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. 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. But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. Cadvisors on every server provide container names. 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). There is a maximum of 120 samples each chunk can hold. Visit 1.1.1.1 from any device to get started with 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. We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. That map uses labels hashes as keys and a structure called memSeries as values. Use it to get a rough idea of how much memory is used per time series and dont assume its that exact number. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, Please dont post the same question under multiple topics / subjects. It doesnt get easier than that, until you actually try to do it. 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. All rights reserved. hackers at 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. 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. Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 0. Name the nodes as Kubernetes Master and Kubernetes Worker. 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. See this article for details. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. Has 90% of ice around Antarctica disappeared in less than a decade? So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 - 05:59, , 22:00 - 23:59. Connect and share knowledge within a single location that is structured and easy to search. 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. The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. What does remote read means in Prometheus? Is a PhD visitor considered as a visiting scholar? 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. whether someone is able to help out. gabrigrec September 8, 2021, 8:12am #8. If we configure a sample_limit of 100 and our metrics response contains 101 samples, then Prometheus wont scrape anything at all. to get notified when one of them is not mounted anymore. Now we should pause to make an important distinction between metrics and time series. This would happen if any time series was no longer being exposed by any application and therefore there was no scrape that would try to append more samples to it. Finally, please remember that some people read these postings as an email So the maximum number of time series we can end up creating is four (2*2). Note that using subqueries unnecessarily is unwise. Please see data model and exposition format pages for more details. This might require Prometheus to create a new chunk if needed. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Operating such a large Prometheus deployment doesnt come without challenges. and can help you on Have you fixed this issue? Making statements based on opinion; back them up with references or personal experience. 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. Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. Lets pick client_python for simplicity, but the same concepts will apply regardless of the language you use. Im new at Grafan and Prometheus. 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. I have a data model where some metrics are namespaced by client, environment and deployment name. Return the per-second rate for all time series with the http_requests_total 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. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. The idea is that if done as @brian-brazil mentioned, there would always be a fail and success metric, because they are not distinguished by a label, but always are exposed. Before that, Vinayak worked as a Senior Systems Engineer at Singapore Airlines. Second rule does the same but only sums time series with status labels equal to "500". 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? Already on GitHub? entire corporate networks, 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. *) in region drops below 4. In our example we have two labels, content and temperature, and both of them can have two different values. Basically our labels hash is used as a primary key inside TSDB. Is what you did above (failures.WithLabelValues) an example of "exposing"? For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. But before that, lets talk about the main components of Prometheus. Also the link to the mailing list doesn't work for me. Timestamps here can be explicit or implicit. This is because the Prometheus server itself is responsible for timestamps. About an argument in Famine, Affluence and Morality. attacks, keep The struct definition for memSeries is fairly big, but all we really need to know is that it has a copy of all the time series labels and chunks that hold all the samples (timestamp & value pairs). Even Prometheus' own client libraries had bugs that could expose you to problems like this. Well occasionally send you account related emails. The speed at which a vehicle is traveling. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Lets adjust the example code to do this. We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. Not the answer you're looking for? 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. 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. This is what i can see on Query Inspector. 2023 The Linux Foundation. Just add offset to the query. 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. Add field from calculation Binary operation. @rich-youngkin Yes, the general problem is non-existent series. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. Being able to answer How do I X? yourself without having to wait for a subject matter expert allows everyone to be more productive and move faster, while also avoiding Prometheus experts from answering the same questions over and over again. Its also worth mentioning that without our TSDB total limit patch we could keep adding new scrapes to Prometheus and that alone could lead to exhausting all available capacity, even if each scrape had sample_limit set and scraped fewer time series than this limit allows. 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. Time arrow with "current position" evolving with overlay number. If so it seems like this will skew the results of the query (e.g., quantiles). We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. 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. Each chunk represents a series of samples for a specific time range. Run the following commands in both nodes to configure the Kubernetes repository. Here at Labyrinth Labs, we put great emphasis on monitoring. This process is also aligned with the wall clock but shifted by one hour. I'm not sure what you mean by exposing a metric. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 following for every instance: we could get the top 3 CPU users grouped by application (app) and process There are a number of options you can set in your scrape configuration block. So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. 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 result is a table of failure reason and its count. 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. But the real risk is when you create metrics with label values coming from the outside world. Both patches give us two levels of protection. accelerate any 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. Every two hours Prometheus will persist chunks from memory onto the disk. Have a question about this project? But you cant keep everything in memory forever, even with memory-mapping parts of data. Our metric will have a single label that stores the request path. This is an example of a nested subquery. The Graph tab allows you to graph a query expression over a specified range of time. A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). If you're looking for a You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. The Linux Foundation has registered trademarks and uses trademarks. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. what error message are you getting to show that theres a problem? Well occasionally send you account related emails. bay, For that lets follow all the steps in the life of a time series inside Prometheus. Secondly this calculation is based on all memory used by Prometheus, not only time series data, so its just an approximation. The subquery for the deriv function uses the default resolution. These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. what does the Query Inspector show for the query you have a problem with? VictoriaMetrics has other advantages compared to Prometheus, ranging from massively parallel operation for scalability, better performance, and better data compression, though what we focus on for this blog post is a rate () function handling. At the moment of writing this post we run 916 Prometheus instances with a total of around 4.9 billion time series. 