prometheus query return 0 if no data

Blocks will eventually be compacted, which means that Prometheus will take multiple blocks and merge them together to form a single block that covers a bigger time range. Once theyre in TSDB its already too late. The simplest construct of a PromQL query is an instant vector selector. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. To make things more complicated you may also hear about samples when reading Prometheus documentation. 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. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. With 1,000 random requests we would end up with 1,000 time series in Prometheus. The containers are named with a specific pattern: notification_checker [0-9] notification_sender [0-9] I need an alert when the number of container of the same pattern (eg. I'm still out of ideas here. Just add offset to the query. If we add another label that can also have two values then we can now export up to eight time series (2*2*2). There are a number of options you can set in your scrape configuration block. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. 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. 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. I have just used the JSON file that is available in below website You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. This makes a bit more sense with your explanation. Has 90% of ice around Antarctica disappeared in less than a decade? I've been using comparison operators in Grafana for a long while. Better to simply ask under the single best category you think fits and see Why is there a voltage on my HDMI and coaxial cables? Operators | Prometheus promql - Prometheus query check if value exist - Stack Overflow To learn more, see our tips on writing great answers. One Head Chunk - containing up to two hours of the last two hour wall clock slot. Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. 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 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. 2023 The Linux Foundation. In AWS, create two t2.medium instances running CentOS. prometheus - Promql: Is it possible to get total count in Query_Range This might require Prometheus to create a new chunk if needed. If so it seems like this will skew the results of the query (e.g., quantiles). (fanout by job name) and instance (fanout by instance of the job), we might So, specifically in response to your question: I am facing the same issue - please explain how you configured your data information which you think might be helpful for someone else to understand Managing the entire lifecycle of a metric from an engineering perspective is a complex process. 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. Using a query that returns "no data points found" in an expression. If you're looking for a Our metric will have a single label that stores the request path. or something like that. This gives us confidence that we wont overload any Prometheus server after applying changes. 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. These will give you an overall idea about a clusters health. Cadvisors on every server provide container names. group by returns a value of 1, so we subtract 1 to get 0 for each deployment and I now wish to add to this the number of alerts that are applicable to each deployment. Play with bool Examples returns the unused memory in MiB for every instance (on a fictional cluster Prometheus Queries: 11 PromQL Examples and Tutorial - ContainIQ Why do many companies reject expired SSL certificates as bugs in bug bounties? Now we should pause to make an important distinction between metrics and time series. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? This is true both for client libraries and Prometheus server, but its more of an issue for Prometheus itself, since a single Prometheus server usually collects metrics from many applications, while an application only keeps its own metrics. Why are trials on "Law & Order" in the New York Supreme Court? 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. The number of times some specific event occurred. You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. There is an open pull request which improves memory usage of labels by storing all labels as a single string. Does a summoned creature play immediately after being summoned by a ready action? Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). rev2023.3.3.43278. This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. How Cloudflare runs Prometheus at scale The TSDB limit patch protects the entire Prometheus from being overloaded by too many time series. notification_sender-. This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. VictoriaMetrics handles rate () function in the common sense way I described earlier! binary operators to them and elements on both sides with the same label set I've added a data source (prometheus) in Grafana. For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. What happens when somebody wants to export more time series or use longer labels? list, which does not convey images, so screenshots etc. without any dimensional information. This is one argument for not overusing labels, but often it cannot be avoided. It will return 0 if the metric expression does not return anything. Already on GitHub? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Those memSeries objects are storing all the time series information. Sign in The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). If the total number of stored time series is below the configured limit then we append the sample as usual. It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. This page will guide you through how to install and connect Prometheus and Grafana. At the same time our patch gives us graceful degradation by capping time series from each scrape to a certain level, rather than failing hard and dropping all time series from affected scrape, which would mean losing all observability of affected applications. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. What is the point of Thrower's Bandolier? Prometheus query check if value exist. Once configured, your instances should be ready for access. Windows 10, how have you configured the query which is causing problems? First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. No Data is showing on Grafana Dashboard - Prometheus - Grafana Labs how have you configured the query which is causing problems? your journey to Zero Trust. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? Time arrow with "current position" evolving with overlay number. Stumbled onto this post for something else unrelated, just was +1-ing this :). 