You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana. Why do many companies reject expired SSL certificates as bugs in bug bounties? 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. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? VictoriaMetrics handles rate () function in the common sense way I described earlier! Better Prometheus rate() Function with VictoriaMetrics On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. Finally getting back to this. Or maybe we want to know if it was a cold drink or a hot one? If the time series doesnt exist yet and our append would create it (a new memSeries instance would be created) then we skip this sample. By default Prometheus will create a chunk per each two hours of wall clock. count() should result in 0 if no timeseries found #4982 - GitHub Find centralized, trusted content and collaborate around the technologies you use most. 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). I'm not sure what you mean by exposing a metric. This process is also aligned with the wall clock but shifted by one hour. That response will have a list of, When Prometheus collects all the samples from our HTTP response it adds the timestamp of that collection and with all this information together we have a. 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 up and get Kubernetes tips delivered straight to your inbox. With this simple code Prometheus client library will create a single metric. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. The result is a table of failure reason and its count. Managed Service for Prometheus Cloud Monitoring Prometheus # ! 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. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. I.e., there's no way to coerce no datapoints to 0 (zero)? Why is this sentence from The Great Gatsby grammatical? 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. The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. Both patches give us two levels of protection. Is a PhD visitor considered as a visiting scholar? Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? How can i turn no data to zero in Loki - Grafana Loki - Grafana Labs This patchset consists of two main elements. Please open a new issue for related bugs. Is a PhD visitor considered as a visiting scholar? Grafana renders "no data" when instant query returns empty dataset I believe it's the logic that it's written, but is there any . but viewed in the tabular ("Console") view of the expression browser. privacy statement. If I now tack on a != 0 to the end of it, all zero values are filtered out: Thanks for contributing an answer to Stack Overflow! @juliusv Thanks for clarifying that. 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. 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. Im new at Grafan and Prometheus. Sign in One of the most important layers of protection is a set of patches we maintain on top of Prometheus. Lets create a demo Kubernetes cluster and set up Prometheus to monitor it. It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. 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 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. Its very easy to keep accumulating time series in Prometheus until you run out of memory. Is that correct? This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. If we configure a sample_limit of 100 and our metrics response contains 101 samples, then Prometheus wont scrape anything at all. Bulk update symbol size units from mm to map units in rule-based symbology. PromQL tutorial for beginners and humans - Medium 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. The idea is that if done as @brian-brazil mentioned, there would always be a fail and success metric, because they are not distinguished by a label, but always are exposed. Prometheus Queries: 11 PromQL Examples and Tutorial - ContainIQ Is it possible to rotate a window 90 degrees if it has the same length and width? I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. 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? There's also count_scalar(), by (geo_region) < bool 4 Well occasionally send you account related emails. For that lets follow all the steps in the life of a time series inside Prometheus. How to react to a students panic attack in an oral exam? Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. 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. Thanks for contributing an answer to Stack Overflow! Cadvisors on every server provide container names. Using a query that returns "no data points found" in an expression. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. what does the Query Inspector show for the query you have a problem with? He has a Bachelor of Technology in Computer Science & Engineering from SRMS. Why are trials on "Law & Order" in the New York Supreme Court? Redoing the align environment with a specific formatting. 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. Once configured, your instances should be ready for access. returns the unused memory in MiB for every instance (on a fictional cluster https://grafana.com/grafana/dashboards/2129. Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. Not the answer you're looking for? Select the query and do + 0. 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. Monitoring our monitoring: how we validate our Prometheus alert rules When Prometheus sends an HTTP request to our application it will receive this response: This format and underlying data model are both covered extensively in Prometheus' own documentation. count the number of running instances per application like this: This documentation is open-source. That map uses labels hashes as keys and a structure called memSeries as values. So it seems like I'm back to square one. All rights reserved. All chunks must be aligned to those two hour slots of wall clock time, so if TSDB was building a chunk for 10:00-11:59 and it was already full at 11:30 then it would create an extra chunk for the 11:30-11:59 time range. Visit 1.1.1.1 from any device to get started with PromQL / How to return 0 instead of ' no data' - Medium While the sample_limit patch stops individual scrapes from using too much Prometheus capacity, which could lead to creating too many time series in total and exhausting total Prometheus capacity (enforced by the first patch), which would in turn affect all other scrapes since some new time series would have to be ignored. Has 90% of ice around Antarctica disappeared in less than a decade? Extra fields needed by Prometheus internals. 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 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. Under which circumstances? attacks. Or do you have some other label on it, so that the metric still only gets exposed when you record the first failued request it? Already on GitHub? There is a single time series for each unique combination of metrics labels. To set up Prometheus to monitor app metrics: Download and install Prometheus. Asking for help, clarification, or responding to other answers. However when one of the expressions returns no data points found the result of the entire expression is no data points found. 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. So the maximum number of time series we can end up creating is four (2*2). Lets adjust the example code to do this. We know that time series will stay in memory for a while, even if they were scraped only once. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Well be executing kubectl commands on the master node only. 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. or something like that. When you add dimensionality (via labels to a metric), you either have to pre-initialize all the possible label combinations, which is not always possible, or live with missing metrics (then your PromQL computations become more cumbersome). 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. whether someone is able to help out. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. Why are physically impossible and logically impossible concepts considered separate in terms of probability? 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Prometheus does offer some options for dealing with high cardinality problems. 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, see our tips on writing great answers. prometheus - Promql: Is it possible to get total count in Query_Range PROMQL: how to add values when there is no data returned? Thanks for contributing an answer to Stack Overflow! This means that Prometheus must check if theres already a time series with identical name and exact same set of labels present. an EC2 regions with application servers running docker containers. One Head Chunk - containing up to two hours of the last two hour wall clock slot. But you cant keep everything in memory forever, even with memory-mapping parts of data. Add field from calculation Binary operation. Thats why what our application exports isnt really metrics or time series - its samples. By default Prometheus will create a chunk per each two hours of wall clock. To make things more complicated you may also hear about samples when reading Prometheus documentation. hackers at Comparing current data with historical data. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Connect and share knowledge within a single location that is structured and easy to search. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. 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. (fanout by job name) and instance (fanout by instance of the job), we might Managing the entire lifecycle of a metric from an engineering perspective is a complex process. 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. Any other chunk holds historical samples and therefore is read-only. 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 entire corporate networks, 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. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. 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. Asking for help, clarification, or responding to other answers. 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. as text instead of as an image, more people will be able to read it and help. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. metric name, as measured over the last 5 minutes: Assuming that the http_requests_total time series all have the labels job 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. We can use these to add more information to our metrics so that we can better understand whats going on. The text was updated successfully, but these errors were encountered: It's recommended not to expose data in this way, partially for this 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. promql - Prometheus query check if value exist - Stack Overflow 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. Have a question about this project? 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. Samples are compressed using encoding that works best if there are continuous updates. Explanation: Prometheus uses label matching in expressions. Sign in How Intuit democratizes AI development across teams through reusability. You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. Now we should pause to make an important distinction between metrics and time series. In both nodes, edit the /etc/hosts file to add the private IP of the nodes. How to tell which packages are held back due to phased updates. type (proc) like this: Assuming this metric contains one time series per running instance, you could This helps Prometheus query data faster since all it needs to do is first locate the memSeries instance with labels matching our query and then find the chunks responsible for time range of the query. If our metric had more labels and all of them were set based on the request payload (HTTP method name, IPs, headers, etc) we could easily end up with millions of time series. result of a count() on a query that returns nothing should be 0 ? The below posts may be helpful for you to learn more about Kubernetes and our company. A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints).