prometheus query return 0 if no data prometheus query return 0 if no data

Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? 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. Is a PhD visitor considered as a visiting scholar? 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. source, what your query is, what the query inspector shows, and any other After running the query, a table will show the current value of each result time series (one table row per output series). Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. Then imported a dashboard from " 1 Node Exporter for Prometheus Dashboard EN 20201010 | Grafana Labs ".Below is my Dashboard which is showing empty results.So kindly check and suggest. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. You're probably looking for the absent function. to get notified when one of them is not mounted anymore. I've created an expression that is intended to display percent-success for a given metric. Are there tables of wastage rates for different fruit and veg? The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. 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. Prometheus metrics can have extra dimensions in form of labels. Yeah, absent() is probably the way to go. privacy statement. 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. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Once Prometheus has a list of samples collected from our application it will save it into TSDB - Time Series DataBase - the database in which Prometheus keeps all the time series. Ive added a data source(prometheus) in Grafana. How to react to a students panic attack in an oral exam? VictoriaMetrics handles rate () function in the common sense way I described earlier! 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. 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. For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. Add field from calculation Binary operation. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. Making statements based on opinion; back them up with references or personal experience. Why are physically impossible and logically impossible concepts considered separate in terms of probability? Just add offset to the query. Run the following commands in both nodes to disable SELinux and swapping: Also, change SELINUX=enforcing to SELINUX=permissive in the /etc/selinux/config file. Are there tables of wastage rates for different fruit and veg? 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. hackers at 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. Having a working monitoring setup is a critical part of the work we do for our clients. To make things more complicated you may also hear about samples when reading Prometheus documentation. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. Return the per-second rate for all time series with the http_requests_total To get a better idea of this problem lets adjust our example metric to track HTTP requests. A common pattern is to export software versions as a build_info metric, Prometheus itself does this too: When Prometheus 2.43.0 is released this metric would be exported as: Which means that a time series with version=2.42.0 label would no longer receive any new samples. 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 cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. rev2023.3.3.43278. information which you think might be helpful for someone else to understand Once we do that we need to pass label values (in the same order as label names were specified) when incrementing our counter to pass this extra information. Why is there a voltage on my HDMI and coaxial cables? That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). 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. 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. Separate metrics for total and failure will work as expected. We know that the more labels on a metric, the more time series it can create. what does the Query Inspector show for the query you have a problem with? However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Our metrics are exposed as a HTTP response. 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. The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. Is a PhD visitor considered as a visiting scholar? I'm displaying Prometheus query on a Grafana table. With our custom patch we dont care how many samples are in a scrape. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. @rich-youngkin Yes, the general problem is non-existent series. A sample is something in between metric and time series - its a time series value for a specific timestamp. 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. Prometheus is a great and reliable tool, but dealing with high cardinality issues, especially in an environment where a lot of different applications are scraped by the same Prometheus server, can be challenging. 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. What this means is that a single metric will create one or more time series. 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. By clicking Sign up for GitHub, you agree to our terms of service and For operations between two instant vectors, the matching behavior can be modified. Finally, please remember that some people read these postings as an email 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. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. scheduler exposing these metrics about the instances it runs): The same expression, but summed by application, could be written like this: If the same fictional cluster scheduler exposed CPU usage metrics like the What does remote read means in Prometheus? windows. To avoid this its in general best to never accept label values from untrusted sources. Now, lets install Kubernetes on the master node using kubeadm. node_cpu_seconds_total: This returns the total amount of CPU time. 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. attacks. Next you will likely need to create recording and/or alerting rules to make use of your time series. Another reason is that trying to stay on top of your usage can be a challenging task. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. 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. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. But before that, lets talk about the main components of Prometheus. notification_sender-. Extra fields needed by Prometheus internals. All regular expressions in Prometheus use RE2 syntax. But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. This process is also aligned with the wall clock but shifted by one hour. With this simple code Prometheus client library will create a single metric. Is it possible to rotate a window 90 degrees if it has the same length and width? So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. 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. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. @zerthimon You might want to use 'bool' with your comparator Prometheus will keep each block on disk for the configured retention period. 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 So the maximum number of time series we can end up creating is four (2*2). This article covered a lot of ground. Is that correct? Cadvisors on every server provide container names. One Head Chunk - containing up to two hours of the last two hour wall clock slot. 