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following for every instance: we could get the top 3 CPU users grouped by application (app) and process Play with bool Lets create a demo Kubernetes cluster and set up Prometheus to monitor it. Youll be executing all these queries in the Prometheus expression browser, so lets get started. Operating such a large Prometheus deployment doesnt come without challenges. 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. Youve learned about the main components of Prometheus, and its query language, PromQL. There are a number of options you can set in your scrape configuration block. 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. You can query Prometheus metrics directly with its own query language: PromQL. Looking to learn more? Just add offset to the query. Using regular expressions, you could select time series only for jobs whose What is the point of Thrower's Bandolier? more difficult for those people to help. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. 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. Or maybe we want to know if it was a cold drink or a hot one? Doubling the cube, field extensions and minimal polynoms. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. Under which circumstances? The main reason why we prefer graceful degradation is that we want our engineers to be able to deploy applications and their metrics with confidence without being subject matter experts in Prometheus. By clicking Sign up for GitHub, you agree to our terms of service and I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. After a few hours of Prometheus running and scraping metrics we will likely have more than one chunk on our time series: Since all these chunks are stored in memory Prometheus will try to reduce memory usage by writing them to disk and memory-mapping. 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. 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. But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. 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. That map uses labels hashes as keys and a structure called memSeries as values. 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. 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. want to sum over the rate of all instances, so we get fewer output time series, Please open a new issue for related bugs. but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. To get a better idea of this problem lets adjust our example metric to track HTTP requests. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. A time series that was only scraped once is guaranteed to live in Prometheus for one to three hours, depending on the exact time of that scrape. 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. Im new at Grafan and Prometheus. Return the per-second rate for all time series with the http_requests_total Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. For example, this expression 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. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. Cadvisors on every server provide container names. @juliusv Thanks for clarifying that. feel that its pushy or irritating and therefore ignore it. @zerthimon The following expr works for me Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. 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. We had a fair share of problems with overloaded Prometheus instances in the past and developed a number of tools that help us deal with them, including custom patches. notification_sender-. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. Are you not exposing the fail metric when there hasn't been a failure yet? On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. Well occasionally send you account related emails. You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. Is that correct? Is a PhD visitor considered as a visiting scholar? This scenario is often described as cardinality explosion - some metric suddenly adds a huge number of distinct label values, creates a huge number of time series, causes Prometheus to run out of memory and you lose all observability as a result. The Graph tab allows you to graph a query expression over a specified range of time. If we make a single request using the curl command: We should see these time series in our application: But what happens if an evil hacker decides to send a bunch of random requests to our application? 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). without any dimensional information. In the screenshot below, you can see that I added two queries, A and B, but only . 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. gabrigrec September 8, 2021, 8:12am #8. Find centralized, trusted content and collaborate around the technologies you use most. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. Sign up and get Kubernetes tips delivered straight to your inbox. Already on GitHub? name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 The text was updated successfully, but these errors were encountered: It's recommended not to expose data in this way, partially for this reason. 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? Once it has a memSeries instance to work with it will append our sample to the Head Chunk. I'm displaying Prometheus query on a Grafana table. 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. 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. 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. Use Prometheus to monitor app performance metrics. Chunks will consume more memory as they slowly fill with more samples, after each scrape, and so the memory usage here will follow a cycle - we start with low memory usage when the first sample is appended, then memory usage slowly goes up until a new chunk is created and we start again. it works perfectly if one is missing as count() then returns 1 and the rule fires. 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. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. 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. With 1,000 random requests we would end up with 1,000 time series in Prometheus. This is because the Prometheus server itself is responsible for timestamps. Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. Already on GitHub? 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. Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. 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. Returns a list of label names. 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. Is there a solutiuon to add special characters from software and how to do it. What am I doing wrong here in the PlotLegends specification? Internet-scale applications efficiently, 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. Once you cross the 200 time series mark, you should start thinking about your metrics more. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. By default Prometheus will create a chunk per each two hours of wall clock. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. PROMQL: how to add values when there is no data returned? 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 metrics can have extra dimensions in form of labels. The speed at which a vehicle is traveling. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. This would happen if any time series was no longer being exposed by any application and therefore there was no scrape that would try to append more samples to it. Next you will likely need to create recording and/or alerting rules to make use of your time series. Managed Service for Prometheus https://goo.gle/3ZgeGxv Not the answer you're looking for? Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. 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). *) in region drops below 4. Using a query that returns "no data points found" in an expression. The result is a table of failure reason and its count. - grafana-7.1.0-beta2.windows-amd64, how did you install it? What video game is Charlie playing in Poker Face S01E07? A common pattern is to export software versions as a build_info metric, Prometheus itself does this too: When Prometheus 2.43.0 is released this metric would be exported as: Which means that a time series with version=2.42.0 label would no longer receive any new samples. Where does this (supposedly) Gibson quote come from? The region and polygon don't match. 