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

So perhaps the behavior I'm running into applies to any metric with a label, whereas a metric without any labels would behave as @brian-brazil indicated? This thread has been automatically locked since there has not been any recent activity after it was closed. The region and polygon don't match. What happens when somebody wants to export more time series or use longer labels? Sign up and get Kubernetes tips delivered straight to your inbox. which outputs 0 for an empty input vector, but that outputs a scalar That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). 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. 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. Using a query that returns "no data points found" in an - GitHub are going to make it This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. Or maybe we want to know if it was a cold drink or a hot one? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. I have just used the JSON file that is available in below website 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. Once you cross the 200 time series mark, you should start thinking about your metrics more. 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. To this end, I set up the query to instant so that the very last data point is returned but, when the query does not return a value - say because the server is down and/or no scraping took place - the stat panel produces no data. Do new devs get fired if they can't solve a certain bug? Find centralized, trusted content and collaborate around the technologies you use most. 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. 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. Second rule does the same but only sums time series with status labels equal to "500". If instead of beverages we tracked the number of HTTP requests to a web server, and we used the request path as one of the label values, then anyone making a huge number of random requests could force our application to create a huge number of time series. To select all HTTP status codes except 4xx ones, you could run: Return the 5-minute rate of the http_requests_total metric for the past 30 minutes, with a resolution of 1 minute. Which in turn will double the memory usage of our Prometheus server. This holds true for a lot of labels that we see are being used by engineers. The more labels we have or the more distinct values they can have the more time series as a result. If your expression returns anything with labels, it won't match the time series generated by vector(0). 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. Next you will likely need to create recording and/or alerting rules to make use of your time series. Thank you for subscribing! If you do that, the line will eventually be redrawn, many times over. *) in region drops below 4. Theres only one chunk that we can append to, its called the Head Chunk. 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. The number of time series depends purely on the number of labels and the number of all possible values these labels can take. Is there a solutiuon to add special characters from software and how to do it. PROMQL: how to add values when there is no data returned? TSDB will try to estimate when a given chunk will reach 120 samples and it will set the maximum allowed time for current Head Chunk accordingly. 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. Windows 10, how have you configured the query which is causing problems? Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Lets see what happens if we start our application at 00:25, allow Prometheus to scrape it once while it exports: And then immediately after the first scrape we upgrade our application to a new version: At 00:25 Prometheus will create our memSeries, but we will have to wait until Prometheus writes a block that contains data for 00:00-01:59 and runs garbage collection before that memSeries is removed from memory, which will happen at 03:00. Can airtags be tracked from an iMac desktop, with no iPhone? Now comes the fun stuff. I'm displaying Prometheus query on a Grafana table. Samples are compressed using encoding that works best if there are continuous updates. This page will guide you through how to install and connect Prometheus and Grafana. without any dimensional information. These will give you an overall idea about a clusters health. Why are physically impossible and logically impossible concepts considered separate in terms of probability? Have a question about this project? Inside the Prometheus configuration file we define a scrape config that tells Prometheus where to send the HTTP request, how often and, optionally, to apply extra processing to both requests and responses. Thanks for contributing an answer to Stack Overflow! 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. 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. Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. Its very easy to keep accumulating time series in Prometheus until you run out of memory. @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). Have a question about this project? count() should result in 0 if no timeseries found #4982 - GitHub This garbage collection, among other things, will look for any time series without a single chunk and remove it from memory. Its the chunk responsible for the most recent time range, including the time of our scrape. Returns a list of label names. Finally you will want to create a dashboard to visualize all your metrics and be able to spot trends. 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. 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. syntax. Return the per-second rate for all time series with the http_requests_total 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. By merging multiple blocks together, big portions of that index can be reused, allowing Prometheus to store more data using the same amount of storage space. It will return 0 if the metric expression does not return anything. The struct definition for memSeries is fairly big, but all we really need to know is that it has a copy of all the time series labels and chunks that hold all the samples (timestamp & value pairs). 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. Is a PhD visitor considered as a visiting scholar? One of the most important layers of protection is a set of patches we maintain on top of Prometheus. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Well be executing kubectl commands on the master node only. Why do many companies reject expired SSL certificates as bugs in bug bounties? For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. This scenario is often described as cardinality explosion - some metric suddenly adds a huge number of distinct label values, creates a huge number of time series, causes Prometheus to run out of memory and you lose all observability as a result. Monitor Confluence with Prometheus and Grafana | Confluence Data Center Combined thats a lot of different metrics. A sample is something in between metric and time series - its a time series value for a specific timestamp. Youll be executing all these queries in the Prometheus expression browser, so lets get started. However when one of the expressions returns no data points found the result of the entire expression is no data points found. But you cant keep everything in memory forever, even with memory-mapping parts of data. to your account, What did you do? But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. Querying examples | Prometheus Is a PhD visitor considered as a visiting scholar? Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. Ive deliberately kept the setup simple and accessible from any address for demonstration. Next, create a Security Group to allow access to the instances. To avoid this its in general best to never accept label values from untrusted sources. If this query also returns a positive value, then our cluster has overcommitted the memory. Returns a list of label values for the label in every metric. Are there tables of wastage rates for different fruit and veg? How Cloudflare runs Prometheus at scale Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. 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. privacy statement. notification_sender-. If we add another label that can also have two values then we can now export up to eight time series (2*2*2). It doesnt get easier than that, until you actually try to do it. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. 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. With 1,000 random requests we would end up with 1,000 time series in Prometheus. to get notified when one of them is not mounted anymore. How can i turn no data to zero in Loki - Grafana Loki - Grafana Labs 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. Minimising the environmental effects of my dyson brain. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, 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. 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). I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. 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. 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. Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. PromQL / How to return 0 instead of ' no data' - Medium I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. Add field from calculation Binary operation. By clicking Sign up for GitHub, you agree to our terms of service and 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. If both the nodes are running fine, you shouldnt get any result for this query. 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. How to follow the signal when reading the schematic? Where does this (supposedly) Gibson quote come from? To make things more complicated you may also hear about samples when reading Prometheus documentation. Why is there a voltage on my HDMI and coaxial cables? I'd expect to have also: Please use the prometheus-users mailing list for questions. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. and can help you on 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. 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. Finally, please remember that some people read these postings as an email (fanout by job name) and instance (fanout by instance of the job), we might rev2023.3.3.43278. 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. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. The Head Chunk is never memory-mapped, its always stored in memory. 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 more labels you have and the more values each label can take, the more unique combinations you can create and the higher the cardinality. If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. 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. These queries are a good starting point. Please dont post the same question under multiple topics / subjects. We covered some of the most basic pitfalls in our previous blog post on Prometheus - Monitoring our monitoring. The below posts may be helpful for you to learn more about Kubernetes and our company. Managing the entire lifecycle of a metric from an engineering perspective is a complex process. You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana. 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. You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. Making statements based on opinion; back them up with references or personal experience. 2023 The Linux Foundation. This is because the Prometheus server itself is responsible for timestamps. 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. Asking for help, clarification, or responding to other answers. 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. The simplest way of doing this is by using functionality provided with client_python itself - see documentation here. 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. Select the query and do + 0. Any other chunk holds historical samples and therefore is read-only. Does a summoned creature play immediately after being summoned by a ready action? What sort of strategies would a medieval military use against a fantasy giant? 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. No Data is showing on Grafana Dashboard - Prometheus - Grafana Labs 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. This article covered a lot of ground. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. No, only calling Observe() on a Summary or Histogram metric will add any observations (and only calling Inc() on a counter metric will increment it). The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. more difficult for those people to help. Basically our labels hash is used as a primary key inside TSDB. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. Subscribe to receive notifications of new posts: Subscription confirmed. Run the following commands in both nodes to install kubelet, kubeadm, and kubectl. Better Prometheus rate() Function with VictoriaMetrics positions. I used a Grafana transformation which seems to work. Prometheus does offer some options for dealing with high cardinality problems. gabrigrec September 8, 2021, 8:12am #8. 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. Not the answer you're looking for? 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 Our metric will have a single label that stores the request path. 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. You can calculate how much memory is needed for your time series by running this query on your Prometheus server: Note that your Prometheus server must be configured to scrape itself for this to work. If we let Prometheus consume more memory than it can physically use then it will crash. 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 our example case its a Counter class object. To your second question regarding whether I have some other label on it, the answer is yes I do. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. Timestamps here can be explicit or implicit. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. There is an open pull request on the Prometheus repository. Both patches give us two levels of protection.