11:19:47.482 GMT LOG: skipping missing configuration file "/rdsdbdata/config/nf" Postgres Shared Memory Value: 35386589184 bytes 11:19:47.453 GMT LOG: skipping missing configuration file "/rdsdbdata/config/nf" :~/Documents/aws$ aws rds download-db-log-file-portion -db-instance-identifier dwe-pg -log-file-name error/postgres.log | tail -15 Keep in mind that you need check the instance type, because that defines your amount of memory and CPUs.īy using the command line utilities we can also check the PostgreSQL log file, which confirms why the instance is not able to start up: :~/Documents/aws$ aws rds describe-db-log-files -db-instance-identifier dwe-pgĭESCRIBEDBLOGFILES 1586431187000 error/postgres.log 13626ĭESCRIBEDBLOGFILES 1586267878000 error/postgresql.log.-13 8632ĭESCRIBEDBLOGFILES 1586269968000 error/postgresql.log.-14 6211ĭESCRIBEDBLOGFILES 1586426381000 error/postgresql.log.-09 8236ĭESCRIBEDBLOGFILES 1586429793000 error/postgresql.log.-10 6096ĭESCRIBEDBLOGFILES 1586431182000 error/postgresql.log.-11 4024 So, be careful, when you have a DB Parameter Group you are using for more than one instance and you want to change settings like shared_buffers. Maybe the reason AWS is not checking that is, that DB Parameter Groups can be used by several instances which all can run on different instance types. On the one hand this is expected, on the other hand I would have expected that there are some sanity checks in the background that prevent you from doing that. We’ve managed to create a configuration set that will prevent the RDS from starting up. Will the instance come up after rebooting and what value will we see for shared_buffers? Checking the current setting of shared_buffers we see that PostgreSQL uses 3GB from that 16GB for caching: postgres=> show shared_buffers Currently the instance is running db.m5.xlarge, which means we should have 16GB of memory available. What you always need to be careful about it the instance type. Postgres=> show max_locks_per_transaction SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256, compression: off) SSL connection has been closed unexpectedly Rebooting the instance applies the parameter and the DB Parameter Group is in sync again: postgres=> show autovacuum_naptime įATAL: terminating connection due to administrator command What happens if we change a static parameter using the AWS console? For dynamic parameters you have the choice to apply a new value immediately or “pending-reboot”. You can already spot an important bit in the command: ApplyMethod=immediate. Changing the same parameter on the command line: $ aws rds modify-db-parameter-group -db-parameter-group-name dbi-dwe-pg12 -parameters="ParameterName=autovacuum_naptime, ParameterValue=10, ApplyMethod=immediate" Using the AWS command line utilities for these tasks usually is much easier and tasks can be automated. Once the changes are saved you’ll notice that the status in the configuration section changes to “applying”:Ī few moments later the DB Parameter Group is “in-sync” again and the parameter is applied to the RDS instance: postgres=> show autovacuum_naptime The parameter we’ll change is “ autovacuum_naptime“, and we’ll change it from 15 to 20: Let’s go and change one of the parameters using the AWS console: That means nothing changed or needs to be applied as all parameters of the instance have the same values as specified in the DB Parameter Group. Looking at our current configuration of the PostgreSQL RDS instance we can see that our DB Parameter Group is “in-sync”: In this post we’ll look at how you can do that and, especially, what you should avoid. You should also be aware that changing parameters can not be done like you usually do it but you need to do that by changing the DB parameter groups. (Essentially, I want to pull out secrets from a parameter store as part of this).If you followed that last posts about DB Parameter Groups, Subnet Groups and Setting up the RDS instance you should have a running RDS instance. The goal is to do it through a script without having to enter every line one by one. I'm after a guide or recommendation on possible ways to execute items below programmatically: However, as explained in Can we use DDL Commands in a prepared statement (PostgreSQL)?, this doesn't appear to be possible without using EXECUTE and wrapping it in a function. I'm using Java which has PreparedStatements. The problem is that I want to execute these commands from an external client (e.g. My original question related to the typical commands described in Managing PostgreSQL users and roles which include recommendations for creating roles, databases, schemas and setting permissions. I asked this earlier question on the best approaches to initialize a PostgreSQL database with AWS RDS inside a VPC.
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