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. What happens when somebody wants to export more time series or use longer labels? What is the point of Thrower's Bandolier? job and handler labels: Return a whole range of time (in this case 5 minutes up to the query time) In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . Is it possible to rotate a window 90 degrees if it has the same length and width? whether someone is able to help out. We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. I've been using comparison operators in Grafana for a long while. There is an open pull request on the Prometheus repository. The reason why we still allow appends for some samples even after were above sample_limit is that appending samples to existing time series is cheap, its just adding an extra timestamp & value pair. rate (http_requests_total [5m]) [30m:1m] or something like that. 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. Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. Once Prometheus has a list of samples collected from our application it will save it into TSDB - Time Series DataBase - the database in which Prometheus keeps all the time series. 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 Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. 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. PromQL / How to return 0 instead of ' no data' - Medium The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. I used a Grafana transformation which seems to work. Here at Labyrinth Labs, we put great emphasis on monitoring. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 - 05:59, , 22:00 - 23:59. The next layer of protection is checks that run in CI (Continuous Integration) when someone makes a pull request to add new or modify existing scrape configuration for their application. If the error message youre getting (in a log file or on screen) can be quoted To set up Prometheus to monitor app metrics: Download and install Prometheus. What this means is that a single metric will create one or more time series. But before that, lets talk about the main components of Prometheus. Second rule does the same but only sums time series with status labels equal to "500". A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). What is the point of Thrower's Bandolier? as text instead of as an image, more people will be able to read it and help. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. gabrigrec September 8, 2021, 8:12am #8. I made the changes per the recommendation (as I understood it) and defined separate success and fail 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. 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. The simplest construct of a PromQL query is an instant vector selector. What sort of strategies would a medieval military use against a fantasy giant? This article covered a lot of ground. 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. 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. 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. to get notified when one of them is not mounted anymore. 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. bay, Does a summoned creature play immediately after being summoned by a ready action? The below posts may be helpful for you to learn more about Kubernetes and our company. To learn more, see our tips on writing great answers. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. If your expression returns anything with labels, it won't match the time series generated by vector(0). by (geo_region) < bool 4 I'm displaying Prometheus query on a Grafana table. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. It will return 0 if the metric expression does not return anything. 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). Not the answer you're looking for? Name the nodes as Kubernetes Master and Kubernetes Worker. list, which does not convey images, so screenshots etc. The TSDB limit patch protects the entire Prometheus from being overloaded by too many time series. - grafana-7.1.0-beta2.windows-amd64, how did you install it? Operators | Prometheus How To Query Prometheus on Ubuntu 14.04 Part 1 - DigitalOcean which outputs 0 for an empty input vector, but that outputs a scalar You're probably looking for the absent function. Once you cross the 200 time series mark, you should start thinking about your metrics more. Finally you will want to create a dashboard to visualize all your metrics and be able to spot trends. 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. I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. Why are trials on "Law & Order" in the New York Supreme Court? I can get the deployments in the dev, uat, and prod environments using this query: So we can see that tenant 1 has 2 deployments in 2 different environments, whereas the other 2 have only one. Have a question about this project? 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). Those memSeries objects are storing all the time series information. Sign in Is there a solutiuon to add special characters from software and how to do it. from and what youve done will help people to understand your problem. 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. 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. However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. 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. A time series is an instance of that metric, with a unique combination of all the dimensions (labels), plus a series of timestamp & value pairs - hence the name time series. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. count(container_last_seen{name="container_that_doesn't_exist"}), What did you see instead? and can help you on but viewed in the tabular ("Console") view of the expression browser. How to react to a students panic attack in an oral exam? We covered some of the most basic pitfalls in our previous blog post on Prometheus - Monitoring our monitoring. There's also count_scalar(), These are the sane defaults that 99% of application exporting metrics would never exceed. Find centralized, trusted content and collaborate around the technologies you use most. 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. You signed in with another tab or window. Every two hours Prometheus will persist chunks from memory onto the disk. 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. Having a working monitoring setup is a critical part of the work we do for our clients. Please dont post the same question under multiple topics / subjects. Return all time series with the metric http_requests_total: Return all time series with the metric http_requests_total and the given Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. 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. your journey to Zero Trust. rev2023.3.3.43278. However, the queries you will see here are a baseline" audit. 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. Do new devs get fired if they can't solve a certain bug? Cadvisors on every server provide container names. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. Where does this (supposedly) Gibson quote come from? 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. This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. attacks. How do I align things in the following tabular environment? It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. which version of Grafana are you using? Run the following commands in both nodes to disable SELinux and swapping: Also, change SELINUX=enforcing to SELINUX=permissive in the /etc/selinux/config file. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. 