mhist

simple measurement history logger

This is a very simple measurement database, that receives measurements (consisting of name, value and optionally a timestamp) through tcp or http. If you don't send a timestamp with the measurement, the current time is used (there are rarely reasons to send a different timestamp). Measurements are stored on disk

For realtime updates you can subscribe to mhist.

assumptions

• measurements are received by mhist in the order they are generated
• there are only two types of measurements: numerical and categorical
• measurement types don't change for a certain measurement name.
• it is known in advance how much memory and diskspace can be used by mhist.
• when retrieving measurements you want to retrieve measurements of all names more often than just certain names.

setup

This uses go mod for dependency management

To see how to change the default configuration, run go run main/main.go -h

endpoints

see the proto definition

todos

• add tests for subscription logic
• add raw measurement type, where the value is just bytes (value is written to value log file, position in file and length written to current "index" file)
• add in memory file index, minimising the filesystem list calls