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. Once configured, your instances should be ready for access. Samples are compressed using encoding that works best if there are continuous updates. I'm displaying Prometheus query on a Grafana table. 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. 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. Internally time series names are just another label called __name__, so there is no practical distinction between name and labels. PROMQL: how to add values when there is no data returned? That map uses labels hashes as keys and a structure called memSeries as values. You're probably looking for the absent function. In this blog post well cover some of the issues one might encounter when trying to collect many millions of time series per Prometheus instance. 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. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). The number of time series depends purely on the number of labels and the number of all possible values these labels can take. We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. 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. 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. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. instance_memory_usage_bytes: This shows the current memory used. If you need to obtain raw samples, then a range query must be sent to /api/v1/query. Not the answer you're looking for? Redoing the align environment with a specific formatting. The region and polygon don't match. The text was updated successfully, but these errors were encountered: This is correct. 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. an EC2 regions with application servers running docker containers. 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. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, PromQL / How to return 0 instead of ' no data' - Medium To better handle problems with cardinality its best if we first get a better understanding of how Prometheus works and how time series consume memory. This is what i can see on Query Inspector. or Internet application, ward off DDoS windows. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. 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. What does remote read means in Prometheus? In our example we have two labels, content and temperature, and both of them can have two different values. This garbage collection, among other things, will look for any time series without a single chunk and remove it from memory. 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. It will return 0 if the metric expression does not return anything. (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. There is a maximum of 120 samples each chunk can hold. 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. If the error message youre getting (in a log file or on screen) can be quoted 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. gabrigrec September 8, 2021, 8:12am #8. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . Once it has a memSeries instance to work with it will append our sample to the Head Chunk. What this means is that a single metric will create one or more time series. I'd expect to have also: Please use the prometheus-users mailing list for questions. How do you get out of a corner when plotting yourself into a corner, Partner is not responding when their writing is needed in European project application. 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. This works fine when there are data points for all queries in the expression. Once theyre in TSDB its already too late. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. The Head Chunk is never memory-mapped, its always stored in memory. After sending a request it will parse the response looking for all the samples exposed there. The below posts may be helpful for you to learn more about Kubernetes and our company. 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. Sign in What happens when somebody wants to export more time series or use longer labels? Querying basics | Prometheus To avoid this its in general best to never accept label values from untrusted sources. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. new career direction, check out our open Hello, I'm new at Grafan and Prometheus. The speed at which a vehicle is traveling. Time series scraped from applications are kept in memory. At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. 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: 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. 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. Once we appended sample_limit number of samples we start to be selective. This process is also aligned with the wall clock but shifted by one hour. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. 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. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. The more labels you have, or the longer the names and values are, the more memory it will use. Each Prometheus is scraping a few hundred different applications, each running on a few hundred servers. 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. Its least efficient when it scrapes a time series just once and never again - doing so comes with a significant memory usage overhead when compared to the amount of information stored using that memory. 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. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. And this brings us to the definition of cardinality in the context of metrics. 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. If this query also returns a positive value, then our cluster has overcommitted the memory. In AWS, create two t2.medium instances running CentOS. information which you think might be helpful for someone else to understand You can verify this by running the kubectl get nodes command on the master node. Grafana renders "no data" when instant query returns empty dataset Is it possible to rotate a window 90 degrees if it has the same length and width? 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. 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. 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. Now comes the fun stuff. Theres no timestamp anywhere actually. The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. After running the query, a table will show the current value of each result time series (one table row per output series). Has 90% of ice around Antarctica disappeared in less than a decade? This pod wont be able to run because we dont have a node that has the label disktype: ssd. With any monitoring system its important that youre able to pull out the right data. In our example case its a Counter class object. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. 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. 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. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. 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. 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. notification_sender-. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. But the real risk is when you create metrics with label values coming from the outside world. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Show or hide query result depending on variable value in Grafana, Understanding the CPU Busy Prometheus query, Group Label value prefixes by Delimiter in Prometheus, Why time duration needs double dot for Prometheus but not for Victoria metrics, Using a Grafana Histogram with Prometheus Buckets. Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. *) in region drops below 4. 4 Managed Service for Prometheus | 4 Managed Service for If we make a single request using the curl command: We should see these time series in our application: But what happens if an evil hacker decides to send a bunch of random requests to our application? Next, create a Security Group to allow access to the instances. Sign up and get Kubernetes tips delivered straight to your inbox. This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. Why is there a voltage on my HDMI and coaxial cables? whether someone is able to help out. One of the most important layers of protection is a set of patches we maintain on top of Prometheus. Each chunk represents a series of samples for a specific time range. will get matched and propagated to the output. Timestamps here can be explicit or implicit. How can I group labels in a Prometheus query? I can get the deployments in the dev, uat, and prod environments using this query: So we can see that tenant 1 has 2 deployments in 2 different environments, whereas the other 2 have only one. All regular expressions in Prometheus use RE2 syntax. 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. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. 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. For that reason we do tolerate some percentage of short lived time series even if they are not a perfect fit for Prometheus and cost us more memory. - grafana-7.1.0-beta2.windows-amd64, how did you install it? which outputs 0 for an empty input vector, but that outputs a scalar list, which does not convey images, so screenshots etc. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. Object, url:api/datasources/proxy/2/api/v1/query_range?query=wmi_logical_disk_free_bytes%7Binstance%3D~%22%22%2C%20volume%20!~%22HarddiskVolume.%2B%22%7D&start=1593750660&end=1593761460&step=20&timeout=60s, Powered by Discourse, best viewed with JavaScript enabled, 1 Node Exporter for Prometheus Dashboard EN 20201010 | Grafana Labs, https://grafana.com/grafana/dashboards/2129. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. This means that Prometheus must check if theres already a time series with identical name and exact same set of labels present. There is a single time series for each unique combination of metrics labels. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. privacy statement. 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. 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. I've been using comparison operators in Grafana for a long while. syntax. Both rules will produce new metrics named after the value of the record field. 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. 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. By clicking Sign up for GitHub, you agree to our terms of service and Which in turn will double the memory usage of our Prometheus server. There's also count_scalar(), Operators | Prometheus Are there tables of wastage rates for different fruit and veg? Making statements based on opinion; back them up with references or personal experience. For that lets follow all the steps in the life of a time series inside Prometheus. Lets create a demo Kubernetes cluster and set up Prometheus to monitor it. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. 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. So lets start by looking at what cardinality means from Prometheus' perspective, when it can be a problem and some of the ways to deal with it. About an argument in Famine, Affluence and Morality. Minimising the environmental effects of my dyson brain. Thanks for contributing an answer to Stack Overflow! Have a question about this project? 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. node_cpu_seconds_total: This returns the total amount of CPU time. ***> wrote: You signed in with another tab or window. However when one of the expressions returns no data points found the result of the entire expression is no data points found. We know that the more labels on a metric, the more time series it can create. 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. With this simple code Prometheus client library will create a single metric. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. "no data". Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Asking for help, clarification, or responding to other answers. count() should result in 0 if no timeseries found #4982 - GitHub website You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. Bulk update symbol size units from mm to map units in rule-based symbology.