Dynamic changes in terraform configuration file

[kperi...@nvidia.com]

 could anyone have suggestions for my case :

is anyway we can fetch/quiry data from database[mysql] & update the terraform configuration ?

What if some value in terraform configuration as to change dynamically, It's not good to manually edit configuration file manually. Anyone have any suggestion/ideas Please let me know.

Thanks.

[Oliver Schrenk]

Terraform novice here, so there might be a more  terraform way but is writing  a script that populates a variables file an option?

In addition to that script, you write a wrapper bash script, first executing your database script and then runs terraform?

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[kperi...@nvidia.com]

Thanks for kind response Oliver, I understand I can use the script to update DB data & create terraform  configuration [json] file based on the DB data but just thinking it doesn't seems effective way to do. 

Is terraform have any inbuild/ external tool feature where we can pull data from DB & modify/update/create the configuration file ? [without our custom script]   I searched for this requirement but am unable to get right solution !! :( 

[Anshu Prateek]

You will have to make use of https://www.terraform.io/docs/providers/external/data_source.html to work w. data from DB. You will still need a wrapper script to get the data in required format.

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[Steven Nemetz]

Depends a little on what type of data you are trying to get and use.

All methods require a custom script to get the data from the database and format it, unless a provider was written with database data sources. The MySQL provider currently doesn't have data sources.

Methods:

1. Wrapper or pre-terraform scripts
• This could create a .tfvar or .tf file (hcl or json)
• Could create TF_VAR_ environment variables
• As a wrapper, would build the terraform command line with all the variables
  
2. external/data_source provider
• In this case terraform runs your script and the output must be json, which Terraform will read in and can be referenced

All of these methods work for string variables.

If you need something other than strings, then there can be differences in the methods.

Terraform json parser is not true json, which prevents it's use for complex data structures.

I'd advise against uses complex data structures. But if you do need them, you may be forced to generate a hcl file

They are other obscure methods, that I'd recommend not using.

[Kumaresan]

Thanks all got some really good stuff :)