Json parsing in Ansible

Question

I have to parse the output of the following command:

mongo <dbname> --eval "db.isMaster()"

which gives output as follows:

 {
    "hosts" : [
        "xxx:<port>",
        "xxx:<port>",
        "xxx:<port>"
    ],
    "setName" : "xxx",
    "setVersion" : xxx,
    "ismaster" : true,
    "secondary" : false,
    "primary" : "xxx",
    "me" : "xxx",
    "electionId" : ObjectId("xxxx"),
    "maxBsonObjectSize" : xxx,
    "maxMessageSizeBytes" : xxxx,
    "maxWriteBatchSize" : xxx,
    "localTime" : ISODate("xxx"),
    "maxWireVersion" : 4,
    "minWireVersion" : 0,
    "ok" : 1
}

I need to parse the above output to check the value of "ismaster" is true. Please let me know how i can do this in ansible.

At the moment i am simply checking that the text "ismaster" : true is shown in the output using the following code:

  tasks:
     - name: Check if the mongo node is primary
       shell: mongo <dbname> --eval "db.isMaster()"
       register: output_text

     - name: Run command on master
       shell: <command to execute>
       when: "'\"ismaster\\\" : true,' in output_text.stdout"

However it would be nice to use Ansible's json processing to check the same. Please advise.

Solution

There are quite a bit of helpful filters in Ansible.

Try: when: (output_text.stdout | from_json).ismaster

Comments

[trial999]

Getting this error when i try to do this: "The conditional check '(output_text.stdout | from_json).ismaster' failed. The error was: No JSON object could be decoded\n\nThe error appears to have been in 'xxxx': line xx, column x, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n - name: Run command on master\n ^ here\n"}

[Konstantin Suvorov]

Ouch... you have not pure JSON stuff like ObjectId() and ISODate(). Not sure there is an easy fix for this.

[trial999]

Have used a this command instead which outputs a "true". mongo <dbname> --eval "db.isMaster().ismaster". Thanks for guiding.

[Pier]

My 2 cents: Usually, at least from my point of view, using the shell module means you are not doing it right...