Why mongodb is reset after push to openshift

I am deploying my application written using sails.js onto the openshift.

It works properly but however when i commit something new.

It will then build again and clean up all my data in the mongodb.

So I wonder any reasons?

Sorry i am new to openshift

Is it normal mongodb will be cleaned up after stop/start MongoDB cartridge?
How to keep the data remained in the mongodb? do i need to perform save when stop and restore when start?
I am curious how it automatically build and restart the cartridge? I am using the node.js cartidge and have looked into action_hooks but no obvious hint. Just wonder how and why it will trigger both nodejs and mongodb cartridge restart?

Thanks

Here is my log message

remote: Stopping NodeJS cartridge
remote: Stopping MongoDB cartridge
remote: Saving away previously installed Node modules
remote: Building git ref 'master', commit 937dacf
remote: 
remote:   - Checking to see if Node.js version  is installed ... 
remote:   - Downloading and extracting http://nodejs.org/dist/v/node-v-linux-x64.tar.gz ... 
remote:   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
remote:                                  Dload  Upload   Total   Spent    Left  Speed
remote:   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--    remote: 100   162  100   162    0     0    179      0 --:--:-- --:--:-- --:--:--    remote: 100   162  100   162    0     0    179      0 --:--:-- --:--:-- --:--:--   179
remote: 
remote: gzip: stdin: not in gzip format
remote: tar: Child returned status 1
remote: tar: Error is not recoverable: exiting now
remote:   - Done installing Node.js version 
remote: Building NodeJS cartridge
remote: grep: /var/lib/openshift/id/app-root/runtime/repo//package.json: No such file or directory
remote: grep: /var/lib/openshift/id/app-root/runtime/repo//package.json: No such file or directory
remote:   - PATH set to include custom node version () from
remote:        /var/lib/openshift/id/app-root/data//node-v-linux-x64/bin 
remote:     PATH = /var/lib/openshift/id/app-root/data//node-v-linux-x64/bin:/var/lib/openshift/id//.node_modules/.bin:/bin:/usr/bin:/usr/sbin
remote:   - Installing dependencies w/ new version of npm ... 
remote: 
remote: npm info it worked if it ends with ok
remote: npm info using npm@1.3.6
remote: npm info using node@v0.10.26
remote: npm info preinstall app@0.0.1
remote: npm info build /var/lib/openshift/id/app-root/runtime/repo
remote: npm info linkStuff app@0.0.1
remote: npm info build /var/lib/openshift/id/app-root/runtime/repo/node_modules/config-multipaas
remote: npm info preinstall config-multipaas@0.1.0
remote: npm info linkStuff config-multipaas@0.1.0
remote: npm info install config-multipaas@0.1.0
remote: npm info postinstall config-multipaas@0.1.0
remote: npm info build /var/lib/openshift/id/app-root/runtime/repo/node_modules/restify
remote: npm info preinstall restify@2.8.5
remote: npm info linkStuff restify@2.8.5
remote: npm info install restify@2.8.5
remote: npm info postinstall restify@2.8.5
remote: npm info install app@0.0.1
remote: npm info postinstall app@0.0.1
remote: npm info prepublish app@0.0.1
remote: npm info ok 
remote: Preparing build for deployment
remote: Deployment id is c2e64369
remote: Activating deployment
remote: Starting MongoDB cartridge
remote:   - Checking to see if Node.js version  is installed ... 
remote:   - Downloading and extracting http://nodejs.org/dist/v/node-v-linux-x64.tar.gz ... 
remote:   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
remote:                                  Dload  Upload   Total   Spent    Left  Speed
remote:   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--    remote: 100   162  100   162    0     0    282      0 --:--:-- --:--:-- --:--:--   283
remote: 
remote: gzip: stdin: not in gzip format
remote: tar: Child returned status 1
remote: tar: Error is not recoverable: exiting now
remote:   - Done installing Node.js version 
remote: 
remote:   - pre_start_nodejs: Adding Node.js version  binaries to path
remote:   - PATH set to include custom node version () from
remote:        /var/lib/openshift/id/app-root/data//node-v-linux-x64/bin 
remote:     PATH = /var/lib/openshift/id/app-root/data//node-v-linux-x64/bin:/var/lib/openshift/id//.node_modules/.bin:/bin:/usr/bin:/usr/sbin
remote: Running "clean:dev" (clean) task
remote: 
remote: Running "jst:dev" (jst) task
remote: >> Destination not written because compiled files were empty.
remote: 
remote: Running "less:dev" (less) task
remote: File .tmp/public/styles/importer.css created: 0 B → 619 B
remote: 
remote: Running "copy:dev" (copy) task
remote: Copied 11 files
remote: 
remote: Running "coffee:dev" (coffee) task
remote: 
remote: Running "concat:js" (concat) task
remote: File ".tmp/public/concat/production.js" created.
remote: 
remote: Running "concat:css" (concat) task
remote: File ".tmp/public/concat/production.css" created.
remote: 
remote: Running "uglify:dist" (uglify) task
remote: File .tmp/public/min/production.min.js created: 177.15 kB → 122.79 kB
remote: 
remote: Running "cssmin:dist" (cssmin) task
remote: File .tmp/public/min/production.min.css created: 6.09 kB → 4.34 kB
remote: 
remote: Running "sails-linker:prodJs" (sails-linker) task
remote: padding length 4
remote: File "views/layout.ejs" updated.
remote: 
remote: Running "sails-linker:prodStyles" (sails-linker) task
remote: padding length 4
remote: File "views/layout.ejs" updated.
remote: 
remote: Running "sails-linker:devTpl" (sails-linker) task
remote: padding length 4
remote: File "views/layout.ejs" updated.
remote: 
remote: Running "sails-linker:prodJsJade" (sails-linker) task
remote: 
remote: Running "sails-linker:prodStylesJade" (sails-linker) task
remote: 
remote: Running "sails-linker:devTplJade" (sails-linker) task
remote: 
remote: Done, without errors.
remote: Starting NodeJS cartridge
remote: Result: success
remote: Activation status: success
remote: Deployment completed with status: success

It usually shouldn't clean out your data. You may have your application set up incorrectly. You may want to go through and check everything is set up correctly.