This is the modified flow with our patch: By running go_memstats_alloc_bytes / prometheus_tsdb_head_series query we know how much memory we need per single time series (on average), we also know how much physical memory we have available for Prometheus on each server, which means that we can easily calculate the rough number of time series we can store inside Prometheus, taking into account the fact the theres garbage collection overhead since Prometheus is written in Go: memory available to Prometheus / bytes per time series = our capacity. We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. These are the sane defaults that 99% of application exporting metrics would never exceed. Its the chunk responsible for the most recent time range, including the time of our scrape. type (proc) like this: Assuming this metric contains one time series per running instance, you could Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes?
4 Managed Service for Prometheus | 4 Managed Service for Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. 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.
Using a query that returns "no data points found" in an - GitHub 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. At the same time our patch gives us graceful degradation by capping time series from each scrape to a certain level, rather than failing hard and dropping all time series from affected scrape, which would mean losing all observability of affected applications. 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 a sample lacks any explicit timestamp then it means that the sample represents the most recent value - its the current value of a given time series, and the timestamp is simply the time you make your observation at. Not the answer you're looking for? notification_sender-. Next, create a Security Group to allow access to the instances. 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. Time arrow with "current position" evolving with overlay number. For a list of trademarks of The Linux Foundation, please see our Trademark Usage page. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. Once we appended sample_limit number of samples we start to be selective. 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. If your expression returns anything with labels, it won't match the time series generated by vector(0). In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. Sign in The containers are named with a specific pattern: notification_checker [0-9] notification_sender [0-9] I need an alert when the number of container of the same pattern (eg. Finally, please remember that some people read these postings as an email Making statements based on opinion; back them up with references or personal experience. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. Cadvisors on every server provide container names. Using regular expressions, you could select time series only for jobs whose You're probably looking for the absent function. All rights reserved. Sign in I've added a data source (prometheus) in Grafana. help customers build Yeah, absent() is probably the way to go. We know that time series will stay in memory for a while, even if they were scraped only once. No error message, it is just not showing the data while using the JSON file from that website. Connect and share knowledge within a single location that is structured and easy to search. list, which does not convey images, so screenshots etc. our free app that makes your Internet faster and safer. 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? Cadvisors on every server provide container names. Internally time series names are just another label called __name__, so there is no practical distinction between name and labels. t]. name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 Even Prometheus' own client libraries had bugs that could expose you to problems like this. privacy statement. This works fine when there are data points for all queries in the expression. You signed in with another tab or window. Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. attacks, keep Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. @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). Thirdly Prometheus is written in Golang which is a language with garbage collection. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. Prometheus metrics can have extra dimensions in form of labels. About an argument in Famine, Affluence and Morality. 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. This had the effect of merging the series without overwriting any values. Hello, I'm new at Grafan and Prometheus. I'm still out of ideas here. Prometheus's query language supports basic logical and arithmetic operators. Bulk update symbol size units from mm to map units in rule-based symbology. If we add another label that can also have two values then we can now export up to eight time series (2*2*2). count(container_last_seen{name="container_that_doesn't_exist"}), What did you see instead? First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. 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. 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. How do you get out of a corner when plotting yourself into a corner, Partner is not responding when their writing is needed in European project application. Find centralized, trusted content and collaborate around the technologies you use most. 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. 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. - I am using this in windows 10 for testing, which Operating System (and version) are you running it under? Is a PhD visitor considered as a visiting scholar? Our metrics are exposed as a HTTP response. I'm displaying Prometheus query on a Grafana table. I made the changes per the recommendation (as I understood it) and defined separate success and fail metrics. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. 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. I was then able to perform a final sum by over the resulting series to reduce the results down to a single result, dropping the ad-hoc labels in the process. Return all time series with the metric http_requests_total: Return all time series with the metric http_requests_total and the given Lets see what happens if we start our application at 00:25, allow Prometheus to scrape it once while it exports: And then immediately after the first scrape we upgrade our application to a new version: At 00:25 Prometheus will create our memSeries, but we will have to wait until Prometheus writes a block that contains data for 00:00-01:59 and runs garbage collection before that memSeries is removed from memory, which will happen at 03:00. Better Prometheus rate() Function with VictoriaMetrics 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. SSH into both servers and run the following commands to install Docker. rev2023.3.3.43278. After sending a request it will parse the response looking for all the samples exposed there. This pod wont be able to run because we dont have a node that has the label disktype: ssd. 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. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. If the error message youre getting (in a log file or on screen) can be quoted Once you cross the 200 time series mark, you should start thinking about your metrics more. This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. Every two hours Prometheus will persist chunks from memory onto the disk. 