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. what does the Query Inspector show for the query you have a problem with? In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . If we let Prometheus consume more memory than it can physically use then it will crash. bay, result of a count() on a query that returns nothing should be 0 ? A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). If we add another label that can also have two values then we can now export up to eight time series (2*2*2). what error message are you getting to show that theres a problem? This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. 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. 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. the problem you have. However when one of the expressions returns no data points found the result of the entire expression is no data points found. To learn more, see our tips on writing great answers. what error message are you getting to show that theres a problem? We can use these to add more information to our metrics so that we can better understand whats going on. to get notified when one of them is not mounted anymore. The actual amount of physical memory needed by Prometheus will usually be higher as a result, since it will include unused (garbage) memory that needs to be freed by Go runtime. "no data". To avoid this its in general best to never accept label values from untrusted sources. job and handler labels: Return a whole range of time (in this case 5 minutes up to the query time) The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. 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. Have you fixed this issue? (pseudocode): This gives the same single value series, or no data if there are no alerts. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. 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. will get matched and propagated to the output. an EC2 regions with application servers running docker containers. Run the following commands in both nodes to configure the Kubernetes repository. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. 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. To get a better understanding of the impact of a short lived time series on memory usage lets take a look at another example. Sign in Every two hours Prometheus will persist chunks from memory onto the disk. 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. You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana. This had the effect of merging the series without overwriting any values. If you need to obtain raw samples, then a range query must be sent to /api/v1/query. 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. Thanks, Can airtags be tracked from an iMac desktop, with no iPhone? Often it doesnt require any malicious actor to cause cardinality related problems. If you're looking for a I'm still out of ideas here. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. However, the queries you will see here are a baseline" audit. For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. 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. See this article for details. Ive added a data source(prometheus) in Grafana. The more any application does for you, the more useful it is, the more resources it might need. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. Finally, please remember that some people read these postings as an email 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. attacks. 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. Is it a bug? 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. Thats why what our application exports isnt really metrics or time series - its samples. But you cant keep everything in memory forever, even with memory-mapping parts of data. @rich-youngkin Yes, the general problem is non-existent series. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Theres no timestamp anywhere actually. Well be executing kubectl commands on the master node only. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. 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. Prometheus does offer some options for dealing with high cardinality problems. Time arrow with "current position" evolving with overlay number. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. 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. We covered some of the most basic pitfalls in our previous blog post on Prometheus - Monitoring our monitoring. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Time series scraped from applications are kept in memory. What sort of strategies would a medieval military use against a fantasy giant? Can I tell police to wait and call a lawyer when served with a search warrant? For that lets follow all the steps in the life of a time series inside Prometheus. In both nodes, edit the /etc/hosts file to add the private IP of the nodes. 1 Like. I used a Grafana transformation which seems to work. All chunks must be aligned to those two hour slots of wall clock time, so if TSDB was building a chunk for 10:00-11:59 and it was already full at 11:30 then it would create an extra chunk for the 11:30-11:59 time range. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. Is it possible to create a concave light? Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. Here at Labyrinth Labs, we put great emphasis on monitoring. @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). from and what youve done will help people to understand your problem. Cadvisors on every server provide container names. So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . 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. To learn more, see our tips on writing great answers. There will be traps and room for mistakes at all stages of this process. 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. This works fine when there are data points for all queries in the expression. I know prometheus has comparison operators but I wasn't able to apply them. and can help you on No error message, it is just not showing the data while using the JSON file from that website. Managed Service for Prometheus Cloud Monitoring Prometheus # ! Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. How do I align things in the following tabular environment? your journey to Zero Trust. Basically our labels hash is used as a primary key inside TSDB. 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. 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. I'm not sure what you mean by exposing a metric. All regular expressions in Prometheus use RE2 syntax. We protect Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. Will this approach record 0 durations on every success? t]. These queries are a good starting point. It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. With our custom patch we dont care how many samples are in a scrape. The Prometheus data source plugin provides the following functions you can use in the Query input field. In this blog post well cover some of the issues one might encounter when trying to collect many millions of time series per Prometheus instance. For that reason we do tolerate some percentage of short lived time series even if they are not a perfect fit for Prometheus and cost us more memory. Our metrics are exposed as a HTTP response. What is the point of Thrower's Bandolier? A metric is an observable property with some defined dimensions (labels). Its the chunk responsible for the most recent time range, including the time of our scrape. as text instead of as an image, more people will be able to read it and help. 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. How can I group labels in a Prometheus query? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA.