Hadoop sequence file download

I found a workaround for this question. Since downloading sequence file will give you header and other magic word in the binary file, the way I avoid this problem is to transform my original binary file into Base64 String and store it as Text in HDFS and when downloading the encoded binary files, I decode it back to my original binary file. I know this will take extra time but currently I don't find any other solution to this problem.

The hard part to directly remove headers and other magic words in the sequence file is that Hadoop may insert some word "Sync" in between my binary file. This would split the file as Key Value pairs and the value would have only the binary file contents which you can use to create your binary file.

Here is a code snippet to split a sequence file that is made of multiple images and split that into individual binary files and write it into local file system. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Java - Download sequence file in Hadoop Ask Question. Asked 6 years, 1 month ago.

Active 4 years, 2 months ago. Value A sync-marker every few k bytes or so. The format for the BlockCompressedWriter is as follows: BlockCompressed Writer Format Header Record Block A sync-marker to help in seeking to a random point in the file and then seeking to next record block. No labels. Content Tools. Powered by Atlassian Confluence 7. They use all of the techniques described in the previous section.

There are a number of errors when creating the file, but this is due to errors in the original csv. The write and read times are an average of 2 executions, both executed from the master node. The Record Compression barely saves space here, reducing the file by only 1 block, and is 3 times slower to read. The Block Compression however, reduces number of blocks from 10 to 4.

What matters is that the read time is only slightly slower. This is a great deal, because it means that when working on this dataset in MapReduce, we will only need 4 mappers instead of 10, with only a very little decompression overhead.

In the next post we will see how to use the Sequence File that we created in a MapReduce job. Hadoop Basics. Your email address will not be published. Your Comment. Your Name. Your Email. Your Website URL. Ask Question. Asked 6 years ago. Active 2 years, 2 months ago. Viewed 20k times. Improve this question. Soghra Gargari Soghra Gargari 1 1 gold badge 3 3 silver badges 9 9 bronze badges. I guess it would be better if you can put a specific question out of your research.

The point is that there are many resources about the sequence files in the internet. But I wondered if someone can easily illustrate the structure of sequence file? I mean what is exactly the key and the value which we should consider in a sequence file. Hadoop Sequence File. Add a comment. If something is missing or you have something to share about the topic please write a comment. Your email address will not be published.

Save my name, email, and site URL in my browser for next time I post a comment. This site uses Akismet to reduce spam. Learn how your comment data is processed. Some of the features of the Sequence files in Hadoop are as follows- Stores data in binary form so works well in scenarios where you want to store images in HDFS , model complex data structures as key, value pair.

Sequence files in Hadoop support both compression and splitting.