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. Separate metrics for total and failure will work as expected. I've added a data source (prometheus) in Grafana. Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. returns the unused memory in MiB for every instance (on a fictional cluster The only exception are memory-mapped chunks which are offloaded to disk, but will be read into memory if needed by queries. By default Prometheus will create a chunk per each two hours of wall clock. To your second question regarding whether I have some other label on it, the answer is yes I do. The more labels you have and the more values each label can take, the more unique combinations you can create and the higher the cardinality. the problem you have. how have you configured the query which is causing problems? to your account. Is a PhD visitor considered as a visiting scholar? Managing the entire lifecycle of a metric from an engineering perspective is a complex process. Internally all time series are stored inside a map on a structure called Head. Time series scraped from applications are kept in memory. The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. PROMQL: how to add values when there is no data returned? Better to simply ask under the single best category you think fits and see What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Once we appended sample_limit number of samples we start to be selective. I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). For example, I'm using the metric to record durations for quantile reporting. 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. This selector is just a metric name. an EC2 regions with application servers running docker containers. 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. Asking for help, clarification, or responding to other answers. Using regular expressions, you could select time series only for jobs whose The reason why we still allow appends for some samples even after were above sample_limit is that appending samples to existing time series is cheap, its just adding an extra timestamp & value pair. Is it possible to create a concave light? Can airtags be tracked from an iMac desktop, with no iPhone? 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. Is it a bug? 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. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) 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. The process of sending HTTP requests from Prometheus to our application is called scraping. 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 simplest way of doing this is by using functionality provided with client_python itself - see documentation here. our free app that makes your Internet faster and safer. *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. Simple, clear and working - thanks a lot. Can airtags be tracked from an iMac desktop, with no iPhone? Please open a new issue for related bugs. All regular expressions in Prometheus use RE2 syntax. Once theyre in TSDB its already too late. How to show that an expression of a finite type must be one of the finitely many possible values? 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. I'm displaying Prometheus query on a Grafana table. The more labels we have or the more distinct values they can have the more time series as a result. Find centralized, trusted content and collaborate around the technologies you use most. rev2023.3.3.43278. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. will get matched and propagated to the output. This garbage collection, among other things, will look for any time series without a single chunk and remove it from memory. This is one argument for not overusing labels, but often it cannot be avoided. 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. Thanks for contributing an answer to Stack Overflow! are going to make it or something like that. privacy statement. Once it has a memSeries instance to work with it will append our sample to the Head Chunk. 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. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. Asking for help, clarification, or responding to other answers. Explanation: Prometheus uses label matching in expressions. I've been using comparison operators in Grafana for a long while. Are there tables of wastage rates for different fruit and veg? What happens when somebody wants to export more time series or use longer labels? Looking to learn more? 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 difference with standard Prometheus starts when a new sample is about to be appended, but TSDB already stores the maximum number of time series its allowed to have. 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. To set up Prometheus to monitor app metrics: Download and install Prometheus. Find centralized, trusted content and collaborate around the technologies you use most. If this query also returns a positive value, then our cluster has overcommitted the memory. 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. Yeah, absent() is probably the way to go. Theres only one chunk that we can append to, its called the Head Chunk. The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. privacy statement. Why is this sentence from The Great Gatsby grammatical? As we mentioned before a time series is generated from metrics. Stumbled onto this post for something else unrelated, just was +1-ing this :). These queries are a good starting point. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. 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. The more any application does for you, the more useful it is, the more resources it might need. Find centralized, trusted content and collaborate around the technologies you use most. 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. Why is there a voltage on my HDMI and coaxial cables? 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. To do that, run the following command on the master node: Next, create an SSH tunnel between your local workstation and the master node by running the following command on your local machine: If everything is okay at this point, you can access the Prometheus console at http://localhost:9090. What am I doing wrong here in the PlotLegends specification? an EC2 regions with application servers running docker containers. 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. Our patched logic will then check if the sample were about to append belongs to a time series thats already stored inside TSDB or is it a new time series that needs to be created. 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. However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. There's also count_scalar(), If we add another label that can also have two values then we can now export up to eight time series (2*2*2). Bulk update symbol size units from mm to map units in rule-based symbology. By clicking Sign up for GitHub, you agree to our terms of service and Where does this (supposedly) Gibson quote come from? Asking for help, clarification, or responding to other answers. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. Connect and share knowledge within a single location that is structured and easy to search. source, what your query is, what the query inspector shows, and any other The number of times some specific event occurred. 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. or Internet application, ward off DDoS 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. Thats why what our application exports isnt really metrics or time series - its samples. Both rules will produce new metrics named after the value of the record field. node_cpu_seconds_total: This returns the total amount of CPU time. It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. These will give you an overall idea about a clusters health. Examples Which in turn will double the memory usage of our Prometheus server. I have just used the JSON file that is available in below website You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. syntax. We will also signal back to the scrape logic that some samples were skipped. Thanks for contributing an answer to Stack Overflow! Having better insight into Prometheus internals allows us to maintain a fast and reliable observability platform without too much red tape, and the tooling weve developed around it, some of which is open sourced, helps our engineers avoid most common pitfalls and deploy with confidence.