Simple, clear and working - thanks a lot. Visit 1.1.1.1 from any device to get started with 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. Operating such a large Prometheus deployment doesnt come without challenges. How to react to a students panic attack in an oral exam? Each Prometheus is scraping a few hundred different applications, each running on a few hundred servers. By clicking Sign up for GitHub, you agree to our terms of service and What video game is Charlie playing in Poker Face S01E07? We know that each time series will be kept in memory. We use Prometheus to gain insight into all the different pieces of hardware and software that make up our global network. Time arrow with "current position" evolving with overlay number. 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. your journey to Zero Trust. This is an example of a nested subquery. @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). There is a maximum of 120 samples each chunk can hold. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. 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. This process is also aligned with the wall clock but shifted by one hour. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. vishnur5217 May 31, 2020, 3:44am 1. Have a question about this project? SSH into both servers and run the following commands to install Docker. 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. If both the nodes are running fine, you shouldnt get any result for this query. rev2023.3.3.43278. I'd expect to have also: Please use the prometheus-users mailing list for questions. The TSDB limit patch protects the entire Prometheus from being overloaded by too many time series. How to follow the signal when reading the schematic? How Intuit democratizes AI development across teams through reusability. By default Prometheus will create a chunk per each two hours of wall clock. The subquery for the deriv function uses the default resolution. Are there tables of wastage rates for different fruit and veg? 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. This patchset consists of two main elements. Is it a bug? 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 is the standard flow with a scrape that doesnt set any sample_limit: With our patch we tell TSDB that its allowed to store up to N time series in total, from all scrapes, at any time. returns the unused memory in MiB for every instance (on a fictional cluster new career direction, check out our open A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). This helps us avoid a situation where applications are exporting thousands of times series that arent really needed. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. 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. Examples 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. @zerthimon The following expr works for me @rich-youngkin Yes, the general problem is non-existent series. Other Prometheus components include a data model that stores the metrics, client libraries for instrumenting code, and PromQL for querying the metrics. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before . 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. Another reason is that trying to stay on top of your usage can be a challenging task. I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. I've added a data source (prometheus) in Grafana. The Prometheus data source plugin provides the following functions you can use in the Query input field. Well occasionally send you account related emails. For example, /api/v1/query?query=http_response_ok [24h]&time=t would return raw samples on the time range (t-24h . There is no equivalent functionality in a standard build of Prometheus, if any scrape produces some samples they will be appended to time series inside TSDB, creating new time series if needed. Im new at Grafan and Prometheus. 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? 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! 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. 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. If your expression returns anything with labels, it won't match the time series generated by vector(0). Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. 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. Why are trials on "Law & Order" in the New York Supreme Court? Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. We can use these to add more information to our metrics so that we can better understand whats going on. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). How is Jesus " " (Luke 1:32 NAS28) different from a prophet (, Luke 1:76 NAS28)? https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. On Thu, Dec 15, 2016 at 6:24 PM, Lior Goikhburg ***@***. Windows 10, how have you configured the query which is causing problems? Prometheus is a great and reliable tool, but dealing with high cardinality issues, especially in an environment where a lot of different applications are scraped by the same Prometheus server, can be challenging. our free app that makes your Internet faster and safer. 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. Yeah, absent() is probably the way to go. If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. There is a single time series for each unique combination of metrics labels. Is what you did above (failures.WithLabelValues) an example of "exposing"? 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. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. With any monitoring system its important that youre able to pull out the right data. For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Why are trials on "Law & Order" in the New York Supreme Court? How to show that an expression of a finite type must be one of the finitely many possible values? Of course there are many types of queries you can write, and other useful queries are freely available. I believe it's the logic that it's written, but is there any . Prometheus metrics can have extra dimensions in form of labels. 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. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. 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. Extra fields needed by Prometheus internals. Note that using subqueries unnecessarily is unwise. Return the per-second rate for all time series with the http_requests_total 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. PromQL allows querying historical data and combining / comparing it to the current data. For example, this expression want to sum over the rate of all instances, so we get fewer output time series, https://grafana.com/grafana/dashboards/2129. This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. 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). which outputs 0 for an empty input vector, but that outputs a scalar Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. We know that time series will stay in memory for a while, even if they were scraped only once. All regular expressions in Prometheus use RE2 syntax. Basically our labels hash is used as a primary key inside TSDB. Are you not exposing the fail metric when there hasn't been a failure yet? But before that, lets talk about the main components of Prometheus. Cadvisors on every server provide container names. Samples are compressed using encoding that works best if there are continuous updates. That map uses labels hashes as keys and a structure called memSeries as values. We know that the more labels on a metric, the more time series it can create. There is an open pull request on the Prometheus repository. However, if i create a new panel manually with a basic commands then i can see the data on the dashboard. Can I tell police to wait and call a lawyer when served with a search warrant? In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. ncdu: What's going on with this second size column? 