Apache Sqoop is a top-level open-source project from Apache Software Foundation. It enables users to transfer bulk data between the Hadoop ecosystem and relational databases. Here Hadoop ecosystem includes Hadoop Distributed File System (HDFS), Hive, HBase, HCatalog, etc. Relational databases supported at this time are MySQL, PostgreSQL, Oracle, SQL Server, Teradata, and DB2.
Apache Sqoop is similar to the DistCP (Distributed Copy) utility that is available in Hadoop. The DistCP utility can be used to transfer data between clusters, whereas Sqoop can be used to transfer data only between Hadoop and RDBMS. It supports file systems like flat files(CSV/TSV), binary formats like (Avro and Hadoop Sequence files).
Check Sqoop Version
hduser@hmaster:~$ sqoop version
17/11/04 16:35:00 INFO sqoop.Sqoop: Running Sqoop version: 1.4.6
Sqoop 1.4.6
Connect Sqoop to MySQL database
Copy the Database Connector jar{mysql-connector-java-5.1.44.jar} into the $SQOOP_HOME/lib directory
Ref:http://mvnrepository.com/artifact/mysql/mysql-connector-java
In my case, copy the connector jar files to $SQOOP_HOME/lib/
cp /home/hduser/mysql-connector-java-5.1.44.jar /usr/local/sqoop/lib
List the databases using Sqoop
sqoop list-databases --connect jdbc:mysql://localhost:3306/ --username root -password admin
List the database of a particular table using Sqoop
sqoop list-tables --connect jdbc:mysql://localhost:3306/employees --username root -password admin
Import MySQL table in HDFS directory
Employee database consists of many tables
mysql> use employees;
Database changed
mysql> show tables;
+----------------------+
| Tables_in_employees |
+----------------------+
| current_dept_emp |
| departments |
| dept_emp |
| dept_emp_latest_date |
| dept_manager |
| employees |
| salaries |
| titles |
+----------------------+
8 rows in set (0.00 sec)
Import employees Table from employee database
sqoop import --connect jdbc:mysql://localhost:3306/employees --username root -password admin --table employees --target-dir /database/employees/employees
Once the import is completed, you can verify by checking the GUI and hadoop fs command.
Using the GUI
Using the Hadoop file system command
hduser@hmaster:~$ hadoop fs -ls /database/employees/employees/
17/11/04 23:22:04 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Found 5 items
-rw-r--r-- 1 hduser supergroup 0 2017-11-04 23:09 /database/employees/employees/_SUCCESS
-rw-r--r-- 1 hduser supergroup 4548041 2017-11-04 23:09 /database/employees/employees/part-m-00000
-rw-r--r-- 1 hduser supergroup 2550561 2017-11-04 23:09 /database/employees/employees/part-m-00001
-rw-r--r-- 1 hduser supergroup 2086360 2017-11-04 23:09 /database/employees/employees/part-m-00002
-rw-r--r-- 1 hduser supergroup 4637031 2017-11-04 23:09 /database/employees/employees/part-m-00003
Read first 10 lines of the file to check the records
hduser@hmaster:~$ hadoop fs -cat /database/employees/employees/part-m-00000 | head -n 10
17/11/04 23:27:40 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
10001,1953-09-02,Georgi,Facello,M,1986-06-26
10002,1964-06-02,Bezalel,Simmel,F,1985-11-21
10003,1959-12-03,Parto,Bamford,M,1986-08-28
10004,1954-05-01,Chirstian,Koblick,M,1986-12-01
10005,1955-01-21,Kyoichi,Maliniak,M,1989-09-12
10006,1953-04-20,Anneke,Preusig,F,1989-06-02
10007,1957-05-23,Tzvetan,Zielinski,F,1989-02-10
10008,1958-02-19,Saniya,Kalloufi,M,1994-09-15
10009,1952-04-19,Sumant,Peac,F,1985-02-18
10010,1963-06-01,Duangkaew,Piveteau,F,1989-08-24
cat: Unable to write to output stream.
Controlling Parallelism in Sqoop
Sqoop imports data in parallel from most database sources. You can specify the number of map tasks (parallel processes) to use to perform the import by using the -m or --num-mappers argument.
sqoop import --connect jdbc:msql://localhost:3306/employees --username root -password admin --table salaries -m 2 --target-dir /database/employees/salaries
Below are the MapReduce counters and other information when running this Job, which shows that 2 mappers were used to run this job.
17/11/04 23:19:11 INFO mapreduce.Job: Running job: job_1509849001630_0002
17/11/04 23:19:17 INFO mapreduce.Job: Job job_1509849001630_0002 running in uber mode : false
17/11/04 23:19:17 INFO mapreduce.Job: map 0% reduce 0%
17/11/04 23:19:27 INFO mapreduce.Job: map 50% reduce 0%
17/11/04 23:19:28 INFO mapreduce.Job: map 100% reduce 0%
17/11/04 23:19:28 INFO mapreduce.Job: Job job_1509849001630_0002 completed successfully
17/11/04 23:19:28 INFO mapreduce.Job: Counters: 30
File System Counters
FILE: Number of bytes read=0
FILE: Number of bytes written=311846
FILE: Number of read operations=0
FILE: Number of large read operations=0
FILE: Number of write operations=0
HDFS: Number of bytes read=232
HDFS: Number of bytes written=98781181
HDFS: Number of read operations=8
HDFS: Number of large read operations=0
HDFS: Number of write operations=4
Job Counters
Launched map tasks=2
Other local map tasks=2
Total time spent by all maps in occupied slots (ms)=15309
Total time spent by all reduces in occupied slots (ms)=0
Total time spent by all map tasks (ms)=15309
Total vcore-milliseconds taken by all map tasks=15309
Total megabyte-milliseconds taken by all map tasks=15676416
Map-Reduce Framework
Map input records=2844047
Map output records=2844047
Input split bytes=232
Spilled Records=0
Failed Shuffles=0
Merged Map outputs=0
GC time elapsed (ms)=452
CPU time spent (ms)=13760
Physical memory (bytes) snapshot=402960384
Virtual memory (bytes) snapshot=3858165760
Total committed heap usage (bytes)=310378496
File Input Format Counters
Bytes Read=0
File Output Format Counters
Bytes Written=98781181
17/11/04 23:19:28 INFO mapreduce.ImportJobBase: Transferred 94.2051 MB in 19.3542 seconds (4.8674 MB/sec)
17/11/04 23:19:28 INFO mapreduce.ImportJobBase: Retrieved 2844047 records.
To verify the output, first, check the files in the Hadoop file system.
hduser@hmaster:~$ hadoop fs -ls /database/employees/salaries
17/11/04 23:39:20 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Found 3 items
-rw-r--r-- 1 hduser supergroup 0 2017-11-04 23:19 /database/employees/salaries/_SUCCESS
-rw-r--r-- 1 hduser supergroup 50698979 2017-11-04 23:19 /database/employees/salaries/part-m-00000
-rw-r--r-- 1 hduser supergroup 48082202 2017-11-04 23:19 /database/employees/salaries/part-m-00001
Once files are verified in HDFS, we can use the following command to check sample records.
hduser@hmaster:~$ hadoop fs -cat /database/employees/salaries/part-m-00000 | head -n 10
17/11/04 23:40:09 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
10001,60117,1986-06-26,1987-06-26
10001,62102,1987-06-26,1988-06-25
10001,66074,1988-06-25,1989-06-25
10001,66596,1989-06-25,1990-06-25
10001,66961,1990-06-25,1991-06-25
10001,71046,1991-06-25,1992-06-24
10001,74333,1992-06-24,1993-06-24
10001,75286,1993-06-24,1994-06-24
10001,75994,1994-06-24,1995-06-24
10001,76884,1995-06-24,1996-06-23
cat: Unable to write to output stream.
As we can see, that the data from MySQL salaries table was imported into HDFS.
Importing RDBMS table in Hadoop using Sqoop with No primary key column
Usually, we import an RDBMS table in Hadoop using Sqoop Import when it has a primary key column. If it doesn’t have the primary key column, it will give you the below error-
ERROR tool.ImportTool: Error during import: No primary key could be found for table <table_name>. Please specify one with –split-by or perform a sequential import with ‘-m 1’
If your table doesn’t have the primary key column, you need to specify -m 1 option for importing the data, or you have to provide –split-by argument with some column name.
Here are the scripts which you can use to import an RDBMS table in Hadoop using Sqoop when you don’t have a primary key column.
sqoop import \
–connect jdbc:mysql://localhost/dbname \
–username root \
–password root \
–table user \
–target-dir /user/root/user_data \
–columns “first_name, last_name, created_date”
-m 1
or
sqoop import \
–connect jdbc:mysql://localhost/ dbname\
–username root \
–password root \
–table user \
–target-dir /user/root/user_data \
–columns “first_name, last_name, created_date”
Conclusion
In this blog post, we learned about Apache Sqoop and its usage.
Please share this blog post on social media and leave a comment with any questions or suggestions.
References
