In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. Our metrics are exposed as a HTTP response. I.e., there's no way to coerce no datapoints to 0 (zero)? Hello, I'm new at Grafan and Prometheus. 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. or something like that. Also the link to the mailing list doesn't work for me. All rights reserved. In the screenshot below, you can see that I added two queries, A and B, but only . 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. In AWS, create two t2.medium instances running CentOS. attacks, keep 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. For that lets follow all the steps in the life of a time series inside Prometheus. @juliusv Thanks for clarifying that. 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 Of course there are many types of queries you can write, and other useful queries are freely available. 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. The Prometheus data source plugin provides the following functions you can use in the Query input field. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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. @rich-youngkin Yes, the general problem is non-existent series. This gives us confidence that we wont overload any Prometheus server after applying changes. Using a query that returns "no data points found" in an expression. 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. Well occasionally send you account related emails. 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. Its the chunk responsible for the most recent time range, including the time of our scrape. For operations between two instant vectors, the matching behavior can be modified. Simple, clear and working - thanks a lot. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . 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. Thanks for contributing an answer to Stack Overflow! job and handler labels: Return a whole range of time (in this case 5 minutes up to the query time) First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. Have a question about this project? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Even Prometheus' own client libraries had bugs that could expose you to problems like this. our free app that makes your Internet faster and safer. On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. About an argument in Famine, Affluence and Morality. I know prometheus has comparison operators but I wasn't able to apply them. 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. First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. t]. Is a PhD visitor considered as a visiting scholar? information which you think might be helpful for someone else to understand See this article for details. Has 90% of ice around Antarctica disappeared in less than a decade? There is an open pull request on the Prometheus repository. 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. One of the most important layers of protection is a set of patches we maintain on top of Prometheus. All regular expressions in Prometheus use RE2 syntax. So it seems like I'm back to square one. Even i am facing the same issue Please help me on this. 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. It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. attacks. The more any application does for you, the more useful it is, the more resources it might need. it works perfectly if one is missing as count() then returns 1 and the rule fires. The only exception are memory-mapped chunks which are offloaded to disk, but will be read into memory if needed by queries. If the error message youre getting (in a log file or on screen) can be quoted what does the Query Inspector show for the query you have a problem with? Asking for help, clarification, or responding to other answers. 1 Like. In addition to that in most cases we dont see all possible label values at the same time, its usually a small subset of all possible combinations. Adding labels is very easy and all we need to do is specify their names. 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. I can't work out how to add the alerts to the deployments whilst retaining the deployments for which there were no alerts returned: If I use sum with or, then I get this, depending on the order of the arguments to or: If I reverse the order of the parameters to or, I get what I am after: But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. Labels are stored once per each memSeries instance. 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. Not the answer you're looking for? This had the effect of merging the series without overwriting any values. 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. 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. Sign up and get Kubernetes tips delivered straight to your inbox. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? By clicking Sign up for GitHub, you agree to our terms of service and Theres no timestamp anywhere actually. 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. Internet-scale applications efficiently, rev2023.3.3.43278. Our patched logic will then check if the sample were about to append belongs to a time series thats already stored inside TSDB or is it a new time series that needs to be created. That map uses labels hashes as keys and a structure called memSeries as values. Its not going to get you a quicker or better answer, and some people might It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? The Head Chunk is never memory-mapped, its always stored in memory. 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. more difficult for those people to help. These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. 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. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. Managing the entire lifecycle of a metric from an engineering perspective is a complex process. What is the point of Thrower's Bandolier? How to follow the signal when reading the schematic? This thread has been automatically locked since there has not been any recent activity after it was closed. For example, I'm using the metric to record durations for quantile reporting. In general, having more labels on your metrics allows you to gain more insight, and so the more complicated the application you're trying to monitor, the more need for extra labels. Is it a bug? Once configured, your instances should be ready for access. without any dimensional information. At this point, both nodes should be ready. 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. 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. gabrigrec September 8, 2021, 8:12am #8. Before running this query, create a Pod with the following specification: If this query returns a positive value, then the cluster has overcommitted the CPU. 