prometheus query return 0 if no data

Well be executing kubectl commands on the master node only. Visit 1.1.1.1 from any device to get started with Cardinality is the number of unique combinations of all labels. Once we do that we need to pass label values (in the same order as label names were specified) when incrementing our counter to pass this extra information. See this article for details. By default Prometheus will create a chunk per each two hours of wall clock. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Bulk update symbol size units from mm to map units in rule-based symbology. Run the following command on the master node: Once the command runs successfully, youll see joining instructions to add the worker node to the cluster. See these docs for details on how Prometheus calculates the returned results. Explanation: Prometheus uses label matching in expressions. This is optional, but may be useful if you don't already have an APM, or would like to use our templates and sample queries. To do that, run the following command on the master node: Next, create an SSH tunnel between your local workstation and the master node by running the following command on your local machine: If everything is okay at this point, you can access the Prometheus console at http://localhost:9090. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. The difference with standard Prometheus starts when a new sample is about to be appended, but TSDB already stores the maximum number of time series its allowed to have. Why are physically impossible and logically impossible concepts considered separate in terms of probability? Please open a new issue for related bugs. The real power of Prometheus comes into the picture when you utilize the alert manager to send notifications when a certain metric breaches a threshold. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. Once we appended sample_limit number of samples we start to be selective. This is true both for client libraries and Prometheus server, but its more of an issue for Prometheus itself, since a single Prometheus server usually collects metrics from many applications, while an application only keeps its own metrics. Once it has a memSeries instance to work with it will append our sample to the Head Chunk. How to filter prometheus query by label value using greater-than, PromQL - Prometheus - query value as label, Why time duration needs double dot for Prometheus but not for Victoria metrics, How do you get out of a corner when plotting yourself into a corner. attacks, keep What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Just add offset to the query. Any other chunk holds historical samples and therefore is read-only. Stumbled onto this post for something else unrelated, just was +1-ing this :). 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. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, Managed Service for Prometheus https://goo.gle/3ZgeGxv Minimising the environmental effects of my dyson brain. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. Why are trials on "Law & Order" in the New York Supreme Court? Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. Both rules will produce new metrics named after the value of the record field. There is a maximum of 120 samples each chunk can hold. @zerthimon You might want to use 'bool' with your comparator Combined thats a lot of different metrics. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 - 05:59, , 22:00 - 23:59. Run the following commands on the master node to set up Prometheus on the Kubernetes cluster: Next, run this command on the master node to check the Pods status: Once all the Pods are up and running, you can access the Prometheus console using kubernetes port forwarding. Operating such a large Prometheus deployment doesnt come without challenges. However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. This holds true for a lot of labels that we see are being used by engineers. privacy statement. With our custom patch we dont care how many samples are in a scrape. The struct definition for memSeries is fairly big, but all we really need to know is that it has a copy of all the time series labels and chunks that hold all the samples (timestamp & value pairs). The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. count the number of running instances per application like this: This documentation is open-source. Redoing the align environment with a specific formatting. Doubling the cube, field extensions and minimal polynoms. Those limits are there to catch accidents and also to make sure that if any application is exporting a high number of time series (more than 200) the team responsible for it knows about it. For example, I'm using the metric to record durations for quantile reporting. Please see data model and exposition format pages for more details. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . Managed Service for Prometheus Cloud Monitoring Prometheus # ! At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. Having better insight into Prometheus internals allows us to maintain a fast and reliable observability platform without too much red tape, and the tooling weve developed around it, some of which is open sourced, helps our engineers avoid most common pitfalls and deploy with confidence. Returns a list of label names. This helps Prometheus query data faster since all it needs to do is first locate the memSeries instance with labels matching our query and then find the chunks responsible for time range of the query. Instead we count time series as we append them to TSDB. How can I group labels in a Prometheus query? PromQL allows you to write queries and fetch information from the metric data collected by Prometheus. Heres a screenshot that shows exact numbers: Thats an average of around 5 million time series per instance, but in reality we have a mixture of very tiny and very large instances, with the biggest instances storing around 30 million time series each. What is the point of Thrower's Bandolier? Each time series stored inside Prometheus (as a memSeries instance) consists of: The amount of memory needed for labels will depend on the number and length of these. vishnur5217 May 31, 2020, 3:44am 1. So perhaps the behavior I'm running into applies to any metric with a label, whereas a metric without any labels would behave as @brian-brazil indicated? PROMQL: how to add values when there is no data returned? Add field from calculation Binary operation. 