BooblikConfigTest

Diagram

BooblikConfig loading precedence

The configuration follows a strict hierarchy where environment variables take the highest precedence, followed by properties defined in a file, and finally falling back to hardcoded defaults if no value is provided (BooblikConfig.kt:79-91). For example, an environment variable like BOOBLIK_PORT will override a booblik.port setting found in a properties file (BooblikConfigTest.kt:46-47).

TopicName and partition count parsing

The configuration parses a comma-separated string of topics into a map where each TopicName is associated with an integer representing its partition count (BooblikConfig.kt:144-154). The format required is name:partitions (e.g., orders:3, clicks:1), and the parser ensures that each topic has at least one partition (BooblikConfig.kt:152).

Validation of SegmentMode and FetchMode

Enum-based settings are strictly validated against their allowed values during the loading process (BooblikConfig.kt:106-114). The following table summarizes the configuration parameters:

Failure modes and startup refusal

The broker is designed to refuse to boot if configuration errors are detected, preventing "surprises at three in the morning" (BooblikConfigTest.kt:16). Specific failure modes include:

• Type Mismatches: Providing a non-integer value for a numeric field (e.g., booblik.port=nine-thousand) results in an IllegalStateException (BooblikConfigTest.kt:67).
• Invalid Ranges: Port numbers must be within 0..65535 (BooblikConfig.kt:50).
• Logical Errors: A segment capacity of zero or an empty topic list will trigger an IllegalArgumentException (BooblikConfigTest.kt:74-78).

FlushPolicy and retention configuration

The configuration supports complex policies for data durability and lifecycle management (BooblikConfig.kt:130-136):

Key files

Behaviour that does surprise

• The load function in BooblikConfig.kt will throw an error if a file path is provided but the file does not exist, whereas it is perfectly fine to load with no file at all (BooblikConfig.kt:82-85).
• The SegmentMode.MAPPED value is the default, but the configuration allows for other modes via the enum helper (BooblikConfig.kt:122-126).
• The BooblikConfig class uses an init block to perform secondary validation on values like port and segmentCapacity after they have been parsed (BooblikConfig.kt:49-55).