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. ward off DDoS source, what your query is, what the query inspector shows, and any other Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. With any monitoring system its important that youre able to pull out the right data. Passing sample_limit is the ultimate protection from high cardinality. Thank you for subscribing! The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. We know that the more labels on a metric, the more time series it can create. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. How can I group labels in a Prometheus query? Secondly this calculation is based on all memory used by Prometheus, not only time series data, so its just an approximation. 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? 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Thirdly Prometheus is written in Golang which is a language with garbage collection. You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. This pod wont be able to run because we dont have a node that has the label disktype: ssd. want to sum over the rate of all instances, so we get fewer output time series, 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. 2023 The Linux Foundation. To learn more, see our tips on writing great answers. Do new devs get fired if they can't solve a certain bug? but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply Once theyre in TSDB its already too late. Ive added a data source(prometheus) in Grafana. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. Why are trials on "Law & Order" in the New York Supreme Court? By clicking Sign up for GitHub, you agree to our terms of service and Once it has a memSeries instance to work with it will append our sample to the Head Chunk. The Linux Foundation has registered trademarks and uses trademarks. Instead we count time series as we append them to TSDB. Can I tell police to wait and call a lawyer when served with a search warrant? As we mentioned before a time series is generated from metrics. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Another reason is that trying to stay on top of your usage can be a challenging task. This is a deliberate design decision made by Prometheus developers. Cadvisors on every server provide container names. Finally getting back to this. 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. With this simple code Prometheus client library will create a single metric. To get a better idea of this problem lets adjust our example metric to track HTTP requests. This makes a bit more sense with your explanation. 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. Having a working monitoring setup is a critical part of the work we do for our clients. I have just used the JSON file that is available in below website as text instead of as an image, more people will be able to read it and help. "no data". Second rule does the same but only sums time series with status labels equal to "500". Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. 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. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? One Head Chunk - containing up to two hours of the last two hour wall clock slot. Run the following commands in both nodes to install kubelet, kubeadm, and kubectl. If this query also returns a positive value, then our cluster has overcommitted the memory. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, What video game is Charlie playing in Poker Face S01E07? The number of times some specific event occurred. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. It will return 0 if the metric expression does not return anything. I'm displaying Prometheus query on a Grafana table. 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. If we try to append a sample with a timestamp higher than the maximum allowed time for current Head Chunk, then TSDB will create a new Head Chunk and calculate a new maximum time for it based on the rate of appends. One thing you could do though to ensure at least the existence of failure series for the same series which have had successes, you could just reference the failure metric in the same code path without actually incrementing it, like so: That way, the counter for that label value will get created and initialized to 0. windows. Better to simply ask under the single best category you think fits and see prometheus-promql query based on label value, Select largest label value in Prometheus query, Prometheus Query Overall average under a time interval, Prometheus endpoint of all available metrics. Redoing the align environment with a specific formatting. 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. What this means is that a single metric will create one or more time series. Both of the representations below are different ways of exporting the same time series: Since everything is a label Prometheus can simply hash all labels using sha256 or any other algorithm to come up with a single ID that is unique for each time series. We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. I used a Grafana transformation which seems to work. 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. ncdu: What's going on with this second size column? At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Lets adjust the example code to do this. Prometheus does offer some options for dealing with high cardinality problems. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. Going back to our metric with error labels we could imagine a scenario where some operation returns a huge error message, or even stack trace with hundreds of lines. We know that time series will stay in memory for a while, even if they were scraped only once. Find centralized, trusted content and collaborate around the technologies you use most. This patchset consists of two main elements. I have a data model where some metrics are namespaced by client, environment and deployment name. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. For example, this expression your journey to Zero Trust. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. We can use these to add more information to our metrics so that we can better understand whats going on. Making statements based on opinion; back them up with references or personal experience. 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. The process of sending HTTP requests from Prometheus to our application is called scraping. Separate metrics for total and failure will work as expected. Is it possible to create a concave light? A sample is something in between metric and time series - its a time series value for a specific timestamp. 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. are going to make it Is a PhD visitor considered as a visiting scholar? The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. 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. 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.
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