![]() Once a message is sent into a Kafka Topic then it will receive a partition number and an offset id. So headers are pairs of key-value and you can have many of those in part of one message and it is common to set them in case you’re trying to add metadata to your messages. We also have optional headers for your message. ![]() For example, none means no compression but we have four different kinds of compressions available in Kafka that are mentioned below. For example, your message can be compressed and so the compression type can be indicated as part of your message. So the Key-Value is some of the two most important things in your message but there are other things that go into your message. So we have the key which is a binary field that can be null and then we have the value which is the content of your message and again this can be null as well. So this is a very very important property of Kafka because that means if you need ordering for a specific field, for example, if you have cars and you want to get all the GPS positions in order for that particular car then you need to make sure to have your message key set as the unique identifier for your car i.e carID and so in our car GPS example that we have discussed in this article, Topics, Partitions, and Offsets in Apache Kafka, we need to choose the message key to be equal to carID so that we have all the car positions for that one specific car in order as part of the same partition. This is why it’s called Round Robin, but in case you send a key with your message, all the messages that share the same key will always go to the same partition. So that means that your first message is going to be sent to partition 0, and then your second message to partition 1 and then partition 2, and so on. So alongside the message value, we can choose to send a message key and that key can be whatever you want it could be a string, it could be a number whatever you want and it turns out that if you don’t send the key, the key is set to null then the data will be sent in a Round Robin fashion to make it very simple. ISRO CS Syllabus for Scientist/Engineer Exam.ISRO CS Original Papers and Official Keys.GATE CS Original Papers and Official Keys.DevOps Engineering - Planning to Production.Python Backend Development with Django(Live).Android App Development with Kotlin(Live).Full Stack Development with React & Node JS(Live).Java Programming - Beginner to Advanced.Data Structure & Algorithm-Self Paced(C++/JAVA).Data Structure & Algorithm Classes (Live).Pay special attention to operator order when chaining arithmetic operators. Entries for which no matching entry in the right-hand vector can be found are not part of the result. The result is propagated into the result vector with the grouping labels becoming the output label set. if a time series vector is multiplied by 2, the result is another vector in which every sample value of the original vector is multiplied by 2.īetween two vectors, a binary arithmetic operator is applied to each entry in the left-hand side vector and its matching element in the right-hand vector. ![]() They evaluate to another literal that is the result of the operator applied to both scalar operands ( 1 + 1 = 2).īetween a vector and a literal, the operator is applied to the value of every data sample in the vector, e.g. The following binary arithmetic operators exist in Loki:īinary arithmetic operators are defined between two literals (scalars), a literal and a vector, and two vectors.īetween two literals, the behavior is obvious: Metric queries extend log queries to calculate values.Log queries return the contents of log lines.LogQL uses labels and operators for filtering. Queries act as if they are a distributed grep to aggregate log sources. LogQL is Grafana Loki’s PromQL-inspired query language.
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