By default Prometheus will create a chunk per each two hours of wall clock. By default Prometheus will create a chunk per each two hours of wall clock. These queries are a good starting point. About an argument in Famine, Affluence and Morality. Is it possible to rotate a window 90 degrees if it has the same length and width? 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. 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 believe it's the logic that it's written, but is there any conditions that can be used if there's no data recieved it returns a 0. what I tried doing is putting a condition or an absent function,but not sure if thats the correct approach. The simplest way of doing this is by using functionality provided with client_python itself - see documentation here. The Graph tab allows you to graph a query expression over a specified range of time. You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. 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. 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. This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 0. How do I align things in the following tabular environment? Heres a screenshot that shows exact numbers: Thats an average of around 5 million time series per instance, but in reality we have a mixture of very tiny and very large instances, with the biggest instances storing around 30 million time series each. Both rules will produce new metrics named after the value of the record field. The Prometheus data source plugin provides the following functions you can use in the Query input field. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. Doubling the cube, field extensions and minimal polynoms. 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. To avoid this its in general best to never accept label values from untrusted sources. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. Why are trials on "Law & Order" in the New York Supreme Court? Once it has a memSeries instance to work with it will append our sample to the Head Chunk. 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. and can help you on 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. 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. Is it a bug? 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. So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. But the real risk is when you create metrics with label values coming from the outside world. 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. 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. Theres no timestamp anywhere actually. 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. are going to make it To get a better understanding of the impact of a short lived time series on memory usage lets take a look at another example. 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. You can verify this by running the kubectl get nodes command on the master node. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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). 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. Also the link to the mailing list doesn't work for me. Lets adjust the example code to do this. Select the query and do + 0. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. Returns a list of label values for the label in every metric. If this query also returns a positive value, then our cluster has overcommitted the memory. How is Jesus " " (Luke 1:32 NAS28) different from a prophet (, Luke 1:76 NAS28)? 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. Can I tell police to wait and call a lawyer when served with a search warrant? For operations between two instant vectors, the matching behavior can be modified. Asking for help, clarification, or responding to other answers. We can use these to add more information to our metrics so that we can better understand whats going on. Sign in Well occasionally send you account related emails. Well occasionally send you account related emails. Not the answer you're looking for? You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. 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. To your second question regarding whether I have some other label on it, the answer is yes I do. Stumbled onto this post for something else unrelated, just was +1-ing this :). Have you fixed this issue? 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. or Internet application, The process of sending HTTP requests from Prometheus to our application is called scraping. 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. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. 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. Once you cross the 200 time series mark, you should start thinking about your metrics more. Is that correct? We had a fair share of problems with overloaded Prometheus instances in the past and developed a number of tools that help us deal with them, including custom patches. - grafana-7.1.0-beta2.windows-amd64, how did you install it? 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. 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Is it possible to create a concave light? The more labels you have, or the longer the names and values are, the more memory it will use. 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. 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? 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). help customers build returns the unused memory in MiB for every instance (on a fictional cluster For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. (pseudocode): summary = 0 + sum (warning alerts) + 2*sum (alerts (critical alerts)) This gives the same single value series, or no data if there are no alerts. TSDB used in Prometheus is a special kind of database that was highly optimized for a very specific workload: This means that Prometheus is most efficient when continuously scraping the same time series over and over again. 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. 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. You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. Our metric will have a single label that stores the request path. A sample is something in between metric and time series - its a time series value for a specific timestamp. 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. 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. PROMQL: how to add values when there is no data returned? 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