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count() should result in 0 if no timeseries found #4982 - GitHub The Prometheus data source plugin provides the following functions you can use in the Query input field. it works perfectly if one is missing as count() then returns 1 and the rule fires. You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. Are you not exposing the fail metric when there hasn't been a failure yet? PROMQL: how to add values when there is no data returned? Can airtags be tracked from an iMac desktop, with no iPhone? 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. We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. Once you cross the 200 time series mark, you should start thinking about your metrics more. It would be easier if we could do this in the original query though. A sample is something in between metric and time series - its a time series value for a specific timestamp. This article covered a lot of ground. Theres only one chunk that we can append to, its called the Head Chunk. To get a better understanding of the impact of a short lived time series on memory usage lets take a look at another example. To learn more about our mission to help build a better Internet, start here. 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. @zerthimon The following expr works for me count(container_last_seen{name="container_that_doesn't_exist"}), What did you see instead? So the maximum number of time series we can end up creating is four (2*2). Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. Returns a list of label names. Another reason is that trying to stay on top of your usage can be a challenging task. One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. For example, the following query will show the total amount of CPU time spent over the last two minutes: And the query below will show the total number of HTTP requests received in the last five minutes: There are different ways to filter, combine, and manipulate Prometheus data using operators and further processing using built-in functions. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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. 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. Is a PhD visitor considered as a visiting scholar? 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. There will be traps and room for mistakes at all stages of this 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. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. Cadvisors on every server provide container names. - grafana-7.1.0-beta2.windows-amd64, how did you install it? Its not going to get you a quicker or better answer, and some people might Why do many companies reject expired SSL certificates as bugs in bug bounties? As we mentioned before a time series is generated from metrics. hackers at The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. website 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. 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. Is a PhD visitor considered as a visiting scholar? That map uses labels hashes as keys and a structure called memSeries as values. name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. 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. How do I align things in the following tabular environment? t]. ncdu: What's going on with this second size column? Already on GitHub? Operators | 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. However, the queries you will see here are a baseline" audit. So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. Is there a solutiuon to add special characters from software and how to do it. This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. See this article for details. Once we appended sample_limit number of samples we start to be selective. help customers build Monitor Confluence with Prometheus and Grafana | Confluence Data Center For example, /api/v1/query?query=http_response_ok [24h]&time=t would return raw samples on the time range (t-24h . VictoriaMetrics handles rate () function in the common sense way I described earlier! This means that Prometheus must check if theres already a time series with identical name and exact same set of labels present. The Head Chunk is never memory-mapped, its always stored in memory. First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. The more any application does for you, the more useful it is, the more resources it might need. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. Are there tables of wastage rates for different fruit and veg? Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. Why are physically impossible and logically impossible concepts considered separate in terms of probability? Each time series will cost us resources since it needs to be kept in memory, so the more time series we have, the more resources metrics will consume. To your second question regarding whether I have some other label on it, the answer is yes I do. whether someone is able to help out. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. These flags are only exposed for testing and might have a negative impact on other parts of 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. Already on GitHub? 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. 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. Chunks that are a few hours old are written to disk and removed from memory. Youll be executing all these queries in the Prometheus expression browser, so lets get started. 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. In AWS, create two t2.medium instances running CentOS. How to follow the signal when reading the schematic? This thread has been automatically locked since there has not been any recent activity after it was closed. Not the answer you're looking for? And this brings us to the definition of cardinality in the context of metrics. to get notified when one of them is not mounted anymore. 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. If the time series already exists inside TSDB then we allow the append to continue. count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). Managed Service for Prometheus https://goo.gle/3ZgeGxv Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. 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. 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. 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. To make things more complicated you may also hear about samples when reading Prometheus documentation. Is that correct? Its the chunk responsible for the most recent time range, including the time of our scrape. Not the answer you're looking for? But you cant keep everything in memory forever, even with memory-mapping parts of data. Why are trials on "Law & Order" in the New York Supreme Court? Querying examples | Prometheus PromLabs | Blog - Selecting Data in PromQL (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. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents.