Everything you do in Launch has the ultimate goal of producing a set of files to control the behavior of your application at run-time. This set of files is called a build.
Builds need to be hosted somewhere so client devices can retrieve them at run-time as needed.
Launch can either manage the hosting of these files for you or you can do it yourself.
Adobe does not actually host the builds for you. Instead, they are delivered to a third-party content delivery network (CDN) that has a contract with Adobe.
The primary CDN provider is Akamai. Files hosted on Akamai have a domain of assets.adobedtm.com.
The primary reason to use managed hosting is convenience. It is easier to create the required host, and you don't have to worry about maintenance.
Akamai is robust when serving content to a global, high-volume audience of Web visitors. Akamai runs redundant networks of load-balanced, geo-optimized nodes to serve content as quickly as possible to visitors wherever they are located throughout the world.
Specifically, Akamai runs more than 137,000 servers in 87 countries within more than 1,150 networks. In terms of redundancy, Akamai does not just route from one server to another. Akamai routes from one node of servers to another node of servers as needed. In other words, each node consists of multiple servers for redundancy within a node, so a server going down is not an issue because the other servers in the node take over. If a node goes down, Akamai serves from the next closest one, with the same cached content. Nodes are dynamically selected based on visitor location, traffic load, and other factors, so content is consistently served from the best local node for each visitor.
Akamai also has access to nodes in China, so end-users in China get traffic from nodes that are geographically close to them.
No. Launch can do nothing from the client side if the library is unavailable.
When you choose to have Adobe manage your hosting, you do not have control over the headers on the response, so the Adobe defaults are inherited. There is no way to get custom headers when you have Adobe manage your hosting.
The cache control headers Adobe uses for managed hosting are as follows:
Production builds: Cache control headers are set to 60 minutes
Staging builds with "-staging" in the filename: Cache control headers are set to 0 minutes
Dev builds with "-development" in the filename: Cache control headers are set to 0 minutes
Note: It is up to browsers to receive and respect the cache control headers. Some browsers might ignore them.
Important: Cache control headers were added in Spring of 2018. Environments that do not have "-development" or "-staging" in their Environment embed codes were created prior to that time. These environments will need to be recreated if you want to take advantage of these new cache control headers. If you don't re-create the environments, you'll have the same 60-minute cache control as the production libraries.
To have Adobe manage your hosting, you need to create a Managed by Adobe host, then assign your environments to use this host. See Hosts for more info.
If you don't want Adobe to manage your hosted files, you must host them yourself. To host your files, you need to get the completed builds from Launch and to be responsible for getting the files through your company's release cycle onto company managed servers.
There are a number of reasons to choose to host your own build files.
Some browsers block the assets.adobedtm.com domain based on the privacy settings the end-user has configured
Self-hosting reduces the required number of DNS lookups
You require use of HTTP/2
You have specific headers you need to set for security
Your cache control requirements differ from the Adobe default settings
You want more control over the location of edge nodes
Your organization has security and legal requirements that prevent you from using the Adobe-managed option
There are two methods you can use to acquire completed builds so that you can self-host.
You can have Launch deliver builds as a packaged .zip file (encryption optional). You can then unzip the package and insert the contents into your release cycle to place them on your own servers.
Use a Managed by Adobe host and select the Archive option on your environment. The environment provides a download link. Whenever a build is created, you can retrieve it from the provided download link.
You can have Launch deliver builds directly to an SFTP server that you created. You take responsibility to get these filed into your release cycle and push them live.
To perform a direct delivery, you should create an SFTP host and assign that host to your environment. Whenever you build a library in that environment, the files are delivered to your SFTP server.