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. 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. Subscribe to receive notifications of new posts: Subscription confirmed. One thing you could do though to ensure at least the existence of failure series for the same series which have had successes, you could just reference the failure metric in the same code path without actually incrementing it, like so: That way, the counter for that label value will get created and initialized to 0. The Graph tab allows you to graph a query expression over a specified range of time. Is it possible to rotate a window 90 degrees if it has the same length and width? No, only calling Observe() on a Summary or Histogram metric will add any observations (and only calling Inc() on a counter metric will increment it). At the same time our patch gives us graceful degradation by capping time series from each scrape to a certain level, rather than failing hard and dropping all time series from affected scrape, which would mean losing all observability of affected applications. Finally we maintain a set of internal documentation pages that try to guide engineers through the process of scraping and working with metrics, with a lot of information thats specific to our environment. VictoriaMetrics has other advantages compared to Prometheus, ranging from massively parallel operation for scalability, better performance, and better data compression, though what we focus on for this blog post is a rate () function handling. There is no equivalent functionality in a standard build of Prometheus, if any scrape produces some samples they will be appended to time series inside TSDB, creating new time series if needed. I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. Each time series will cost us resources since it needs to be kept in memory, so the more time series we have, the more resources metrics will consume. On the worker node, run the kubeadm joining command shown in the last step. You signed in with another tab or window. This is the modified flow with our patch: By running go_memstats_alloc_bytes / prometheus_tsdb_head_series query we know how much memory we need per single time series (on average), we also know how much physical memory we have available for Prometheus on each server, which means that we can easily calculate the rough number of time series we can store inside Prometheus, taking into account the fact the theres garbage collection overhead since Prometheus is written in Go: memory available to Prometheus / bytes per time series = our capacity. No Data is showing on Grafana Dashboard - Prometheus - Grafana Labs There is an open pull request on the Prometheus repository. Names and labels tell us what is being observed, while timestamp & value pairs tell us how that observable property changed over time, allowing us to plot graphs using this data. Using regular expressions, you could select time series only for jobs whose I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). Our metric will have a single label that stores the request path. So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. What sort of strategies would a medieval military use against a fantasy giant? Cadvisors on every server provide container names. Finally getting back to this. I have a query that gets a pipeline builds and its divided by the number of change request open in a 1 month window, which gives a percentage. A sample is something in between metric and time series - its a time series value for a specific timestamp. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. The speed at which a vehicle is traveling. Does a summoned creature play immediately after being summoned by a ready action? 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 Here is the extract of the relevant options from Prometheus documentation: Setting all the label length related limits allows you to avoid a situation where extremely long label names or values end up taking too much memory. With 1,000 random requests we would end up with 1,000 time series in Prometheus. If such a stack trace ended up as a label value it would take a lot more memory than other time series, potentially even megabytes. To learn more, see our tips on writing great answers. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. About an argument in Famine, Affluence and Morality. It doesnt get easier than that, until you actually try to do it. Good to know, thanks for the quick response! Our CI would check that all Prometheus servers have spare capacity for at least 15,000 time series before the pull request is allowed to be merged. Or maybe we want to know if it was a cold drink or a hot one? (pseudocode): summary = 0 + sum (warning alerts) + 2*sum (alerts (critical alerts)) This gives the same single value series, or no data if there are no alerts. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. In Prometheus pulling data is done via PromQL queries and in this article we guide the reader through 11 examples that can be used for Kubernetes specifically. Lets adjust the example code to do this. The more labels we have or the more distinct values they can have the more time series as a result. So just calling WithLabelValues() should make a metric appear, but only at its initial value (0 for normal counters and histogram bucket counters, NaN for summary quantiles). Grafana renders "no data" when instant query returns empty dataset Making statements based on opinion; back them up with references or personal experience. We know that the more labels on a metric, the more time series it can create. t]. What is the point of Thrower's Bandolier? Is a PhD visitor considered as a visiting scholar? If we have a scrape with sample_limit set to 200 and the application exposes 201 time series, then all except one final time series will be accepted. But the real risk is when you create metrics with label values coming from the outside world. If this query also returns a positive value, then our cluster has overcommitted the memory. If we let Prometheus consume more memory than it can physically use then it will crash. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. Windows 10, how have you configured the query which is causing problems? There's also count_scalar(), result of a count() on a query that returns nothing should be 0 ? About an argument in Famine, Affluence and Morality. website What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? These will give you an overall idea about a clusters health. Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. 2023 The Linux Foundation. It might seem simple on the surface, after all you just need to stop yourself from creating too many metrics, adding too many labels or setting label values from untrusted sources. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). We know that time series will stay in memory for a while, even if they were scraped only once. Have a question about this project? The result is a table of failure reason and its count. It will return 0 if the metric expression does not return anything. How to tell which packages are held back due to phased updates. want to sum over the rate of all instances, so we get fewer output time series, Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. No error message, it is just not showing the data while using the JSON file from that website. Having a working monitoring setup is a critical part of the work we do for our clients. What video game is Charlie playing in Poker Face S01E07? rev2023.3.3.43278. This is what i can see on Query Inspector. This garbage collection, among other things, will look for any time series without a single chunk and remove it from memory. To select all HTTP status codes except 4xx ones, you could run: http_requests_total {status!~"4.."} Subquery Return the 5-minute rate of the http_requests_total metric for the past 30 minutes, with a resolution of 1 minute. I can't work out how to add the alerts to the deployments whilst retaining the deployments for which there were no alerts returned: If I use sum with or, then I get this, depending on the order of the arguments to or: If I reverse the order of the parameters to or, I get what I am after: But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Lets see what happens if we start our application at 00:25, allow Prometheus to scrape it once while it exports: And then immediately after the first scrape we upgrade our application to a new version: At 00:25 Prometheus will create our memSeries, but we will have to wait until Prometheus writes a block that contains data for 00:00-01:59 and runs garbage collection before that memSeries is removed from memory, which will happen at 03:00. Prometheus is a great and reliable tool, but dealing with high cardinality issues, especially in an environment where a lot of different applications are scraped by the same Prometheus server, can be challenging. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . or Internet application, That response will have a list of, When Prometheus collects all the samples from our HTTP response it adds the timestamp of that collection and with all this information together we have a. Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. count() should result in 0 if no timeseries found #4982 - GitHub positions. Prometheus - exclude 0 values from query result - Stack Overflow PROMQL: how to add values when there is no data returned? Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. 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. AFAIK it's not possible to hide them through Grafana. 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. To get a better understanding of the impact of a short lived time series on memory usage lets take a look at another example. PromQL queries the time series data and returns all elements that match the metric name, along with their values for a particular point in time (when the query runs). help customers build Adding labels is very easy and all we need to do is specify their names. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. Querying basics | Prometheus To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Connect and share knowledge within a single location that is structured and easy to search. These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. Is there a solutiuon to add special characters from software and how to do it. This makes a bit more sense with your explanation. https://grafana.com/grafana/dashboards/2129. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. your journey to Zero Trust. This means that looking at how many time series an application could potentially export, and how many it actually exports, gives us two completely different numbers, which makes capacity planning a lot harder. I know prometheus has comparison operators but I wasn't able to apply them. I used a Grafana transformation which seems to work. The number of times some specific event occurred. Sign in Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. The Prometheus data source plugin provides the following functions you can use in the Query input field. It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. Has 90% of ice around Antarctica disappeared in less than a decade? One Head Chunk - containing up to two hours of the last two hour wall clock slot.

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