Satellite
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A 'satellite' is used as term for an instance of the OnlineChannel. It involves a java program, which includes the censhare Online Channel, a Jetty webserver and its own database and file system. In general a satellite is running on its own delivery server (hardware) and is connected to a censhare server. Satellites can be hosted in AWS.
A satellite is delivering content tagged with an output-channel. In a productive environment typically at least four satellites are delivering content from one server, two of them providing content in a live- and two of them providing content in a staging-channel.
A satellite is represented in the server as an asset and it is configured by assets on the server.
The initial installation is done on the delivery server within the hosting infrastructure. After installation the satellite connects to the configured censhare application server and user can create a satellite asset (Type Module/Satellite/Satellite instance). The satellite asset has to be related to a satellite configuration group (Type Module/Satellite/Satellite configuration). The Satellite group defines the service configurations and application resources used (these are also assets of cource).
Further configurations can be done via censhare java client.
Operating principle
Warning: The following describes the principle operation and may not be taken literally!
- a satellite is connected to the censhare-server and keeps a local, read-only database in sync
- this database is filtered to content marked for online usage (output-channel)
- a satellite monitors resources in its configuration group and updates itself on change
- a satellite renders the page for each request (caches yes, but not for HTML)
- a satellite can handle multiple sites (e.g. 'live' and 'staging' channel)
Example: blog comment
- Green user creates comment
- Comment is directly stored in the central publishing system
- Comment is published to the web delivery server
- Red users access content directly from the web delivery server
Infrastructure for Satellite Operations
The actual setup for Satellite Operations depends on several parameters such as website functionality, page impressions etc. For the following reasons we recommend for production sites to always chose a high availability setup with at least 2 Satellites operated behind a firewall / loadbalancer cluster:
- Interruption-free updates and maintenance
- Higher availability
- Higher security
- Better scalability and performance
Configuration assets
... are of Type Module/Satellite/Satellite OSGI/Satellite OSGI configuration
Via censhare java client the status of the satellite can be requested and it can also be restarted or shut down.