what does the Query Inspector show for the query you have a problem with? If we add another label that can also have two values then we can now export up to eight time series (2*2*2). windows. 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. Any excess samples (after reaching sample_limit) will only be appended if they belong to time series that are already stored inside TSDB. 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. as text instead of as an image, more people will be able to read it and help. What this means is that a single metric will create one or more time series. This holds true for a lot of labels that we see are being used by engineers. By default Prometheus will create a chunk per each two hours of wall clock. Querying examples | Prometheus If you're looking for a 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. Internet-scale applications efficiently, Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Explanation: Prometheus uses label matching in expressions. This would happen if any time series was no longer being exposed by any application and therefore there was no scrape that would try to append more samples to it. 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. In both nodes, edit the /etc/hosts file to add the private IP of the nodes. accelerate any To get a better idea of this problem lets adjust our example metric to track HTTP requests. If this query also returns a positive value, then our cluster has overcommitted the memory. What sort of strategies would a medieval military use against a fantasy giant? 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. By setting this limit on all our Prometheus servers we know that it will never scrape more time series than we have memory for. In our example we have two labels, content and temperature, and both of them can have two different values. The number of time series depends purely on the number of labels and the number of all possible values these labels can take. This garbage collection, among other things, will look for any time series without a single chunk and remove it from memory. 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. With our custom patch we dont care how many samples are in a scrape. Inside the Prometheus configuration file we define a scrape config that tells Prometheus where to send the HTTP request, how often and, optionally, to apply extra processing to both requests and responses. Any other chunk holds historical samples and therefore is read-only. 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. binary operators to them and elements on both sides with the same label set 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. 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. 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. The way labels are stored internally by Prometheus also matters, but thats something the user has no control over. Already on GitHub? This works fine when there are data points for all queries in the expression. 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. what error message are you getting to show that theres a problem? 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. The more any application does for you, the more useful it is, the more resources it might need. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 2023 The Linux Foundation. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? 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. ***> wrote: You signed in with another tab or window. These are the sane defaults that 99% of application exporting metrics would never exceed. But before that, lets talk about the main components of Prometheus. prometheus - Promql: Is it possible to get total count in Query_Range Are there tables of wastage rates for different fruit and veg? Since the default Prometheus scrape interval is one minute it would take two hours to reach 120 samples. Why are trials on "Law & Order" in the New York Supreme Court? 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. Is it a bug? Going back to our time series - at this point Prometheus either creates a new memSeries instance or uses already existing memSeries. Will this approach record 0 durations on every success? Asking for help, clarification, or responding to other answers. 4 Managed Service for Prometheus | 4 Managed Service for Please see data model and exposition format pages for more details. Connect and share knowledge within a single location that is structured and easy to search. For example, I'm using the metric to record durations for quantile reporting. To your second question regarding whether I have some other label on it, the answer is yes I do. I believe it's the logic that it's written, but is there any . 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. Name the nodes as Kubernetes Master and Kubernetes Worker. Prometheus Authors 2014-2023 | Documentation Distributed under CC-BY-4.0. A simple request for the count (e.g., rio_dashorigin_memsql_request_fail_duration_millis_count) returns no datapoints). The TSDB limit patch protects the entire Prometheus from being overloaded by too many time series. notification_sender-. This might require Prometheus to create a new chunk if needed. Im new at Grafan and Prometheus. 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. I am always registering the metric as defined (in the Go client library) by prometheus.MustRegister(). Although, sometimes the values for project_id doesn't exist, but still end up showing up as one. Since labels are copied around when Prometheus is handling queries this could cause significant memory usage increase. On the worker node, run the kubeadm joining command shown in the last step. Prometheus lets you query data in two different modes: The Console tab allows you to evaluate a query expression at the current time. are going to make it If we let Prometheus consume more memory than it can physically use then it will crash. Simply adding a label with two distinct values to all our metrics might double the number of time series we have to deal with. If you look at the HTTP response of our example metric youll see that none of the returned entries have timestamps. 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. 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. It will return 0 if the metric expression does not return anything. This thread has been automatically locked since there has not been any recent activity after it was closed. but still preserve the job dimension: If we have two different metrics with the same dimensional labels, we can apply Once it has a memSeries instance to work with it will append our sample to the Head Chunk. "no data". Sign in entire corporate networks, To avoid this its in general best to never accept label values from untrusted sources. To select all HTTP status codes except 4xx ones, you could run: Return the 5-minute rate of the http_requests_total metric for the past 30 minutes, with a resolution of 1 minute. We know that each time series will be kept in memory. Once theyre in TSDB its already too late. Extra fields needed by Prometheus internals. t]. which outputs 0 for an empty input vector, but that outputs a scalar I.e., there's no way to coerce no datapoints to 0 (zero)? This works fine when there are data points for all queries in the expression. Or maybe we want to know if it was a cold drink or a hot one? Our metric will have a single label that stores the request path. This is in contrast to a metric without any dimensions, which always gets exposed as exactly one present series and is initialized to 0. For that lets follow all the steps in the life of a time series inside Prometheus. Cadvisors on every server provide container names. website 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. by (geo_region) < bool 4 PromQL tutorial for beginners and humans - Medium This is because once we have more than 120 samples on a chunk efficiency of varbit encoding drops. Hmmm, upon further reflection, I'm wondering if this will throw the metrics off. Find centralized, trusted content and collaborate around the technologies you use most. How Cloudflare runs Prometheus at scale If we were to continuously scrape a lot of time series that only exist for a very brief period then we would be slowly accumulating a lot of memSeries in memory until the next garbage collection. There is a single time series for each unique combination of metrics labels. to get notified when one of them is not mounted anymore. How Intuit democratizes AI development across teams through reusability. PROMQL: how to add values when there is no data returned? Please dont post the same question under multiple topics / subjects. prometheus promql Share Follow edited Nov 12, 2020 at 12:27 privacy statement. Now comes the fun stuff. As we mentioned before a time series is generated from 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. Comparing current data with historical data. Querying basics | Prometheus You can run a variety of PromQL queries to pull interesting and actionable metrics from your Kubernetes cluster. Often it doesnt require any malicious actor to cause cardinality related problems. Up until now all time series are stored entirely in memory and the more time series you have, the higher Prometheus memory usage youll see. Sign in After sending a request it will parse the response looking for all the samples exposed there. your journey to Zero Trust. Better Prometheus rate() Function with VictoriaMetrics 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. Thanks, 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. All rights reserved. what does the Query Inspector show for the query you have a problem with? 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. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Is a PhD visitor considered as a visiting scholar? By merging multiple blocks together, big portions of that index can be reused, allowing Prometheus to store more data using the same amount of storage space. What is the point of Thrower's Bandolier? 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. Even Prometheus' own client libraries had bugs that could expose you to problems like this. You can use these queries in the expression browser, Prometheus HTTP API, or visualization tools like Grafana. Even i am facing the same issue Please help me on this. This page will guide you through how to install and connect Prometheus and Grafana. So the maximum number of time series we can end up creating is four (2*2). 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. Then you must configure Prometheus scrapes in the correct way and deploy that to the right Prometheus server. Prometheus provides a functional query language called PromQL (Prometheus Query Language) that lets the user select and aggregate time series data in real time. However when one of the expressions returns no data points found the result of the entire expression is no data points found. Selecting data from Prometheus's TSDB forms the basis of almost any useful PromQL query before .