- At an time onlyu ONE broker can be a leader for a given partition
- Only that leader can receive and serve data for a partition
- The other brokers will synchronize tghe data
- Therefore each partition has one leader and multiple ISR(in-sync replica)
- Topics should have a replication factor > 1 (usually between 2 and 3)
- This way if a broker is down, another broker can seve the data
- Example: Topic-A with 2 partitions and replication factor of 2
- Example: we lost Broker 102
- Result: Broker 101 and 103 can still serve the data
- Example of Topic-A with 3 partitions
- Example of Topic-B with 2 partitions
- Note: Data is distributed and Broker 103 doesn't have any Topic B data
- A Kafka cluster is composed of multiple brokers(servers)
- Each broker is identified with its ID(integer)
- Each broker contains certain topic partitions
- After connectiong to any broker (called a bootstrap broker), you will be connected to the entire cluster
- A good number to get started is 3 brokers, but some big clusters have over 100 brokers
- In these examples we choose to number brokers starting at 100(arbitrary)
- Topics: a particular stream of data
1) Similar to a table in a database(without all the constraints)
2) You can have as many topics as you want
3) A topic is identified by its name
- Topics are split in partitions
1) Each partition is orderd
2) Each message within a partition gets an incremental id, called offet
- E.g. offset 3 in partition 0 doesn't represent the same data as offset 3 in partition 1
- Order is guaranteed only within a partition (not across partitions)
- Data is kept only for a limited time (default is noe week)
- Once the data is written to a partition, it can't be changed (immutability)
- Data is assigned randomly to a partition unless a key is provided (more on this later)
- Say you have a fleet of trucks, each truck reports its GPS position to Kaflk.
- You can have a topic trucks_gps that contains the position of all trucks.
- Each truck will send a message to Kafka every 20 seconds, each message will contain the truck ID and the truck position (latitude and longitude
- We choose to create that topic with 10 partitions(arbitrary number)
- Netflix uses Kafka to apply recommendations in real-time while you're watching TV shows
- Uber uses Kafka to gather user, taxi and trip data in real-time to compute and forecast demand, and compute surge pricing in real-time
-LinkedIn uses Kafka to prevent spam, collect user interactgions to make better connection recommendations in real time.
-Remember that Kafka is only used as a transportation mechanism!