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. To set up Prometheus to monitor app metrics: Download and install Prometheus. what error message are you getting to show that theres a problem? The text was updated successfully, but these errors were encountered: This is correct. 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. Adding labels is very easy and all we need to do is specify their names. privacy statement. You can calculate how much memory is needed for your time series by running this query on your Prometheus server: Note that your Prometheus server must be configured to scrape itself for this to work. Just add offset to the query. Why are physically impossible and logically impossible concepts considered separate in terms of probability? I'm displaying Prometheus query on a Grafana table. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. 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. I've created an expression that is intended to display percent-success for a given metric. Its very easy to keep accumulating time series in Prometheus until you run out of memory. While the sample_limit patch stops individual scrapes from using too much Prometheus capacity, which could lead to creating too many time series in total and exhausting total Prometheus capacity (enforced by the first patch), which would in turn affect all other scrapes since some new time series would have to be ignored. He has a Bachelor of Technology in Computer Science & Engineering from SRMS. Is a PhD visitor considered as a visiting scholar? You're probably looking for the absent function. However when one of the expressions returns no data points found the result of the entire expression is no data points found. Subscribe to receive notifications of new posts: Subscription confirmed. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. This holds true for a lot of labels that we see are being used by engineers. This thread has been automatically locked since there has not been any recent activity after it was closed. ward off DDoS Is it possible to rotate a window 90 degrees if it has the same length and width? Not the answer you're looking for? 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. Please see data model and exposition format pages for more details. 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 . Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. 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. Each chunk represents a series of samples for a specific time range. What is the point of Thrower's Bandolier? With 1,000 random requests we would end up with 1,000 time series in Prometheus. 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. If so it seems like this will skew the results of the query (e.g., quantiles). This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. PromQL allows you to write queries and fetch information from the metric data collected by Prometheus. Select the query and do + 0. Why is there a voltage on my HDMI and coaxial cables? Connect and share knowledge within a single location that is structured and easy to search. You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. Or maybe we want to know if it was a cold drink or a hot one? It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) Run the following commands in both nodes to configure the Kubernetes repository. Returns a list of label names. In our example case its a Counter class object. from and what youve done will help people to understand your problem. Asking for help, clarification, or responding to other answers. or something like that. If we let Prometheus consume more memory than it can physically use then it will crash. Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. We covered some of the most basic pitfalls in our previous blog post on Prometheus - Monitoring our monitoring. 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. And this brings us to the definition of cardinality in the context of metrics. I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. Each time series stored inside Prometheus (as a memSeries instance) consists of: The amount of memory needed for labels will depend on the number and length of these. Combined thats a lot of different metrics. 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. - grafana-7.1.0-beta2.windows-amd64, how did you install it? 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. Cardinality is the number of unique combinations of all labels. *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. 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. name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 In AWS, create two t2.medium instances running CentOS. For that lets follow all the steps in the life of a time series inside Prometheus. 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. For operations between two instant vectors, the matching behavior can be modified. In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. notification_sender-. What sort of strategies would a medieval military use against a fantasy giant? For example, if someone wants to modify sample_limit, lets say by changing existing limit of 500 to 2,000, for a scrape with 10 targets, thats an increase of 1,500 per target, with 10 targets thats 10*1,500=15,000 extra time series that might be scraped. The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. Thanks for contributing an answer to Stack Overflow! You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. more difficult for those people to help. But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. Does a summoned creature play immediately after being summoned by a ready action? 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. count the number of running instances per application like this: This documentation is open-source. Has 90% of ice around Antarctica disappeared in less than a decade? Prometheus does offer some options for dealing with high cardinality problems. Looking at memory usage of such Prometheus server we would see this pattern repeating over time: The important information here is that short lived time series are expensive. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Finally you will want to create a dashboard to visualize all your metrics and be able to spot trends. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. but it does not fire if both are missing because than count() returns no data the workaround is to additionally check with absent() but it's on the one hand annoying to double-check on each rule and on the other hand count should be able to "count" zero . Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. 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. (pseudocode): This gives the same single value series, or no data if there are no alerts. 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. 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.