Add FEI

tf/README.md

@@ -24,6 +24,41 @@ Once you have applied a plan the changes to the terraform config should be
 pushed to the `main` branch immediately so that we minimize the change of other
 people applying stale configurations.
 
+### FEI (Frequently Encountered Issues)
+
+#### What to do if you get a locked state
+
+```
+% terraform plan
+╷
+│ Error: Error acquiring the state lock
+│
+│ Error message: operation error DynamoDB: PutItem, https response error StatusCode: 400, RequestID:
+│ IBL35BESTVD1GQID3TRON01ADFVV4KQNSO5AEMVJF66Q9ASUAAJG, ConditionalCheckFailedException: The conditional request failed
+│ Lock Info:
+│   ID:        7622a128-79f1-2179-815a-d821369a815e
+│   Path:      ooni-production-terraform-state/terraform.tfstate
+│   Operation: OperationTypeApply
+│   Who:       [email protected]
+│   Version:   1.7.0
+│   Created:   2024-02-05 11:51:45.398054 +0000 UTC
+│   Info:
+│
+│
+│ Terraform acquires a state lock to protect the state from being written
+│ by multiple users at the same time. Please resolve the issue above and try
+│ again. For most commands, you can disable locking with the "-lock=false"
+│ flag, but this is not recommended.
+```
+
+```
+% terraform force-unlock -force 7622a128-79f1-2179-815a-d821369a815e
+Terraform state has been successfully unlocked!
+
+The state has been unlocked, and Terraform commands should now be able to
+obtain a new lock on the remote state.
+```
+
 ### Notes
 
 https://www.terraform-best-practices.com/naming