LMR: Little MapReduce (or Local MapReduce)

lmr is a tool for executing MapReduce-shaped tasks on a workstation. It's similar to tools like xargs or parallel but provides a bit more structure around job execution, failure handling, caching, and output management.

LMR is currently experimental, and may undergo significant API changes before a proper v1 release. Depend on it at your own risk.

Reference

Mapper Protocol

A mapper is provided as the first argument, and is required. A mapper can be a binary on the PATH, any executable file, or a shell command. The mapper is executed for each input chunk. The chunk is provided on stdin. By default any mapper stdout is grouped under a "default" key. Additional outputs keys can be created by writing to files in the "results" dir. This directory is provided to the mapper script in the LMR_RESULTS_DIR environment variable. For example, executing echo ... > $LMR_RESULTS_DIR/foo would produce an output with the foo key.

Roadmap

• Mapper
  • Better error messages on stage failure
  • Configurable parallelism
  • Optional Resubmission
  • Chunk output caching
    • Cache management commands
    • Configurable Cache Size
  • Progress Bar
  • Performance stats on map stages
• Reducer
  • Keyed output protocol. E.g. what happens when there are multiple keys?
  • Script reducer
  • Canned reducers
    • Concat + custom separator
    • Json Array
    • sum
• Project
  • Code Health
    • CI
    • Tests
    • Lints
    • Separate Modules
  • Example in docs
  • Binary builds