• Hadoop core HDFS distributed file system


    1. HDFS overview In the framework of Hadoop distributed system, the most important basic function is the file system This abstract class is used to represent our file system. There are many sub implementation classes under this abstract class. Which one to use depends on our specific implementation class. In our actual work, the most […]

  • How to expand the dolphin DB cluster horizontally and vertically?


    With the expansion of business, the amount of data continues to accumulate, the data capacity and computing power of the database system will gradually be overwhelmed, so an excellent database system must have good scalability. The data nodes in the dolphin DB cluster are integrated with computing and storage, so to improve the computing power […]

  • STL_ Stack container


    1、 Introduction to stack Stack is a first in last out (Filo) data structure with only one exit. The stack container allows adding elements, removing elements, and getting the top elements of the stack, but there is no other way to access other elements of the stack except the top. In other words, stack does […]

  • STL_ Queue container


    1、 Introduction to queue All elements in and out of the queue must meet the “first in, first out” condition. Only the top element of the queue can be accessed by the outside world. The queue does not provide traversal function or iterator. Queue simply decorates deque container and becomes another kind of container. #include […]

  • Database ‖ Hadoop cluster upgrade process sharing of thousands of nodes


    The last time I did itOver a trillionTroubleshooting of Hadoop namenodeThrough four days of hard work, we finally solved the bottleneck problem of Hadoop 2.6.0, but life is often Murphy’s law, and the worst possibilities you try to avoid may eventually happen. In order to avoid the second bottleneck of namenode, I decided to upgrade […]

  • Online modification of oplog size by mongodb


    From mongodb 3.6, you can use the command replsetresizeoplog to modify the oplog size of replica set members,Start with the secondary node, and then go to the primary node.The test environment of this paper is mongodb 4.2. You can view the size of oplog through the command handong1:PRIMARY> use local switched to db local handong1:PRIMARY> […]

  • STL_ List container


    1、 Introduction to list Linked list is a kind of non continuous and non sequential storage structure on physical storage unit. The logical order of data elements is realized by the pointer link order in linked list. The linked list is composed of a series of nodes (each element in the linked list is called […]

  • Recovery of mongodb database after MIS deletion


    Reprinted:http://forum.foxera.com/mongo… Method 1: restore through oplogIf the mongodb replica set is deployed, there is still a glimmer of hope that the data can be recovered as much as possible through oplog. Every modification of the mongodb replica set will record an oplog, so when the database is deleted by mistake, the existing oplog can be […]

  • Graphical HTTP authority Guide (5) | HTTP caching


    About the author Mr. lemon, senior operation and Maintenance Engineer (self claimed), SRE expert (target), dreams of buying a Porsche at the age of 35. Like to study the underlying technology, think that the underlying foundation is the king. All new technologies are inseparable from the operating system (CPU, memory, disk), network and so on. […]

  • Kafka (2): data reliability, fault handling


    1、 Preface In the last article, we discussed Kafka’s workflow, storage mechanism and partition strategy, and clarified how the data produced by producers are stored and how to query data according to offsetKafka (1): workflow, storage mechanism, partition strategy So how does Kafka ensure data reliability? How to guarantee the accuracy of exactly only? How […]

  • Object copy and weakmap


    1、 Shallow copy When we copy data, if the data is areference typeAnd copy itOnly the pointer to the object is passedThen it belongs to shallow copy. Since only pointers are passed in the copy process,A new reference type object is not recreatedSoThey share the same memory spaceThat is, the pointer points to the same […]

  • Crontab configuration does not work in Ubuntu


    Operating system: kylin V4 based on Ubuntu 15.04 The configuration of crontab on kylin is correct, but crontab doesn’t work. Configuration method A document was prepared in advance crontab.conf , contains only the following, printed every minute */1 * * * * echo test Copy the file to the crontab configuration corresponding to the root […]