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. Basically our labels hash is used as a primary key inside TSDB. Please help improve it by filing issues or pull requests. Or do you have some other label on it, so that the metric still only gets exposed when you record the first failued request it? Prometheus - exclude 0 values from query result - Stack Overflow That's the query ( Counter metric): sum (increase (check_fail {app="monitor"} [20m])) by (reason) The result is a table of failure reason and its count. The process of sending HTTP requests from Prometheus to our application is called scraping. Its least efficient when it scrapes a time series just once and never again - doing so comes with a significant memory usage overhead when compared to the amount of information stored using that memory. Connect and share knowledge within a single location that is structured and easy to search. The more labels you have and the more values each label can take, the more unique combinations you can create and the higher the cardinality. 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. Will this approach record 0 durations on every success? returns the unused memory in MiB for every instance (on a fictional cluster We know what a metric, a sample and a time series is. Well occasionally send you account related emails. This is a deliberate design decision made by Prometheus developers. Already on GitHub? https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. If this query also returns a positive value, then our cluster has overcommitted the memory. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? PromQL allows you to write queries and fetch information from the metric data collected by Prometheus. Any other chunk holds historical samples and therefore is read-only. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. This makes a bit more sense with your explanation. These checks are designed to ensure that we have enough capacity on all Prometheus servers to accommodate extra time series, if that change would result in extra time series being collected. an EC2 regions with application servers running docker containers. @juliusv Thanks for clarifying that. While the sample_limit patch stops individual scrapes from using too much Prometheus capacity, which could lead to creating too many time series in total and exhausting total Prometheus capacity (enforced by the first patch), which would in turn affect all other scrapes since some new time series would have to be ignored. 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. All regular expressions in Prometheus use RE2 syntax. 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. Both of the representations below are different ways of exporting the same time series: Since everything is a label Prometheus can simply hash all labels using sha256 or any other algorithm to come up with a single ID that is unique for each time series. VictoriaMetrics handles rate () function in the common sense way I described earlier! Looking to learn more? PromLabs | Blog - Selecting Data in PromQL 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. 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. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) PROMQL: how to add values when there is no data returned? 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. You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. AFAIK it's not possible to hide them through Grafana. By default Prometheus will create a chunk per each two hours of wall clock. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. 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. Timestamps here can be explicit or implicit. 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. Have you fixed this issue? There is an open pull request which improves memory usage of labels by storing all labels as a single string. How Cloudflare runs Prometheus at scale If a sample lacks any explicit timestamp then it means that the sample represents the most recent value - its the current value of a given time series, and the timestamp is simply the time you make your observation at. Time arrow with "current position" evolving with overlay number. The Head Chunk is never memory-mapped, its always stored in memory. I'd expect to have also: Please use the prometheus-users mailing list for questions. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. 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). name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. 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. The text was updated successfully, but these errors were encountered: It's recommended not to expose data in this way, partially for this reason. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 Connect and share knowledge within a single location that is structured and easy to search. Internally all time series are stored inside a map on a structure called Head. 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. Prometheus does offer some options for dealing with high cardinality problems. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. 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. All rights reserved. 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. In reality though this is as simple as trying to ensure your application doesnt use too many resources, like CPU or memory - you can achieve this by simply allocating less memory and doing fewer computations. I've created an expression that is intended to display percent-success for a given metric. That map uses labels hashes as keys and a structure called memSeries as values. attacks, keep Monitoring our monitoring: how we validate our Prometheus alert rules So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. Both patches give us two levels of protection. 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. it works perfectly if one is missing as count() then returns 1 and the rule fires. This thread has been automatically locked since there has not been any recent activity after it was closed. For that lets follow all the steps in the life of a time series inside Prometheus. 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. SSH into both servers and run the following commands to install Docker. Not the answer you're looking for? ward off DDoS Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. This single sample (data point) will create a time series instance that will stay in memory for over two and a half hours using resources, just so that we have a single timestamp & value pair. 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. The more labels we have or the more distinct values they can have the more time series as a result. 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. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. rev2023.3.3.43278. The subquery for the deriv function uses the default resolution. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. Ive deliberately kept the setup simple and accessible from any address for demonstration. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. There is a single time series for each unique combination of metrics labels. Comparing current data with historical data. This works fine when there are data points for all queries in the expression. Add field from calculation Binary operation. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . 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. Thats why what our application exports isnt really metrics or time series - its samples. 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. Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. 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. First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. Windows 10, how have you configured the query which is causing problems? Another reason is that trying to stay on top of your usage can be a challenging task. what does the Query Inspector show for the query you have a problem with? 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. In general, having more labels on your metrics allows you to gain more insight, and so the more complicated the application you're trying to monitor, the more need for extra labels. Although you can tweak some of Prometheus' behavior and tweak it more for use with short lived time series, by passing one of the hidden flags, its generally discouraged to do so. or Internet application, ward off DDoS 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.