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

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. Its least efficient when it scrapes a time series just once and never again - doing so comes with a significant memory usage overhead when compared to the amount of information stored using that memory. Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. One Head Chunk - containing up to two hours of the last two hour wall clock slot. ward off DDoS 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. This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. Stumbled onto this post for something else unrelated, just was +1-ing this :). 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. 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. returns the unused memory in MiB for every instance (on a fictional cluster 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. Redoing the align environment with a specific formatting. Asking for help, clarification, or responding to other answers. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. This means that our memSeries still consumes some memory (mostly labels) but doesnt really do anything. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. The process of sending HTTP requests from Prometheus to our application is called scraping. 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. 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. Thirdly Prometheus is written in Golang which is a language with garbage collection. In AWS, create two t2.medium instances running CentOS. Making statements based on opinion; back them up with references or personal experience. With our custom patch we dont care how many samples are in a scrape. But before that, lets talk about the main components of Prometheus. To your second question regarding whether I have some other label on it, the answer is yes I do. If we make a single request using the curl command: We should see these time series in our application: But what happens if an evil hacker decides to send a bunch of random requests to our application? How Intuit democratizes AI development across teams through reusability. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. Connect and share knowledge within a single location that is structured and easy to search. whether someone is able to help out. Connect and share knowledge within a single location that is structured and easy to search. Its also worth mentioning that without our TSDB total limit patch we could keep adding new scrapes to Prometheus and that alone could lead to exhausting all available capacity, even if each scrape had sample_limit set and scraped fewer time series than this limit allows. Connect and share knowledge within a single location that is structured and easy to search. We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. Is what you did above (failures.WithLabelValues) an example of "exposing"? In both nodes, edit the /etc/hosts file to add the private IP of the nodes. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. If the error message youre getting (in a log file or on screen) can be quoted What is the point of Thrower's Bandolier? Passing sample_limit is the ultimate protection from high cardinality. Does Counterspell prevent from any further spells being cast on a given turn? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Thanks, 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. 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. Looking to learn more? 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. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. This article covered a lot of ground. Operating such a large Prometheus deployment doesnt come without challenges. With any monitoring system its important that youre able to pull out the right data. 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 . Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. gabrigrec September 8, 2021, 8:12am #8. This is because the Prometheus server itself is responsible for timestamps. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Managed Service for Prometheus https://goo.gle/3ZgeGxv How do I align things in the following tabular environment? Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. Bulk update symbol size units from mm to map units in rule-based symbology. In the screenshot below, you can see that I added two queries, A and B, but only . Run the following commands in both nodes to configure the Kubernetes repository. 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. Are there tables of wastage rates for different fruit and veg? rev2023.3.3.43278. You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana. Finally getting back to this. For example, this expression Have a question about this project? For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. 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. 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. You signed in with another tab or window. 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? We know that each time series will be kept in memory. Under which circumstances? Returns a list of label values for the label in every metric. I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. Timestamps here can be explicit or implicit. 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. Its not going to get you a quicker or better answer, and some people might We know that the more labels on a metric, the more time series it can create. Looking at memory usage of such Prometheus server we would see this pattern repeating over time: The important information here is that short lived time series are expensive. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. Even i am facing the same issue Please help me on this. 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. or Internet application, 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. our free app that makes your Internet faster and safer. 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. Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. What sort of strategies would a medieval military use against a fantasy giant? Now comes the fun stuff. You can query Prometheus metrics directly with its own query language: PromQL. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. Is a PhD visitor considered as a visiting scholar? When Prometheus collects metrics it records the time it started each collection and then it will use it to write timestamp & value pairs for each time series. syntax. All rights reserved. We can use these to add more information to our metrics so that we can better understand whats going on. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. Once it has a memSeries instance to work with it will append our sample to the Head Chunk. It would be easier if we could do this in the original query though. Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. To learn more about our mission to help build a better Internet, start here. To make things more complicated you may also hear about samples when reading Prometheus documentation. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) No error message, it is just not showing the data while using the JSON file from that website. Extra fields needed by Prometheus internals. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. but viewed in the tabular ("Console") view of the expression browser. The number of times some specific event occurred. So, specifically in response to your question: I am facing the same issue - please explain how you configured your data 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. 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. 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. In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . positions. Thanks for contributing an answer to Stack Overflow! So the maximum number of time series we can end up creating is four (2*2). After sending a request it will parse the response looking for all the samples exposed there. 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. I'm displaying Prometheus query on a Grafana table. Better to simply ask under the single best category you think fits and see which Operating System (and version) are you running it under? Doubling the cube, field extensions and minimal polynoms. the problem you have. Find centralized, trusted content and collaborate around the technologies you use most. The more labels you have, or the longer the names and values are, the more memory it will use. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. 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. The problem is that the table is also showing reasons that happened 0 times in the time frame and I don't want to display them. 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. source, what your query is, what the query inspector shows, and any other Sign up for a free GitHub account to open an issue and contact its maintainers and the community. These will give you an overall idea about a clusters health. Is it a bug? You can verify this by running the kubectl get nodes command on the master node. Managed Service for Prometheus Cloud Monitoring Prometheus # ! Is there a single-word adjective for "having exceptionally strong moral principles"? hackers at 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. Already on GitHub? Prometheus is a great and reliable tool, but dealing with high cardinality issues, especially in an environment where a lot of different applications are scraped by the same Prometheus server, can be challenging. 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. Explanation: Prometheus uses label matching in expressions. Well occasionally send you account related emails. Having a working monitoring setup is a critical part of the work we do for our clients. Examples Asking for help, clarification, or responding to other answers. 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? I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). Internally all time series are stored inside a map on a structure called Head. 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. 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. will get matched and propagated to the output. 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. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. instance_memory_usage_bytes: This shows the current memory used. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. This allows Prometheus to scrape and store thousands of samples per second, our biggest instances are appending 550k samples per second, while also allowing us to query all the metrics simultaneously. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. These queries will give you insights into node health, Pod health, cluster resource utilization, etc. If both the nodes are running fine, you shouldnt get any result for this query. 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. 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. privacy statement. Internet-scale applications efficiently, 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. 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. Comparing current data with historical data. 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. This holds true for a lot of labels that we see are being used by engineers. 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. 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. There is an open pull request on the Prometheus repository. Combined thats a lot of different metrics. If the time series already exists inside TSDB then we allow the append to continue. an EC2 regions with application servers running docker containers. These are the sane defaults that 99% of application exporting metrics would never exceed. This is an example of a nested subquery. 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. Both rules will produce new metrics named after the value of the record field. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. 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. 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. Im new at Grafan and Prometheus. If your expression returns anything with labels, it won't match the time series generated by vector(0). list, which does not convey images, so screenshots etc. Why is this sentence from The Great Gatsby grammatical? 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. That map uses labels hashes as keys and a structure called memSeries as values. 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. Sign in To subscribe to this RSS feed, copy and paste this URL into your RSS reader. without any dimensional information. Sign up and get Kubernetes tips delivered straight to your inbox. 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. Is it possible to rotate a window 90 degrees if it has the same length and width? Windows 10, how have you configured the query which is causing problems? First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. 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. Run the following command on the master node: Once the command runs successfully, youll see joining instructions to add the worker node to the cluster.