If we add another label that can also have two values then we can now export up to eight time series (2*2*2). Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. 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. @juliusv Thanks for clarifying that. Prometheus and PromQL (Prometheus Query Language) are conceptually very simple, but this means that all the complexity is hidden in the interactions between different elements of the whole metrics pipeline. Is there a solutiuon to add special characters from software and how to do it. Both rules will produce new metrics named after the value of the record field. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? privacy statement. Not the answer you're looking for? First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. Second rule does the same but only sums time series with status labels equal to "500". This works fine when there are data points for all queries in the expression. Adding labels is very easy and all we need to do is specify their names. With our example metric we know how many mugs were consumed, but what if we also want to know what kind of beverage it was? Prometheus will keep each block on disk for the configured retention period. This page will guide you through how to install and connect Prometheus and Grafana. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Prometheus promQL query is not showing 0 when metric data does not exists, PromQL - how to get an interval between result values, PromQL delta for each elment in values array, Trigger alerts according to the environment in alertmanger, Prometheus alertmanager includes resolved alerts in a new alert. 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 We protect Lets create a demo Kubernetes cluster and set up Prometheus to monitor it. want to sum over the rate of all instances, so we get fewer output time series, Managing the entire lifecycle of a metric from an engineering perspective is a complex process. Is what you did above (failures.WithLabelValues) an example of "exposing"? 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. Sign in 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. 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. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. If we try to append a sample with a timestamp higher than the maximum allowed time for current Head Chunk, then TSDB will create a new Head Chunk and calculate a new maximum time for it based on the rate of appends. Does Counterspell prevent from any further spells being cast on a given turn? Thanks, Our metric will have a single label that stores the request path. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. Having a working monitoring setup is a critical part of the work we do for our clients. Object, url:api/datasources/proxy/2/api/v1/query_range?query=wmi_logical_disk_free_bytes%7Binstance%3D~%22%22%2C%20volume%20!~%22HarddiskVolume.%2B%22%7D&start=1593750660&end=1593761460&step=20&timeout=60s, Powered by Discourse, best viewed with JavaScript enabled, 1 Node Exporter for Prometheus Dashboard EN 20201010 | Grafana Labs, https://grafana.com/grafana/dashboards/2129. Ive added a data source(prometheus) in Grafana. 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. This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. 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. In both nodes, edit the /etc/hosts file to add the private IP of the nodes. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Once it has a memSeries instance to work with it will append our sample to the Head Chunk. Cardinality is the number of unique combinations of all labels. @rich-youngkin Yes, the general problem is non-existent series. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. or something like that. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. what does the Query Inspector show for the query you have a problem with? 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. 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. This also has the benefit of allowing us to self-serve capacity management - theres no need for a team that signs off on your allocations, if CI checks are passing then we have the capacity you need for your applications. This thread has been automatically locked since there has not been any recent activity after it was closed. returns the unused memory in MiB for every instance (on a fictional cluster Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. 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. I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. Blocks will eventually be compacted, which means that Prometheus will take multiple blocks and merge them together to form a single block that covers a bigger time range. 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. 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. the problem you have. There is a maximum of 120 samples each chunk can hold. You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. Why are physically impossible and logically impossible concepts considered separate in terms of probability? It's worth to add that if using Grafana you should set 'Connect null values' proeprty to 'always' in order to get rid of blank spaces in the graph. All rights reserved. Is there a way to write the query so that a default value can be used if there are no data points - e.g., 0. It would be easier if we could do this in the original query though. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. However when one of the expressions returns no data points found the result of the entire expression is no data points found.In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found.Is there a way to write the query so that a . With our custom patch we dont care how many samples are in a scrape. I'm not sure what you mean by exposing a metric. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. source, what your query is, what the query inspector shows, and any other But you cant keep everything in memory forever, even with memory-mapping parts of data. Sign in rate (http_requests_total [5m]) [30m:1m] Where does this (supposedly) Gibson quote come from? First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. Connect and share knowledge within a single location that is structured and easy to search. This gives us confidence that we wont overload any Prometheus server after applying changes. 