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. Creating new time series on the other hand is a lot more expensive - we need to allocate new memSeries instances with a copy of all labels and keep it in memory for at least an hour. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. 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. Can airtags be tracked from an iMac desktop, with no iPhone? Find centralized, trusted content and collaborate around the technologies you use most. job and handler labels: Return a whole range of time (in this case 5 minutes up to the query time) 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. There is a maximum of 120 samples each chunk can hold. By clicking Sign up for GitHub, you agree to our terms of service and We know that the more labels on a metric, the more time series it can create. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. PromQL / How to return 0 instead of ' no data' - Medium To get a better idea of this problem lets adjust our example metric to track HTTP requests. Next, create a Security Group to allow access to the instances. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. Another reason is that trying to stay on top of your usage can be a challenging task. 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. I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). Passing sample_limit is the ultimate protection from high cardinality. 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. 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. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. Are you not exposing the fail metric when there hasn't been a failure yet? 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. 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. Looking to learn more? rev2023.3.3.43278. Chunks that are a few hours old are written to disk and removed from memory. https://grafana.com/grafana/dashboards/2129. What sort of strategies would a medieval military use against a fantasy giant? On the worker node, run the kubeadm joining command shown in the last step. Please help improve it by filing issues or pull requests. When using Prometheus defaults and assuming we have a single chunk for each two hours of wall clock we would see this: Once a chunk is written into a block it is removed from memSeries and thus from memory. All regular expressions in Prometheus use RE2 syntax. Secondly this calculation is based on all memory used by Prometheus, not only time series data, so its just an approximation. The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. PromQL allows you to write queries and fetch information from the metric data collected by Prometheus. Has 90% of ice around Antarctica disappeared in less than a decade? Making statements based on opinion; back them up with references or personal experience. Those limits are there to catch accidents and also to make sure that if any application is exporting a high number of time series (more than 200) the team responsible for it knows about it. In our example case its a Counter class object. 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. Making statements based on opinion; back them up with references or personal experience. what does the Query Inspector show for the query you have a problem with? We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. 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. How to follow the signal when reading the schematic? 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. 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. 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. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. Since this happens after writing a block, and writing a block happens in the middle of the chunk window (two hour slices aligned to the wall clock) the only memSeries this would find are the ones that are orphaned - they received samples before, but not anymore. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. For example, /api/v1/query?query=http_response_ok [24h]&time=t would return raw samples on the time range (t-24h . I don't know how you tried to apply the comparison operators, but if I use this very similar query: I get a result of zero for all jobs that have not restarted over the past day and a non-zero result for jobs that have had instances restart. How Intuit democratizes AI development across teams through reusability. *) in region drops below 4. Is a PhD visitor considered as a visiting scholar? Prometheus metrics can have extra dimensions in form of labels. 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. Timestamps here can be explicit or implicit. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. by (geo_region) < bool 4 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? 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. Please dont post the same question under multiple topics / subjects. At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. @zerthimon The following expr works for me This holds true for a lot of labels that we see are being used by engineers. Name the nodes as Kubernetes Master and Kubernetes Worker. 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. But you cant keep everything in memory forever, even with memory-mapping parts of data. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. notification_sender-. but it does not fire if both are missing because than count() returns no data the workaround is to additionally check with absent() but it's on the one hand annoying to double-check on each rule and on the other hand count should be able to "count" zero . On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. With our custom patch we dont care how many samples are in a scrape. After running the query, a table will show the current value of each result time series (one table row per output series). or Internet application, First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. ***> wrote: You signed in with another tab or window. to get notified when one of them is not mounted anymore. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. See this article for details. If the error message youre getting (in a log file or on screen) can be quoted This thread has been automatically locked since there has not been any recent activity after it was closed. Prometheus's query language supports basic logical and arithmetic operators. syntax. 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. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. A sample is something in between metric and time series - its a time series value for a specific timestamp. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. Can I tell police to wait and call a lawyer when served with a search warrant?