DDevelopment & Design

Journal.IO 1.3 released

AboutJust a moment ago (in February 17th) Journal.IO 1.3 has been released. Journal.IO (https://github.com/sbtourist/Journal.IO) is a lightweight, zero-dependency journal storage implementation written in Java. We use it in our project for storing appl…AboutJust a moment ago (in February 17th) Journal.IO 1.3 has been released. Journal.IO (https://github.com/sbtourist/Journal.IO) is a lightweight, zero-dependency journal storage implementation written in Java. We use it in our project for storing appl…

About

Just a moment ago (in February 17th) Journal.IO 1.3 has been released. Journal.IO (https://github.com/sbtourist/Journal.IO) is a lightweight, zero-dependency journal storage implementation written in Java. We use it in our project for storing application events (Event Sourcing pattern). It is a good, stable solution if you want to have simple in use event storage e.g. if you want to implement lightweight queuing mechanism and JMS is overhead for you.

New version resolves some bugs and improves delete operation performance. Unfortunately new version uses new log format which isn’t backward compatible. Therefore we decide to write a simple migrating tool for migrate 1.2 version compatible logs to 1.3 version.

Migrator

Migrator was written in groovy. It is available on github (https://github.com/arkadius/journalioMigration). Also link to the tool is available from official Journal.IO homepage. To use it simply run:

oldLogsRoot is recursively scanned for logs which are migrated parallel in 5 threads (used ASYNC read mode additionally speed up this process). Migrated logs are written in the same hierarchy in newLogsRoot.

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DDevelopment & Design

Need to make a quick json fixes – JSONPath for rescue

From time to time I have a need to do some fixes in my json data. In a world of flat files I do this with grep/sed/awk tool chain. How to handle it for JSON? Searching for a solution I came across the JSONPath. It quite mature tool (from 2007) but I haven't hear about it so I decided to share my experience with others.

First of all you can try it without pain online: http://jsonpath.curiousconcept.com/. Full syntax is described at http://goessner.net/articles/JsonPath/



But also you can download python binding and run it from command line:
$ sudo apt-get install python-jsonpath-rw
$ sudo apt-get install python-setuptools
$ sudo easy_install -U jsonpath

After that you can use inside python or with simple cli wrapper:
#!/usr/bin/python
import sys, json, jsonpath

path = sys.argv[1]

result = jsonpath.jsonpath(json.load(sys.stdin), path)
print json.dumps(result, indent=2)

… you can use it in your shell e.g. for json:
{
"store": {
"book": [
      {
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
      },
      {
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
      },
      {
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"price": 8.99
      },
      {
"category": "fiction",
"author": "J. R. R. Tolkien",
"title": "The Lord of the Rings",
"isbn": "0-395-19395-8",
"price": 22.99
      }
    ],
"bicycle": {
"color": "red",
"price": 19.95
    }
  }
}

You can print only book nodes with price lower than 10 by:
$ jsonpath '$..book[?(@.price

Result:
[
  {
"category": "reference",
"price": 8.95,
"title": "Sayings of the Century",
"author": "Nigel Rees"
  },
  {
"category": "fiction",
"price": 8.99,
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"author": "Herman Melville"
  }
]

Have a nice JSON hacking!From time to time I have a need to do some fixes in my json data. In a world of flat files I do this with grep/sed/awk tool chain. How to handle it for JSON? Searching for a solution I came across the JSONPath. It quite mature tool (from 2007) but I haven't hear about it so I decided to share my experience with others.