Is it possible to rotate a window 90 degrees if it has the same length and width? It doesnt get easier than that, until you actually try to do it. promql - Prometheus query check if value exist - Stack Overflow Does a summoned creature play immediately after being summoned by a ready action? Both rules will produce new metrics named after the value of the record field. One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. 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. gabrigrec September 8, 2021, 8:12am #8. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. syntax. Return all time series with the metric http_requests_total: Return all time series with the metric http_requests_total and the given 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. (fanout by job name) and instance (fanout by instance of the job), we might rev2023.3.3.43278. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. To avoid this its in general best to never accept label values from untrusted sources. The region and polygon don't match. Managed Service for Prometheus Cloud Monitoring Prometheus # ! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Once we appended sample_limit number of samples we start to be selective. Time arrow with "current position" evolving with overlay number. Monitor Confluence with Prometheus and Grafana | Confluence Data Center Do new devs get fired if they can't solve a certain bug? I then hide the original query. result of a count() on a query that returns nothing should be 0 This thread has been automatically locked since there has not been any recent activity after it was closed. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Samples are compressed using encoding that works best if there are continuous updates. 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. If you're looking for a count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) Internally all time series are stored inside a map on a structure called Head. (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. 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. You can query Prometheus metrics directly with its own query language: PromQL. 2023 The Linux Foundation. This might require Prometheus to create a new chunk if needed. ***> wrote: You signed in with another tab or window. I'm still out of ideas here. windows. - grafana-7.1.0-beta2.windows-amd64, how did you install it? Querying examples | Prometheus The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. Internet-scale applications efficiently, 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. Making statements based on opinion; back them up with references or personal experience. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. 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. How is Jesus " " (Luke 1:32 NAS28) different from a prophet (, Luke 1:76 NAS28)? 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. What happens when somebody wants to export more time series or use longer labels? 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. No error message, it is just not showing the data while using the JSON file from that website. how have you configured the query which is causing problems? AFAIK it's not possible to hide them through Grafana. PROMQL: how to add values when there is no data returned? your journey to Zero Trust. 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. What does remote read means in Prometheus? The text was updated successfully, but these errors were encountered: This is correct. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. But you cant keep everything in memory forever, even with memory-mapping parts of data. PROMQL: how to add values when there is no data returned? By default Prometheus will create a chunk per each two hours of wall clock. 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. as text instead of as an image, more people will be able to read it and help. prometheus - Promql: Is it possible to get total count in Query_Range 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. Explanation: Prometheus uses label matching in expressions. You signed in with another tab or window. With our custom patch we dont care how many samples are in a scrape. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. Run the following commands in both nodes to configure the Kubernetes repository. The Prometheus data source plugin provides the following functions you can use in the Query input field. In both nodes, edit the /etc/sysctl.d/k8s.conf file to add the following two lines: Then reload the IPTables config using the sudo sysctl --system command. Thirdly Prometheus is written in Golang which is a language with garbage collection. But the real risk is when you create metrics with label values coming from the outside world. Using a query that returns "no data points found" in an expression. So it seems like I'm back to square one. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. This is what i can see on Query Inspector. Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. 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. rev2023.3.3.43278. In addition to that in most cases we dont see all possible label values at the same time, its usually a small subset of all possible combinations. Now we should pause to make an important distinction between metrics and time series. How do I align things in the following tabular environment? The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. What is the point of Thrower's Bandolier? One thing you could do though to ensure at least the existence of failure series for the same series which have had successes, you could just reference the failure metric in the same code path without actually incrementing it, like so: That way, the counter for that label value will get created and initialized to 0. Separate metrics for total and failure will work as expected. 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. Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. Also the link to the mailing list doesn't work for me. The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. 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. This also has the benefit of allowing us to self-serve capacity management - theres no need for a team that signs off on your allocations, if CI checks are passing then we have the capacity you need for your applications. This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. 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. There is an open pull request which improves memory usage of labels by storing all labels as a single string. For example, /api/v1/query?query=http_response_ok [24h]&time=t would return raw samples on the time range (t-24h . 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. @zerthimon The following expr works for me You can verify this by running the kubectl get nodes command on the master node. To get a better understanding of the impact of a short lived time series on memory usage lets take a look at another example. Cardinality is the number of unique combinations of all labels. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. will get matched and propagated to the output. Using regular expressions, you could select time series only for jobs whose A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. Often it doesnt require any malicious actor to cause cardinality related problems. To learn more, see our tips on writing great answers. There's also count_scalar(), The text was updated successfully, but these errors were encountered: It's recommended not to expose data in this way, partially for this reason. Has 90% of ice around Antarctica disappeared in less than a decade? Does Counterspell prevent from any further spells being cast on a given turn? 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 1,000 random requests we would end up with 1,000 time series in Prometheus. I have a data model where some metrics are namespaced by client, environment and deployment name. Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. Select the query and do + 0. We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. For example, I'm using the metric to record durations for quantile reporting. Theres only one chunk that we can append to, its called the Head Chunk. Youve learned about the main components of Prometheus, and its query language, PromQL. This is an example of a nested subquery. This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. Prometheus - exclude 0 values from query result - Stack Overflow You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. Can airtags be tracked from an iMac desktop, with no iPhone? See this article for details. Just add offset to the query. Even Prometheus' own client libraries had bugs that could expose you to problems like this. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. Secondly this calculation is based on all memory used by Prometheus, not only time series data, so its just an approximation. It's worth to add that if using Grafana you should set 'Connect null values' proeprty to 'always' in order to get rid of blank spaces in the graph. SSH into both servers and run the following commands to install Docker. list, which does not convey images, so screenshots etc. Yeah, absent() is probably the way to go. But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. 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. Is there a single-word adjective for "having exceptionally strong moral principles"? 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. A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). Although you can tweak some of Prometheus' behavior and tweak it more for use with short lived time series, by passing one of the hidden flags, its generally discouraged to do so. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. binary operators to them and elements on both sides with the same label set If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. 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. The Graph tab allows you to graph a query expression over a specified range of time. Of course there are many types of queries you can write, and other useful queries are freely available. In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. Is that correct? 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. Redoing the align environment with a specific formatting. 1 Like. PromQL tutorial for beginners and humans - Medium The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. Already on GitHub? 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. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. What this means is that using Prometheus defaults each memSeries should have a single chunk with 120 samples on it for every two hours of data. 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. This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 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. Since we know that the more labels we have the more time series we end up with, you can see when this can become a problem. 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. 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. 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. to your account. are going to make it I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). Using a query that returns "no data points found" in an - GitHub Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. 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. 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). This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. 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. Not the answer you're looking for? Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. However, the queries you will see here are a baseline" audit. result of a count() on a query that returns nothing should be 0 ? No Data is showing on Grafana Dashboard - Prometheus - Grafana Labs Is a PhD visitor considered as a visiting scholar? A sample is something in between metric and time series - its a time series value for a specific timestamp. 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. Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. A metric is an observable property with some defined dimensions (labels). Play with bool Short story taking place on a toroidal planet or moon involving flying, How to handle a hobby that makes income in US, Doubling the cube, field extensions and minimal polynoms, Follow Up: struct sockaddr storage initialization by network format-string. There is an open pull request on the Prometheus repository. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. 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. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. Its not going to get you a quicker or better answer, and some people might Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. @juliusv Thanks for clarifying that. 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. Please help improve it by filing issues or pull requests. This patchset consists of two main elements. Lets create a demo Kubernetes cluster and set up Prometheus to monitor it. Finally getting back to this. There is a single time series for each unique combination of metrics labels. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. 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. You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. If a sample lacks any explicit timestamp then it means that the sample represents the most recent value - its the current value of a given time series, and the timestamp is simply the time you make your observation at. 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. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. 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. With this simple code Prometheus client library will create a single metric. Returns a list of label values for the label in every metric. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. How can I group labels in a Prometheus query? I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. 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. Are there tables of wastage rates for different fruit and veg? If this query also returns a positive value, then our cluster has overcommitted the memory. Subscribe to receive notifications of new posts: Subscription confirmed. Making statements based on opinion; back them up with references or personal experience. The below posts may be helpful for you to learn more about Kubernetes and our company. 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.