api programming for beginners

);SOCKFD is a server socket descriptor that is being monitored, and addr is usually a pointer to a sockaddr_in variable that holds the client address that made the connection request the Connect () function is used to establish a TCP connection to the remote server with its function prototype:int Connect (int sockfd, struct sockaddr *serv_addr, int addrlen);int Send (int sockfd, const void *msg, int len, int flags); int recv (int sockfd,void *buf,int len,unsigned int flags);int sendto (int sockf

We create two files in the/data/join of HDFs:Upload the first file name is 1.txtContent first column is date, second column UID (normal user ID)Upload a second file name of 2.txtContent first column is date, second column UID (normal user ID)perform upload to HDFs:HDFs command-line query:Web Console Management Queries:First, set the date format on the command line:Then declare two case Class:register, LoginRead the first file (1.txt) and do the following:Take operation:This is done by reading th

Below is a look at the use of Union:Use the collect operation to see the results of the execution:Then look at the use of Groupbykey:Execution Result:The join operation is the process of a Cartesian product operation, as shown in the following example:To perform a join operation on RDD3 and RDD4:Use collect to view execution results:It can be seen that the join operation is exactly a Cartesian product operation;The reduce itself, which is an action-type operation in an RDD operation, causes the

HDFs = Mypath.getfilesystem (conf);//Get File systemif (Hdfs.isdirectory (MyPath)){//If this output path exists in the file system, delete theHdfs.delete (MyPath, true);} Job Wcjob = new Job (conf, "WC");//Build a Job object named TestanagramSet the jar package for the classes that are used by the entire jobWcjob.setjarbyclass (Wcrunner.class);Mapper and reducer classes used by this jobWcjob.setmapperclass (Wcmapper.class);Wcjob.setreducerclass (Wcreducer.class);Specify the output data kv type

();Uri uri = new Uri ("hdfs://hadoopmaster:9000");FileSystem is the core class for user-operated HDFs, which obtains the HDFs file system for the URIFileSystem FileSystem = Filesystem.get (URI, conf);Source file pathPath Srcpath = new path (source);Destination PathPath Dstpath = new Path (dest);See if the destination path existsif (! ( Filesystem.exists (Dstpath))) {If the path does not exist, create it immediatelyFilesystem.mkdirs (Dstpath);}Get local file nameString filename = source.substrin

description and submission classespublic class Flowsumrunner extends configured implements tool{public int run (string[] arg0) throws Exception {Configuration conf = new configuration ();Job Job = job.getinstance (conf);Job.setjarbyclass (Flowsumrunner.class);Job.setmapperclass (Flowsummapper.class);Job.setreducerclass (Flowsumreducer.class);Job.setmapoutputkeyclass (Text.class);Job.setmapoutputvalueclass (Flowbean.class);Job.setoutputkeyclass (Text.class);Job.setoutputvalueclass (Flowbean.clas

= Mypath.getfilesystem (conf);if (Hdfs.isdirectory (MyPath)){Hdfs.delete (MyPath, true);}@SuppressWarnings ("deprecation")Job Job = new Job (conf, "gender");//Create a new taskJob.setjarbyclass (Gender.class);//Main classJob.setmapperclass (pcmapper.class);//mapperJob.setreducerclass (pcreducer.class);//reducerJob.setpartitionerclass (Myhashpartitioner.class);Job.setpartitionerclass (Pcpartitioner.class);//Set Partitioner classJob.setnumreducetasks (3);//reduce number set to 3Job.setmapoutputke

(Firstpartitioner.class);//partition functionJob.setsortcomparatorclass (Keycomparator.class);//This course does not have custom sortcomparator, but instead uses Intpair's own sortJob.setgroupingcomparatorclass (Groupingcomparator.class);//Group functionJob.setmapoutputkeyclass (Intpair.class);Job.setmapoutputvalueclass (Intwritable.class);Job.setoutputkeyclass (Text.class);Job.setoutputvalueclass (Intwritable.class);Job.setinputformatclass (Textinputformat.class);Job.setoutputformatclass (Text

Linux inter-process communication (IPC) Programming Practice (7) use of shared memory-System V shared memory (API) The system call mmap mentioned in the previous blog map a common file to implement shared memory. The System V shared memory described in this article is to map files in the shm of a special file System to implement shared memory communication between processes. That is to say, each shared memo