ntail

ntail is a simple CLI utility written in Node.js which reads logs from files, parses then and outputs JSON formatted data.

It is especially useful when used in Kubernetes, as a sidecar for instance, when writing logs to stdout is not possible.

ntail checks for new files matching patterns every 10 seconds.

Usage

Local

Create a config.yaml file using config.dist.yaml sample as a base.

NODE_ENV=production CONFIG_PATH=/path/to/config.yaml npm start

Docker

docker pull clickandmortar/ntail
docker run \
  -v $PWD/path/to/logs:/logs \
  -v $PWD/config.yaml:/config.yaml \
  -e CONFIG_PATH=/config.yaml \
  clickandmortar/ntail

Configuration

files:
  - pattern: "/path/to/*.log"
    # Input log line sample: [2020-07-15 15:00:25] hello ntail
    format: "^\\[(?<date>[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2})\\] (?<message>.*)$"
    # Output raw log line if regex format does not match
    fallback: true

Format property

• This property may be an array of regexes, output of the first one matching will be used
• Escape character (\) needs to be escaped in the YAML config (\\)

Development

cp config.dist.yaml config.yaml
npm install
npm run dev

⚠️ Application currently does not restart on config file change.

Building Docker image

make build
make push

Enhancements

• Allow adding tags in JSON output per file pattern in config
• Restart app in development mode when YAML config changes