If this query also returns a positive value, then our cluster has overcommitted the memory. Creating new time series on the other hand is a lot more expensive - we need to allocate new memSeries instances with a copy of all labels and keep it in memory for at least an hour. Is a PhD visitor considered as a visiting scholar? By default we allow up to 64 labels on each time series, which is way more than most metrics would use. Before running the query, create a Pod with the following specification: Before running the query, create a PersistentVolumeClaim with the following specification: This will get stuck in Pending state as we dont have a storageClass called manual" in our cluster. A sample is something in between metric and time series - its a time series value for a specific timestamp. information which you think might be helpful for someone else to understand Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Prometheus query check if value exist. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Show or hide query result depending on variable value in Grafana, Understanding the CPU Busy Prometheus query, Group Label value prefixes by Delimiter in Prometheus, Why time duration needs double dot for Prometheus but not for Victoria metrics, Using a Grafana Histogram with Prometheus Buckets. Is a PhD visitor considered as a visiting scholar? No error message, it is just not showing the data while using the JSON file from that website. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. which outputs 0 for an empty input vector, but that outputs a scalar 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. Under which circumstances? So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. I believe it's the logic that it's written, but is there any conditions that can be used if there's no data recieved it returns a 0. what I tried doing is putting a condition or an absent function,but not sure if thats the correct approach. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, 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. To this end, I set up the query to instant so that the very last data point is returned but, when the query does not return a value - say because the server is down and/or no scraping took place - the stat panel produces no data. This page will guide you through how to install and connect Prometheus and Grafana. binary operators to them and elements on both sides with the same label set Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. The Head Chunk is never memory-mapped, its always stored in memory. which Operating System (and version) are you running it under? Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. whether someone is able to help out. 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. Windows 10, how have you configured the query which is causing problems? With any monitoring system its important that youre able to pull out the right data. Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. We know that time series will stay in memory for a while, even if they were scraped only once. If the error message youre getting (in a log file or on screen) can be quoted A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). The Graph tab allows you to graph a query expression over a specified range of time. What is the point of Thrower's Bandolier? Hello, I'm new at Grafan and Prometheus. I've created an expression that is intended to display percent-success for a given metric. Labels are stored once per each memSeries instance. Since we know that the more labels we have the more time series we end up with, you can see when this can become a problem. Are there tables of wastage rates for different fruit and veg? Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. This means that our memSeries still consumes some memory (mostly labels) but doesnt really do anything. Thanks, Looking at memory usage of such Prometheus server we would see this pattern repeating over time: The important information here is that short lived time series are expensive. We covered some of the most basic pitfalls in our previous blog post on Prometheus - Monitoring our monitoring. feel that its pushy or irritating and therefore ignore it. 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. For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. The thing with a metric vector (a metric which has dimensions) is that only the series for it actually get exposed on /metrics which have been explicitly initialized. 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. For example, the following query will show the total amount of CPU time spent over the last two minutes: And the query below will show the total number of HTTP requests received in the last five minutes: There are different ways to filter, combine, and manipulate Prometheus data using operators and further processing using built-in functions. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. Well occasionally send you account related emails. Prometheus's query language supports basic logical and arithmetic operators. 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. Is what you did above (failures.WithLabelValues) an example of "exposing"? Good to know, thanks for the quick response! To get a better understanding of the impact of a short lived time series on memory usage lets take a look at another example. What video game is Charlie playing in Poker Face S01E07? PromQL allows querying historical data and combining / comparing it to the current data. Run the following commands in both nodes to configure the Kubernetes repository. Connect and share knowledge within a single location that is structured and easy to search. @zerthimon You might want to use 'bool' with your comparator notification_sender-. Next, create a Security Group to allow access to the instances. 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. A metric is an observable property with some defined dimensions (labels). Both rules will produce new metrics named after the value of the record field. 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. Now we should pause to make an important distinction between metrics and time series. what does the Query Inspector show for the query you have a problem with? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. If we try to visualize how the perfect type of data Prometheus was designed for looks like well end up with this: A few continuous lines describing some observed properties. help customers build (fanout by job name) and instance (fanout by instance of the job), we might That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). The Prometheus data source plugin provides the following functions you can use in the Query input field. It would be easier if we could do this in the original query though. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. The simplest construct of a PromQL query is an instant vector selector. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. Can I tell police to wait and call a lawyer when served with a search warrant? Name the nodes as Kubernetes Master and Kubernetes Worker. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. Is a PhD visitor considered as a visiting scholar? But you cant keep everything in memory forever, even with memory-mapping parts of data. If instead of beverages we tracked the number of HTTP requests to a web server, and we used the request path as one of the label values, then anyone making a huge number of random requests could force our application to create a huge number of time series. This is because the Prometheus server itself is responsible for timestamps. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. 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. If you're looking for a By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. This works fine when there are data points for all queries in the expression. We will also signal back to the scrape logic that some samples were skipped. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Instead we count time series as we append them to TSDB. node_cpu_seconds_total: This returns the total amount of CPU time. SSH into both servers and run the following commands to install Docker. Internally all time series are stored inside a map on a structure called Head. Short story taking place on a toroidal planet or moon involving flying, How to handle a hobby that makes income in US, Doubling the cube, field extensions and minimal polynoms, Follow Up: struct sockaddr storage initialization by network format-string. The problem is that the table is also showing reasons that happened 0 times in the time frame and I don't want to display them. 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. By clicking Sign up for GitHub, you agree to our terms of service and This pod wont be able to run because we dont have a node that has the label disktype: ssd. without any dimensional information. Ive added a data source(prometheus) in Grafana. I believe it's the logic that it's written, but is there any . Every time we add a new label to our metric we risk multiplying the number of time series that will be exported to Prometheus as the result. privacy statement. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. VictoriaMetrics handles rate () function in the common sense way I described earlier! Being able to answer How do I X? yourself without having to wait for a subject matter expert allows everyone to be more productive and move faster, while also avoiding Prometheus experts from answering the same questions over and over again. Its not going to get you a quicker or better answer, and some people might Please dont post the same question under multiple topics / subjects. Asking for help, clarification, or responding to other answers. At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. Our patched logic will then check if the sample were about to append belongs to a time series thats already stored inside TSDB or is it a new time series that needs to be created. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. However when one of the expressions returns no data points found the result of the entire expression is no data points found. to your account. The containers are named with a specific pattern: notification_checker [0-9] notification_sender [0-9] I need an alert when the number of container of the same pattern (eg. Is it possible to rotate a window 90 degrees if it has the same length and width? Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . To better handle problems with cardinality its best if we first get a better understanding of how Prometheus works and how time series consume memory. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How to follow the signal when reading the schematic? In our example we have two labels, content and temperature, and both of them can have two different values. Even i am facing the same issue Please help me on this. (pseudocode): This gives the same single value series, or no data if there are no alerts. But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. This article covered a lot of ground. You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. notification_sender-. Using a query that returns "no data points found" in an expression. Asking for help, clarification, or responding to other answers. name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 Secondly this calculation is based on all memory used by Prometheus, not only time series data, so its just an approximation. So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. See these docs for details on how Prometheus calculates the returned results. Going back to our metric with error labels we could imagine a scenario where some operation returns a huge error message, or even stack trace with hundreds of lines. 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. Examples 1 Like. Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. Second rule does the same but only sums time series with status labels equal to "500". Internally time series names are just another label called __name__, so there is no practical distinction between name and labels. 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). Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 0. Finally getting back to this. *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. You're probably looking for the absent function. Visit 1.1.1.1 from any device to get started with 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). By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Since this happens after writing a block, and writing a block happens in the middle of the chunk window (two hour slices aligned to the wall clock) the only memSeries this would find are the ones that are orphaned - they received samples before, but not anymore. the problem you have. Already on GitHub? What happens when somebody wants to export more time series or use longer labels? I don't know how you tried to apply the comparison operators, but if I use this very similar query: I get a result of zero for all jobs that have not restarted over the past day and a non-zero result for jobs that have had instances restart. This means that Prometheus must check if theres already a time series with identical name and exact same set of labels present. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? I was then able to perform a final sum by over the resulting series to reduce the results down to a single result, dropping the ad-hoc labels in the process.