If the time series already exists inside TSDB then we allow the append to continue. whether someone is able to help out. I believe it's the logic that it's written, but is there any . from and what youve done will help people to understand your problem. 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. notification_sender-. 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. At this point, both nodes should be ready. In the same blog post we also mention one of the tools we use to help our engineers write valid Prometheus alerting rules. 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. To your second question regarding whether I have some other label on it, the answer is yes I do. Asking for help, clarification, or responding to other answers. privacy statement. 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. 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. rev2023.3.3.43278. windows. Creating new time series on the other hand is a lot more expensive - we need to allocate new memSeries instances with a copy of all labels and keep it in memory for at least an hour. Of course there are many types of queries you can write, and other useful queries are freely available. With 1,000 random requests we would end up with 1,000 time series in Prometheus. Find centralized, trusted content and collaborate around the technologies you use most. To avoid this its in general best to never accept label values from untrusted sources. These queries are a good starting point. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. Cadvisors on every server provide container names. 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. for the same vector, making it a range vector: Note that an expression resulting in a range vector cannot be graphed directly, Are there tables of wastage rates for different fruit and veg? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Secondly this calculation is based on all memory used by Prometheus, not only time series data, so its just an approximation. After running the query, a table will show the current value of each result time series (one table row per output series). If both the nodes are running fine, you shouldnt get any result for this query. These are the sane defaults that 99% of application exporting metrics would never exceed. In this article, you will learn some useful PromQL queries to monitor the performance of Kubernetes-based systems. What sort of strategies would a medieval military use against a fantasy giant? Does Counterspell prevent from any further spells being cast on a given turn? What sort of strategies would a medieval military use against a fantasy giant? About an argument in Famine, Affluence and Morality. In my case there haven't been any failures so rio_dashorigin_serve_manifest_duration_millis_count{Success="Failed"} returns no data points found. For instance, the following query would return week-old data for all the time series with node_network_receive_bytes_total name: node_network_receive_bytes_total offset 7d One Head Chunk - containing up to two hours of the last two hour wall clock slot. Separate metrics for total and failure will work as expected. Not the answer you're looking for? or something like that. The text was updated successfully, but these errors were encountered: This is correct. 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. Object, url:api/datasources/proxy/2/api/v1/query_range?query=wmi_logical_disk_free_bytes%7Binstance%3D~%22%22%2C%20volume%20!~%22HarddiskVolume.%2B%22%7D&start=1593750660&end=1593761460&step=20&timeout=60s, Powered by Discourse, best viewed with JavaScript enabled, 1 Node Exporter for Prometheus Dashboard EN 20201010 | Grafana Labs, https://grafana.com/grafana/dashboards/2129. 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. By clicking Sign up for GitHub, you agree to our terms of service and To learn more, see our tips on writing great answers. attacks, keep This might require Prometheus to create a new chunk if needed. We can add more metrics if we like and they will all appear in the HTTP response to the metrics endpoint. This works fine when there are data points for all queries in the expression. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? We covered some of the most basic pitfalls in our previous blog post on Prometheus - Monitoring our monitoring. Select the query and do + 0. Using regular expressions, you could select time series only for jobs whose The below posts may be helpful for you to learn more about Kubernetes and our company. What does remote read means in Prometheus? 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. Asking for help, clarification, or responding to other answers. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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. By default Prometheus will create a chunk per each two hours of wall clock. 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. Well be executing kubectl commands on the master node only. 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. 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. I used a Grafana transformation which seems to work. Internally time series names are just another label called __name__, so there is no practical distinction between name and labels. Sign in Looking to learn more? 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. Once configured, your instances should be ready for access. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. The more labels we have or the more distinct values they can have the more time series as a result. Second rule does the same but only sums time series with status labels equal to "500". To learn more about our mission to help build a better Internet, start here. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Finally getting back to this. 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. 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? To make things more complicated you may also hear about samples when reading Prometheus documentation. There's also count_scalar(), You can verify this by running the kubectl get nodes command on the master node. count(container_last_seen{environment="prod",name="notification_sender.*",roles=".application-server."}) 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. Making statements based on opinion; back them up with references or personal experience. 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). This means that our memSeries still consumes some memory (mostly labels) but doesnt really do anything. 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. Already on GitHub? @zerthimon You might want to use 'bool' with your comparator And this brings us to the definition of cardinality in the context of metrics. I've created an expression that is intended to display percent-success for a given metric. Redoing the align environment with a specific formatting. Has 90% of ice around Antarctica disappeared in less than a decade? 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. PromQL allows you to write queries and fetch information from the metric data collected by Prometheus. Play with bool Its the chunk responsible for the most recent time range, including the time of our scrape. A common pattern is to export software versions as a build_info metric, Prometheus itself does this too: When Prometheus 2.43.0 is released this metric would be exported as: Which means that a time series with version=2.42.0 label would no longer receive any new samples. This holds true for a lot of labels that we see are being used by engineers. 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. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. 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. 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. count(ALERTS) or (1-absent(ALERTS)), Alternatively, count(ALERTS) or vector(0). It would be easier if we could do this in the original query though. Even Prometheus' own client libraries had bugs that could expose you to problems like this. 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. Finally we maintain a set of internal documentation pages that try to guide engineers through the process of scraping and working with metrics, with a lot of information thats specific to our environment. Is it possible to create a concave light? What happens when somebody wants to export more time series or use longer labels? 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. No error message, it is just not showing the data while using the JSON file from that website. How to follow the signal when reading the schematic? Those memSeries objects are storing all the time series information. In the following steps, you will create a two-node Kubernetes cluster (one master and one worker) in AWS. With our custom patch we dont care how many samples are in a scrape. We have hundreds of data centers spread across the world, each with dedicated Prometheus servers responsible for scraping all metrics. Prometheus simply counts how many samples are there in a scrape and if thats more than sample_limit allows it will fail the scrape. This process is also aligned with the wall clock but shifted by one hour. I.e., there's no way to coerce no datapoints to 0 (zero)? Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. 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. 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). Prometheus's query language supports basic logical and arithmetic operators. The most basic layer of protection that we deploy are scrape limits, which we enforce on all configured scrapes. There will be traps and room for mistakes at all stages of this process. 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. Having a working monitoring setup is a critical part of the work we do for our clients. On the worker node, run the kubeadm joining command shown in the last step. Run the following commands in both nodes to configure the Kubernetes repository. 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. One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. This is optional, but may be useful if you don't already have an APM, or would like to use our templates and sample queries. For Prometheus to collect this metric we need our application to run an HTTP server and expose our metrics there. 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. 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. 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. This thread has been automatically locked since there has not been any recent activity after it was closed. How to react to a students panic attack in an oral exam? 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. 11 Queries | Kubernetes Metric Data with PromQL, wide variety of applications, infrastructure, APIs, databases, and other sources. Are there tables of wastage rates for different fruit and veg? I'm not sure what you mean by exposing a metric. 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. Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. without any dimensional information. Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. To get a better idea of this problem lets adjust our example metric to track HTTP requests. See this article for details. You can query Prometheus metrics directly with its own query language: PromQL. Please dont post the same question under multiple topics / subjects. It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. Time series scraped from applications are kept in memory. 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. Especially when dealing with big applications maintained in part by multiple different teams, each exporting some metrics from their part of the stack. If your expression returns anything with labels, it won't match the time series generated by vector(0). Perhaps I misunderstood, but it looks like any defined metrics that hasn't yet recorded any values can be used in a larger expression. As we mentioned before a time series is generated from metrics. 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. your journey to Zero Trust. 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. At this point we should know a few things about Prometheus: With all of that in mind we can now see the problem - a metric with high cardinality, especially one with label values that come from the outside world, can easily create a huge number of time series in a very short time, causing cardinality explosion. You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. 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. 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. syntax. For that lets follow all the steps in the life of a time series inside Prometheus. This patchset consists of two main elements. I've been using comparison operators in Grafana for a long while. This means that Prometheus must check if theres already a time series with identical name and exact same set of labels present. But before that, lets talk about the main components of Prometheus. There is a maximum of 120 samples each chunk can hold. 