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

Any other chunk holds historical samples and therefore is read-only. Lets see what happens if we start our application at 00:25, allow Prometheus to scrape it once while it exports: And then immediately after the first scrape we upgrade our application to a new version: At 00:25 Prometheus will create our memSeries, but we will have to wait until Prometheus writes a block that contains data for 00:00-01:59 and runs garbage collection before that memSeries is removed from memory, which will happen at 03:00. Examples I have just used the JSON file that is available in below website In the screenshot below, you can see that I added two queries, A and B, but only . In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. You can verify this by running the kubectl get nodes command on the master node. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. Instead we count time series as we append them to TSDB. One Head Chunk - containing up to two hours of the last two hour wall clock slot. Doubling the cube, field extensions and minimal polynoms. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. I believe it's the logic that it's written, but is there any conditions that can be used if there's no data recieved it returns a 0. what I tried doing is putting a condition or an absent function,but not sure if thats the correct approach. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Is there a solutiuon to add special characters from software and how to do it. Simple, clear and working - thanks a lot. VictoriaMetrics handles rate () function in the common sense way I described earlier! Are there tables of wastage rates for different fruit and veg? bay, Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. This page will guide you through how to install and connect Prometheus and Grafana. 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. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. This would happen if any time series was no longer being exposed by any application and therefore there was no scrape that would try to append more samples to it. 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. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. It doesnt get easier than that, until you actually try to do it. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. 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. The number of times some specific event occurred. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. 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. Cadvisors on every server provide container names. Have a question about this project? Return all time series with the metric http_requests_total: Return all time series with the metric http_requests_total and the given But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. Well be executing kubectl commands on the master node only. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. For example, I'm using the metric to record durations for quantile reporting. binary operators to them and elements on both sides with the same label set Have you fixed this issue? Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) So just calling WithLabelValues() should make a metric appear, but only at its initial value (0 for normal counters and histogram bucket counters, NaN for summary quantiles). Managed Service for Prometheus Cloud Monitoring Prometheus # ! metric name, as measured over the last 5 minutes: Assuming that the http_requests_total time series all have the labels job While the sample_limit patch stops individual scrapes from using too much Prometheus capacity, which could lead to creating too many time series in total and exhausting total Prometheus capacity (enforced by the first patch), which would in turn affect all other scrapes since some new time series would have to be ignored. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. hackers at About an argument in Famine, Affluence and Morality. This makes a bit more sense with your explanation. There is a single time series for each unique combination of metrics labels. There is a maximum of 120 samples each chunk can hold. These will give you an overall idea about a clusters health. 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. Second rule does the same but only sums time series with status labels equal to "500". Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. Why is this sentence from The Great Gatsby grammatical? Returns a list of label values for the label in every metric. ward off DDoS The only exception are memory-mapped chunks which are offloaded to disk, but will be read into memory if needed by queries. There are a number of options you can set in your scrape configuration block. In our example case its a Counter class object. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. Connect and share knowledge within a single location that is structured and easy to search. 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. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . 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. So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. 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. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. @rich-youngkin Yeah, what I originally meant with "exposing" a metric is whether it appears in your /metrics endpoint at all (for a given set of labels). Already on GitHub? See these docs for details on how Prometheus calculates the returned results. However when one of the expressions returns no data points found the result of the entire expression is no data points found.In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found.Is there a way to write the query so that a . (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. 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. 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. It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. What is the point of Thrower's Bandolier? 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. A sample is something in between metric and time series - its a time series value for a specific timestamp. This is one argument for not overusing labels, but often it cannot be avoided. Well occasionally send you account related emails. It will return 0 if the metric expression does not return anything. 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. 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. an EC2 regions with application servers running docker containers. First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. The result is a table of failure reason and its count. You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. Comparing current data with historical data. The Head Chunk is never memory-mapped, its always stored in memory. A time series that was only scraped once is guaranteed to live in Prometheus for one to three hours, depending on the exact time of that scrape. If your expression returns anything with labels, it won't match the time series generated by vector(0). Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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. Making statements based on opinion; back them up with references or personal experience. to your account. You're probably looking for the absent function. Use Prometheus to monitor app performance metrics. The process of sending HTTP requests from Prometheus to our application is called scraping. 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. 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. 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. website 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. Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. If so it seems like this will skew the results of the query (e.g., quantiles). With our example metric we know how many mugs were consumed, but what if we also want to know what kind of beverage it was? 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. Subscribe to receive notifications of new posts: Subscription confirmed. Is a PhD visitor considered as a visiting scholar? How to follow the signal when reading the schematic? In both nodes, edit the /etc/hosts file to add the private IP of the nodes. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. will get matched and propagated to the output. Both rules will produce new metrics named after the value of the record field. I was then able to perform a final sum by over the resulting series to reduce the results down to a single result, dropping the ad-hoc labels in the process. The text was updated successfully, but these errors were encountered: It's recommended not to expose data in this way, partially for this reason. I.e., there's no way to coerce no datapoints to 0 (zero)? Next you will likely need to create recording and/or alerting rules to make use of your time series. For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. 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). To learn more, see our tips on writing great answers. Using a query that returns "no data points found" in an expression. and can help you on This process is also aligned with the wall clock but shifted by one hour. PROMQL: how to add values when there is no data returned? Both patches give us two levels of protection. Even Prometheus' own client libraries had bugs that could expose you to problems like this. Even i am facing the same issue Please help me on this. Explanation: Prometheus uses label matching in expressions. Redoing the align environment with a specific formatting. This had the effect of merging the series without overwriting any values. 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. Is that correct? But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. When Prometheus sends an HTTP request to our application it will receive this response: This format and underlying data model are both covered extensively in Prometheus' own documentation. 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. Hello, I'm new at Grafan and Prometheus. This gives us confidence that we wont overload any Prometheus server after applying changes. Prometheus does offer some options for dealing with high cardinality problems. (fanout by job name) and instance (fanout by instance of the job), we might Time arrow with "current position" evolving with overlay number. are going to make it Passing sample_limit is the ultimate protection from high cardinality. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. more difficult for those people to help. If you do that, the line will eventually be redrawn, many times over. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. 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. So, specifically in response to your question: I am facing the same issue - please explain how you configured your data Internally all time series are stored inside a map on a structure called Head. windows.