The LogCloud is a dedicated transaction logging and recovery service so your cloud application nodes themselves do not need any persistent storage. All transaction logging and recovery is taken care of by the LogCloud, so application nodes can come and go without affecting transaction recovery.
A typical LogCloud deployment is shown in the figure below:
Let's discuss the important actors and how they collaborate:
One or more transactional application nodes use the LogCloud for maintaining (and recovering) their transaction logs, because in cloud environments application-level disk access may not be available. These application nodes could either be mirrored application deployments in a cluster, or a set of collaborating transactional REST microservices. In the former case each application node probably has the same configuration, in the latter case it concerns different microservice application nodes each with their own configuration.
A dedicated node hosts the LogCloud for transaction logging and recovery purposes. In order to work correctly, this service needs disk access (for log storage) and access to the same XA resources that are used by the application nodes.
The backend resources used by the application nodes are the ones that need to be recovered by the LogCloud. So it's logical that the LogCloud needs access to those. In the config section below we'll clarify how this access is achieved.
Each application node must be configured to log to the LogCloud instance, by doing all of the following:
Determine the folder on the host where you will start the LogCloud. Then, make sure to do the following:
As application nodes start and initialise their connection pools, these connections will be mirrored on the LogCloud. So there is no immediate need to configure the user/password for recovery: this will be sent over by the application nodes.
The backend resources need to be configured for XA transactions, but that is outside the scope of the LogCloud documentation (since that has to be done for all XA transaction uses).