Enhance Image to support MASTER-SLAVE replication

[mschaefers]

I'd like to change the image (by PR) to allow configuration of either Multi-Master or Master-Slave configuration of replication. Is this a feature you would like to incorporate? If so, this is my proposed way of doing it:

LDAP_REPLICATION can have the following values:

• true for backwards compatibility means Multi-Master and will issue a warning for deprecation.
• N_MASTER is the preferred value for defining Multi-Master and will not change the current behavior
• SINGLE_MASTER defines the image to be the master of a Master-Slave setup
• SLAVE defines the image to be one of probably many slaves of a Master-Slave setup
• false disables replication (no changes).

1. In case of LDAP_REPLICATION=SLAVE, we can use LDAP_REPLICATION_HOSTS to define the host of the single master instance, or we can use a new variable LDAP_REPLICATION_MASTER.
   LDAP_REPLICATION_HOSTS_CONFIG_SYNC_REPL and LDAP_REPLICATION_HOSTS_DB_SYNC_REPL will be used for replication config.

2. In case of LDAP_REPLICATION=SINGLE_MASTER there is probably nothing more to define. We just make sure that syncprov is enabled to allow sync requests from any slaves.

Happy to hear your thoughts.

[flightdutch]

I try to create master-slave system and analyzing 2 files:

• docker-openldap/image/service/slapd/startup.sh
• docker-openldap/image/environment/default.startup.yaml
  and i found - LDAP_REPLICATION has only 2 real values: true or false
  because other values - doesn't turn on replication procedures
  so - system can work as multi master
  Can you help to create master-slave system?
  thanks

[melanger]

@BertrandGouny Hi, I would be happy to help with this issue. Currently I am building a custom docker image with master-slave replication, but it would be great to have it already available.

How about the following changes?

• LDAP_REPLICATION: false | true -> LDAP_REPLICATION: false | SLAVE | SINGLE_MASTER | MULTI_MASTER | true
• for LDAP_REPLICATION: SLAVE, new required config options LDAP_REPLICATION_MASTER, LDAP_REPLICATION_PASSWORD (solves Security improvment : allow substitution for credentials keyword (olcSyncrepl) #406)
• replication-enable.ldif and replication-disable.ldif can be split into two parts (slave & master) and 0/1/2 of them will be executed depending on LDAP_REPLICATION
• update README and example configs accordingly