prometheus query return 0 if no data

or Internet application, result of a count() on a query that returns nothing should be 0 ? Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. binary operators to them and elements on both sides with the same label set Add field from calculation Binary operation. Connect and share knowledge within a single location that is structured and easy to search. So there would be a chunk for: 00:00 - 01:59, 02:00 - 03:59, 04:00 - 05:59, , 22:00 - 23:59. When using Prometheus defaults and assuming we have a single chunk for each two hours of wall clock we would see this: Once a chunk is written into a block it is removed from memSeries and thus from memory. After a few hours of Prometheus running and scraping metrics we will likely have more than one chunk on our time series: Since all these chunks are stored in memory Prometheus will try to reduce memory usage by writing them to disk and memory-mapping. 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. These will give you an overall idea about a clusters health. A time series is an instance of that metric, with a unique combination of all the dimensions (labels), plus a series of timestamp & value pairs - hence the name time series. If the time series doesnt exist yet and our append would create it (a new memSeries instance would be created) then we skip this sample. It would be easier if we could do this in the original query though. Prometheus will keep each block on disk for the configured retention period. Is there a solutiuon to add special characters from software and how to do it. 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. 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. 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 . will get matched and propagated to the output. Having good internal documentation that covers all of the basics specific for our environment and most common tasks is very important. 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. If the time series already exists inside TSDB then we allow the append to continue. 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. We know that the more labels on a metric, the more time series it can create. In our example we have two labels, content and temperature, and both of them can have two different values. If your expression returns anything with labels, it won't match the time series generated by vector(0). 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? 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. 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. 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. PROMQL: how to add values when there is no data returned? I have just used the JSON file that is available in below website For operations between two instant vectors, the matching behavior can be modified. an EC2 regions with application servers running docker containers. If we add another label that can also have two values then we can now export up to eight time series (2*2*2). Here are two examples of instant vectors: You can also use range vectors to select a particular time range. This is the standard Prometheus flow for a scrape that has the sample_limit option set: The entire scrape either succeeds or fails. 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. The main motivation seems to be that dealing with partially scraped metrics is difficult and youre better off treating failed scrapes as incidents. 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. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Using a query that returns "no data points found" in an expression. The speed at which a vehicle is traveling. following for every instance: we could get the top 3 CPU users grouped by application (app) and process There is a maximum of 120 samples each chunk can hold. How can I group labels in a Prometheus query? For that lets follow all the steps in the life of a time series inside Prometheus. This gives us confidence that we wont overload any Prometheus server after applying changes. There are a number of options you can set in your scrape configuration block. Extra fields needed by Prometheus internals. Here at Labyrinth Labs, we put great emphasis on monitoring. Theres only one chunk that we can append to, its called the Head Chunk. Comparing current data with historical data. count(container_last_seen{name="container_that_doesn't_exist"}), What did you see instead? How to show that an expression of a finite type must be one of the finitely many possible values? All they have to do is set it explicitly in their scrape configuration. Visit 1.1.1.1 from any device to get started with Does a summoned creature play immediately after being summoned by a ready action? @rich-youngkin Yes, the general problem is non-existent series. Once you cross the 200 time series mark, you should start thinking about your metrics more. All regular expressions in Prometheus use RE2 syntax. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. Instead we count time series as we append them to TSDB. To make things more complicated you may also hear about samples when reading Prometheus documentation. Lets create a demo Kubernetes cluster and set up Prometheus to monitor it. Use Prometheus to monitor app performance metrics. an EC2 regions with application servers running docker containers. Finally we do, by default, set sample_limit to 200 - so each application can export up to 200 time series without any action. The simplest construct of a PromQL query is an instant vector selector. Neither of these solutions seem to retain the other dimensional information, they simply produce a scaler 0. Find centralized, trusted content and collaborate around the technologies you use most. How do I align things in the following tabular environment? ncdu: What's going on with this second size column? Sign up and get Kubernetes tips delivered straight to your inbox. Are there tables of wastage rates for different fruit and veg? Once theyre in TSDB its already too late. Where does this (supposedly) Gibson quote come from? It doesnt get easier than that, until you actually try to do it. That map uses labels hashes as keys and a structure called memSeries as values. The subquery for the deriv function uses the default resolution. to get notified when one of them is not mounted anymore. Cadvisors on every server provide container names. This makes a bit more sense with your explanation. Knowing that it can quickly check if there are any time series already stored inside TSDB that have the same hashed value. Our HTTP response will now show more entries: As we can see we have an entry for each unique combination of labels. This process is also aligned with the wall clock but shifted by one hour. Not the answer you're looking for? Simple, clear and working - thanks a lot. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? 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. Chunks that are a few hours old are written to disk and removed from memory. One or more for historical ranges - these chunks are only for reading, Prometheus wont try to append anything here. Once configured, your instances should be ready for access. To avoid this its in general best to never accept label values from untrusted sources. To learn more, see our tips on writing great answers. In the screenshot below, you can see that I added two queries, A and B, but only . To your second question regarding whether I have some other label on it, the answer is yes I do. Here is the extract of the relevant options from Prometheus documentation: Setting all the label length related limits allows you to avoid a situation where extremely long label names or values end up taking too much memory. I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). Why do many companies reject expired SSL certificates as bugs in bug bounties? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Why is there a voltage on my HDMI and coaxial cables? If this query also returns a positive value, then our cluster has overcommitted the memory. For example, this expression Samples are stored inside chunks using "varbit" encoding which is a lossless compression scheme optimized for time series data. Prometheus's query language supports basic logical and arithmetic operators. 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 I believe it's the logic that it's written, but is there any . This means that our memSeries still consumes some memory (mostly labels) but doesnt really do anything. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Operating such a large Prometheus deployment doesnt come without challenges. That way even the most inexperienced engineers can start exporting metrics without constantly wondering Will this cause an incident?. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. Each Prometheus is scraping a few hundred different applications, each running on a few hundred servers. By default Prometheus will create a chunk per each two hours of wall clock. to your account. 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. website So I still can't use that metric in calculations ( e.g., success / (success + fail) ) as those calculations will return no datapoints. 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. 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. PromQL allows you to write queries and fetch information from the metric data collected by Prometheus. 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. what does the Query Inspector show for the query you have a problem with? You set up a Kubernetes cluster, installed Prometheus on it ,and ran some queries to check the clusters health. by (geo_region) < bool 4 Sign up for a free GitHub account to open an issue and contact its maintainers and the community. 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. These flags are only exposed for testing and might have a negative impact on other parts of Prometheus server. Run the following commands in both nodes to disable SELinux and swapping: Also, change SELINUX=enforcing to SELINUX=permissive in the /etc/selinux/config file. In order to make this possible, it's necessary to tell Prometheus explicitly to not trying to match any labels by . To set up Prometheus to monitor app metrics: Download and install Prometheus. Making statements based on opinion; back them up with references or personal experience. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. 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. *) in region drops below 4. alert also has to fire if there are no (0) containers that match the pattern in region. Im new at Grafan and Prometheus. 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. Have you fixed this issue? Also the link to the mailing list doesn't work for me. But I'm stuck now if I want to do something like apply a weight to alerts of a different severity level, e.g. 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. Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. Thanks for contributing an answer to Stack Overflow! Often it doesnt require any malicious actor to cause cardinality related problems. Its not difficult to accidentally cause cardinality problems and in the past weve dealt with a fair number of issues relating to it. And this brings us to the definition of cardinality in the context of metrics. Is that correct? I'd expect to have also: Please use the prometheus-users mailing list for questions. Chunks will consume more memory as they slowly fill with more samples, after each scrape, and so the memory usage here will follow a cycle - we start with low memory usage when the first sample is appended, then memory usage slowly goes up until a new chunk is created and we start again. Well occasionally send you account related emails. Connect and share knowledge within a single location that is structured and easy to search. Samples are compressed using encoding that works best if there are continuous updates. This process helps to reduce disk usage since each block has an index taking a good chunk of disk space. 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. 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. Its the chunk responsible for the most recent time range, including the time of our scrape. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Prometheus promQL query is not showing 0 when metric data does not exists, PromQL - how to get an interval between result values, PromQL delta for each elment in values array, Trigger alerts according to the environment in alertmanger, Prometheus alertmanager includes resolved alerts in a new alert. 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). @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). 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. What is the point of Thrower's Bandolier? See these docs for details on how Prometheus calculates the returned results. Return all time series with the metric http_requests_total: Return all time series with the metric http_requests_total and the given Why are trials on "Law & Order" in the New York Supreme Court? If the total number of stored time series is below the configured limit then we append the sample as usual. Run the following commands on the master node, only copy the kubeconfig and set up Flannel CNI. Time series scraped from applications are kept in memory. 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. 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. Now we should pause to make an important distinction between metrics and time series. Thank you for subscribing! Our metric will have a single label that stores the request path. Is there a single-word adjective for "having exceptionally strong moral principles"? This is what i can see on Query Inspector. Managing the entire lifecycle of a metric from an engineering perspective is a complex process. This means that looking at how many time series an application could potentially export, and how many it actually exports, gives us two completely different numbers, which makes capacity planning a lot harder. 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. Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. Have a question about this project? 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. We will examine their use cases, the reasoning behind them, and some implementation details you should be aware of. So, specifically in response to your question: I am facing the same issue - please explain how you configured your data

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