Each Prometheus is scraping a few hundred different applications, each running on a few hundred servers. These will give you an overall idea about a clusters health. Have a question about this project? PromQL allows querying historical data and combining / comparing it to the current data. 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. Time arrow with "current position" evolving with overlay number. There are a number of options you can set in your scrape configuration block. which Operating System (and version) are you running it under? These queries will give you insights into node health, Pod health, cluster resource utilization, etc. How Intuit democratizes AI development across teams through reusability. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Youve learned about the main components of Prometheus, and its query language, PromQL. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) Is a PhD visitor considered as a visiting scholar? (pseudocode): This gives the same single value series, or no data if there are no alerts. Here at Labyrinth Labs, we put great emphasis on monitoring. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. Well occasionally send you account related emails. count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. This is optional, but may be useful if you don't already have an APM, or would like to use our templates and sample queries. 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. 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. I'm sure there's a proper way to do this, but in the end, I used label_replace to add an arbitrary key-value label to each sub-query that I wished to add to the original values, and then applied an or to each. 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. 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. new career direction, check out our open Doubling the cube, field extensions and minimal polynoms. With any monitoring system its important that youre able to pull out the right data. You can verify this by running the kubectl get nodes command on the master node. Is what you did above (failures.WithLabelValues) an example of "exposing"? Not the answer you're looking for? to your account, What did you do? The process of sending HTTP requests from Prometheus to our application is called scraping. Note that using subqueries unnecessarily is unwise. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. On the worker node, run the kubeadm joining command shown in the last step. This patchset consists of two main elements. This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. Once it has a memSeries instance to work with it will append our sample to the Head Chunk. There's also count_scalar(), Examples The Prometheus data source plugin provides the following functions you can use in the Query input field. 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. Thanks for contributing an answer to Stack Overflow! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. If you do that, the line will eventually be redrawn, many times over. 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. The only exception are memory-mapped chunks which are offloaded to disk, but will be read into memory if needed by queries. So, specifically in response to your question: I am facing the same issue - please explain how you configured your data *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. following for every instance: we could get the top 3 CPU users grouped by application (app) and process Thirdly Prometheus is written in Golang which is a language with garbage collection. 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. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. 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? 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. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Subscribe to receive notifications of new posts: Subscription confirmed. Find centralized, trusted content and collaborate around the technologies you use most. On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. Does a summoned creature play immediately after being summoned by a ready action? The text was updated successfully, but these errors were encountered: It's recommended not to expose data in this way, partially for this reason. This is the modified flow with our patch: By running go_memstats_alloc_bytes / prometheus_tsdb_head_series query we know how much memory we need per single time series (on average), we also know how much physical memory we have available for Prometheus on each server, which means that we can easily calculate the rough number of time series we can store inside Prometheus, taking into account the fact the theres garbage collection overhead since Prometheus is written in Go: memory available to Prometheus / bytes per time series = our capacity. This process is also aligned with the wall clock but shifted by one hour. Even i am facing the same issue Please help me on this. So the maximum number of time series we can end up creating is four (2*2). positions. 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. or Internet application, The simplest construct of a PromQL query is an instant vector selector. Comparing current data with historical data. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. Well be executing kubectl commands on the master node only. 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. At this point, both nodes should be ready. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. want to sum over the rate of all instances, so we get fewer output time series, Why are trials on "Law & Order" in the New York Supreme Court? See these docs for details on how Prometheus calculates the returned results. For example, if someone wants to modify sample_limit, lets say by changing existing limit of 500 to 2,000, for a scrape with 10 targets, thats an increase of 1,500 per target, with 10 targets thats 10*1,500=15,000 extra time series that might be scraped. This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. After sending a request it will parse the response looking for all the samples exposed there. Bulk update symbol size units from mm to map units in rule-based symbology. 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. To get a better idea of this problem lets adjust our example metric to track HTTP requests. I've added a data source (prometheus) in Grafana. The more labels you have and the more values each label can take, the more unique combinations you can create and the higher the cardinality. Labels are stored once per each memSeries instance. By clicking Sign up for GitHub, you agree to our terms of service and A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). 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. 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. 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. 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. 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. 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. Before running the query, create a Pod with the following specification: Before running the query, create a PersistentVolumeClaim with the following specification: This will get stuck in Pending state as we dont have a storageClass called manual" in our cluster. How do I align things in the following tabular environment? Explanation: Prometheus uses label matching in expressions. What am I doing wrong here in the PlotLegends specification? Both patches give us two levels of protection. Time series scraped from applications are kept in memory.