Tailing JSON logs with lnav on AWS Elastic Beanstalk through eb ssh

-rails_semantic_json_logging_viewing_lnav_aws_elastic_beanstalk.md

Using Rails Semantic Logger for logging, JSON logs can be tailed on AWS Elastic Beanstalk with lnav JSON log viewer from an eb ssh command line session with this config.

lnav.config.yml

# .ebextensions/lnav.config
files:
  # ./logs to quick view logs from eb ssh
  "/home/ec2-user/logs" :
    mode: "000777"
    owner: root
    group: root
    content: |
      /home/ec2-user/lnav/lnav -i /var/app/current/lnav_log_viewer_format.json
      /home/ec2-user/lnav/lnav /var/app/current/log/application_log.json

  "/home/ec2-user/lnav.zip" :
    mode: "000777"
    owner: root
    group: root
    source: https://github.com/tstack/lnav/releases/download/v0.8.5/lnav-0.8.5-linux-64bit.zip

commands:
  lnav_unzip:
    command: command: if [ ! -d "lnav" ]; then unzip lnav.zip; rm -f lnav.zip; mv lnav* lnav; fi
    cwd: /home/ec2-user/

lnav_log_viewer_format.json

// app_root/lnav_log_viewer_format.json
{
  "json_log": {
    "title": "JSON log",
    "description": "Rails Semantic Logger JSON format",
    "json": true,
    "file-pattern": ".*\\.json$",
    "timestamp-field": "timestamp",
    "timestamp-format": ["%Y-%m-%dT%H:%M:%S.%fZ"],
    "level-field": "level",
    "value": {
      "host": {
        "kind": "string",
        "hidden": true
      },
      "application": {
        "kind": "string",
        "hidden": true
      },
      "level": {
        "kind": "string",
        "identifier": true
      },
      "level_index": {
        "kind": "integer",
        "hidden": true
      },
      "pid": {
        "kind": "integer",
        "hidden": true
      },
      "thread": {
        "kind": "string",
        "hidden": true
      },
      "named_tags": {
        "kind": "json"
      },
      "duration_ms": {
        "kind": "float",
        "hidden": true
      },
      "duration": {
        "kind": "string",
        "hidden": true
      },
      "name": {
        "kind": "string"
      },
      "message": {
        "kind": "string"
      },
      "payload": {
        "kind": "json"
      },
      "file": {
        "kind": "string",
        "hidden": true
      },
      "line": {
        "kind": "integer",
        "hidden": true
      },
      "exception": {
        "kind": "json"
      },
      "exception/message": {
        "kind": "string"
      },
      "exception/stack_trace": {
        "kind": "string"
      }
    },  
    "line-format": [
      {
        "field": "timestamp",
        "timestamp-format": "%H:%M:%S.%f"
      },
      "|",
      {
        "field": "level"
      },
      "|",
      {
        "field": "name"
      },
      "|",
      {
        "field": "message"
      },
      {
        "field": "exception"
      },
      "|",
      {
        "field": "named_tags"
      },
      "|",
      {
        "field": "payload"
      }
    ],
    "hide-extra": false,
    "multiline": true
  }
}