HOW TO CHOOSE SS TABLES TO COMPACT SSTables are separated by density leveling in levels determined by the fan factors of the compaction setup. The amount of SSTables on a level, however, cannot be used as a trigger because there may be non-overlapping SSTables, unlike in size leveling where SSTables are anticipated to cover the entire token area. In this case, read queries are less effective. Use sharding, which decreases the size of individual compaction operations and executes many compactions on a level concurrently, to address this. The amount of overlapping SSTables in a bucket dictates ..read more

FUNCTIONS IN PYTHON FUNCTION: A function is a block of code that performs a specific task. Functions are defined by using the def keyword which follows by function name and parentheses which may have parameters. Any function can accept zero or more parameters. The body of the function contains the code that performs a specific task. Function returns a value using the return keyword, this makes a function to pass data back to the code from where it is called. To execute any function, you need to call it by the function name followed by parentheses. Example: def squareroot(x): #defines ..read more

STRATEGIES OF COMPACTION Unified Compaction Strategy (UCS) Size-Tiered Compaction Strategy (STCS) Leveled Compaction Strategy (LCS) Time Window Compaction Strategy (TWCS)   UNIFIED COMPACTION STRATEGY: For the majority of workloads, including mixed read-write, time-series, read-heavy, and write-heavy workloads, the UnifiedCompactionStrategy (UCS) is advised. UCS may be made to behave like any legacy compaction strategy, thus there’s no need to employ them.Compaction approach UCS incorporates new features along with the greatest aspects of previous strategies. With a novel sharding method ..read more

CHANGE DATA CAPTURE When a configurable size-on-disk for the CDC log is reached, Change Data Capture (CDC) offers a technique to refuse writes to certain tables and flag them for archiving. By setting the table property cdc=true (either when creating the table or modifying it), an operator can enable CDC on a table. A hard link to the CommitLogSegment is made in the directory designated by cassandra. yaml at the time of the segment’s creation. A <segment_name>_cdc.idx file is also created with the integer offset of how much data from the original segment is persisted to disk when a segm ..read more

APACHE CASSANDRA INSTALLATIONS These are the guidelines for setting up the supported Apache Cassandra releases on Linux systems. Cassandra runs on a wide array of Linux distributions including (but not limited to): ⦁ Ubuntu, most notably LTS releases 16.04 to 18.04. ⦁ CentOS & RedHat Enterprise Linux (RHEL) including 6.6 to 7.7. ⦁ Amazon Linux AMIs including 2016.09 through to Linux 2 ⦁ Debian versions 8 & 9 ⦁ SUSE Enterprise Linux 12 This is neither a prescriptive nor a complete list of operating system platforms. Nonetheless, users would be wise to carry out thorough tests on their ..read more

BLOOM FILTERS WHAT ARE BLOOM FILTERS: Cassandra combines data from RAM (in memtables) and disk (in SSTables) in the read path. Cassandra uses a data structure called a bloom filter to avoid having to go through each and every SSTable data file to find the partition that is being requested. Cassandra can decide one of two probable states using bloom filters, a probabilistic data structure: either the data absolutely does not exist in the provided file, or the data probably does. Bloom filters can be made more accurate by allowing them to use more RAM, even when they cannot ensure that the data ..read more

Creating a new Docker Image/container from existing Container And run the new container. Step 1: Create an initial Base Container – for an App Let’s get started by creating a running container. So that we don’t get bogged down in the details of any particular container, We can use nginx. The Docker create command will create a new container. docker create --name nginx_base -p 80:80 nginx:alpine Step 2: Inspect Images If you look at the list of images on your system You will now see the nginx:alpine image: docker images -a Step 3: Inspect Containers- created but not started. Not ..read more

CASSANDRA BACKUPS WHAT ARE BACKUPS: Immutable SSTable files are used by Apache Cassandra to store data. The backup copies of the database data that are kept as SSTable files in the Apache Cassandra database are called backups. There are various uses for backups, some of which are as follows: ⦁ To preserve a copy of the data. ⦁ To be able to restore a table in the event that a node, partition, or network failure causes the loss of table data. ⦁ For portability, to be able to move the SSTable files to another computer.   TYPES OF BACKUPS IN APACHE CASSANDRA: A snapshot is a hard link-creat ..read more

Creating Docker Container using Docker file: Use Case of Docker: Consider a team working on a Java application. Various groups are involved in the Software Development lifecycle: designing, development, testing, production, deployment, etc. Step 1: The developer will create an environment that includes a Tomcat server. Step 2:  The tester must test the application after it has been developed. The tester will now create a new Tomcat environment to test the application from scratch. Step 3: The application will be deployed to the production server when the testing is completed. Again ..read more

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