jsonlines-processor

JSON Lines streaming processor for CLI

A JSON Lines is called newline-delimited JSON and used for structured logs.

Install

$ npm install -g jsonlines-processor

How to Use

Create logic.js

exports.process = async function(item) {
  // filter
  if (item.target === 'my_require') {
    return item;
  } else if (item instanceof Array) {
    // Return multiple items
    item.forEach(it => {
      if (it.target === 'my_require') {
        this.push(it);
      }
    });
  }
}

// Optional
exports.finalize = async function(items) {
  // sort
  return this.sort(items, 'age')
}

exports.before = async function(cliArg1, cliArg2) {
  // const anotherLogs = await this.readJSONLinesFile('./another.log')
  // const userMap = this.keyBy(anotherLogs, 'user.name')
  // await startServer()
}

exports.after = async function(items) {
  // await shutdownServer()
}

Run command

$ gunzip -c application-json.log.gz | jlp logic.js > output_json.log

Helper function

Following utility methods can be called in process, finalize, before or after functions

sort(items, [key], [direct])

Arguments

• items:Array - The array to process
• [key]:String - Target field name. item itself if not specified
• [direct]:String - Ascending if not specified, else descending

Returns

• Array - the new array of sorted items

keyBy(items, key)

Arguments

• items:Array - The array to process
• key:String - The iteratee to transform key

Returns

• Object - the composed aggregate object.

sum(items, [key])

Arguments

• items:Array - The array to process
• [key]:String - Target field name. item itself if not specified

Returns

• Number - the total value for each items

readJSONLinesFile(fileName)

Arguments

• fileName:String - JSON Lines file path

Returns

• Array - the new array of JSON object

readTSVFile(fileName)

Arguments

• fileName:String - TSV file path

Returns

• Array - Returns the new array of array item

Examples

example-json.log

{"name":"Hanako","age":16,"score":41}
{"name":"Taro","age":18,"score":81}
{"name":"Mike","age":15,"score":72}
{"name":"Ken","age":17,"score":90}

logic1.js

Extracting the name and score of only item whose age is greater than 16, and sorting items by their score in descending order

exports.process = async ({ name, age, score }) => {
  if (age > 16) {
    return { name, score }
  }
}

exports.finalize = async function(items) {
  return this.sort(items, 'score', 'desc')
}

Result

$ jlp logic1.js < example-json.log
{"name":"Ken",score:90}
{"name":"Taro",score:81}

License

MIT