Why are trials on "Law & Order" in the New York Supreme Court? What sort of strategies would a medieval military use against a fantasy giant? Managed Service for Prometheus https://goo.gle/3ZgeGxv With any monitoring system its important that youre able to pull out the right data. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Finally, please remember that some people read these postings as an email Using regular expressions, you could select time series only for jobs whose I'm sure there's a proper way to do this, but in the end, I used label_replace to add an arbitrary key-value label to each sub-query that I wished to add to the original values, and then applied an or to each. 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. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. Often it doesnt require any malicious actor to cause cardinality related problems. Will this approach record 0 durations on every success? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Every two hours Prometheus will persist chunks from memory onto the disk. Internally all time series are stored inside a map on a structure called Head. Samples are compressed using encoding that works best if there are continuous updates. All they have to do is set it explicitly in their scrape configuration. 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. We know that the more labels on a metric, the more time series it can create. following for every instance: we could get the top 3 CPU users grouped by application (app) and process Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. A sample is something in between metric and time series - its a time series value for a specific timestamp. Is it a bug? Operating such a large Prometheus deployment doesnt come without challenges. 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. Also the link to the mailing list doesn't work for me. 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. This works well if errors that need to be handled are generic, for example Permission Denied: But if the error string contains some task specific information, for example the name of the file that our application didnt have access to, or a TCP connection error, then we might easily end up with high cardinality metrics this way: Once scraped all those time series will stay in memory for a minimum of one hour. count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). 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. type (proc) like this: Assuming this metric contains one time series per running instance, you could 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. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. 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? 1 Like. In both nodes, edit the /etc/sysctl.d/k8s.conf file to add the following two lines: Then reload the IPTables config using the sudo sysctl --system command. more difficult for those people to help. The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. Can airtags be tracked from an iMac desktop, with no iPhone? How to react to a students panic attack in an oral exam? This is an example of a nested subquery. The below posts may be helpful for you to learn more about Kubernetes and our company. Prometheus has gained a lot of market traction over the years, and when combined with other open-source tools like Grafana, it provides a robust monitoring solution. the problem you have. Prometheus does offer some options for dealing with high cardinality problems. ***> wrote: You signed in with another tab or window. For example our errors_total metric, which we used in example before, might not be present at all until we start seeing some errors, and even then it might be just one or two errors that will be recorded. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. This works fine when there are data points for all queries in the expression. vishnur5217 May 31, 2020, 3:44am 1. Thirdly Prometheus is written in Golang which is a language with garbage collection. Asking for help, clarification, or responding to other answers. Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. There's also count_scalar(), https://grafana.com/grafana/dashboards/2129. Next you will likely need to create recording and/or alerting rules to make use of your time series. Here at Labyrinth Labs, we put great emphasis on monitoring. 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. 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. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. 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. Select the query and do + 0. Is there a single-word adjective for "having exceptionally strong moral principles"? 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. 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. If we add another label that can also have two values then we can now export up to eight time series (2*2*2). it works perfectly if one is missing as count() then returns 1 and the rule fires. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . gabrigrec September 8, 2021, 8:12am #8. Making statements based on opinion; back them up with references or personal experience. 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. There is a single time series for each unique combination of metrics labels. The number of time series depends purely on the number of labels and the number of all possible values these labels can take. Is it possible to create a concave light? Is a PhD visitor considered as a visiting scholar? positions. By default Prometheus will create a chunk per each two hours of wall clock. 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. Is what you did above (failures.WithLabelValues) an example of "exposing"? Internet-scale applications efficiently, 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. @zerthimon You might want to use 'bool' with your comparator We protect 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. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 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. This patchset consists of two main elements. Finally getting back to this. Managed Service for Prometheus Cloud Monitoring Prometheus # ! Cadvisors on every server provide container names. So the maximum number of time series we can end up creating is four (2*2). By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. *) in region drops below 4. Why are physically impossible and logically impossible concepts considered separate in terms of probability? Its the chunk responsible for the most recent time range, including the time of our scrape. 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. 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. This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. 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. 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. 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. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) 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. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. Both patches give us two levels of protection. Why do many companies reject expired SSL certificates as bugs in bug bounties? If all the label values are controlled by your application you will be able to count the number of all possible label combinations. Good to know, thanks for the quick response! The number of times some specific event occurred. rev2023.3.3.43278. 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 . But before doing that it needs to first check which of the samples belong to the time series that are already present inside TSDB and which are for completely new time series. I've added a data source (prometheus) in Grafana. Separate metrics for total and failure will work as expected. In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. how have you configured the query which is causing problems? It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. Finally you will want to create a dashboard to visualize all your metrics and be able to spot trends. Play with bool The Graph tab allows you to graph a query expression over a specified range of time. 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. 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. Yeah, absent() is probably the way to go. How to show that an expression of a finite type must be one of the finitely many possible values? Or maybe we want to know if it was a cold drink or a hot one? @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). If so it seems like this will skew the results of the query (e.g., quantiles). To learn more, see our tips on writing great answers. For that lets follow all the steps in the life of a time series inside Prometheus. 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. The idea is that if done as @brian-brazil mentioned, there would always be a fail and success metric, because they are not distinguished by a label, but always are exposed. Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. Im new at Grafan and Prometheus. How do I align things in the following tabular environment? We know that time series will stay in memory for a while, even if they were scraped only once. The Head Chunk is never memory-mapped, its always stored in memory. Doubling the cube, field extensions and minimal polynoms. Labels are stored once per each memSeries instance. 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. 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 but it does not fire if both are missing because than count() returns no data the workaround is to additionally check with absent() but it's on the one hand annoying to double-check on each rule and on the other hand count should be able to "count" zero . This thread has been automatically locked since there has not been any recent activity after it was closed. 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. What does remote read means in Prometheus? I'm displaying Prometheus query on a Grafana table. As we mentioned before a time series is generated from metrics. 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. First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. Using a query that returns "no data points found" in an expression. and can help you on If we let Prometheus consume more memory than it can physically use then it will crash. 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. 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. This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. It will return 0 if the metric expression does not return anything. Comparing current data with historical data. Prometheus's query language supports basic logical and arithmetic operators. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. source, what your query is, what the query inspector shows, and any other The speed at which a vehicle is traveling. We know that each time series will be kept in memory. It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. Find centralized, trusted content and collaborate around the technologies you use most. Next, create a Security Group to allow access to the instances. Ive added a data source(prometheus) in Grafana. or something like that. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. To make things more complicated you may also hear about samples when reading Prometheus documentation. your journey to Zero Trust. 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 we appended sample_limit number of samples we start to be selective. 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. After running the query, a table will show the current value of each result time series (one table row per output series). To your second question regarding whether I have some other label on it, the answer is yes I do. Well occasionally send you account related emails. 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). This holds true for a lot of labels that we see are being used by engineers. For a list of trademarks of The Linux Foundation, please see our Trademark Usage page.
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prometheus query return 0 if no data