Technology Ramblings

Why Cloudformation template is preferred over boto3 to provision infrastructure in AWS? 1. Zero cost. There is no cost for using the CloudFormation template to provision resources. On the other hand, if the resources are provisioned using boto3 in lambda, execution does cost money. Even if the price is negligible, every penny helps. 2. Scaleability. If the resource provision takes more than 15 minutes, it is impossible to provide the resource using lambda directly. In provisioning large resources with heavy bootstrap installations, it could be possible to hit those limits. 3. Fail-Safe. When the resource provision fails for any reason, lambda doesn't take responsibility to clean up the resources instantiated so far unless it is handled explicitly. On the other hand, CloudFormation Stack does a clean rollback by reverting to the initial state. It does save money if the resources are cleaned up appropriately. 4. Less error-prone. There is only one way (declarative using JSON or YAML)...

The problem: A large scale manufacturing organization aggregates data from different sources, maintains it in a single Oracle table, and the number of records is in the order of a little over a billion. A monthly process has to fetch the data from Oracle to HDFS.  The constraint: Ideally, only the difference for each month could be fetched. But, there is little to no control over the Oracle data source and there is no reliable way to identify the delta. Hence, all the data have to be fetched all the time. To give a perspective, if the table is exported as a CSV from a SQL Client (say, SQL Developer), it takes more than 20 hours to download the table. The tool: Sqoop is the standard tool used to import data from the relational database to HDFS. The solution: $ sqoop import -D **oracle.row.fetch.size=50000 --fetch-size 15000 --num-mappers 40** --table ` <schema>.<table_name> ` -connect ` <jdbc_connection_url> `   --username ` <user> ` -P --target-dir...

Six ways to land robotic rovers on Mars Mars Rover problem is a popular problem statement used by companies to check object orientation and test-driven development skills. In this article, we'll take the core problem statement and see how the solution evolves through six different levels. Knowledge of high school level maths and little python helps to follow this article. The actual Problem Statement: A squad of robotic rovers is to be landed by NASA on a plateau on Mars. This plateau, which is curiously rectangular, must be navigated by the rovers so that their on-board cameras can get a complete view of the surrounding terrain to send back to Earth. A rover's position is represented by a combination of x and y coordinates and a letter representing one of the four cardinal compass points. The plateau is divided up into a grid to simplify navigation. An example position might be 0, 0, N, which means the rover is in the bottom left corner facing North. In order t...