Mongosh json output

[Rhys_Campbell]

Hello All,

mongo outputs json in the following format…

    root@124d7cfb725d:/# mongo --eval "db.adminCommand('listDatabases')"
    MongoDB shell version v5.0.0
    connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
    Implicit session: session { "id" : UUID("61ef35d1-7e31-43e1-87bb-e3f27405a1c1") }
    MongoDB server version: 5.0.0
    {
    	"databases" : [
    		{
    			"name" : "admin",
    			"sizeOnDisk" : NumberLong(40960),
    			"empty" : false
    		},
    		{
    			"name" : "config",
    			"sizeOnDisk" : NumberLong(12288),
    			"empty" : false
    		},
    		{
    			"name" : "local",
    			"sizeOnDisk" : NumberLong(40960),
    			"empty" : false
    		}
    	],
    	"totalSize" : NumberLong(94208),
    	"totalSizeMb" : NumberLong(0),
    	"ok" : 1
    }

while mongosh in 5.0 does the following…

    root@124d7cfb725d:/# mongosh --eval "db.adminCommand('listDatabases')"
    Current Mongosh Log ID:	60fab3516abd6eae1265d3d6
    Connecting to:		mongodb://127.0.0.1:27017/?directConnection=true&serverSelectionTimeoutMS=2000
    Using MongoDB:		5.0.0
    Using Mongosh:		1.0.0

    For mongosh info see: https://docs.mongodb.com/mongodb-shell/

    ------
       The server generated these startup warnings when booting:
       2021-07-23T12:09:57.899+00:00: Using the XFS filesystem is strongly recommended with the WiredTiger storage engine. See http://dochub.mongodb.org/core/prodnotes-filesystem
       2021-07-23T12:09:58.535+00:00: Access control is not enabled for the database. Read and write access to data and configuration is unrestricted
    ------

    {
      databases: [
        { name: 'admin', sizeOnDisk: Long("40960"), empty: false },
        { name: 'config', sizeOnDisk: Long("61440"), empty: false },
        { name: 'local', sizeOnDisk: Long("40960"), empty: false }
      ],
      totalSize: Long("143360"),
      totalSizeMb: Long("0"),
      ok: 1
    }

I get the following error with an existing application…

Expecting property name enclosed in double quotes: line 2 column 3 (char 4)

It would be nice if the outputted json was parsable without further processing or at least an option to allow this.

Cheers,

Rhys

[Sergey_Petushkov]

Hey Rhys, thanks for opening this issue! Can you please tell us what application are you using for parsing this output?

[Rhys_Campbell]

Hello Sergey,

https://docs.ansible.com/ansible/latest/collections/community/mongodb/mongodb_shell_module.html

Using various Python versions. It’s just a simple json.loads(). With 5.0 I was already having to strip out the Extended JSON stuff when using the old mongo shell. The new mongosh shell has additional issues.

Rhys

[Anna_Henningsen]

Hey Rhys, if you are looking to parse output from mongosh programmatically, we are recommending to wrap the result with EJSON.stringify; for example:

$ /tmp/mongosh-1.0.1-linux-x64/bin/mongosh [...] --eval "EJSON.stringify(db.adminCommand('listDatabases'))"
Current Mongosh Log ID:	60fad826709a27c53c9cb992
Connecting to:		mongodb+srv://<credentials>@[...]/
Using MongoDB:		4.4.7
Using Mongosh:		1.0.1

For mongosh info see: https://docs.mongodb.com/mongodb-shell/

{"databases":[{"name":"test","sizeOnDisk":589824,"empty":false},{"name":"admin","sizeOnDisk":335872,"empty":false},{"name":"local","sizeOnDisk":3412008960,"empty":false}],"totalSize":3573481472,"ok":1,"$clusterTime":{"clusterTime":{"$timestamp":{"t":1627052073,"i":1}},"signature":{"hash":{"$binary":{"base64":"0YqoHxcwf2/Vv8T5c+aUOj+bXoM=","subType":"00"}},"keyId":6928827991380197000}},"operationTime":{"$timestamp":{"t":1627052073,"i":1}}}

That’s always programmatically parseable. And if you want something prettier/more human-friendly, you can use EJSON.stringify(result, null, ' '), while still maintaining machine readability.

Does this help you?

[Rhys_Campbell]

Hello Anna,

With a bit of effort that’s probably workable. Consistent output across tools would probably prevent a lot of tooling bugs though. But c’est la vie.

Cheers,

R