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. 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. 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). 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. Making statements based on opinion; back them up with references or personal experience. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The below posts may be helpful for you to learn more about Kubernetes and our company. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. How Intuit democratizes AI development across teams through reusability. 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 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. For example, I'm using the metric to record durations for quantile reporting. At this point, both nodes should be ready. 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. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. Prometheus does offer some options for dealing with high cardinality problems. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) 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? This scenario is often described as cardinality explosion - some metric suddenly adds a huge number of distinct label values, creates a huge number of time series, causes Prometheus to run out of memory and you lose all observability as a result. Each Prometheus is scraping a few hundred different applications, each running on a few hundred servers. 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. 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. To get a better idea of this problem lets adjust our example metric to track HTTP requests. Any other chunk holds historical samples and therefore is read-only. Prometheus Queries: 11 PromQL Examples and Tutorial - ContainIQ This might require Prometheus to create a new chunk if needed. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Looking to learn more? Each chunk represents a series of samples for a specific time range. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. Not the answer you're looking for? In our example we have two labels, content and temperature, and both of them can have two different values. count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). A sample is something in between metric and time series - its a time series value for a specific timestamp. Better to simply ask under the single best category you think fits and see 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. 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. Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. Good to know, thanks for the quick response! 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. metric name, as measured over the last 5 minutes: Assuming that the http_requests_total time series all have the labels job Adding labels is very easy and all we need to do is specify their names. Better Prometheus rate() Function with VictoriaMetrics 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. So it seems like I'm back to square one. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. to get notified when one of them is not mounted anymore. Has 90% of ice around Antarctica disappeared in less than a decade? See this article for details. Prometheus - exclude 0 values from query result - Stack Overflow returns the unused memory in MiB for every instance (on a fictional cluster Extra metrics exported by Prometheus itself tell us if any scrape is exceeding the limit and if that happens we alert the team responsible for it. Combined thats a lot of different metrics. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. I'm not sure what you mean by exposing a metric. 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. 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. attacks. to your account, What did you do? But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. Cadvisors on every server provide container names. an EC2 regions with application servers running docker containers. which outputs 0 for an empty input vector, but that outputs a scalar The only exception are memory-mapped chunks which are offloaded to disk, but will be read into memory if needed by queries. Once configured, your instances should be ready for access. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. This is what i can see on Query Inspector. Cardinality is the number of unique combinations of all labels. an EC2 regions with application servers running docker containers. Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? About an argument in Famine, Affluence and Morality. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . Managed Service for Prometheus Cloud Monitoring Prometheus # ! 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 2023 The Linux Foundation. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. 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. With this simple code Prometheus client library will create a single metric. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. Run the following commands in both nodes to configure the Kubernetes repository. 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. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? This is one argument for not overusing labels, but often it cannot be avoided. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. There is an open pull request which improves memory usage of labels by storing all labels as a single string. 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. 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. It doesnt get easier than that, until you actually try to do it. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. notification_sender-. This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. what error message are you getting to show that theres a problem? If both the nodes are running fine, you shouldnt get any result for this query. Returns a list of label values for the label in every metric. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. Well occasionally send you account related emails. Run the following commands in both nodes to install kubelet, kubeadm, and kubectl. What does remote read means in Prometheus? Stumbled onto this post for something else unrelated, just was +1-ing this :). However, the queries you will see here are a baseline" audit. The thing with a metric vector (a metric which has dimensions) is that only the series for it actually get exposed on /metrics which have been explicitly initialized. After running the query, a table will show the current value of each result time series (one table row per output series). Prometheus query check if value exist. privacy statement. If the time series already exists inside TSDB then we allow the append to continue. 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. You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. 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. The region and polygon don't match. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. Both rules will produce new metrics named after the value of the record field. The number of time series depends purely on the number of labels and the number of all possible values these labels can take. Youve learned about the main components of Prometheus, and its query language, PromQL. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. which version of Grafana are you using? No, only calling Observe() on a Summary or Histogram metric will add any observations (and only calling Inc() on a counter metric will increment it). 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. are going to make it We can use these to add more information to our metrics so that we can better understand whats going on. type (proc) like this: Assuming this metric contains one time series per running instance, you could Im new at Grafan and Prometheus. 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. Why are trials on "Law & Order" in the New York Supreme Court? 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. Internet-scale applications efficiently, Not the answer you're looking for? There will be traps and room for mistakes at all stages of this process. You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. No error message, it is just not showing the data while using the JSON file from that website. PromQL allows querying historical data and combining / comparing it to the current data. 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. In the screenshot below, you can see that I added two queries, A and B, but only . On the worker node, run the kubeadm joining command shown in the last step. 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. 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. To your second question regarding whether I have some other label on it, the answer is yes I do. So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. Operating such a large Prometheus deployment doesnt come without challenges. Asking for help, clarification, or responding to other answers. Add field from calculation Binary operation. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. Why are physically impossible and logically impossible concepts considered separate in terms of probability? Every two hours Prometheus will persist chunks from memory onto the disk. If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? bay, Is what you did above (failures.WithLabelValues) an example of "exposing"? Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? 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. This makes a bit more sense with your explanation. Already on GitHub? @zerthimon You might want to use 'bool' with your comparator In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . result of a count() on a query that returns nothing should be 0