Live and Preview Configuration Cycle

The previous pages explained the different configuration elements of the HST configuration. We pretty much discussed all the node types using a running configuration example. Also the previous pages frequently mention the Channel Manager and Channel Editor to add new channels and modify existing channels in a runtime production environment. 

However they did not yet explain how it works with respect to:

1. Making changes to a channel without having them directly live
2. Working with multiple webmasters concurrently within the same channel.

Preview configuration

In general, in a production environment, there is always a preview configuration for a channel, unless there have not yet been any webmasters that started editing the channel. This typically is the case only after the first deploy or just or after first creation of a new site from a blueprint. In that case, the relevant configuration parts for site example are as follows:

Configuration with no preview yet:

+ hst:hst
  + hst:channels
  |   + example
  + hst:configurations
  |    + example
  + hst:hosts
  |    + dev-localhost
  |       + localhost
  |           + hst:root
  + hst:sites
      + example

When a webmaster starts editing the site example through the Channel Editor, after they click on [Edit Channel] the live configuration gets cloned to have a separate preview configuration:

Configuration with preview:

+ hst:hst
  + hst:channels
  |   + example
  |   + example-preview
  + hst:configurations
  |    + example
  |    + example-preview
  + hst:hosts
  |    + dev-localhost
  |       + localhost
  |           + hst:root
  + hst:sites
      + example

Above can be seen, that below the hst:hosts or hst:sites nothing changes as a result of creating a preview.(note that in 7.8.x and earlier version, there used to be a hst:sites/example-preview site node. This node is not needed any more in 7.9.0 and when present, it is simply ignored). What has been added are a preview for

1. hst:channels/example-preview
2. hst:configurations/example-preview

All changes the webmaster now makes through the Channel Editor end up below one of the above preview nodes. A change results in certain parts of the configuration parts getting locked by that webmaster.  Since only parts of a channel configuration get locked, multiple webmasters can work in one and the same channel concurrently. Note thus that there is 1 preview configuration shared by all webmasters and other CMS users who can preview a document. 

After a webmaster has made changes, they can 

1. Publish changes, in which case their preview changes become live. In the stored HST configuration this effectively means that :
   • Locks from the webmaster are removed
   • Changed preview configuration is copied to the live configuration
2. Discard changes, in which case their preview changes are deleted. In the stored hst configuration this effectively means that :
   • Locks from the webmaster are removed
   • Changed preview configuration is removed

Locking:

Locking of configuration nodes differ per configuration section and whether the nodes are in the hst:workspace or not. See chapter Locking for more details.