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I'm getting a failure converting to a multi-AZ RDS...
# general
s
I'm getting a failure converting to a multi-AZ RDS cluster:
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+-  ├─ aws:rds:Cluster                postgres   replace     [diff: ~availabilityZones,dbClusterInstanceClass]
Error:
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error: 1 error occurred:
    	* creating RDS Cluster (...): DBClusterAlreadyExistsFault: DB Cluster already exists
    	status code: 400, request id: ...
I'm still testing the deployment, so I'm going to bring the whole thing down and go from there, just wondering if this is expected. 
deletionProtection
is disabled.
b
did you set an explicit name for the db?
s
clusterIdentifier
? If so, yes.
b
set delete before replace before changing the properties
s
Right on, thanks a bunch 🙂
In general, is the recommended approach to not set explicit names except where absolutely necessary, in order to let Pulumi bring stuff up while the previous incarnation still exists?
b
yes ideally
s
I've had a few cases where it was to resolve a circular dependency, e.g. having to specify an ARN for something else before the resource was up, although that's usually policies and I could attach the policy after the dependencies are created. Otherwise, it's for interacting with things outside of Pulumi which expect the resources to have certain names, which is a harder problem to fix, but I could potentially audit what those are and dump the rest.
Tbh for the RDS situation, I'll eventually look into whether I can have Pulumi migrate data from one to another while they are both up, if there are hooks to do such a thing.
On a related note, I'm running into this now with 
finalSnapshotIdentifier
. I would generate a tag based on the date, but then it's going to end up modifying/replacing the cluster every run. Is there a way to ask Pulumi for a unique (hopefully prefixed) identifier that will be persisted in state?
This is what I'm referring to:
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error: deleting urn:pulumi:...::...::aws:rds/cluster:Cluster::postgres: 1 error occurred:
    	* deleting RDS Cluster (...): DBClusterSnapshotAlreadyExistsFault: Cannot create the cluster snapshot because one with the identifier ... already exists.
b
yeah, use 
pulumi-random
to generate a random id 🙂
s
@billowy-army-68599 Nice! I've set that up with 
finalSnapshotIdentifier
like so:
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finalSnapshotIdentifier: postgresRetainFinalSnapshot ? postgresFinalSnapshotNameRandom.hex : undefined,
Hopefully that looks reasonable. I feel like 
keepers
might be relevant, but it says to look at the 
random.Provider
docs, which don't explain too much 😉
Now I'm getting a dependency issue again bringing down a security group, but this time the explicit 
dependsOn
is there, which is troubling:
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error: deleting urn:pulumi:...::...::aws:rds/subnetGroup:SubnetGroup::...: 1 error occurred:
    	* deleting RDS Subnet Group (...): InvalidDBSubnetGroupStateFault: Cannot delete the subnet group '...' because at least one database cluster: ... is still using it.
But the dependency is there for the cluster:
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{ dependsOn: [postgresSg], deleteBeforeReplace: true },
Know what might be up?
g
Think that’s the opposite? The subnet group depends on the cluster too, at least you cannot delete it until the cluster is gone.
s
@gentle-daybreak-46874 If you can't delete the SG until the cluster is gone, then the cluster depends on the SG. 
dependsOn: [x, y]
means the resource needs to come up after 
x
and 
y
, and be brought down before 
x
and 
y
.
@billowy-army-68599 Does the usage of 
pulumi-random
above seem legit?
I'm thinking it will be treated like any other dependent resource and will only come down when the cluster goes down, which is basically what a final snapshot should have.
But maybe it needs to be cross-linked with 
keepers: {x: somethingFromCluster.apply(x => ...)
.
Since it's higher in the dependency hierarchy, that may work fine when I'm bringing the whole deployment down, but not convinced it's enough without 
keepers
for a recreate.
On the other hand, this looks a little bit fishy to me 🙂
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const postgresSgName = `${deployTag}-postgres-sg`;
const postgresClusterIdentifier = `${deployTag}-postgres`;
let postgresFinalSnapshotNameRandomKeepers: Record<string, string> = {};
const postgresFinalSnapshotNameRandom = new random.RandomId('postgres-final-snapshot-random', {
  prefix: `${deployTag}-postgres-final-snapshot-`,
  byteLength: 4,
  keepers: postgresFinalSnapshotNameRandomKeepers,
});
const postgresCluster = new aws.rds.Cluster(...);
postgresCluster.id.apply((id) => (postgresFinalSnapshotNameRandomKeepers['clusterId'] = id));
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