prometheus query return 0 if no data

Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. If the error message youre getting (in a log file or on screen) can be quoted by (geo_region) < bool 4 Youve learned about the main components of Prometheus, and its query language, PromQL. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. 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. This pod wont be able to run because we dont have a node that has the label disktype: ssd. 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. Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? from and what youve done will help people to understand your problem. This would happen if any time series was no longer being exposed by any application and therefore there was no scrape that would try to append more samples to it. Run the following commands in both nodes to configure the Kubernetes repository. In the screenshot below, you can see that I added two queries, A and B, but only . You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. About an argument in Famine, Affluence and Morality. entire corporate networks, What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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 is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. Stumbled onto this post for something else unrelated, just was +1-ing this :). Better to simply ask under the single best category you think fits and see 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. which Operating System (and version) are you running it under? So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . Connect and share knowledge within a single location that is structured and easy to search. vishnur5217 May 31, 2020, 3:44am 1. 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. However, the queries you will see here are a baseline" audit. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. Use Prometheus to monitor app performance metrics. Well occasionally send you account related emails. Minimising the environmental effects of my dyson brain. The simplest construct of a PromQL query is an instant vector selector. 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. https://grafana.com/grafana/dashboards/2129. 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. 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. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. It might seem simple on the surface, after all you just need to stop yourself from creating too many metrics, adding too many labels or setting label values from untrusted sources. Thirdly Prometheus is written in Golang which is a language with garbage collection. Prometheus allows us to measure health & performance over time and, if theres anything wrong with any service, let our team know before it becomes a problem. I.e., there's no way to coerce no datapoints to 0 (zero)? Connect and share knowledge within a single location that is structured and easy to search. 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. These are the sane defaults that 99% of application exporting metrics would never exceed. I was then able to perform a final sum by over the resulting series to reduce the results down to a single result, dropping the ad-hoc labels in the process. Theres no timestamp anywhere actually. After sending a request it will parse the response looking for all the samples exposed there. The difference with standard Prometheus starts when a new sample is about to be appended, but TSDB already stores the maximum number of time series its allowed to have. whether someone is able to help out. I then hide the original query. Not the answer you're looking for? 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. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. Find centralized, trusted content and collaborate around the technologies you use most. The Graph tab allows you to graph a query expression over a specified range of time. Both patches give us two levels of protection. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 - 05:59, , 22:00 - 23:59. 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. You're probably looking for the absent function. 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. result of a count() on a query that returns nothing should be 0 ? 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. Not the answer you're looking for? Chunks that are a few hours old are written to disk and removed from memory. 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 article covered a lot of ground. 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. Asking for help, clarification, or responding to other answers. Prometheus does offer some options for dealing with high cardinality problems. Name the nodes as Kubernetes Master and Kubernetes Worker. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. There are a number of options you can set in your scrape configuration block. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. If both the nodes are running fine, you shouldnt get any result for this query. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) Returns a list of label names. without any dimensional information. 1 Like. What sort of strategies would a medieval military use against a fantasy giant? or Internet application, ward off DDoS When time series disappear from applications and are no longer scraped they still stay in memory until all chunks are written to disk and garbage collection removes them. Select the query and do + 0. 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. Cardinality is the number of unique combinations of all labels. 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. gabrigrec September 8, 2021, 8:12am #8. Hello, I'm new at Grafan and Prometheus. Internet-scale applications efficiently, The more labels you have, or the longer the names and values are, the more memory it will use. To your second question regarding whether I have some other label on it, the answer is yes I do. Using a query that returns "no data points found" in an expression. Extra fields needed by Prometheus internals. Operating such a large Prometheus deployment doesnt come without challenges. If so I'll need to figure out a way to pre-initialize the metric which may be difficult since the label values may not be known a priori. With 1,000 random requests we would end up with 1,000 time series in Prometheus. Already on GitHub? That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). By clicking Sign up for GitHub, you agree to our terms of service and 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. Managed Service for Prometheus Cloud Monitoring Prometheus # ! 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. The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. The result is a table of failure reason and its count. Making statements based on opinion; back them up with references or personal experience. and can help you on The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. 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. 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. SSH into both servers and run the following commands to install Docker. binary operators to them and elements on both sides with the same label set Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. What happens when somebody wants to export more time series or use longer labels? Managing the entire lifecycle of a metric from an engineering perspective is a complex process. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. 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. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 The text was updated successfully, but these errors were encountered: This is correct. Already on GitHub? 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. Its not going to get you a quicker or better answer, and some people might 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. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. 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. How do I align things in the following tabular environment? 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. Once theyre in TSDB its already too late. Play with bool Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. 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. In AWS, create two t2.medium instances running CentOS. Can airtags be tracked from an iMac desktop, with no iPhone? Add field from calculation Binary operation. What video game is Charlie playing in Poker Face S01E07? 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). And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. Our metrics are exposed as a HTTP response. 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. 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. rev2023.3.3.43278. Yeah, absent() is probably the way to go. We know that time series will stay in memory for a while, even if they were scraped only once. VictoriaMetrics handles rate () function in the common sense way I described earlier! 02:00 - create a new chunk for 02:00 - 03:59 time range, 04:00 - create a new chunk for 04:00 - 05:59 time range, 22:00 - create a new chunk for 22:00 - 23:59 time range. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. I'm not sure what you mean by exposing a metric. which outputs 0 for an empty input vector, but that outputs a scalar 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). See these docs for details on how Prometheus calculates the returned results. You can verify this by running the kubectl get nodes command on the master node. For example our errors_total metric, which we used in example before, might not be present at all until we start seeing some errors, and even then it might be just one or two errors that will be recorded. Next you will likely need to create recording and/or alerting rules to make use of your time series. as text instead of as an image, more people will be able to read it and help. 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. To select all HTTP status codes except 4xx ones, you could run: http_requests_total {status!~"4.."} Subquery Return the 5-minute rate of the http_requests_total metric for the past 30 minutes, with a resolution of 1 minute. Cadvisors on every server provide container names. By clicking Sign up for GitHub, you agree to our terms of service and 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.

Soundlogic Bluetooth Speaker 5b309bt Instructions, Articles P