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

You're probably looking for the absent function. Both patches give us two levels of protection. 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. 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. positions. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. In the screenshot below, you can see that I added two queries, A and B, but only . So, specifically in response to your question: I am facing the same issue - please explain how you configured your data Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. 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. whether someone is able to help out. 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. 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. Often it doesnt require any malicious actor to cause cardinality related problems. Well occasionally send you account related emails. @zerthimon The following expr works for me rev2023.3.3.43278. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? https://grafana.com/grafana/dashboards/2129. Is what you did above (failures.WithLabelValues) an example of "exposing"? Please dont post the same question under multiple topics / subjects. 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. 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. How do you get out of a corner when plotting yourself into a corner, Partner is not responding when their writing is needed in European project application. 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. In our example we have two labels, content and temperature, and both of them can have two different values. Can I tell police to wait and call a lawyer when served with a search warrant? The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . 1 Like. To set up Prometheus to monitor app metrics: Download and install Prometheus. To get a better idea of this problem lets adjust our example metric to track HTTP requests. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. 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. There are a number of options you can set in your scrape configuration block. If I now tack on a != 0 to the end of it, all zero values are filtered out: Thanks for contributing an answer to Stack Overflow! This holds true for a lot of labels that we see are being used by engineers. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Why are trials on "Law & Order" in the New York Supreme Court? Each chunk represents a series of samples for a specific time range. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. 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. This is a deliberate design decision made by Prometheus developers. binary operators to them and elements on both sides with the same label set The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. If your expression returns anything with labels, it won't match the time series generated by vector(0). It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. 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? 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. result of a count() on a query that returns nothing should be 0 ? Not the answer you're looking for? This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. Finally getting back to this. Have you fixed this issue? You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana. windows. *) in region drops below 4. 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. The subquery for the deriv function uses the default resolution. Sign in entire corporate networks, Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. Being able to answer How do I X? yourself without having to wait for a subject matter expert allows everyone to be more productive and move faster, while also avoiding Prometheus experts from answering the same questions over and over again. 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. Separate metrics for total and failure will work as expected. I'm not sure what you mean by exposing a metric. 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. Thanks for contributing an answer to Stack Overflow! Is it possible to create a concave light? 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. Every two hours Prometheus will persist chunks from memory onto the disk. Lets adjust the example code to do this. Also the link to the mailing list doesn't work for me. Second rule does the same but only sums time series with status labels equal to "500". Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. Chunks that are a few hours old are written to disk and removed from memory. The Linux Foundation has registered trademarks and uses trademarks. Have a question about this project? We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. 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. Are there tables of wastage rates for different fruit and veg? 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. One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 0. To avoid this its in general best to never accept label values from untrusted sources. About an argument in Famine, Affluence and Morality. The result is a table of failure reason and its count. So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. No error message, it is just not showing the data while using the JSON file from that website. 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. 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. The Head Chunk is never memory-mapped, its always stored in memory. prometheus-promql query based on label value, Select largest label value in Prometheus query, Prometheus Query Overall average under a time interval, Prometheus endpoint of all available metrics. Is there a single-word adjective for "having exceptionally strong moral principles"? 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. 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. 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. 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. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. 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). Sign up for a free GitHub account to open an issue and contact its maintainers and the community. as text instead of as an image, more people will be able to read it and help. This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. 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. 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. This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. In AWS, create two t2.medium instances running CentOS. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. what error message are you getting to show that theres a problem? Its not going to get you a quicker or better answer, and some people might What this means is that a single metric will create one or more time series. In this blog post well cover some of the issues one might encounter when trying to collect many millions of time series per Prometheus instance. This works well if errors that need to be handled are generic, for example Permission Denied: But if the error string contains some task specific information, for example the name of the file that our application didnt have access to, or a TCP connection error, then we might easily end up with high cardinality metrics this way: Once scraped all those time series will stay in memory for a minimum of one hour. 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. This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. 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. Making statements based on opinion; back them up with references or personal experience. 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. To learn more, see our tips on writing great answers. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. Thats why what our application exports isnt really metrics or time series - its samples. which outputs 0 for an empty input vector, but that outputs a scalar On the worker node, run the kubeadm joining command shown in the last step. These queries are a good starting point. 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. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. 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. With this simple code Prometheus client library will create a single metric. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Is it a bug? Extra fields needed by Prometheus internals. You signed in with another tab or window. Its least efficient when it scrapes a time series just once and never again - doing so comes with a significant memory usage overhead when compared to the amount of information stored using that memory. This allows Prometheus to scrape and store thousands of samples per second, our biggest instances are appending 550k samples per second, while also allowing us to query all the metrics simultaneously. All rights reserved. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. If we try to append a sample with a timestamp higher than the maximum allowed time for current Head Chunk, then TSDB will create a new Head Chunk and calculate a new maximum time for it based on the rate of appends. In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. 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've added a data source (prometheus) in Grafana. There will be traps and room for mistakes at all stages of this process. Ive added a data source(prometheus) in Grafana. count(container_last_seen{name="container_that_doesn't_exist"}), What did you see instead? @rich-youngkin Yes, the general problem is non-existent series. What is the point of Thrower's Bandolier? As we mentioned before a time series is generated from metrics. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. Just add offset to the query. Even Prometheus' own client libraries had bugs that could expose you to problems like this. or Internet application, For example, I'm using the metric to record durations for quantile reporting. What video game is Charlie playing in Poker Face S01E07? We know what a metric, a sample and a time series is. The simplest way of doing this is by using functionality provided with client_python itself - see documentation here. returns the unused memory in MiB for every instance (on a fictional cluster This works fine when there are data points for all queries in the expression. by (geo_region) < bool 4 more difficult for those people to help. Short story taking place on a toroidal planet or moon involving flying, How to handle a hobby that makes income in US, Doubling the cube, field extensions and minimal polynoms, Follow Up: struct sockaddr storage initialization by network format-string. Is a PhD visitor considered as a visiting scholar? How to show that an expression of a finite type must be one of the finitely many possible values? Or maybe we want to know if it was a cold drink or a hot one? Both rules will produce new metrics named after the value of the record field. @zerthimon You might want to use 'bool' with your comparator Return the per-second rate for all time series with the http_requests_total Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. new career direction, check out our open I have a data model where some metrics are namespaced by client, environment and deployment name. These are the sane defaults that 99% of application exporting metrics would never exceed. But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. Has 90% of ice around Antarctica disappeared in less than a decade? ncdu: What's going on with this second size column? 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. but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply If a sample lacks any explicit timestamp then it means that the sample represents the most recent value - its the current value of a given time series, and the timestamp is simply the time you make your observation at. 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. So it seems like I'm back to square one. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. Ive deliberately kept the setup simple and accessible from any address for demonstration. But before that, lets talk about the main components of Prometheus. notification_sender-. vishnur5217 May 31, 2020, 3:44am 1. 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. hackers at But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. Thanks, The TSDB limit patch protects the entire Prometheus from being overloaded by too many time series. This is an example of a nested subquery. Examples Using regular expressions, you could select time series only for jobs whose *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. Prometheus will keep each block on disk for the configured retention period. Does Counterspell prevent from any further spells being cast on a given turn? 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. 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. Doubling the cube, field extensions and minimal polynoms. Once configured, your instances should be ready for access. (pseudocode): This gives the same single value series, or no data if there are no alerts. Well be executing kubectl commands on the master node only. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). Can airtags be tracked from an iMac desktop, with no iPhone? This had the effect of merging the series without overwriting any values. How to react to a students panic attack in an oral exam? We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. 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. notification_sender-. Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. 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). To your second question regarding whether I have some other label on it, the answer is yes I do. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . 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. the problem you have. I'm displaying Prometheus query on a Grafana table. This page will guide you through how to install and connect Prometheus and Grafana. Also, providing a reasonable amount of information about where youre starting Does a summoned creature play immediately after being summoned by a ready action? This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. Which in turn will double the memory usage of our Prometheus server. Our metric will have a single label that stores the request path. accelerate any Theres no timestamp anywhere actually. If such a stack trace ended up as a label value it would take a lot more memory than other time series, potentially even megabytes. On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. This article covered a lot of ground. Sign in I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network.