positions. new career direction, check out our open In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. 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. - grafana-7.1.0-beta2.windows-amd64, how did you install it? binary operators to them and elements on both sides with the same label set 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. rev2023.3.3.43278. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . This had the effect of merging the series without overwriting any values. an EC2 regions with application servers running docker containers. I've created an expression that is intended to display percent-success for a given metric. website 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. 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. 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 thread has been automatically locked since there has not been any recent activity after it was closed. privacy statement. entire corporate networks, Asking for help, clarification, or responding to other answers. The more any application does for you, the more useful it is, the more resources it might need. A metric can be anything that you can express as a number, for example: To create metrics inside our application we can use one of many Prometheus client libraries. This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. 1 Like. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Its very easy to keep accumulating time series in Prometheus until you run out of memory. 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. You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. Good to know, thanks for the quick response! 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. 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. Prometheus - exclude 0 values from query result - Stack Overflow 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. Please see data model and exposition format pages for more details. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Name the nodes as Kubernetes Master and Kubernetes Worker. 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. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. 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. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. Now we should pause to make an important distinction between metrics and time series. Minimising the environmental effects of my dyson brain. Ive deliberately kept the setup simple and accessible from any address for demonstration. your journey to Zero Trust. Under which circumstances? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. metric name, as measured over the last 5 minutes: Assuming that the http_requests_total time series all have the labels job 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. If, on the other hand, we want to visualize the type of data that Prometheus is the least efficient when dealing with, well end up with this instead: Here we have single data points, each for a different property that we measure. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. With this simple code Prometheus client library will create a single metric. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. count the number of running instances per application like this: This documentation is open-source. 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. Note that using subqueries unnecessarily is unwise. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. 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. privacy statement. The speed at which a vehicle is traveling. No error message, it is just not showing the data while using the JSON file from that website. Connect and share knowledge within a single location that is structured and easy to search. 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. and can help you on Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. I've added a data source (prometheus) in Grafana. 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. 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. At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. 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. 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. If we configure a sample_limit of 100 and our metrics response contains 101 samples, then Prometheus wont scrape anything at all. I'm still out of ideas here. A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). Of course there are many types of queries you can write, and other useful queries are freely available. 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. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? 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. which version of Grafana are you using? If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? Return all time series with the metric http_requests_total: Return all time series with the metric http_requests_total and the given You can verify this by running the kubectl get nodes command on the master node. Once configured, your instances should be ready for access. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. whether someone is able to help out. This article covered a lot of ground. Making statements based on opinion; back them up with references or personal experience. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. I'm not sure what you mean by exposing a metric. promql - Prometheus query check if value exist - Stack Overflow 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. PROMQL: how to add values when there is no data returned? or something like that. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. 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). Im new at Grafan and Prometheus. 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. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. Using a query that returns "no data points found" in an expression. That map uses labels hashes as keys and a structure called memSeries as values. 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. These are the sane defaults that 99% of application exporting metrics would never exceed. Finally getting back to this. 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. Returns a list of label values for the label in every metric. Asking for help, clarification, or responding to other answers. If the error message youre getting (in a log file or on screen) can be quoted One of the first problems youre likely to hear about when you start running your own Prometheus instances is cardinality, with the most dramatic cases of this problem being referred to as cardinality explosion. 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 AWS, create two t2.medium instances running CentOS. Is that correct? 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 have just used the JSON file that is available in below website 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. 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 What is the point of Thrower's Bandolier? Explanation: Prometheus uses label matching in expressions. What video game is Charlie playing in Poker Face S01E07? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . 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. However when one of the expressions returns no data points found the result of the entire expression is no data points found. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Once we appended sample_limit number of samples we start to be selective. following for every instance: we could get the top 3 CPU users grouped by application (app) and process Prometheus query check if value exist. So the maximum number of time series we can end up creating is four (2*2). Have a question about this project? 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. 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. How to follow the signal when reading the schematic? Finally we maintain a set of internal documentation pages that try to guide engineers through the process of scraping and working with metrics, with a lot of information thats specific to our environment. 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. @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). Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) Does Counterspell prevent from any further spells being cast on a given turn? 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. Next, create a Security Group to allow access to the instances. Managed Service for Prometheus https://goo.gle/3ZgeGxv You signed in with another tab or window. Subscribe to receive notifications of new posts: Subscription confirmed. Comparing current data with historical data. 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. The more labels we have or the more distinct values they can have the more time series as a result. I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. Also the link to the mailing list doesn't work for me. count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). 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. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. https://grafana.com/grafana/dashboards/2129. 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. VictoriaMetrics handles rate () function in the common sense way I described earlier! So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. Is a PhD visitor considered as a visiting scholar? Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. Hello, I'm new at Grafan and Prometheus. A sample is something in between metric and time series - its a time series value for a specific timestamp. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. What does remote read means in Prometheus? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 There will be traps and room for mistakes at all stages of this process. How can I group labels in a Prometheus query? It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. which Operating System (and version) are you running it under? 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. And this brings us to the definition of cardinality in the context of metrics. Are there tables of wastage rates for different fruit and veg? Cadvisors on every server provide container names. If so it seems like this will skew the results of the query (e.g., quantiles). Combined thats a lot of different metrics. We know that time series will stay in memory for a while, even if they were scraped only once. notification_sender-. Not the answer you're looking for? At this point we should know a few things about Prometheus: With all of that in mind we can now see the problem - a metric with high cardinality, especially one with label values that come from the outside world, can easily create a huge number of time series in a very short time, causing cardinality explosion. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. About an argument in Famine, Affluence and Morality. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. Labels are stored once per each memSeries instance. Looking to learn more? This process is also aligned with the wall clock but shifted by one hour. Making statements based on opinion; back them up with references or personal experience. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. How to show that an expression of a finite type must be one of the finitely many possible values? (pseudocode): This gives the same single value series, or no data if there are no alerts. Yeah, absent() is probably the way to go. 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. By default Prometheus will create a chunk per each two hours of wall clock. 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. Using the Prometheus data source - Amazon Managed Grafana Is what you did above (failures.WithLabelValues) an example of "exposing"? Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. How to react to a students panic attack in an oral exam? without any dimensional information. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. count() should result in 0 if no timeseries found #4982 - GitHub After sending a request it will parse the response looking for all the samples exposed there. Find centralized, trusted content and collaborate around the technologies you use most. Also, providing a reasonable amount of information about where youre starting Is there a single-word adjective for "having exceptionally strong moral principles"? Not the answer you're looking for? This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. AFAIK it's not possible to hide them through Grafana. 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? These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. 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. 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. 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. 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. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. For operations between two instant vectors, the matching behavior can be modified. gabrigrec September 8, 2021, 8:12am #8. 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. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply Querying basics | Prometheus You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. Can airtags be tracked from an iMac desktop, with no iPhone? 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. 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.