This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. will get matched and propagated to the output. This article covered a lot of ground. Theres only one chunk that we can append to, its called the Head Chunk. an EC2 regions with application servers running docker containers. For instance, the following query would return week-old data for all the time series with node_network_receive_bytes_total name: node_network_receive_bytes_total offset 7d Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. privacy statement. bay, 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. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. 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. 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. What is the point of Thrower's Bandolier? 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. Youve learned about the main components of Prometheus, and its query language, PromQL. The speed at which a vehicle is traveling. The Linux Foundation has registered trademarks and uses trademarks. 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. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? to your account, What did you do? To avoid this its in general best to never accept label values from untrusted sources. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. Better to simply ask under the single best category you think fits and see For example, I'm using the metric to record durations for quantile reporting. 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. Not the answer you're looking for? Have a question about this project? I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). 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. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. 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. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. This is a deliberate design decision made by Prometheus developers. 2023 The Linux Foundation. by (geo_region) < bool 4 But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. Why are trials on "Law & Order" in the New York Supreme Court? which Operating System (and version) are you running it under? 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. 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. 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. You can verify this by running the kubectl get nodes command on the master node. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. Why is there a voltage on my HDMI and coaxial cables? Thank you for subscribing! Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. Are there tables of wastage rates for different fruit and veg? This thread has been automatically locked since there has not been any recent activity after it was closed. 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. This works fine when there are data points for all queries in the expression. If your expression returns anything with labels, it won't match the time series generated by vector(0). Both patches give us two levels of protection. 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. which outputs 0 for an empty input vector, but that outputs a scalar Cardinality is the number of unique combinations of all labels. 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. Up until now all time series are stored entirely in memory and the more time series you have, the higher Prometheus memory usage youll see. 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). So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . If so I'll need to figure out a way to pre-initialize the metric which may be difficult since the label values may not be known a priori. Each Prometheus is scraping a few hundred different applications, each running on a few hundred servers. 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. how have you configured the query which is causing problems? syntax. Doubling the cube, field extensions and minimal polynoms. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. Internet-scale applications efficiently, (fanout by job name) and instance (fanout by instance of the job), we might Improving your monitoring setup by integrating Cloudflares analytics data into Prometheus and Grafana Pint is a tool we developed to validate our Prometheus alerting rules and ensure they are always working website 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. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. Our metric will have a single label that stores the request path. On the worker node, run the kubeadm joining command shown in the last step. Why is this sentence from The Great Gatsby grammatical? We know that time series will stay in memory for a while, even if they were scraped only once. Or maybe we want to know if it was a cold drink or a hot one? 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. Its the chunk responsible for the most recent time range, including the time of our scrape. list, which does not convey images, so screenshots etc. rev2023.3.3.43278. 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. what error message are you getting to show that theres a problem? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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 . If you do that, the line will eventually be redrawn, many times over. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. count the number of running instances per application like this: This documentation is open-source. 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. Connect and share knowledge within a single location that is structured and easy to search. If this query also returns a positive value, then our cluster has overcommitted the memory. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. Passing sample_limit is the ultimate protection from high cardinality. help customers build 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. Does a summoned creature play immediately after being summoned by a ready action? This is one argument for not overusing labels, but often it cannot be avoided. To do that, run the following command on the master node: Next, create an SSH tunnel between your local workstation and the master node by running the following command on your local machine: If everything is okay at this point, you can access the Prometheus console at http://localhost:9090. By clicking Sign up for GitHub, you agree to our terms of service and Prometheus does offer some options for dealing with high cardinality problems. 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. more difficult for those people to help. 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. Finally, please remember that some people read these postings as an email Is a PhD visitor considered as a visiting scholar? The Head Chunk is never memory-mapped, its always stored in memory. In our example we have two labels, content and temperature, and both of them can have two different values. hackers at Why are trials on "Law & Order" in the New York Supreme Court? How to show that an expression of a finite type must be one of the finitely many possible values? entire corporate networks, without any dimensional information. These will give you an overall idea about a clusters health. 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. You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. When Prometheus sends an HTTP request to our application it will receive this response: This format and underlying data model are both covered extensively in Prometheus' own documentation. Simple, clear and working - thanks a lot. Under which circumstances? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. Can airtags be tracked from an iMac desktop, with no iPhone? See this article for details. Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. Is it possible to create a concave light? So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. Connect and share knowledge within a single location that is structured and easy to search. How do I align things in the following tabular environment? 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 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. Well be executing kubectl commands on the master node only. The number of time series depends purely on the number of labels and the number of all possible values these labels can take. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Instead we count time series as we append them to TSDB. Managing the entire lifecycle of a metric from an engineering perspective is a complex process. Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. Adding labels is very easy and all we need to do is specify their names. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. But you cant keep everything in memory forever, even with memory-mapping parts of data. Also, providing a reasonable amount of information about where youre starting By clicking Sign up for GitHub, you agree to our terms of service and Second rule does the same but only sums time series with status labels equal to "500". Those memSeries objects are storing all the time series information. 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. This is what i can see on Query Inspector. 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. Use Prometheus to monitor app performance metrics. Both rules will produce new metrics named after the value of the record field. rev2023.3.3.43278. Timestamps here can be explicit or implicit. It doesnt get easier than that, until you actually try to do it. source, what your query is, what the query inspector shows, and any other node_cpu_seconds_total: This returns the total amount of CPU time. This is an example of a nested subquery. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Are you not exposing the fail metric when there hasn't been a failure yet? Find centralized, trusted content and collaborate around the technologies you use most. 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. In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. How do you get out of a corner when plotting yourself into a corner, Partner is not responding when their writing is needed in European project application. ward off DDoS This holds true for a lot of labels that we see are being used by engineers. count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). There is an open pull request which improves memory usage of labels by storing all labels as a single string. The region and polygon don't match. I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 0. This means that looking at how many time series an application could potentially export, and how many it actually exports, gives us two completely different numbers, which makes capacity planning a lot harder. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? from and what youve done will help people to understand your problem. I have just used the JSON file that is available in below website In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. 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. However, the queries you will see here are a baseline" audit. group by returns a value of 1, so we subtract 1 to get 0 for each deployment and I now wish to add to this the number of alerts that are applicable to each deployment. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Looking to learn more? In Prometheus pulling data is done via PromQL queries and in this article we guide the reader through 11 examples that can be used for Kubernetes specifically. Explanation: Prometheus uses label matching in expressions. What sort of strategies would a medieval military use against a fantasy giant? 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. So the maximum number of time series we can end up creating is four (2*2). Well occasionally send you account related emails. Lets say we have an application which we want to instrument, which means add some observable properties in the form of metrics that Prometheus can read from our application. 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. If we configure a sample_limit of 100 and our metrics response contains 101 samples, then Prometheus wont scrape anything at all. Managed Service for Prometheus https://goo.gle/3ZgeGxv 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? Combined thats a lot of different metrics. Often it doesnt require any malicious actor to cause cardinality related problems. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? This doesnt capture all complexities of Prometheus but gives us a rough estimate of how many time series we can expect to have capacity for. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. @juliusv Thanks for clarifying that. Thirdly Prometheus is written in Golang which is a language with garbage collection. The Prometheus data source plugin provides the following functions you can use in the Query input field. Your needs or your customers' needs will evolve over time and so you cant just draw a line on how many bytes or cpu cycles it can consume. binary operators to them and elements on both sides with the same label set I've been using comparison operators in Grafana for a long while. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. How Intuit democratizes AI development across teams through reusability. 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 Is it possible to rotate a window 90 degrees if it has the same length and width? 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. 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. This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. rev2023.3.3.43278. With our custom patch we dont care how many samples are in a scrape. What is the point of Thrower's Bandolier? What does remote read means in Prometheus? After running the query, a table will show the current value of each result time series (one table row per output series). Run the following commands in both nodes to configure the Kubernetes repository. You signed in with another tab or window. We know what a metric, a sample and a time series is. Using a query that returns "no data points found" in an expression. To your second question regarding whether I have some other label on it, the answer is yes I do. Next, create a Security Group to allow access to the instances. 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. So, specifically in response to your question: I am facing the same issue - please explain how you configured your data Comparing current data with historical data. The more labels you have, or the longer the names and values are, the more memory it will use. How is Jesus " " (Luke 1:32 NAS28) different from a prophet (, Luke 1:76 NAS28)? For that lets follow all the steps in the life of a time series inside Prometheus. attacks, keep By default Prometheus will create a chunk per each two hours of wall clock. Basically our labels hash is used as a primary key inside TSDB. 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. Ive added a data source(prometheus) in Grafana. To get a better idea of this problem lets adjust our example metric to track HTTP requests. Thanks for contributing an answer to Stack Overflow! 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. And this brings us to the definition of cardinality in the context of metrics. 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. AFAIK it's not possible to hide them through Grafana. But the real risk is when you create metrics with label values coming from the outside world. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. or something like that. 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. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. following for every instance: we could get the top 3 CPU users grouped by application (app) and process We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. 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. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. Is there a solutiuon to add special characters from software and how to do it. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. 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. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. Redoing the align environment with a specific formatting. Please help improve it by filing issues or pull requests. feel that its pushy or irritating and therefore ignore it. For example, if someone wants to modify sample_limit, lets say by changing existing limit of 500 to 2,000, for a scrape with 10 targets, thats an increase of 1,500 per target, with 10 targets thats 10*1,500=15,000 extra time series that might be scraped. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. I'm displaying Prometheus query on a Grafana table. 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. You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. I'd expect to have also: Please use the prometheus-users mailing list for questions. 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. Prometheus's query language supports basic logical and arithmetic operators. count(container_last_seen{name="container_that_doesn't_exist"}), What did you see instead? Note that using subqueries unnecessarily is unwise. The more labels we have or the more distinct values they can have the more time series as a result. I was then able to perform a final sum by over the resulting series to reduce the results down to a single result, dropping the ad-hoc labels in the process. The TSDB limit patch protects the entire Prometheus from being overloaded by too many time series.
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