages of this process. For example, I'm using the metric to record durations for quantile reporting. Asking for help, clarification, or responding to other answers. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. To select all HTTP status codes except 4xx ones, you could run: Return the 5-minute rate of the http_requests_total metric for the past 30 minutes, with a resolution of 1 minute. When Prometheus collects metrics it records the time it started each collection and then it will use it to write timestamp & value pairs for each time series. Theres only one chunk that we can append to, its called the Head Chunk. You can calculate how much memory is needed for your time series by running this query on your Prometheus server: Note that your Prometheus server must be configured to scrape itself for this to work. To make things more complicated you may also hear about samples when reading Prometheus documentation. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. By clicking Sign up for GitHub, you agree to our terms of service and See this article for details. Then imported a dashboard from " 1 Node Exporter for Prometheus Dashboard EN 20201010 | Grafana Labs ".Below is my Dashboard which is showing empty results.So kindly check and suggest. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. What am I doing wrong here in the PlotLegends specification? source, what your query is, what the query inspector shows, and any other See these docs for details on how Prometheus calculates the returned results. Prometheus query check if value exist. Prometheus does offer some options for dealing with high cardinality problems. At this point we should know a few things about Prometheus: With all of that in mind we can now see the problem - a metric with high cardinality, especially one with label values that come from the outside world, can easily create a huge number of time series in a very short time, causing cardinality explosion. name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 what error message are you getting to show that theres a problem? This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. @zerthimon The following expr works for me When using Prometheus defaults and assuming we have a single chunk for each two hours of wall clock we would see this: Once a chunk is written into a block it is removed from memSeries and thus from memory. Both patches give us two levels of protection. The result of an expression can either be shown as a graph, viewed as tabular data in Prometheus's expression browser, or consumed by external systems via the HTTP API. If the total number of stored time series is below the configured limit then we append the sample as usual. Lets say we have an application which we want to instrument, which means add some observable properties in the form of metrics that Prometheus can read from our application. Time arrow with "current position" evolving with overlay number. vishnur5217 May 31, 2020, 3:44am 1. In the screenshot below, you can see that I added two queries, A and B, but only . Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 02:00 - create a new chunk for 02:00 - 03:59 time range, 04:00 - create a new chunk for 04:00 - 05:59 time range, 22:00 - create a new chunk for 22:00 - 23:59 time range. Is what you did above (failures.WithLabelValues) an example of "exposing"? Under which circumstances? Monitoring our monitoring: how we validate our Prometheus alert rules returns the unused memory in MiB for every instance (on a fictional cluster Chunks will consume more memory as they slowly fill with more samples, after each scrape, and so the memory usage here will follow a cycle - we start with low memory usage when the first sample is appended, then memory usage slowly goes up until a new chunk is created and we start again. bay, This means that our memSeries still consumes some memory (mostly labels) but doesnt really do anything. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. When you add dimensionality (via labels to a metric), you either have to pre-initialize all the possible label combinations, which is not always possible, or live with missing metrics (then your PromQL computations become more cumbersome). These queries are a good starting point. but viewed in the tabular ("Console") view of the expression browser. an EC2 regions with application servers running docker containers. If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? These queries will give you insights into node health, Pod health, cluster resource utilization, etc. Is it possible to rotate a window 90 degrees if it has the same length and width? If, on the other hand, we want to visualize the type of data that Prometheus is the least efficient when dealing with, well end up with this instead: Here we have single data points, each for a different property that we measure. Now we should pause to make an important distinction between metrics and time series. For example, if someone wants to modify sample_limit, lets say by changing existing limit of 500 to 2,000, for a scrape with 10 targets, thats an increase of 1,500 per target, with 10 targets thats 10*1,500=15,000 extra time series that might be scraped. Grafana renders "no data" when instant query returns empty dataset Extra metrics exported by Prometheus itself tell us if any scrape is exceeding the limit and if that happens we alert the team responsible for it.

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