About an argument in Famine, Affluence and Morality. Use Prometheus to monitor app performance metrics. new career direction, check out our open but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). The number of time series depends purely on the number of labels and the number of all possible values these labels can take. 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. Thanks, To learn more, see our tips on writing great answers. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. 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. This article covered a lot of ground. Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. 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. But before that, lets talk about the main components of Prometheus. Is there a solutiuon to add special characters from software and how to do it. 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 helps us avoid a situation where applications are exporting thousands of times series that arent really needed. All regular expressions in Prometheus use RE2 syntax. which Operating System (and version) are you running it under? What am I doing wrong here in the PlotLegends specification? Does Counterspell prevent from any further spells being cast on a given turn? 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 . 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. These are the sane defaults that 99% of application exporting metrics would never exceed. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Combined thats a lot of different metrics. We know what a metric, a sample and a time series is. The region and polygon don't match. 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. To learn more, see our tips on writing great answers. 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. On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. 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. vishnur5217 May 31, 2020, 3:44am 1. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. an EC2 regions with application servers running docker containers. In our example we have two labels, content and temperature, and both of them can have two different values. Every two hours Prometheus will persist chunks from memory onto the disk. Under which circumstances? 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. Internally time series names are just another label called __name__, so there is no practical distinction between name and labels. Please help improve it by filing issues or pull requests. So perhaps the behavior I'm running into applies to any metric with a label, whereas a metric without any labels would behave as @brian-brazil indicated? Yeah, absent() is probably the way to go. result of a count() on a query that returns nothing should be 0 Well occasionally send you account related emails. Timestamps here can be explicit or implicit. 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. I've created an expression that is intended to display percent-success for a given metric. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? PromQL allows querying historical data and combining / comparing it to the current data. And this brings us to the definition of cardinality in the context of metrics. Using a query that returns "no data points found" in an expression. Does a summoned creature play immediately after being summoned by a ready action? This is what i can see on Query Inspector. Prometheus metrics can have extra dimensions in form of labels. These queries will give you insights into node health, Pod health, cluster resource utilization, etc. Lets create a demo Kubernetes cluster and set up Prometheus to monitor it. Every time we add a new label to our metric we risk multiplying the number of time series that will be exported to Prometheus as the result. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. 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. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. Here are two examples of instant vectors: You can also use range vectors to select a particular time range. How Cloudflare runs Prometheus at scale If so it seems like this will skew the results of the query (e.g., quantiles). Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. metric name, as measured over the last 5 minutes: Assuming that the http_requests_total time series all have the labels job to your account. 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. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Finally you will want to create a dashboard to visualize all your metrics and be able to spot trends. For example, I'm using the metric to record durations for quantile reporting. Name the nodes as Kubernetes Master and Kubernetes Worker. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. We protect This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. 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. will get matched and propagated to the output. For example, this expression Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. privacy statement. 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. However when one of the expressions returns no data points found the result of the entire expression is no data points found. Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. Windows 10, how have you configured the query which is causing problems? type (proc) like this: Assuming this metric contains one time series per running instance, you could This means that Prometheus must check if theres already a time series with identical name and exact same set of labels present. The more labels you have, or the longer the names and values are, the more memory it will use. Explanation: Prometheus uses label matching in expressions. Finally getting back to this. This is an example of a nested subquery. rev2023.3.3.43278. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. The text was updated successfully, but these errors were encountered: This is correct. 4 Managed Service for Prometheus | 4 Managed Service for 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. 1 Like. Have a question about this project? We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. Minimising the environmental effects of my dyson brain. What this means is that a single metric will create one or more time series. how have you configured the query which is causing problems? Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. 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. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Thats why what our application exports isnt really metrics or time series - its samples. This works fine when there are data points for all queries in the expression. Or maybe we want to know if it was a cold drink or a hot one? Why are physically impossible and logically impossible concepts considered separate in terms of probability? which outputs 0 for an empty input vector, but that outputs a scalar or Internet application, whether someone is able to help out. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, How Intuit democratizes AI development across teams through reusability. You can verify this by running the kubectl get nodes command on the master node. 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. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. 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. 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. Looking to learn more? Monitor Confluence with Prometheus and Grafana | Confluence Data Center For instance, the following query would return week-old data for all the time series with node_network_receive_bytes_total name: node_network_receive_bytes_total offset 7d I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Sign in 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. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. 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. Theres no timestamp anywhere actually. t]. 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. A sample is something in between metric and time series - its a time series value for a specific timestamp. Add field from calculation Binary operation. 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. Even Prometheus' own client libraries had bugs that could expose you to problems like this. 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). Where does this (supposedly) Gibson quote come from? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Finally we maintain a set of internal documentation pages that try to guide engineers through the process of scraping and working with metrics, with a lot of information thats specific to our environment. If the error message youre getting (in a log file or on screen) can be quoted ***> wrote: You signed in with another tab or window. 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. One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. Select the query and do + 0. PromQL tutorial for beginners and humans - Medium 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. Time series scraped from applications are kept in memory. positions. 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 believe it's the logic that it's written, but is there any . We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. The thing with a metric vector (a metric which has dimensions) is that only the series for it actually get exposed on /metrics which have been explicitly initialized. 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. There are a number of options you can set in your scrape configuration block. With 1,000 random requests we would end up with 1,000 time series in Prometheus. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. 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). but viewed in the tabular ("Console") view of the expression browser. an EC2 regions with application servers running docker containers. By default Prometheus will create a chunk per each two hours of wall clock. VictoriaMetrics handles rate () function in the common sense way I described earlier! To set up Prometheus to monitor app metrics: Download and install Prometheus. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. The TSDB limit patch protects the entire Prometheus from being overloaded by too many time series. Doubling the cube, field extensions and minimal polynoms. Thanks for contributing an answer to Stack Overflow! 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. Ive deliberately kept the setup simple and accessible from any address for demonstration. Why is there a voltage on my HDMI and coaxial cables? The downside of all these limits is that breaching any of them will cause an error for the entire scrape. Monitoring our monitoring: how we validate our Prometheus alert rules 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. attacks. This pod wont be able to run because we dont have a node that has the label disktype: ssd. Just add offset to the query. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. 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. (fanout by job name) and instance (fanout by instance of the job), we might 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. Are you not exposing the fail metric when there hasn't been a failure yet? Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. Cadvisors on every server provide container names. I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. 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. 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. In AWS, create two t2.medium instances running CentOS. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. 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. Once we appended sample_limit number of samples we start to be selective. 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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. 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 problem you have. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). Making statements based on opinion; back them up with references or personal experience. After running the query, a table will show the current value of each result time series (one table row per output series). Thirdly Prometheus is written in Golang which is a language with garbage collection. To learn more, see our tips on writing great answers. I'm not sure what you mean by exposing a metric. promql - Prometheus query check if value exist - Stack Overflow 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. Find centralized, trusted content and collaborate around the technologies you use most. To learn more about our mission to help build a better Internet, start here. In the screenshot below, you can see that I added two queries, A and B, but only . ncdu: What's going on with this second size column? How to follow the signal when reading the schematic? prometheus promql Share Follow edited Nov 12, 2020 at 12:27 To get a better understanding of the impact of a short lived time series on memory usage lets take a look at another example. Run the following commands in both nodes to configure the Kubernetes repository. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. what error message are you getting to show that theres a problem? To get a better idea of this problem lets adjust our example metric to track HTTP requests. Asking for help, clarification, or responding to other answers. This is a deliberate design decision made by Prometheus developers. 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? I can't work out how to add the alerts to the deployments whilst retaining the deployments for which there were no alerts returned: If I use sum with or, then I get this, depending on the order of the arguments to or: If I reverse the order of the parameters to or, I get what I am after: But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. How Intuit democratizes AI development across teams through reusability. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . I'd expect to have also: Please use the prometheus-users mailing list for questions. Its the chunk responsible for the most recent time range, including the time of our scrape. Object, url:api/datasources/proxy/2/api/v1/query_range?query=wmi_logical_disk_free_bytes%7Binstance%3D~%22%22%2C%20volume%20!~%22HarddiskVolume.%2B%22%7D&start=1593750660&end=1593761460&step=20&timeout=60s, Powered by Discourse, best viewed with JavaScript enabled, 1 Node Exporter for Prometheus Dashboard EN 20201010 | Grafana Labs, https://grafana.com/grafana/dashboards/2129. Please dont post the same question under multiple topics / subjects. Connect and share knowledge within a single location that is structured and easy to search. Hello, I'm new at Grafan and Prometheus. 02:00 - create a new chunk for 02:00 - 03:59 time range, 04:00 - create a new chunk for 04:00 - 05:59 time range, 22:00 - create a new chunk for 22:00 - 23:59 time range. This works fine when there are data points for all queries in the expression. How can i turn no data to zero in Loki - Grafana Loki - Grafana Labs It will record the time it sends HTTP requests and use that later as the timestamp for all collected time series. You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. If we let Prometheus consume more memory than it can physically use then it will crash. I have just used the JSON file that is available in below website These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. Making statements based on opinion; back them up with references or personal experience. However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. Is a PhD visitor considered as a visiting scholar? 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. You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. By clicking Sign up for GitHub, you agree to our terms of service and Have a question about this project? One of the most important layers of protection is a set of patches we maintain on top of Prometheus. Find centralized, trusted content and collaborate around the technologies you use most. 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. Going back to our metric with error labels we could imagine a scenario where some operation returns a huge error message, or even stack trace with hundreds of lines. How to show that an expression of a finite type must be one of the finitely many possible values? 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. This garbage collection, among other things, will look for any time series without a single chunk and remove it from memory. So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. See this article for details. @zerthimon The following expr works for me About an argument in Famine, Affluence and Morality. Has 90% of ice around Antarctica disappeared in less than a decade? If you need to obtain raw samples, then a range query must be sent to /api/v1/query. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? The process of sending HTTP requests from Prometheus to our application is called scraping. 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. @rich-youngkin Yeah, what I originally meant with "exposing" a metric is whether it appears in your /metrics endpoint at all (for a given set of labels). If you're looking for a Any other chunk holds historical samples and therefore is read-only. After a chunk was written into a block and removed from memSeries we might end up with an instance of memSeries that has no chunks. The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. or Internet application, ward off DDoS This is one argument for not overusing labels, but often it cannot be avoided. Managed Service for Prometheus Cloud Monitoring Prometheus # ! Before running the query, create a Pod with the following specification: Before running the query, create a PersistentVolumeClaim with the following specification: This will get stuck in Pending state as we dont have a storageClass called manual" in our cluster. Examples Operating such a large Prometheus deployment doesnt come without challenges. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. returns the unused memory in MiB for every instance (on a fictional cluster Before running this query, create a Pod with the following specification: If this query returns a positive value, then the cluster has overcommitted the CPU. to your account, What did you do?
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prometheus query return 0 if no data