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Using a query that returns "no data points found" in an - GitHub We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. By clicking Sign up for GitHub, you agree to our terms of service and 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? We know that time series will stay in memory for a while, even if they were scraped only once. 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. All rights reserved. Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. For operations between two instant vectors, the matching behavior can be modified. And this brings us to the definition of cardinality in the context of metrics. @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). what error message are you getting to show that theres a problem? How can I group labels in a Prometheus query? whether someone is able to help out. Are there tables of wastage rates for different fruit and veg? In both nodes, edit the /etc/hosts file to add the private IP of the nodes. 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. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. With any monitoring system its important that youre able to pull out the right data. 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. On the worker node, run the kubeadm joining command shown in the last step. 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). Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). Lets adjust the example code to do this. 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? With 1,000 random requests we would end up with 1,000 time series in Prometheus. One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. Using regular expressions, you could select time series only for jobs whose SSH into both servers and run the following commands to install Docker. 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. ***> wrote: You signed in with another tab or window. 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. If the total number of stored time series is below the configured limit then we append the sample as usual. There's also count_scalar(), See these docs for details on how Prometheus calculates the returned results. At this point, both nodes should be ready. by (geo_region) < bool 4 @juliusv Thanks for clarifying that. Prometheus will keep each block on disk for the configured retention period. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. In reality though this is as simple as trying to ensure your application doesnt use too many resources, like CPU or memory - you can achieve this by simply allocating less memory and doing fewer computations. If you need to obtain raw samples, then a range query must be sent to /api/v1/query. Prometheus and PromQL (Prometheus Query Language) are conceptually very simple, but this means that all the complexity is hidden in the interactions between different elements of the whole metrics pipeline. 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. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. 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 clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. If both the nodes are running fine, you shouldnt get any result for this query. Play with bool For example, I'm using the metric to record durations for quantile reporting. Grafana renders "no data" when instant query returns empty dataset Is a PhD visitor considered as a visiting scholar? 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. The more labels you have, or the longer the names and values are, the more memory it will use. For example, /api/v1/query?query=http_response_ok [24h]&time=t would return raw samples on the time range (t-24h . Those limits are there to catch accidents and also to make sure that if any application is exporting a high number of time series (more than 200) the team responsible for it knows about it. 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. 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. 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. This makes a bit more sense with your explanation. Stumbled onto this post for something else unrelated, just was +1-ing this :). Already on GitHub? PromQL allows querying historical data and combining / comparing it to the current data. Theres no timestamp anywhere actually. instance_memory_usage_bytes: This shows the current memory used. Sign in 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. or Internet application, 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. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. - grafana-7.1.0-beta2.windows-amd64, how did you install it? Simple, clear and working - thanks a lot. To select all HTTP status codes except 4xx ones, you could run: Return the 5-minute rate of the http_requests_total metric for the past 30 minutes, with a resolution of 1 minute. 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. Find centralized, trusted content and collaborate around the technologies you use most. Connect and share knowledge within a single location that is structured and easy to search. 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? 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. windows. Find centralized, trusted content and collaborate around the technologies you use most. Or maybe we want to know if it was a cold drink or a hot one? A sample is something in between metric and time series - its a time series value for a specific timestamp. If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. To set up Prometheus to monitor app metrics: Download and install Prometheus. This is one argument for not overusing labels, but often it cannot be avoided. After running the query, a table will show the current value of each result time series (one table row per output series). That map uses labels hashes as keys and a structure called memSeries as values. Of course, this article is not a primer on PromQL; you can browse through the PromQL documentation for more in-depth knowledge. Under which circumstances? This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. Well occasionally send you account related emails. I used a Grafana transformation which seems to work. To learn more, see our tips on writing great answers. 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. If we have a scrape with sample_limit set to 200 and the application exposes 201 time series, then all except one final time series will be accepted. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) Please dont post the same question under multiple topics / subjects. I.e., there's no way to coerce no datapoints to 0 (zero)? We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. returns the unused memory in MiB for every instance (on a fictional cluster are going to make it notification_sender-. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Now, lets install Kubernetes on the master node using kubeadm. AFAIK it's not possible to hide them through Grafana. Prometheus - exclude 0 values from query result - Stack Overflow 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 gives us confidence that we wont overload any Prometheus server after applying changes. I've added a data source (prometheus) in Grafana. This is because the Prometheus server itself is responsible for timestamps. Connect and share knowledge within a single location that is structured and easy to search. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. To this end, I set up the query to instant so that the very last data point is returned but, when the query does not return a value - say because the server is down and/or no scraping took place - the stat panel produces no data. @rich-youngkin Yes, the general problem is non-existent series. your journey to Zero Trust. @zerthimon You might want to use 'bool' with your comparator Has 90% of ice around Antarctica disappeared in less than a decade? (fanout by job name) and instance (fanout by instance of the job), we might 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. Already on GitHub? list, which does not convey images, so screenshots etc. No error message, it is just not showing the data while using the JSON file from that website. In our example we have two labels, content and temperature, and both of them can have two different values. I believe it's the logic that it's written, but is there any . Better Prometheus rate() Function with VictoriaMetrics Setting label_limit provides some cardinality protection, but even with just one label name and huge number of values we can see high cardinality. The speed at which a vehicle is traveling. If you're looking for a PromLabs | Blog - Selecting Data in PromQL With our custom patch we dont care how many samples are in a scrape. rate (http_requests_total [5m]) [30m:1m] Separate metrics for total and failure will work as expected. 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 And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. *) in region drops below 4. But you cant keep everything in memory forever, even with memory-mapping parts of data. 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 single sample (data point) will create a time series instance that will stay in memory for over two and a half hours using resources, just so that we have a single timestamp & value pair. Its not going to get you a quicker or better answer, and some people might or Internet application, ward off DDoS The Head Chunk is never memory-mapped, its always stored in memory. This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. Why do many companies reject expired SSL certificates as bugs in bug bounties? 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. PromQL allows you to write queries and fetch information from the metric data collected by Prometheus. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. 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. I've created an expression that is intended to display percent-success for a given metric. These queries are a good starting point. For that lets follow all the steps in the life of a time series inside Prometheus. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . what does the Query Inspector show for the query you have a problem with? count(container_last_seen{name="container_that_doesn't_exist"}), What did you see instead? Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. Well be executing kubectl commands on the master node only. Its very easy to keep accumulating time series in Prometheus until you run out of memory. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). 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. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. Second rule does the same but only sums time series with status labels equal to "500". This process is also aligned with the wall clock but shifted by one hour. 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. As we mentioned before a time series is generated from metrics. So it seems like I'm back to square one. 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. PROMQL: how to add values when there is no data returned? Select the query and do + 0. In our example case its a Counter class object. 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. Managed Service for Prometheus Cloud Monitoring Prometheus # ! Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. binary operators to them and elements on both sides with the same label set Is it a bug? but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply 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. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. @zerthimon The following expr works for me metric name, as measured over the last 5 minutes: Assuming that the http_requests_total time series all have the labels job I'm still out of ideas here. 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. Prometheus's query language supports basic logical and arithmetic operators. Returns a list of label names. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. 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. If the error message youre getting (in a log file or on screen) can be quoted Why are physically impossible and logically impossible concepts considered separate in terms of probability? I suggest you experiment more with the queries as you learn, and build a library of queries you can use for future projects. Have a question about this project? Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. How to react to a students panic attack in an oral exam? Finally, please remember that some people read these postings as an email Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. How do I align things in the following tabular environment? name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, The only exception are memory-mapped chunks which are offloaded to disk, but will be read into memory if needed by queries. For example our errors_total metric, which we used in example before, might not be present at all until we start seeing some errors, and even then it might be just one or two errors that will be recorded. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 I'm not sure what you mean by exposing a metric. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. Its the chunk responsible for the most recent time range, including the time of our scrape. Time series scraped from applications are kept in memory. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. Why is there a voltage on my HDMI and coaxial cables? want to sum over the rate of all instances, so we get fewer output time series, Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. job and handler labels: Return a whole range of time (in this case 5 minutes up to the query time) Both rules will produce new metrics named after the value of the record field. 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. First rule will tell Prometheus to calculate per second rate of all requests and sum it across all instances of our server. By clicking Sign up for GitHub, you agree to our terms of service and How can i turn no data to zero in Loki - Grafana Loki - Grafana Labs But before doing that it needs to first check which of the samples belong to the time series that are already present inside TSDB and which are for completely new time series. Is it possible to create a concave light? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. privacy statement. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. Please help improve it by filing issues or pull requests. Can airtags be tracked from an iMac desktop, with no iPhone? will get matched and propagated to the output. Once theyre in TSDB its already too late. 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. Doubling the cube, field extensions and minimal polynoms. Connect and share knowledge within a single location that is structured and easy to search. We also limit the length of label names and values to 128 and 512 characters, which again is more than enough for the vast majority of scrapes. What is the point of Thrower's Bandolier? Also the link to the mailing list doesn't work for me. 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. Good to know, thanks for the quick response! These will give you an overall idea about a clusters health. Monitor Confluence with Prometheus and Grafana | Confluence Data Center Asking for help, clarification, or responding to other answers. 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. Redoing the align environment with a specific formatting. I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). With our example metric we know how many mugs were consumed, but what if we also want to know what kind of beverage it was? to get notified when one of them is not mounted anymore. Thanks, Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. Basically our labels hash is used as a primary key inside TSDB. to your account. 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. Ive deliberately kept the setup simple and accessible from any address for demonstration. Prometheus Queries: 11 PromQL Examples and Tutorial - ContainIQ The Graph tab allows you to graph a query expression over a specified range of time. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. help customers build The more any application does for you, the more useful it is, the more resources it might need. Adding labels is very easy and all we need to do is specify their names. Vinayak is an experienced cloud consultant with a knack of automation, currently working with Cognizant Singapore. With this simple code Prometheus client library will create a single metric. The simplest way of doing this is by using functionality provided with client_python itself - see documentation here. After sending a request it will parse the response looking for all the samples exposed there. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Minimising the environmental effects of my dyson brain. Ive added a data source(prometheus) in Grafana. 2023 The Linux Foundation. Does a summoned creature play immediately after being summoned by a ready action? So when TSDB is asked to append a new sample by any scrape, it will first check how many time series are already present. The text was updated successfully, but these errors were encountered: This is correct. For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. 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. 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.