prometheus query return 0 if no data

to your account. Have a question about this project? Internally time series names are just another label called __name__, so there is no practical distinction between name and labels. However, the queries you will see here are a baseline" audit. 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. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . 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. Run the following commands in both nodes to install kubelet, kubeadm, and kubectl. Today, let's look a bit closer at the two ways of selecting data in PromQL: instant vector selectors and range vector selectors. 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. Its also worth mentioning that without our TSDB total limit patch we could keep adding new scrapes to Prometheus and that alone could lead to exhausting all available capacity, even if each scrape had sample_limit set and scraped fewer time series than this limit allows. Return all time series with the metric http_requests_total: Return all time series with the metric http_requests_total and the given There are a number of options you can set in your scrape configuration block. what error message are you getting to show that theres a problem? 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. our free app that makes your Internet faster and safer. it works perfectly if one is missing as count() then returns 1 and the rule fires. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. And this brings us to the definition of cardinality in the context of metrics. 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). 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. Hello, I'm new at Grafan and Prometheus. type (proc) like this: Assuming this metric contains one time series per running instance, you could Once you cross the 200 time series mark, you should start thinking about your metrics more. So, specifically in response to your question: I am facing the same issue - please explain how you configured your data 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. A sample is something in between metric and time series - its a time series value for a specific timestamp. With 1,000 random requests we would end up with 1,000 time series in Prometheus. If this query also returns a positive value, then our cluster has overcommitted the memory. 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. How to follow the signal when reading the schematic? Querying basics | Prometheus new career direction, check out our open Using a query that returns "no data points found" in an expression. There will be traps and room for mistakes at all stages of this process. To make things more complicated you may also hear about samples when reading Prometheus documentation. 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. 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. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. The more labels we have or the more distinct values they can have the more time series as a result. Prometheus and PromQL (Prometheus Query Language) are conceptually very simple, but this means that all the complexity is hidden in the interactions between different elements of the whole metrics pipeline. This gives us confidence that we wont overload any Prometheus server after applying changes. what error message are you getting to show that theres a problem? 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. Well be executing kubectl commands on the master node only. Prometheus - exclude 0 values from query result - Stack Overflow Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) Both of the representations below are different ways of exporting the same time series: Since everything is a label Prometheus can simply hash all labels using sha256 or any other algorithm to come up with a single ID that is unique for each time series. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. Thanks for contributing an answer to Stack Overflow! Another reason is that trying to stay on top of your usage can be a challenging task. Play with bool The Linux Foundation has registered trademarks and uses trademarks. 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. Connect and share knowledge within a single location that is structured and easy to search. Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. 2023 The Linux Foundation. PromQL queries the time series data and returns all elements that match the metric name, along with their values for a particular point in time (when the query runs). *) in region drops below 4. This patchset consists of two main elements. What sort of strategies would a medieval military use against a fantasy giant? What this means is that using Prometheus defaults each memSeries should have a single chunk with 120 samples on it for every two hours of data. @rich-youngkin Yes, the general problem is non-existent series. So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. Chunks will consume more memory as they slowly fill with more samples, after each scrape, and so the memory usage here will follow a cycle - we start with low memory usage when the first sample is appended, then memory usage slowly goes up until a new chunk is created and we start again. One Head Chunk - containing up to two hours of the last two hour wall clock slot. If so it seems like this will skew the results of the query (e.g., quantiles). count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). Why are trials on "Law & Order" in the New York Supreme Court? Does a summoned creature play immediately after being summoned by a ready action? Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? About an argument in Famine, Affluence and Morality. 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. 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. For example, this expression 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. To learn more, see our tips on writing great answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. About an argument in Famine, Affluence and Morality. Better Prometheus rate() Function with VictoriaMetrics If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. Your needs or your customers' needs will evolve over time and so you cant just draw a line on how many bytes or cpu cycles it can consume. 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. Has 90% of ice around Antarctica disappeared in less than a decade? This pod wont be able to run because we dont have a node that has the label disktype: ssd. what does the Query Inspector show for the query you have a problem with? For example, /api/v1/query?query=http_response_ok [24h]&time=t would return raw samples on the time range (t-24h . Run the following commands on the master node to set up Prometheus on the Kubernetes cluster: Next, run this command on the master node to check the Pods status: Once all the Pods are up and running, you can access the Prometheus console using kubernetes port forwarding. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . binary operators to them and elements on both sides with the same label set Internet-scale applications efficiently, Find centralized, trusted content and collaborate around the technologies you use most. The difference with standard Prometheus starts when a new sample is about to be appended, but TSDB already stores the maximum number of time series its allowed to have. 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. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) PromQL allows querying historical data and combining / comparing it to the current data. but viewed in the tabular ("Console") view of the expression browser. But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. The next layer of protection is checks that run in CI (Continuous Integration) when someone makes a pull request to add new or modify existing scrape configuration for their application. 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. How do I align things in the following tabular environment? Which in turn will double the memory usage of our Prometheus server. For example, I'm using the metric to record durations for quantile reporting. There's also count_scalar(), 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. A metric can be anything that you can express as a number, for example: To create metrics inside our application we can use one of many Prometheus client libraries. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. Extra fields needed by Prometheus internals. A time series is an instance of that metric, with a unique combination of all the dimensions (labels), plus a series of timestamp & value pairs - hence the name time series. We will also signal back to the scrape logic that some samples were skipped. Just add offset to the query. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. The simplest construct of a PromQL query is an instant vector selector. privacy statement. Although you can tweak some of Prometheus' behavior and tweak it more for use with short lived time series, by passing one of the hidden flags, its generally discouraged to do so. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. If both the nodes are running fine, you shouldnt get any result for this query. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. If, on the other hand, we want to visualize the type of data that Prometheus is the least efficient when dealing with, well end up with this instead: Here we have single data points, each for a different property that we measure. Name the nodes as Kubernetes Master and Kubernetes Worker. name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. All rights reserved. With this simple code Prometheus client library will create a single metric. 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. The reason why we still allow appends for some samples even after were above sample_limit is that appending samples to existing time series is cheap, its just adding an extra timestamp & value pair. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. The problem is that the table is also showing reasons that happened 0 times in the time frame and I don't want to display them. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? I.e., there's no way to coerce no datapoints to 0 (zero)? A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). prometheus promql Share Follow edited Nov 12, 2020 at 12:27 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. What video game is Charlie playing in Poker Face S01E07? 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. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. It would be easier if we could do this in the original query though. syntax. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. Bulk update symbol size units from mm to map units in rule-based symbology. This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. an EC2 regions with application servers running docker containers. Prometheus Queries: 11 PromQL Examples and Tutorial - ContainIQ Adding labels is very easy and all we need to do is specify their names. 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. are going to make it To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How can i turn no data to zero in Loki - Grafana Loki - Grafana Labs The process of sending HTTP requests from Prometheus to our application is called scraping. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The struct definition for memSeries is fairly big, but all we really need to know is that it has a copy of all the time series labels and chunks that hold all the samples (timestamp & value pairs). There is no equivalent functionality in a standard build of Prometheus, if any scrape produces some samples they will be appended to time series inside TSDB, creating new time series if needed. Managing the entire lifecycle of a metric from an engineering perspective is a complex process. Finally you will want to create a dashboard to visualize all your metrics and be able to spot trends. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Theres only one chunk that we can append to, its called the Head Chunk. We protect By default Prometheus will create a chunk per each two hours of wall clock. Heres a screenshot that shows exact numbers: Thats an average of around 5 million time series per instance, but in reality we have a mixture of very tiny and very large instances, with the biggest instances storing around 30 million time series each. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Not the answer you're looking for? This doesnt capture all complexities of Prometheus but gives us a rough estimate of how many time series we can expect to have capacity for. I believe it's the logic that it's written, but is there any . 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). positions. Using regular expressions, you could select time series only for jobs whose This means that our memSeries still consumes some memory (mostly labels) but doesnt really do anything. but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply In the screenshot below, you can see that I added two queries, A and B, but only . So it seems like I'm back to square one. - grafana-7.1.0-beta2.windows-amd64, how did you install it? That map uses labels hashes as keys and a structure called memSeries as values. 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. Thank you for subscribing! or Internet application, ward off DDoS to your account, What did you do? 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. All regular expressions in Prometheus use RE2 syntax. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). Using the Prometheus data source - Amazon Managed Grafana Have a question about this project? I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. 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. 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. AFAIK it's not possible to hide them through Grafana. 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. Once we appended sample_limit number of samples we start to be selective. How Cloudflare runs Prometheus at scale Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. This is one argument for not overusing labels, but often it cannot be avoided. However when one of the expressions returns no data points found the result of the entire expression is no data points found. Why are physically impossible and logically impossible concepts considered separate in terms of probability? First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. Has 90% of ice around Antarctica disappeared in less than a decade? Comparing current data with historical data. Use Prometheus to monitor app performance metrics. We know that the more labels on a metric, the more time series it can create. It will return 0 if the metric expression does not return anything. As we mentioned before a time series is generated from metrics. Samples are compressed using encoding that works best if there are continuous updates. What am I doing wrong here in the PlotLegends specification? The more any application does for you, the more useful it is, the more resources it might need. How to tell which packages are held back due to phased updates. TSDB will try to estimate when a given chunk will reach 120 samples and it will set the maximum allowed time for current Head Chunk accordingly. We know that each time series will be kept in memory. 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. which Operating System (and version) are you running it under?