It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. If both the nodes are running fine, you shouldnt get any result for this query. Since we know that the more labels we have the more time series we end up with, you can see when this can become a problem. There are a number of options you can set in your scrape configuration block. If we try to visualize how the perfect type of data Prometheus was designed for looks like well end up with this: A few continuous lines describing some observed properties. 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. *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. Improving your monitoring setup by integrating Cloudflares analytics data into Prometheus and Grafana Pint is a tool we developed to validate our Prometheus alerting rules and ensure they are always working website Stumbled onto this post for something else unrelated, just was +1-ing this :). 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. 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. 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. Is it possible to create a concave light? 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. Explanation: Prometheus uses label matching in expressions. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. Looking to learn more? vishnur5217 May 31, 2020, 3:44am 1. It would be easier if we could do this in the original query though. Both rules will produce new metrics named after the value of the record field. Why do many companies reject expired SSL certificates as bugs in bug bounties? How to follow the signal when reading the schematic? At the same time our patch gives us graceful degradation by capping time series from each scrape to a certain level, rather than failing hard and dropping all time series from affected scrape, which would mean losing all observability of affected applications. Please see data model and exposition format pages for more details. - grafana-7.1.0-beta2.windows-amd64, how did you install it? it works perfectly if one is missing as count() then returns 1 and the rule fires. Can I tell police to wait and call a lawyer when served with a search warrant? There is an open pull request on the Prometheus repository. are going to make it A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). In our example we have two labels, content and temperature, and both of them can have two different values. Run the following commands in both nodes to configure the Kubernetes repository. There will be traps and room for mistakes at all stages of this process. What am I doing wrong here in the PlotLegends specification? job and handler labels: Return a whole range of time (in this case 5 minutes up to the query time) 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. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. 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. Prometheus's query language supports basic logical and arithmetic operators. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. Combined thats a lot of different metrics. 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. Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. Asking for help, clarification, or responding to other answers. 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. The text was updated successfully, but these errors were encountered: This is correct. This article covered a lot of ground. Just add offset to the query. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. This garbage collection, among other things, will look for any time series without a single chunk and remove it from memory. On the worker node, run the kubeadm joining command shown in the last step. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. 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 . 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. Find centralized, trusted content and collaborate around the technologies you use most. attacks, keep The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. Please open a new issue for related bugs. Each chunk represents a series of samples for a specific time range. and can help you on 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. One of the most important layers of protection is a set of patches we maintain on top of Prometheus. 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. I'm displaying Prometheus query on a Grafana table. What does remote read means in Prometheus? Thanks for contributing an answer to Stack Overflow! Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . I'm not sure what you mean by exposing a metric. Is what you did above (failures.WithLabelValues) an example of "exposing"? To make things more complicated you may also hear about samples when reading Prometheus documentation. At this point, both nodes should be ready. 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. I'd expect to have also: Please use the prometheus-users mailing list for questions. I have just used the JSON file that is available in below website count the number of running instances per application like this: This documentation is open-source. TSDB used in Prometheus is a special kind of database that was highly optimized for a very specific workload: This means that Prometheus is most efficient when continuously scraping the same time series over and over again. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. Lets adjust the example code to do this. With any monitoring system its important that youre able to pull out the right data. This is a deliberate design decision made by Prometheus developers. I then hide the original query. 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. Monitoring Docker container metrics using cAdvisor, Use file-based service discovery to discover scrape targets, Understanding and using the multi-target exporter pattern, Monitoring Linux host metrics with the Node Exporter. The result of an expression can either be shown as a graph, viewed as tabular data in Prometheus's expression browser, or consumed by external systems via the HTTP API. Prometheus will keep each block on disk for the configured retention period. from and what youve done will help people to understand your problem. 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. Sign up and get Kubernetes tips delivered straight to your inbox. If you do that, the line will eventually be redrawn, many times over. This selector is just a metric name. 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. 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. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Is there a single-word adjective for "having exceptionally strong moral principles"? It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. This works fine when there are data points for all queries in the expression. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. Theres no timestamp anywhere actually. 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. Once theyre in TSDB its already too late. 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. 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. We covered some of the most basic pitfalls in our previous blog post on Prometheus - Monitoring our monitoring. Next, create a Security Group to allow access to the instances. The real power of Prometheus comes into the picture when you utilize the alert manager to send notifications when a certain metric breaches a threshold. What sort of strategies would a medieval military use against a fantasy giant? On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. If you need to obtain raw samples, then a range query must be sent to /api/v1/query. We know that time series will stay in memory for a while, even if they were scraped only once. How do I align things in the following tabular environment? Thanks, Has 90% of ice around Antarctica disappeared in less than a decade? 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. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. Is a PhD visitor considered as a visiting scholar? rev2023.3.3.43278. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) See these docs for details on how Prometheus calculates the returned results. 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! Are there tables of wastage rates for different fruit and veg? What this means is that a single metric will create one or more time series. Time arrow with "current position" evolving with overlay number. 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. We can use these to add more information to our metrics so that we can better understand whats going on. 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. I'm displaying Prometheus query on a Grafana table. Or maybe we want to know if it was a cold drink or a hot one? How to react to a students panic attack in an oral exam? for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. 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. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. what error message are you getting to show that theres a problem? What is the point of Thrower's Bandolier? 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. You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. I used a Grafana transformation which seems to work. After sending a request it will parse the response looking for all the samples exposed there. 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. which Operating System (and version) are you running it under? However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. Theres only one chunk that we can append to, its called the Head Chunk. I know prometheus has comparison operators but I wasn't able to apply them. Already on GitHub? Also the link to the mailing list doesn't work for me. This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. 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. Which in turn will double the memory usage of our Prometheus server. privacy statement. Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. This gives us confidence that we wont overload any Prometheus server after applying changes. If so I'll need to figure out a way to pre-initialize the metric which may be difficult since the label values may not be known a priori. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). whether someone is able to help out. 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. Both patches give us two levels of protection. You signed in with another tab or window. These queries are a good starting point. Not the answer you're looking for? Managed Service for Prometheus Cloud Monitoring Prometheus # ! This makes a bit more sense with your explanation. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Connect and share knowledge within a single location that is structured and easy to search. Often it doesnt require any malicious actor to cause cardinality related problems. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. Returns a list of label names. 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. If the total number of stored time series is below the configured limit then we append the sample as usual. 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. 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. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Its very easy to keep accumulating time series in Prometheus until you run out of memory. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. You can query Prometheus metrics directly with its own query language: PromQL. With our custom patch we dont care how many samples are in a scrape. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. There is an open pull request which improves memory usage of labels by storing all labels as a single string. 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. Using a query that returns "no data points found" in an expression. 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? Run the following commands in both nodes to disable SELinux and swapping: Also, change
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prometheus query return 0 if no data