DDevelopment & Design

Bash’ing your git deployment

Chuck Norris deploys after every commit. Smart men deploy after every successful build on their Continuous Integration server. Educated men, deploy code directly from their distributed version control systems. I, being neither, had to write my deployment script in bash. We’re using git and while doing so I wanted us to:

  • deploy from working copy, but…
  • make sure that you can deploy only if you committed everything
  • make sure that you can deploy only if you pushed everything upstream
  • tag the deployed hash
  • display changelog (all the commits between two last tags)

Here are some BASH procedures I wrote on the way, if you need them:

make sure that you can deploy only if you committed everything 

verifyEverythingIsCommited() {
    gitCommitStatus=$(git status --porcelain)
    if [ "$gitCommitStatus" != "" ]; then
        echo "You have uncommited files."
        echo "Your git status:"
        echo $gitCommitStatus
        echo "Sorry. Rules are rules. Aborting!"
        exit 1
    fi
}

make sure that you can deploy only if you pushed everything upstream 

verifyEverythingIsPushedToOrigin() {
    gitPushStatus=$(git cherry -v)
    if [ "$gitPushStatus" != "" ]; then
        echo "You have local commits that were NOT pushed."
        echo "Your 'git cherry -v' status:"
        echo $gitPushStatus
        echo "Sorry. Rules are rules. Aborting!"
        exit 1
    fi
}

tag the deployed hash Notice: my script takes first parameter as the name of the server to deploy to (this is $1 passed to this procedure). Also notice, that ‘git push’ without the ‘–tags’ does not push your tags. 

tagLastCommit() {
    d=$(date '+%y-%m-%d_%H-%M-%S')
    git tag "$1_$d"
    git push --tags
}

This creates nice looking tags like these: preprod_12-01-11_15-16-24 prod_12-01-12_10-51-33 test_12-01-11_15-11-10 test_12-01-11_15-53-42

display changelog (all the commits between two last tags) 

printChangelog() {
    echo "This is changelog since last deploy. Send it to the client."
    twoLastHashesInOneLine=$(git show-ref --tags -s | tail -n 2 | tr "\\n" "-");
    twoLastHashesInOneLineWithThreeDots=${twoLastHashesInOneLine/-/...};
    twoLastHashesInOneLineWithThreeDotsNoMinusAtTheEnd=$(echo $twoLastHashesInOneLineWithThreeDots | sed 's/-$//');
    git log --pretty=oneline --no-merges --abbrev-commit  $twoLastHashesInOneLineWithThreeDotsNoMinusAtTheEnd
}

The last command gives you a nice log like this: e755c63 deploy: fix for showing changelog from two first tags instead of two last ones 926eb02 pringing changelog between last two tags on deployment 34478b2 added git tagging to deploy

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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.