# Proper way to deploy on production stage

**URL:** <https://forum.serverless.com/t/proper-way-to-deploy-on-production-stage/5482>\
**Category:** Serverless Framework\
**Created:** [August 17, 2018, 12:49pm UTC](https://forum.serverless.com/t/proper-way-to-deploy-on-production-stage/5482 "2018-08-17T12:49:12Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![placplacboom](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.serverless.com/placplacboom/32/2411_2.png) [@placplacboom](https://forum.serverless.com/u/placplacboom)\
**Post date:** [August 17, 2018, 12:49pm UTC](https://forum.serverless.com/t/proper-way-to-deploy-on-production-stage/5482/1 "2018-08-17T12:49:12Z")

</div>

Hello folks!

I’m new to serverless and it’s so smooth on development stage. Right now, I’m migrating a few stacks to prod environment and I’m facing a common error:

`An error occurred: XXXXXX - xxxxx-prod already exists.`

If I’m doing a fresh deploy, it works. But when I want to include new functions, I got this error. i.e: only works on first `sls deploy --stage prod`

My policies are set to Retain on production because I want to keep data save.

How can I deploy new functions and keep my resources without need to change my policy?

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<div class="post-metadata">

**Author:** ![smougenot](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.serverless.com/smougenot/32/1511_2.png) [@smougenot](https://forum.serverless.com/u/smougenot)\
**Post date:** [August 17, 2018, 4:06pm UTC](https://forum.serverless.com/t/proper-way-to-deploy-on-production-stage/5482/2 "2018-08-17T16:06:14Z")

</div>

Hello, no solution but one try!

I’ve the exact same problem with buckets.

I want them to stay what ever happen to the serverless project/function.  
So I used  
`DeletionPolicy: Retain`.

Fine for the first run and until you keep the associate CloudFormation stack living.

But when I drop the stack in order to rebuild with a somehow different design but reusing data (thus the bucket)  
I can not find any way to do that with serverless.

Try :

- add a Condition not to create the bucket (will fail because it exists)
- but now I need this bucket arn to grant permission to the new lambda

Could not find any way to get arn dynamically with serverless  
… maybe I can provide input variables an existing arn (for the existing bucket) or the computed expected bucket arn (it is possible with bucket but not for mush resources)  
… but for other resources the arn might not be computed in advance

Looks like a simple requirement : I do not want to loose my data.  
But can’t figure how to do it with serverless

Code portion to illustrate :

Custom option to disable bucket creation using Conditions

```
---
service:
...
custom:
  createBucket: ${opt:createBucket, 'true'}
...
resources:
  Conditions:
    CreateBucket:
      Fn::Equals:
      - ${self:custom.createBucket}
      - true
  Resources:
      S3BucketMyProjectIngest:
        Type: 'AWS::S3::Bucket'
        DeletionPolicy: 'Retain'
        Condition: 'CreateBucket'
        Properties:
          BucketName: ${self:custom.IngestBucketName}
  ...

```

So not creating those buckets can be achieved with  
`AWS_PROFILE=serverless serverless deploy --createBucket no`

But it fails because of the reference in another resource

```
S3BucketLambdaPermission:
  Type: "AWS::Lambda::Permission"
  Properties:
    FunctionName:
      "Fn::GetAtt":
      - 'ProcessFromS3LambdaFunction'
      - 'Arn'
    ...
    SourceArn:
      "Fn::GetAtt":
      - 'S3BucketMyProjectIngest'
      - 'Arn'

```

Error is obviously about the missing resource (disable by the condition)

```
Template format error: Unresolved resource dependencies [S3BucketMyProjectIngest] in the Resources block of the template

```

Is there a way to achieve this (“I do not want to loose my data”)?

---

<div class="post-metadata">

**Author:** ![buggy](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.serverless.com/buggy/32/177_2.png) [@buggy](https://forum.serverless.com/u/buggy)\
**Post date:** [August 18, 2018, 9:25am UTC](https://forum.serverless.com/t/proper-way-to-deploy-on-production-stage/5482/3 "2018-08-18T09:25:07Z")

</div>

@placplacboom I would expect this happen if you’re removing the stack between deployments but not if you’re only deploying. Serverless uses CloudFormation for deployments and if you tell CloudFormation to create a resource that already exists it will fail. Stack updates, which is what happens if you use `sls deploy` without doing an `sls remove` in between will be ok because the stack will continue using the resource it created earlier.

@placplacboom and @smougenot you should think of `DeletionPolicy: Retain` as a fail safe that stops data from being removed if someone screws up and accidentally deletes the CloudFormation stack. Don’t use it as a way to keep data between deleting and re-creating a stack. If you want to do that then you need to look at putting those resources into their own CloudFormation stack and using cross stack references. See [https://serverless.com/framework/docs/providers/aws/guide/variables/#reference-cloudformation-outputs](https://serverless.com/framework/docs/providers/aws/guide/variables/#reference-cloudformation-outputs) for more information.