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. The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. One of the first problems youre likely to hear about when you start running your own Prometheus instances is cardinality, with the most dramatic cases of this problem being referred to as cardinality explosion. 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 is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. source, what your query is, what the query inspector shows, and any other Well occasionally send you account related emails. Its not going to get you a quicker or better answer, and some people might Visit 1.1.1.1 from any device to get started with The text was updated successfully, but these errors were encountered: It's recommended not to expose data in this way, partially for this reason. See this article for details. Here at Labyrinth Labs, we put great emphasis on monitoring. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. This page will guide you through how to install and connect Prometheus and Grafana. 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. Asking for help, clarification, or responding to other answers. Theres no timestamp anywhere actually. Why is there a voltage on my HDMI and coaxial cables? Are there tables of wastage rates for different fruit and veg? There is an open pull request which improves memory usage of labels by storing all labels as a single string. https://grafana.com/grafana/dashboards/2129. It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. following for every instance: we could get the top 3 CPU users grouped by application (app) and process 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. Another reason is that trying to stay on top of your usage can be a challenging task. What happens when somebody wants to export more time series or use longer labels? 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. prometheus - Promql: Is it possible to get total count in Query_Range So lets start by looking at what cardinality means from Prometheus' perspective, when it can be a problem and some of the ways to deal with it. PROMQL: how to add values when there is no data returned? Although you can tweak some of Prometheus' behavior and tweak it more for use with short lived time series, by passing one of the hidden flags, its generally discouraged to do so. Comparing current data with historical data. This is because the only way to stop time series from eating memory is to prevent them from being appended to TSDB. Separate metrics for total and failure will work as expected. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. 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). which version of Grafana are you using? accelerate any to your account. 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. At this point, both nodes should be ready. Prometheus - exclude 0 values from query result - Stack Overflow (pseudocode): This gives the same single value series, or no data if there are no alerts. to your account, What did you do? @zerthimon The following expr works for me Are there tables of wastage rates for different fruit and veg? If so it seems like this will skew the results of the query (e.g., quantiles). 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. 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. 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. result of a count() on a query that returns nothing should be 0 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). 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. I then hide the original query. If our metric had more labels and all of them were set based on the request payload (HTTP method name, IPs, headers, etc) we could easily end up with millions of time series. In our example we have two labels, content and temperature, and both of them can have two different values. hackers at This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. Any other chunk holds historical samples and therefore is read-only. ***> wrote: You signed in with another tab or window. what does the Query Inspector show for the query you have a problem with? 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. The more labels we have or the more distinct values they can have the more time series as a result. The Linux Foundation has registered trademarks and uses trademarks. https://github.com/notifications/unsubscribe-auth/AAg1mPXncyVis81Rx1mIWiXRDe0E1Dpcks5rIXe6gaJpZM4LOTeb. 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. Subscribe to receive notifications of new posts: Subscription confirmed. "no data". The speed at which a vehicle is traveling. Next you will likely need to create recording and/or alerting rules to make use of your time series. Can airtags be tracked from an iMac desktop, with no iPhone? 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. I have just used the JSON file that is available in below website How to show that an expression of a finite type must be one of the finitely many possible values? 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. Is it possible to rotate a window 90 degrees if it has the same length and width? In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . I cant see how absent() may help me here @juliusv yeah, I tried count_scalar() but I can't use aggregation with it. With any monitoring system its important that youre able to pull out the right data. Prometheus Queries: 11 PromQL Examples and Tutorial - ContainIQ Variable of the type Query allows you to query Prometheus for a list of metrics, labels, or label values. If all the label values are controlled by your application you will be able to count the number of all possible label combinations. 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. Why are trials on "Law & Order" in the New York Supreme Court? What sort of strategies would a medieval military use against a fantasy giant? Thanks, There will be traps and room for mistakes at all stages of this process. Also the link to the mailing list doesn't work for me. For example, this expression To make things more complicated you may also hear about samples when reading Prometheus documentation. The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. If you need to obtain raw samples, then a range query must be sent to /api/v1/query. binary operators to them and elements on both sides with the same label set Using a query that returns "no data points found" in an expression. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. TSDB will try to estimate when a given chunk will reach 120 samples and it will set the maximum allowed time for current Head Chunk accordingly. There is a maximum of 120 samples each chunk can hold. If the total number of stored time series is below the configured limit then we append the sample as usual. Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. These will give you an overall idea about a clusters health. Prometheus will keep each block on disk for the configured retention period. We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. want to sum over the rate of all instances, so we get fewer output time series, Im new at Grafan and Prometheus. You can verify this by running the kubectl get nodes command on the master node. Our metric will have a single label that stores the request path. Add field from calculation Binary operation. But the real risk is when you create metrics with label values coming from the outside world. Even i am facing the same issue Please help me on this. Has 90% of ice around Antarctica disappeared in less than a decade? As we mentioned before a time series is generated from metrics. This is a deliberate design decision made by Prometheus developers.