The present message does not contain any attributes of the entry. For each unchanged entry which remains in the scope, the server sends a present message consisting only of the name of the entry and the synchronization control representing state present. The server sends all requested attributes, be it changed or not, of the updated entries. In the present phase, the server sends the client the entries updated within the search scope since the last synchronization. The refreshOnly operation and the refresh stage of the refreshAndPersist operation can be performed by a present phase or a delete phase. Subsequent updates to the synchronization content in the server have additional entry updates be sent to the client. Instead of finishing the search after returning all entries currently matching the search criteria, the synchronization search remains persistent in the server. The listening is implemented by the refreshAndPersist operation. The server finishes the search operation by returning SearchResultDone at the end of the search operation as in the normal search. The client copy is synchronized to the server copy at the time of polling. The polling is implemented by the refreshOnly operation. The LDAP Sync protocol supports both polling and listening for changes by defining two respective synchronization operations: refreshOnly and refreshAndPersist. For more information, refer to the Internet Draft The LDAP Content Synchronization Operation. This section introduces the LDAP Content Sync protocol only briefly. The LDAP Sync operation is defined as a set of controls and other protocol elements which extend the LDAP search operation. The LDAP Sync protocol allows a client to maintain a synchronized copy of a DIT fragment. The LDAP Content Synchronization Protocol The replica content is also subject to the access privileges of the bind identity of the syncrepl replication connection. The shadow DIT fragment is defined by a general search criteria consisting of base, scope, filter, and attribute list. Syncrepl supports both partial and sparse replications. The consumer server can stop the replication also without the need for provider-side changes and restart. With syncrepl, a consumer server can create a replica without changing provider's configurations and without restarting the provider server, if the consumer server has appropriate access privileges for the DIT fragment to be replicated. The provider keeps track of the consumer servers that have requested the persistent search and sends them necessary updates as the provider replication content gets modified. In its refreshAndPersist mode of synchronization, the provider uses a push-based synchronization. To further optimize the pull-based synchronization, the provider can maintain a per-scope session log as the history store. To optimize the pull-based synchronization, syncrepl utilizes the present phase of the LDAP Sync protocol as well as its delete phase, instead of falling back on frequent full reloads. The information required for the provider to process periodic polling requests is contained in the synchronization cookie of the request itself. In its basic refreshOnly mode synchronization, the provider uses a pull-based synchronization where the consumer servers need not be tracked and no history information is maintained. Syncrepl supports both the pull-based and the push-based synchronization. Syncrepl can automatically resynchronize the consumer replica up-to-date with the current provider content. The consumer replica can be constructed from a consumer-side or a provider-side backup at any synchronization status. Syncrepl also enables convenient management of replicas by maintaining replica status. Because the syncrepl consumer and provider maintain their content status, the consumer can poll the provider content to perform incremental synchronization by asking the entries required to make the consumer replica up-to-date with the provider content. Syncrepl keeps track of the status of the replication content by maintaining and exchanging synchronization cookies. Syncrepl provides a stateful replication which supports both the pull-based and the push-based synchronizations and does not mandate the use of the history store. Syncrepl uses the LDAP Content Synchronization (or LDAP Sync for short) protocol as the replica synchronization protocol. It creates and maintains a consumer replica by connecting to the replication provider to perform the initial DIT content load followed either by periodic content polling or by timely updates upon content changes. A syncrepl engine resides at the consumer-side as one of the slapd (8) threads. The LDAP Sync replication engine, syncrepl for short, is a consumer-side replication engine that enables the consumer LDAP server to maintain a shadow copy of a DIT fragment.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |