prometheus query return 0 if no data prometheus query return 0 if no data

by (geo_region) < bool 4 Next you will likely need to create recording and/or alerting rules to make use of your time series. This makes a bit more sense with your explanation. Run the following commands in both nodes to install kubelet, kubeadm, and kubectl. Prometheus and PromQL (Prometheus Query Language) are conceptually very simple, but this means that all the complexity is hidden in the interactions between different elements of the whole metrics pipeline. 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. the problem you have. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. 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. Does Counterspell prevent from any further spells being cast on a given turn? 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. information which you think might be helpful for someone else to understand Internet-scale applications efficiently, Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. rev2023.3.3.43278. You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. Often it doesnt require any malicious actor to cause cardinality related problems. Also, providing a reasonable amount of information about where youre starting How Intuit democratizes AI development across teams through reusability. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. Both patches give us two levels of protection. How to tell which packages are held back due to phased updates. Thanks for contributing an answer to Stack Overflow! 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. Sign up and get Kubernetes tips delivered straight to your inbox. 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. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. This is true both for client libraries and Prometheus server, but its more of an issue for Prometheus itself, since a single Prometheus server usually collects metrics from many applications, while an application only keeps its own metrics. Making statements based on opinion; back them up with references or personal experience. 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 The simplest construct of a PromQL query is an instant vector selector. Thirdly Prometheus is written in Golang which is a language with garbage collection. 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. This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 0. Internally time series names are just another label called __name__, so there is no practical distinction between name and labels. 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. I'd expect to have also: Please use the prometheus-users mailing list for questions. We know that the more labels on a metric, the more time series it can create. If your expression returns anything with labels, it won't match the time series generated by vector(0). 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. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. To learn more, see our tips on writing great answers. These queries are a good starting point. The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. @zerthimon You might want to use 'bool' with your comparator By default Prometheus will create a chunk per each two hours of wall clock. I have a data model where some metrics are namespaced by client, environment and deployment name. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. I'm displaying Prometheus query on a Grafana table. 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. 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. Will this approach record 0 durations on every success? Not the answer you're looking for? Asking for help, clarification, or responding to other answers. Theres no timestamp anywhere actually. Extra fields needed by Prometheus internals. If we configure a sample_limit of 100 and our metrics response contains 101 samples, then Prometheus wont scrape anything at all. 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. Finally you will want to create a dashboard to visualize all your metrics and be able to spot trends. to your account, What did you do? Im new at Grafan and Prometheus. What this means is that a single metric will create one or more time series. We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. You can query Prometheus metrics directly with its own query language: PromQL. 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. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. node_cpu_seconds_total: This returns the total amount of CPU time. Once theyre in TSDB its already too late. name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 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. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. For example, this expression With our custom patch we dont care how many samples are in a scrape. what error message are you getting to show that theres a problem? By clicking Sign up for GitHub, you agree to our terms of service and To your second question regarding whether I have some other label on it, the answer is yes I do. 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. accelerate any If all the label values are controlled by your application you will be able to count the number of all possible label combinations. There is a maximum of 120 samples each chunk can hold. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. There will be traps and room for mistakes at all stages of this process. 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. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. Is a PhD visitor considered as a visiting scholar? Is it possible to create a concave light? ***> wrote: You signed in with another tab or window. So it seems like I'm back to square one. First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. See these docs for details on how Prometheus calculates the returned results. Have you fixed this issue? In our example case its a Counter class object. 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. Those memSeries objects are storing all the time series information. Please help improve it by filing issues or pull requests. type (proc) like this: Assuming this metric contains one time series per running instance, you could 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. 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. 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. 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. We know what a metric, a sample and a time series is. Play with bool to your account. Add field from calculation Binary operation. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. This patchset consists of two main elements. Once we appended sample_limit number of samples we start to be selective. Prometheus will keep each block on disk for the configured retention period. Bulk update symbol size units from mm to map units in rule-based symbology. You signed in with another tab or window. Good to know, thanks for the quick response! 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. Labels are stored once per each memSeries instance. Or maybe we want to know if it was a cold drink or a hot one? Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) If we add another label that can also have two values then we can now export up to eight time series (2*2*2). To learn more about our mission to help build a better Internet, start here. Finally, please remember that some people read these postings as an email In AWS, create two t2.medium instances running CentOS. Are there tables of wastage rates for different fruit and veg? Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. Note that using subqueries unnecessarily is unwise. Another reason is that trying to stay on top of your usage can be a challenging task. 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. You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. Hello, I'm new at Grafan and Prometheus. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. You're probably looking for the absent function. At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. Combined thats a lot of different metrics. About an argument in Famine, Affluence and Morality. But you cant keep everything in memory forever, even with memory-mapping parts of data. I'm sure there's a proper way to do this, but in the end, I used label_replace to add an arbitrary key-value label to each sub-query that I wished to add to the original values, and then applied an or to each. This selector is just a metric name. Please dont post the same question under multiple topics / subjects. First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. 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. 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. This process is also aligned with the wall clock but shifted by one hour. We know that each time series will be kept in memory. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. 2023 The Linux Foundation. Prometheus does offer some options for dealing with high cardinality problems. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Already on GitHub? I've been using comparison operators in Grafana for a long while. Why do many companies reject expired SSL certificates as bugs in bug bounties? Well occasionally send you account related emails. A sample is something in between metric and time series - its a time series value for a specific timestamp. 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. 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. The below posts may be helpful for you to learn more about Kubernetes and our company. But the real risk is when you create metrics with label values coming from the outside world. 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. Why are trials on "Law & Order" in the New York Supreme Court? Is that correct? Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . 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. I'm not sure what you mean by exposing a metric. What happens when somebody wants to export more time series or use longer labels? How to show that an expression of a finite type must be one of the finitely many possible values? It will return 0 if the metric expression does not return anything. source, what your query is, what the query inspector shows, and any other 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. Under which circumstances? If we let Prometheus consume more memory than it can physically use then it will crash. At this point, both nodes should be ready. Stumbled onto this post for something else unrelated, just was +1-ing this :). 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. We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. Prometheus metrics can have extra dimensions in form of labels. I can get the deployments in the dev, uat, and prod environments using this query: So we can see that tenant 1 has 2 deployments in 2 different environments, whereas the other 2 have only one. as text instead of as an image, more people will be able to read it and help. This pod wont be able to run because we dont have a node that has the label disktype: ssd. I used a Grafana transformation which seems to work. Cadvisors on every server provide container names. These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. Making statements based on opinion; back them up with references or personal experience. want to sum over the rate of all instances, so we get fewer output time series, Please open a new issue for related bugs. returns the unused memory in MiB for every instance (on a fictional cluster Using regular expressions, you could select time series only for jobs whose 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. Even i am facing the same issue Please help me on this. In the screenshot below, you can see that I added two queries, A and B, but only . What am I doing wrong here in the PlotLegends specification? Run the following commands in both nodes to configure the Kubernetes repository. t]. If you do that, the line will eventually be redrawn, many times over. 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. 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. A metric is an observable property with some defined dimensions (labels). So, specifically in response to your question: I am facing the same issue - please explain how you configured your data This is because the Prometheus server itself is responsible for timestamps. To set up Prometheus to monitor app metrics: Download and install Prometheus. The number of times some specific event occurred. The more any application does for you, the more useful it is, the more resources it might need. 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.