Sign up for a free GitHub account to open an issue and contact its maintainers and the community. 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. By clicking Sign up for GitHub, you agree to our terms of service and Passing sample_limit is the ultimate protection from high cardinality. website Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. Once configured, your instances should be ready for access. @juliusv Thanks for clarifying that. If the total number of stored time series is below the configured limit then we append the sample as usual. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. 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 This had the effect of merging the series without overwriting any values. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. 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. Please help improve it by filing issues or pull requests. PromQL tutorial for beginners and humans - Medium PROMQL: how to add values when there is no data returned? an EC2 regions with application servers running docker containers. 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. Combined thats a lot of different metrics. What am I doing wrong here in the PlotLegends specification? We know that time series will stay in memory for a while, even if they were scraped only once. 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. Minimising the environmental effects of my dyson brain. Its the chunk responsible for the most recent time range, including the time of our scrape. I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). These will give you an overall idea about a clusters health. Returns a list of label values for the label in every metric. attacks, keep Prometheus's query language supports basic logical and arithmetic operators. Here is the extract of the relevant options from Prometheus documentation: Setting all the label length related limits allows you to avoid a situation where extremely long label names or values end up taking too much memory. However when one of the expressions returns no data points found the result of the entire expression is no data points found. 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. This selector is just a metric name. 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. Where does this (supposedly) Gibson quote come from? 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. Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. Is there a single-word adjective for "having exceptionally strong moral principles"? Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. This page will guide you through how to install and connect Prometheus and Grafana. With 1,000 random requests we would end up with 1,000 time series in 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. 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. To get a better idea of this problem lets adjust our example metric to track HTTP requests. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. syntax. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Finally getting back to this. which Operating System (and version) are you running it under? Chunks that are a few hours old are written to disk and removed from memory. How to react to a students panic attack in an oral exam? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. These queries are a good starting point. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. Our metrics are exposed as a HTTP response. With our custom patch we dont care how many samples are in a scrape. Returns a list of label names. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Explanation: Prometheus uses label matching in expressions. We know that each time series will be kept in memory. source, what your query is, what the query inspector shows, and any other Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. The next layer of protection is checks that run in CI (Continuous Integration) when someone makes a pull request to add new or modify existing scrape configuration for their application. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. PromQL / How to return 0 instead of ' no data' - Medium for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. rev2023.3.3.43278. Next, create a Security Group to allow access to the instances. I used a Grafana transformation which seems to work. Has 90% of ice around Antarctica disappeared in less than a decade? I then hide the original query. It would be easier if we could do this in the original query though. rate (http_requests_total [5m]) [30m:1m] But the real risk is when you create metrics with label values coming from the outside world. count the number of running instances per application like this: This documentation is open-source. 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. Looking to learn more? We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. Once we appended sample_limit number of samples we start to be selective. No error message, it is just not showing the data while using the JSON file from that website. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. following for every instance: we could get the top 3 CPU users grouped by application (app) and process Timestamps here can be explicit or implicit. Are you not exposing the fail metric when there hasn't been a failure yet? @zerthimon You might want to use 'bool' with your comparator First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. We also limit the length of label names and values to 128 and 512 characters, which again is more than enough for the vast majority of scrapes. 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. Querying examples | Prometheus If we add another label that can also have two values then we can now export up to eight time series (2*2*2). Is a PhD visitor considered as a visiting scholar? it works perfectly if one is missing as count() then returns 1 and the rule fires. If so it seems like this will skew the results of the query (e.g., quantiles). new career direction, check out our open Its not going to get you a quicker or better answer, and some people might Prometheus query check if value exist. Have you fixed this issue? If we configure a sample_limit of 100 and our metrics response contains 101 samples, then Prometheus wont scrape anything at all. which outputs 0 for an empty input vector, but that outputs a scalar 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. But before that, lets talk about the main components of Prometheus. I'm not sure what you mean by exposing a metric. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. I'm displaying Prometheus query on a Grafana table. 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. This thread has been automatically locked since there has not been any recent activity after it was closed. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I'm still out of ideas here. 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 . 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. Sign in Is what you did above (failures.WithLabelValues) an example of "exposing"? It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. returns the unused memory in MiB for every instance (on a fictional cluster These checks are designed to ensure that we have enough capacity on all Prometheus servers to accommodate extra time series, if that change would result in extra time series being collected. The more labels you have and the more values each label can take, the more unique combinations you can create and the higher the cardinality. Once theyre in TSDB its already too late. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. There will be traps and room for mistakes at all stages of this process. What this means is that a single metric will create one or more time series. What happens when somebody wants to export more time series or use longer labels? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Theres no timestamp anywhere actually. Is a PhD visitor considered as a visiting scholar? 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. 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. Im new at Grafan and Prometheus. For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. So just calling WithLabelValues() should make a metric appear, but only at its initial value (0 for normal counters and histogram bucket counters, NaN for summary quantiles). For example, I'm using the metric to record durations for quantile reporting. result of a count() on a query that returns nothing should be 0 ? Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Prometheus Queries: 11 PromQL Examples and Tutorial - ContainIQ Examples Or maybe we want to know if it was a cold drink or a hot one? Find centralized, trusted content and collaborate around the technologies you use most. Thirdly Prometheus is written in Golang which is a language with garbage collection. The simplest construct of a PromQL query is an instant vector selector. Note that using subqueries unnecessarily is unwise. Using a query that returns "no data points found" in an - GitHub Ive added a data source(prometheus) in Grafana. *) in region drops below 4. Even i am facing the same issue Please help me on this. 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. privacy statement. Secondly this calculation is based on all memory used by Prometheus, not only time series data, so its just an approximation. The process of sending HTTP requests from Prometheus to our application is called scraping. There is a maximum of 120 samples each chunk can hold. A metric is an observable property with some defined dimensions (labels). The number of times some specific event occurred. It will return 0 if the metric expression does not return anything. 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. Time arrow with "current position" evolving with overlay number. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. Better to simply ask under the single best category you think fits and see Separate metrics for total and failure will work as expected. You can verify this by running the kubectl get nodes command on the master node. Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. entire corporate networks, 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.