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. In both nodes, edit the /etc/hosts file to add the private IP of the nodes. Every two hours Prometheus will persist chunks from memory onto the disk. https://grafana.com/grafana/dashboards/2129. 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. by (geo_region) < bool 4 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 . How Intuit democratizes AI development across teams through reusability. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. The downside of all these limits is that breaching any of them will cause an error for the entire scrape. The process of sending HTTP requests from Prometheus to our application is called scraping. 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. Can I tell police to wait and call a lawyer when served with a search warrant? 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. If such a stack trace ended up as a label value it would take a lot more memory than other time series, potentially even megabytes. 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. The simplest way of doing this is by using functionality provided with client_python itself - see documentation here. 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. Windows 10, how have you configured the query which is causing problems? Run the following commands in both nodes to install kubelet, kubeadm, and kubectl. 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. Please see data model and exposition format pages for more details. Prometheus will keep each block on disk for the configured retention period. 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. In our example we have two labels, content and temperature, and both of them can have two different values. First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. The region and polygon don't match. Once TSDB knows if it has to insert new time series or update existing ones it can start the real work. That's the query (Counter metric): sum(increase(check_fail{app="monitor"}[20m])) by (reason). If you do that, the line will eventually be redrawn, many times over. Here at Labyrinth Labs, we put great emphasis on monitoring. Now, lets install Kubernetes on the master node using kubeadm. We protect notification_sender-. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. 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 . 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. 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. Our metric will have a single label that stores the request path. rev2023.3.3.43278. 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. Thank you for subscribing! Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. All rights reserved. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) PromQL allows querying historical data and combining / comparing it to the current data. positions. How do I align things in the following tabular environment? Youve learned about the main components of Prometheus, and its query language, PromQL. 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. it works perfectly if one is missing as count() then returns 1 and the rule fires. This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. This allows Prometheus to scrape and store thousands of samples per second, our biggest instances are appending 550k samples per second, while also allowing us to query all the metrics simultaneously. However, the queries you will see here are a baseline" audit. Using a query that returns "no data points found" in an expression. How to filter prometheus query by label value using greater-than, PromQL - Prometheus - query value as label, Why time duration needs double dot for Prometheus but not for Victoria metrics, How do you get out of a corner when plotting yourself into a corner. Its not going to get you a quicker or better answer, and some people might and can help you on You saw how PromQL basic expressions can return important metrics, which can be further processed with operators and functions. This is one argument for not overusing labels, but often it cannot be avoided. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. Returns a list of label values for the label in every metric. Once we do that we need to pass label values (in the same order as label names were specified) when incrementing our counter to pass this extra information. Why is this sentence from The Great Gatsby grammatical? Managing the entire lifecycle of a metric from an engineering perspective is a complex process. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. Youll be executing all these queries in the Prometheus expression browser, so lets get started. The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. Is a PhD visitor considered as a visiting scholar? Under which circumstances? How to tell which packages are held back due to phased updates. feel that its pushy or irritating and therefore ignore it. These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. VictoriaMetrics handles rate () function in the common sense way I described earlier! Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. Prometheus is an open-source monitoring and alerting software that can collect metrics from different infrastructure and applications. which Operating System (and version) are you running it under? Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. For that reason we do tolerate some percentage of short lived time series even if they are not a perfect fit for Prometheus and cost us more memory. And then there is Grafana, which comes with a lot of built-in dashboards for Kubernetes monitoring. Managed Service for Prometheus Cloud Monitoring Prometheus # ! Subscribe to receive notifications of new posts: Subscription confirmed. node_cpu_seconds_total: This returns the total amount of CPU time. Timestamps here can be explicit or implicit. Name the nodes as Kubernetes Master and Kubernetes Worker. Time arrow with "current position" evolving with overlay number. This is because the Prometheus server itself is responsible for timestamps. name match a certain pattern, in this case, all jobs that end with server: All regular expressions in Prometheus use RE2 This would inflate Prometheus memory usage, which can cause Prometheus server to crash, if it uses all available physical memory. Already on GitHub? The number of time series depends purely on the number of labels and the number of all possible values these labels can take. 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. So it seems like I'm back to square one. A sample is something in between metric and time series - its a time series value for a specific timestamp.