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. The main reason why we prefer graceful degradation is that we want our engineers to be able to deploy applications and their metrics with confidence without being subject matter experts in Prometheus. I can't work out how to add the alerts to the deployments whilst retaining the deployments for which there were no alerts returned: If I use sum with or, then I get this, depending on the order of the arguments to or: If I reverse the order of the parameters to or, I get what I am after: But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. Bulk update symbol size units from mm to map units in rule-based symbology. It might seem simple on the surface, after all you just need to stop yourself from creating too many metrics, adding too many labels or setting label values from untrusted sources. By default Prometheus will create a chunk per each two hours of wall clock. Samples are compressed using encoding that works best if there are continuous updates. Cadvisors on every server provide container names. returns the unused memory in MiB for every instance (on a fictional cluster It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. (fanout by job name) and instance (fanout by instance of the job), we might It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. 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. 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. Improving your monitoring setup by integrating Cloudflares analytics data into Prometheus and Grafana Pint is a tool we developed to validate our Prometheus alerting rules and ensure they are always working website whether someone is able to help out. This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. vishnur5217 May 31, 2020, 3:44am 1. Run the following command on the master node: Once the command runs successfully, youll see joining instructions to add the worker node to the cluster. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This is the standard flow with a scrape that doesnt set any sample_limit: With our patch we tell TSDB that its allowed to store up to N time series in total, from all scrapes, at any time. This might require Prometheus to create a new chunk if needed. These queries are a good starting point. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Already on GitHub? How to show that an expression of a finite type must be one of the finitely many possible values? without any dimensional information. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. feel that its pushy or irritating and therefore ignore it. Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. Examples If so it seems like this will skew the results of the query (e.g., quantiles). The Prometheus data source plugin provides the following functions you can use in the Query input field. First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. Under which circumstances? 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. Our patched logic will then check if the sample were about to append belongs to a time series thats already stored inside TSDB or is it a new time series that needs to be created. 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). How Intuit democratizes AI development across teams through reusability. How do I align things in the following tabular environment? will get matched and propagated to the output. I used a Grafana transformation which seems to work. 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 . 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. Comparing current data with historical data. 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. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) to your account. 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. ncdu: What's going on with this second size column? binary operators to them and elements on both sides with the same label set *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. Also, providing a reasonable amount of information about where youre starting We can use these to add more information to our metrics so that we can better understand whats going on. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. Connect and share knowledge within a single location that is structured and easy to search. Lets say we have an application which we want to instrument, which means add some observable properties in the form of metrics that Prometheus can read from our application. No error message, it is just not showing the data while using the JSON file from that website. 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. By default Prometheus will create a chunk per each two hours of wall clock. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. That map uses labels hashes as keys and a structure called memSeries as values. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Minimising the environmental effects of my dyson brain. t]. privacy statement. Also the link to the mailing list doesn't work for me. Explanation: Prometheus uses label matching in expressions. gabrigrec September 8, 2021, 8:12am #8. If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. Adding labels is very easy and all we need to do is specify their names. By clicking Sign up for GitHub, you agree to our terms of service and 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. These will give you an overall idea about a clusters health. This had the effect of merging the series without overwriting any values. 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. The process of sending HTTP requests from Prometheus to our application is called scraping. 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. 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. 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). AFAIK it's not possible to hide them through Grafana. Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. So it seems like I'm back to square one. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. (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. Windows 10, how have you configured the query which is causing problems? 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. Finally we maintain a set of internal documentation pages that try to guide engineers through the process of scraping and working with metrics, with a lot of information thats specific to our environment. There is an open pull request which improves memory usage of labels by storing all labels as a single string. the problem you have. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. 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. We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. The below posts may be helpful for you to learn more about Kubernetes and our company. which Operating System (and version) are you running it under? as text instead of as an image, more people will be able to read it and help. Name the nodes as Kubernetes Master and Kubernetes Worker. However when one of the expressions returns no data points found the result of the entire expression is no data points found. 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. 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 the total number of stored time series is below the configured limit then we append the sample as usual. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. Has 90% of ice around Antarctica disappeared in less than a decade? Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. Why are trials on "Law & Order" in the New York Supreme Court? Find centralized, trusted content and collaborate around the technologies you use most. Thirdly Prometheus is written in Golang which is a language with garbage collection. @zerthimon The following expr works for me In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. It doesnt get easier than that, until you actually try to do it. This page will guide you through how to install and connect Prometheus and Grafana.