Multiple clients cannot write to the same HDFS file concurrently as HDFS works on a write-once-read-many model, which means that once a file is written, it becomes immutable and can only be read and not written again. If multiple clients try to write to the same HDFS file at the same time , it can cause data inconsistency and data loss . However, it is possible for multiple clients to write to different files in the same directory or to write to the same file serially by acquiring a lock or using a queuing mechanism to synchronize the write operations. This is because Hadoop Distributed File System (HDFS) implements a single-writer multiple-reader model, where data can only be written by one client, and other clients can only read that data.
When multiple clients attempt to write on the same Hadoop Distributed File System (HDFS) file simultaneously, several scenarios and consequences arise. It's important to note that HDFS is designed to handle such concurrent write operations efficiently, ensuring data consistency and reliability. The behavior and outcomes can be explained based on the fundamental characteristics and mechanisms of HDFS.
Data Consistency
Block Allocation
Coordination and Synchronization
Client Interaction
Write Pipelining
When multiple clients attempt to write on the same HDFS file simultaneously, HDFS ensures data consistency by allocating separate blocks for each client's writes and coordinating their interactions through the NameNode. HDFS's design supports parallelism, fault tolerance, and efficient resource utilization, enabling concurrent writes without conflicts or data integrity issues.
"HDFS provides support only for exclusive writes so when one client is already writing the file, the other client cannot open the file in write mode. When the client requests the NameNode to open the file for writing, NameNode provides lease to the client for writing to the file. So, if another client requests for lease on the same it will be rejected."