YAML Config for MongoDB 2.7.9 - WiredTiger, zlib compression

mongo_wt_zlib.conf

storage:
    dbPath: "/ssd/db/wt_zlib"
    engine: "wiredTiger"
    wiredTiger:
        collectionConfig: "block_compressor=zlib"
systemLog:
    destination: file
    path: "/data/wt_zlib/mongodb.log"
processManagement:
    fork: true

Don't know if this syntax was valid with the release of 2.8, but at least with 3.4, the correct syntax is:

storage:
  dbPath: "/ssd/db/wt_zlib"
  engine: "wiredTiger"
  wiredTiger:
      collectionConfig:
        blockCompressor: "zlib"