prometheus query return 0 if no data

Now we should pause to make an important distinction between metrics and time series. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. Yeah, absent() is probably the way to go. @juliusv Thanks for clarifying that. 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. In this query, you will find nodes that are intermittently switching between Ready" and NotReady" status continuously. One of the most important layers of protection is a set of patches we maintain on top of Prometheus. 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. By clicking Sign up for GitHub, you agree to our terms of service and rev2023.3.3.43278. Separate metrics for total and failure will work as expected. 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. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. 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. Arithmetic binary operators The following binary arithmetic operators exist in Prometheus: + (addition) - (subtraction) * (multiplication) / (division) % (modulo) ^ (power/exponentiation) The advantage of doing this is that memory-mapped chunks dont use memory unless TSDB needs to read them. It enables us to enforce a hard limit on the number of time series we can scrape from each application instance. This is the last line of defense for us that avoids the risk of the Prometheus server crashing due to lack of memory. list, which does not convey images, so screenshots etc. This thread has been automatically locked since there has not been any recent activity after it was closed. 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. hackers at Note that using subqueries unnecessarily is unwise. to get notified when one of them is not mounted anymore. I'd expect to have also: Please use the prometheus-users mailing list for questions. After sending a request it will parse the response looking for all the samples exposed there. 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. By clicking Sign up for GitHub, you agree to our terms of service and Using a query that returns "no data points found" in an - GitHub 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. Finally, please remember that some people read these postings as an email Windows 10, how have you configured the query which is causing problems? 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. @rich-youngkin Yes, the general problem is non-existent series. Stumbled onto this post for something else unrelated, just was +1-ing this :). Redoing the align environment with a specific formatting. To learn more, see our tips on writing great answers. The Head Chunk is never memory-mapped, its always stored in memory. binary operators to them and elements on both sides with the same label set privacy statement. Well be executing kubectl commands on the master node only. source, what your query is, what the query inspector shows, and any other But the key to tackling high cardinality was better understanding how Prometheus works and what kind of usage patterns will be problematic. How to follow the signal when reading the schematic? It saves these metrics as time-series data, which is used to create visualizations and alerts for IT teams. The containers are named with a specific pattern: I need an alert when the number of container of the same pattern (eg. 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 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. Those memSeries objects are storing all the time series information. If so it seems like this will skew the results of the query (e.g., quantiles). But before that, lets talk about the main components of Prometheus. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. It doesnt get easier than that, until you actually try to do it. Improving your monitoring setup by integrating Cloudflares analytics data into Prometheus and Grafana Pint is a tool we developed to validate our Prometheus alerting rules and ensure they are always working website Once the last chunk for this time series is written into a block and removed from the memSeries instance we have no chunks left. new career direction, check out our open A common class of mistakes is to have an error label on your metrics and pass raw error objects as values. You must define your metrics in your application, with names and labels that will allow you to work with resulting time series easily. Theres only one chunk that we can append to, its called the Head Chunk. Any other chunk holds historical samples and therefore is read-only. Use Prometheus to monitor app performance metrics. to your account. If we add another label that can also have two values then we can now export up to eight time series (2*2*2). If the total number of stored time series is below the configured limit then we append the sample as usual. By default we allow up to 64 labels on each time series, which is way more than most metrics would use. Im new at Grafan and Prometheus. This is a deliberate design decision made by Prometheus developers. Explanation: Prometheus uses label matching in expressions. Why is this sentence from The Great Gatsby grammatical? In our example we have two labels, content and temperature, and both of them can have two different values. After a chunk was written into a block and removed from memSeries we might end up with an instance of memSeries that has no chunks. How to show that an expression of a finite type must be one of the finitely many possible values? 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. First is the patch that allows us to enforce a limit on the total number of time series TSDB can store at any time. or Internet application, ward off DDoS One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. Operating such a large Prometheus deployment doesnt come without challenges. (pseudocode): This gives the same single value series, or no data if there are no alerts. This makes a bit more sense with your explanation. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 . About an argument in Famine, Affluence and Morality. @zerthimon The following expr works for me Next, create a Security Group to allow access to the instances. Why do many companies reject expired SSL certificates as bugs in bug bounties? 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. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. 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. Grafana renders "no data" when instant query returns empty dataset Can airtags be tracked from an iMac desktop, with no iPhone? Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 0. This selector is just a metric name. it works perfectly if one is missing as count() then returns 1 and the rule fires. Prometheus - exclude 0 values from query result - Stack Overflow Managed Service for Prometheus https://goo.gle/3ZgeGxv Next you will likely need to create recording and/or alerting rules to make use of your time series. but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply prometheus promql Share Follow edited Nov 12, 2020 at 12:27 Well occasionally send you account related emails. I believe it's the logic that it's written, but is there any conditions that can be used if there's no data recieved it returns a 0. what I tried doing is putting a condition or an absent function,but not sure if thats the correct approach. This is what i can see on Query Inspector. I'm displaying Prometheus query on a Grafana table. I've added a data source (prometheus) in Grafana. 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. When Prometheus collects metrics it records the time it started each collection and then it will use it to write timestamp & value pairs for each time series. If we have a scrape with sample_limit set to 200 and the application exposes 201 time series, then all except one final time series will be accepted. To make things more complicated you may also hear about samples when reading Prometheus documentation. an EC2 regions with application servers running docker containers. 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. By default Prometheus will create a chunk per each two hours of wall clock. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Simple succinct answer. Prometheus - exclude 0 values from query result, How Intuit democratizes AI development across teams through reusability. By default Prometheus will create a chunk per each two hours of wall clock. 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. We know what a metric, a sample and a time series is. syntax. With our custom patch we dont care how many samples are in a scrape. 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. 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. How to tell which packages are held back due to phased updates. 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. This is one argument for not overusing labels, but often it cannot be avoided. Minimising the environmental effects of my dyson brain. Can I tell police to wait and call a lawyer when served with a search warrant? Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Will this approach record 0 durations on every success? If the error message youre getting (in a log file or on screen) can be quoted 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. Asking for help, clarification, or responding to other answers. Once configured, your instances should be ready for access. 4 Managed Service for Prometheus | 4 Managed Service for On the worker node, run the kubeadm joining command shown in the last step. ward off DDoS The process of sending HTTP requests from Prometheus to our application is called scraping. positions. Making statements based on opinion; back them up with references or personal experience. Select the query and do + 0. To learn more, see our tips on writing great answers. Good to know, thanks for the quick response! In our example case its a Counter class object. Operators | Prometheus The second patch modifies how Prometheus handles sample_limit - with our patch instead of failing the entire scrape it simply ignores excess time series. 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. 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. Thank you for subscribing! help customers build *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. 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. PromLabs | Blog - Selecting Data in PromQL

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