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. Thanks for contributing an answer to Stack Overflow! Each chunk represents a series of samples for a specific time range. I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). Windows 10, how have you configured the query which is causing problems? What sort of strategies would a medieval military use against a fantasy giant? Return all time series with the metric http_requests_total: Return all time series with the metric http_requests_total and the given Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. website Is a PhD visitor considered as a visiting scholar? Why do many companies reject expired SSL certificates as bugs in bug bounties? And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. list, which does not convey images, so screenshots etc. This makes a bit more sense with your explanation. Now, lets install Kubernetes on the master node using kubeadm. 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. result of a count() on a query that returns nothing should be 0 ? Prometheus query check if value exist. To your second question regarding whether I have some other label on it, the answer is yes I do. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. What this means is that using Prometheus defaults each memSeries should have a single chunk with 120 samples on it for every two hours of data. A sample is something in between metric and time series - its a time series value for a specific timestamp. A metric is an observable property with some defined dimensions (labels). 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. accelerate any But before that, lets talk about the main components of Prometheus. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 an EC2 regions with application servers running docker containers. After a chunk was written into a block and removed from memSeries we might end up with an instance of memSeries that has no chunks. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. To learn more, see our tips on writing great answers. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. what error message are you getting to show that theres a problem? You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. Play with bool 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. If we were to continuously scrape a lot of time series that only exist for a very brief period then we would be slowly accumulating a lot of memSeries in memory until the next garbage collection. This is a deliberate design decision made by Prometheus developers. It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. 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. If our metric had more labels and all of them were set based on the request payload (HTTP method name, IPs, headers, etc) we could easily end up with millions of time series. How can I group labels in a Prometheus query? Finally, please remember that some people read these postings as an email This allows Prometheus to scrape and store thousands of samples per second, our biggest instances are appending 550k samples per second, while also allowing us to query all the metrics simultaneously. attacks, keep I have a data model where some metrics are namespaced by client, environment and deployment name. We can use these to add more information to our metrics so that we can better understand whats going on. Which in turn will double the memory usage of our Prometheus server. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. I.e., there's no way to coerce no datapoints to 0 (zero)? entire corporate networks, Passing sample_limit is the ultimate protection from high cardinality. Bulk update symbol size units from mm to map units in rule-based symbology. But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. 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. Has 90% of ice around Antarctica disappeared in less than a decade? Is it possible to create a concave light? Monitoring Docker container metrics using cAdvisor, Use file-based service discovery to discover scrape targets, Understanding and using the multi-target exporter pattern, Monitoring Linux host metrics with the Node Exporter. "no data". The more any application does for you, the more useful it is, the more resources it might need. What is the point of Thrower's Bandolier? Doubling the cube, field extensions and minimal polynoms. Have a question about this project? When time series disappear from applications and are no longer scraped they still stay in memory until all chunks are written to disk and garbage collection removes them. 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. If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. 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. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. count the number of running instances per application like this: This documentation is open-source. The number of times some specific event occurred. Examples There is a single time series for each unique combination of metrics labels. Both patches give us two levels of protection. The TSDB limit patch protects the entire Prometheus from being overloaded by too many time series. 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. 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. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. 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. Not the answer you're looking for? 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. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. syntax. 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. These queries will give you insights into node health, Pod health, cluster resource utilization, etc. We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. 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. 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? If the total number of stored time series is below the configured limit then we append the sample as usual. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. To get rid of such time series Prometheus will run head garbage collection (remember that Head is the structure holding all memSeries) right after writing a block. TSDB will try to estimate when a given chunk will reach 120 samples and it will set the maximum allowed time for current Head Chunk accordingly. I'm displaying Prometheus query on a Grafana table. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. To learn more about our mission to help build a better Internet, start here. In addition to that in most cases we dont see all possible label values at the same time, its usually a small subset of all possible combinations. Making statements based on opinion; back them up with references or personal experience. and can help you on About an argument in Famine, Affluence and Morality. Asking for help, clarification, or responding to other answers. The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. To set up Prometheus to monitor app metrics: Download and install Prometheus. 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. 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. Better to simply ask under the single best category you think fits and see node_cpu_seconds_total: This returns the total amount of CPU time. You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana.