By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Prometheus query check if value exist. Sign up and get Kubernetes tips delivered straight to your inbox. Asking for help, clarification, or responding to other answers. Find centralized, trusted content and collaborate around the technologies you use most. an EC2 regions with application servers running docker containers. 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. In general, having more labels on your metrics allows you to gain more insight, and so the more complicated the application you're trying to monitor, the more need for extra labels. scheduler exposing these metrics about the instances it runs): The same expression, but summed by application, could be written like this: If the same fictional cluster scheduler exposed CPU usage metrics like the This works fine when there are data points for all queries in the expression. 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. Any other chunk holds historical samples and therefore is read-only. We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. syntax. Find centralized, trusted content and collaborate around the technologies you use most. 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. For example, I'm using the metric to record durations for quantile reporting. All they have to do is set it explicitly in their scrape configuration. and can help you on Better to simply ask under the single best category you think fits and see One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. Inside the Prometheus configuration file we define a scrape config that tells Prometheus where to send the HTTP request, how often and, optionally, to apply extra processing to both requests and responses. windows. 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. By default Prometheus will create a chunk per each two hours of wall clock. 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. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. 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. If your expression returns anything with labels, it won't match the time series generated by vector(0). Using a query that returns "no data points found" in an expression. So the maximum number of time series we can end up creating is four (2*2). 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. 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. 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. "no data". I've created an expression that is intended to display percent-success for a given metric. The actual amount of physical memory needed by Prometheus will usually be higher as a result, since it will include unused (garbage) memory that needs to be freed by Go runtime. Redoing the align environment with a specific formatting. To get a better understanding of the impact of a short lived time series on memory usage lets take a look at another example. 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. more difficult for those people to help. Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. 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. 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! Monitor the health of your cluster and troubleshoot issues faster with pre-built dashboards that just work. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. What is the point of Thrower's Bandolier? The Prometheus data source plugin provides the following functions you can use in the Query input field. count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). AFAIK it's not possible to hide them through Grafana. I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. Secondly this calculation is based on all memory used by Prometheus, not only time series data, so its just an approximation. This means that our memSeries still consumes some memory (mostly labels) but doesnt really do anything. Cadvisors on every server provide container names. 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. The only exception are memory-mapped chunks which are offloaded to disk, but will be read into memory if needed by queries. Run the following command on the master node: Once the command runs successfully, youll see joining instructions to add the worker node to the cluster. Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. 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. This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. https://grafana.com/grafana/dashboards/2129. At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. Under which circumstances? 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. You signed in with another tab or window. 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. Our CI would check that all Prometheus servers have spare capacity for at least 15,000 time series before the pull request is allowed to be merged. These will give you an overall idea about a clusters health. but viewed in the tabular ("Console") view of the expression browser. returns the unused memory in MiB for every instance (on a fictional cluster hackers at Has 90% of ice around Antarctica disappeared in less than a decade? Finally getting back to this. These queries will give you insights into node health, Pod health, cluster resource utilization, etc. - grafana-7.1.0-beta2.windows-amd64, how did you install it? If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. Name the nodes as Kubernetes Master and Kubernetes Worker. 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. Passing sample_limit is the ultimate protection from high cardinality. By clicking Sign up for GitHub, you agree to our terms of service and 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. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) Sign in In Prometheus pulling data is done via PromQL queries and in this article we guide the reader through 11 examples that can be used for Kubernetes specifically. 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. What happens when somebody wants to export more time series or use longer labels? To learn more about our mission to help build a better Internet, start here. What video game is Charlie playing in Poker Face S01E07? Is it suspicious or odd to stand by the gate of a GA airport watching the planes? 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. To learn more, see our tips on writing great answers. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 what error message are you getting to show that theres a problem? t]. 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. 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. 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 . Sign in 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. How to follow the signal when reading the schematic? So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. Are there tables of wastage rates for different fruit and veg? Returns a list of label names. how have you configured the query which is causing problems? I'm still out of ideas here. Second rule does the same but only sums time series with status labels equal to "500". Select the query and do + 0. If you do that, the line will eventually be redrawn, many times over. The text was updated successfully, but these errors were encountered: This is correct. 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. How can I group labels in a Prometheus query? Once theyre in TSDB its already too late. Hello, I'm new at Grafan and Prometheus. I've added a data source (prometheus) in Grafana. Even i am facing the same issue Please help me on this. Why is this sentence from The Great Gatsby grammatical? Each chunk represents a series of samples for a specific time range. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Theres only one chunk that we can append to, its called the Head Chunk. 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. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. Prometheus allows us to measure health & performance over time and, if theres anything wrong with any service, let our team know before it becomes a problem. entire corporate networks, Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. Is it possible to rotate a window 90 degrees if it has the same length and width? 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. count(container_last_seen{name="container_that_doesn't_exist"}), What did you see instead? Have a question about this project? Yeah, absent() is probably the way to go. Prometheus does offer some options for dealing with high cardinality problems. Stumbled onto this post for something else unrelated, just was +1-ing this :). This process is also aligned with the wall clock but shifted by one hour. 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. Time arrow with "current position" evolving with overlay number. With any monitoring system its important that youre able to pull out the right data. It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. Lets say we have an application which we want to instrument, which means add some observable properties in the form of metrics that Prometheus can read from our application. Our metric will have a single label that stores the request path. from and what youve done will help people to understand your problem. Please dont post the same question under multiple topics / subjects. Next you will likely need to create recording and/or alerting rules to make use of your time series. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. Instead we count time series as we append them to TSDB. Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. We protect In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. or something like that. Cardinality is the number of unique combinations of all labels. to get notified when one of them is not mounted anymore. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. If we add another label that can also have two values then we can now export up to eight time series (2*2*2). Run the following commands in both nodes to configure the Kubernetes repository. 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. About an argument in Famine, Affluence and Morality. 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. This article covered a lot of ground. 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 process helps to reduce disk usage since each block has an index taking a good chunk of disk space. For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. I can get the deployments in the dev, uat, and prod environments using this query: So we can see that tenant 1 has 2 deployments in 2 different environments, whereas the other 2 have only one. For operations between two instant vectors, the matching behavior can be modified. A metric is an observable property with some defined dimensions (labels). Can airtags be tracked from an iMac desktop, with no iPhone? will get matched and propagated to the output. Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. 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). The number of time series depends purely on the number of labels and the number of all possible values these labels can take. I then hide the original query. Where does this (supposedly) Gibson quote come from? positions. There are a number of options you can set in your scrape configuration block. 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. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 - 05:59, , 22:00 - 23:59. Finally, please remember that some people read these postings as an email rate (http_requests_total [5m]) [30m:1m] vishnur5217 May 31, 2020, 3:44am 1. Visit 1.1.1.1 from any device to get started with You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. By clicking Sign up for GitHub, you agree to our terms of service and I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. 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. Can airtags be tracked from an iMac desktop, with no iPhone? This helps Prometheus query data faster since all it needs to do is first locate the memSeries instance with labels matching our query and then find the chunks responsible for time range of the query. Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. or Internet application, If the error message youre getting (in a log file or on screen) can be quoted 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. After running the query, a table will show the current value of each result time series (one table row per output series). I'm not sure what you mean by exposing a metric. 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. How to react to a students panic attack in an oral exam? Asking for help, clarification, or responding to other answers. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. Does Counterspell prevent from any further spells being cast on a given turn? your journey to Zero Trust. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. 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. And this brings us to the definition of cardinality in the context of metrics. Lets create a demo Kubernetes cluster and set up Prometheus to monitor it. Looking to learn more? Doubling the cube, field extensions and minimal polynoms. 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 have a query that gets a pipeline builds and its divided by the number of change request open in a 1 month window, which gives a percentage. Or do you have some other label on it, so that the metric still only gets exposed when you record the first failued request it? what does the Query Inspector show for the query you have a problem with? Also, providing a reasonable amount of information about where youre starting To learn more, see our tips on writing great answers. 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. Internally all time series are stored inside a map on a structure called Head. 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). By default Prometheus will create a chunk per each two hours of wall clock. notification_sender-. Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. This patchset consists of two main elements. Is a PhD visitor considered as a visiting scholar? As we mentioned before a time series is generated from metrics. (pseudocode): This gives the same single value series, or no data if there are no alerts. what error message are you getting to show that theres a problem? 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 a PhD visitor considered as a visiting scholar? I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). I believe it's the logic that it's written, but is there any . Youll be executing all these queries in the Prometheus expression browser, so lets get started. Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. Find centralized, trusted content and collaborate around the technologies you use most. 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. These are the sane defaults that 99% of application exporting metrics would never exceed. gabrigrec September 8, 2021, 8:12am #8. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. website job and handler labels: Return a whole range of time (in this case 5 minutes up to the query time) That's the query ( Counter metric): sum (increase (check_fail {app="monitor"} [20m])) by (reason) The result is a table of failure reason and its count. To set up Prometheus to monitor app metrics: Download and install Prometheus. Once configured, your instances should be ready for access. Lets adjust the example code to do this. The simplest way of doing this is by using functionality provided with client_python itself - see documentation here. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. 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. Its very easy to keep accumulating time series in Prometheus until you run out of memory. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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. Now comes the fun stuff. For that lets follow all the steps in the life of a time series inside Prometheus. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. If we let Prometheus consume more memory than it can physically use then it will crash. to your account, What did you do? We know what a metric, a sample and a time series is. 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. Managed Service for Prometheus Cloud Monitoring Prometheus # ! A sample is something in between metric and time series - its a time series value for a specific timestamp. by (geo_region) < bool 4 This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. Have a question about this project? If so it seems like this will skew the results of the query (e.g., quantiles). Each Prometheus is scraping a few hundred different applications, each running on a few hundred servers. 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. To avoid this its in general best to never accept label values from untrusted sources. information which you think might be helpful for someone else to understand No error message, it is just not showing the data while using the JSON file from that website. Extra fields needed by Prometheus internals. If you need to obtain raw samples, then a range query must be sent to /api/v1/query. Use Prometheus to monitor app performance metrics. (fanout by job name) and instance (fanout by instance of the job), we might If all the label values are controlled by your application you will be able to count the number of all possible label combinations. Now, lets install Kubernetes on the master node using kubeadm. The more any application does for you, the more useful it is, the more resources it might need. Making statements based on opinion; back them up with references or personal experience. 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. 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. I.e., there's no way to coerce no datapoints to 0 (zero)? This might require Prometheus to create a new chunk if needed. it works perfectly if one is missing as count() then returns 1 and the rule fires. list, which does not convey images, so screenshots etc. But before that, lets talk about the main components of Prometheus. 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.
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