Many of the features of a Postgres server may be influenced by settings specified in configuration files:
• The postgresql.conf file determines Postgres server behavior as it pertains to auditing, authentication, file locations, resource usage, query planning, statistic gathering, error handling and more.
• The pgpool.conf file determines the behavior of EDB Ark as it pertains to load balancing.
• The pg_hba.conf file controls the type of authentication that should be used when a client application connects to an EDB Ark service. By default, the pg_hba.conf file is configured to require clients to provide a valid md5-encrypted password.
• The pg_ident.conf file contains user mappings for external authentication methods (like LDAP or GSSAPI). Each entry within the pg_ident.conf file maps an external user name to his corresponding Postgres user name.To modify configuration file settings, you must ssh to the server, and manually edit the file. By default, on an Advanced Server cluster, configuration files reside in:
3. Reload or restart the server. For detailed information about reloading the server, see Section 12.4, Controlling the Server.When you add or remove nodes from a cluster, EDB Ark takes a backup of your pg_hba.conf and pgpool.conf configuration files. Configuration file backups are appended with the date that the backup was taken and a unique identifier; for example, pg_hba.conf.20140319-140903 identifies a backup of the pg_hba.conf file.When modifying a configuration file, you should make changes only to those files that are not appended with a timestamp and identifier.Please note that changing parameter settings can have unintended consequences, ranging from degraded performance to system crashes. Consequently, we recommend that only an advanced user who accepts these risks, and has experience with both Postgres and cloud environments modify parameter settings.
• Always make a snapshot backup of your data before making parameter changes. For information about taking a backup, refer to Section 6, Managing Backups and Recovery.
• Make parameter changes on a copy of the existing configuration that is in use for the master or replicas. That way, if the parameter changes prove detrimental it will be easy for you to re-apply the original settings. If you are making changes to configuration files through ssh, make a backup of the configuration files before making any changes, so they can be easily restored.When adjusting parameters, be mindful of that fact that the master node in the cluster processes both read and write requests, while the replica nodes in the cluster accept only read requests. You can tune the master node and the replica nodes independently to quickly have an impact (either positive or negative) on your write or read performance.