I m having a hard time setting up read replica for a Postgre

Question

I m having a hard time setting up read replica for a Postgres RDS server My first attempt failed with `error modifying DB Instance read replicaf4d753f InvalidParameterCombination Cannot change master user password on an RDS postgres Read Replica because it uses physical replication and therefore cannot differ from its parent` even though the replica was created and visible in the console Is there a trick I m missing

silly-address-30441 · Answer

My code is ```const readReplica = new aws rds Instance read replica engine postgres engineVersion 13 instanceClass instanceClass allocatedStorage 5 dbSubnetGroupName dbSubnetGroup id vpcSecurityGroupIds dbSecurityGroup id name dbName username dbUsername password dbPassword allowMajorVersionUpgrade false autoMinorVersionUpgrade true storageEncrypted true maxAllocatedStorage 500 deletionProtection true performanceInsightsEnabled true backupRetentionPeriod 30 replicateSourceDb db arn ```

billowy-army-68599 · Answer

it looks like the dbpassword isn t the same as your master instance

silly-address-30441 · Answer

That s almost exactly the same code that generates my main instance so I don t know how that would happen

silly-address-30441 · Answer

```username dbUsername password dbPassword ```

silly-address-30441 · Answer

pulls from the same place

billowy-army-68599 · Answer

I don t think you need to set the master password and username on replicas try removing those params

silly-address-30441 · Answer

yeah looking at <https github com terraform aws modules terraform aws rds issues 103> I was just about to try that

silly-address-30441 · Answer

Yep that worked Thank you

silly-address-30441 · Answer

Hm but oddly if I run `pulumi up` a second time it wants to change it again

silly-address-30441 · Answer

I created a read replica and it looks fine

silly-address-30441 · Answer

but the second time I run pulumi up I get ` aws rds Instance read replica update diff ~replicateSourceDb `

silly-address-30441 · Answer

and I believe that will fail if I run it again

silly-address-30441 · Answer

Yep ``` aws rds Instance read replica error 1 error occurred updating urn pulumi dev core aws rds instance Instance read replica 1 error occurred cannot elect new source database for replication```

billowy-army-68599 · Answer

you ll need to see `ignoreChanges` perhaps

silly-address-30441 · Answer

huh nifty I ve never used that before

silly-address-30441 · Answer

I wonder why I need that here

silly-address-30441 · Answer

But adding ` ignoreChanges replicateSourceDb `

silly-address-30441 · Answer

seems to work