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HDFS TO COS
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Last updated: 2024-01-06 16:15:35
HDFS TO COS
Last updated: 2024-01-06 16:15:35
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Overview

The HDFS TO COS tool is used to copy data from HDFS to Tencent Cloud COS（Cloud Object Storage）.

Operating Environments

Operating system

Linux or Windows

Software dependency

JDK v1.7 or v1.8

Installation and configuration

For more information on environment installation and configuration, see Java.

Configuration Method

1. Install Hadoop v2.7.2 or higher. For detailed directions, see Hadoop.
2. Download the HDFS TO COS tool from GitHub and decompress it.
3. Copy the core-site.xml file of the HDFS cluster to be synced to the conf folder. The core-site.xml file contains the configuration information of NameNode.
4. In the cos_info.conf configuration file, configure the bucket, region, and API key information. The bucket name is formed by connecting a user-defined string and the system-generated APPID with a hyphen, for example, examplebucket-1250000000.
5. Specify the configuration file location in the command line parameter. The default location is conf/cos_info.conf.
Note:
If the command line parameter conflicts with the configuration file, the command line parameter shall apply.

Usage

Note:
Linux is used as an example below.

Viewing help

./hdfs_to_cos_cmd -h

Copying a file

Copy from HDFS to COS. If a file with the same name as the file to be copied already exists in COS, the former will be overwritten.
./hdfs_to_cos_cmd --hdfs_path=/tmp/hive --cos_path=/hdfs/20170224/
Copy from HDFS to COS. If a file with the same name and length as the file to be copied already exists in COS, the latter will be skipped (this is suitable for repeated copy).
./hdfs_to_cos_cmd --hdfs_path=/tmp/hive --cos_path=/hdfs/20170224/ -skip_if_len_match
Only the length is checked here, as the overheads would be very high if the digests of files in Hadoop are calculated.
Copy from HDFS to COS. If the Har directory (Hadoop archive file) exists in HDFS, the .har files can be automatically decompressed by specifying the --decompress_har parameter:
./hdfs_to_cos_cmd --decompress_har --hdfs_path=/tmp/hive --cos_path=/hdfs/20170224/
If the --decompress_har parameter is not specified, the directory will be copied as an ordinary HDFS directory, that is, the files in the Har directory such as index and masterindex will be copied as-is.

Directory information

conf: configuration file, which is used to store `core-site.xml` and `cos_info.conf`
log: log directory
src: Java source program
dep: compiled executable JAR package

FAQs and Help

Configuration information

Please make sure that the entered configuration information is correct, including bucket, region, and API key information. The bucket name is formed by connecting the user-defined string and system-generated APPID with a hyphen, such as examplebucket-1250000000. Please also make sure that the time on the server is in sync with the local time (if there is a difference of about 1 minute, it is okay, but if the difference is large, please set the server time correctly).

DataNode

Please make sure that the server where the copy program is located can also access the DataNode. The NameNode uses a public IP address and can be accessed, but the DataNode where the obtained block is located uses a private IP address and cannot be accessed directly; therefore, it is recommended that the copy program be placed in a Hadoop node for execution, so that both the NameNode and DataNode can be accessed.

Permissions

Please use the current account to download a file with the Hadoop command, check whether everything is correct, and then use the synchronization tool to sync the data in Hadoop.

File overwriting

Files that already exist in COS will be overwritten by default in case of repeated upload, unless you explicitly specify the -skip_if_len_match parameter, which indicates to skip files during upload if they have the same length as existing files.

cos path

cos path is considered as a directory by default, and files that are eventually copied from HDFS will be stored in this directory.

Copying data from Tencent Cloud EMR HDFS

To copy data from Tencent Cloud EMR HDFS to COS, you are advised to use the high-performance DistCp tool. For more information, see Migrating Data Between HDFS and COS.
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