Table of Contents
Starting the execution of deployment with cdist-deploy-to(1), cdist passes through different stages, each can be triggered and debugged on its own. Reading the source of the cdist-deploy-to executable shows the scripts responsible for each stage.
Before running the user facing stages, cdist prepares the target host to contain cdist binaries and creates a clean environment for the configuration run.
Related documentation: - Source of cdist-deploy-to
In this stage information is collected about the target host using so called explorers. Every existing explorer is run on the target and the output of all explorers are copied back into the local cache. The results can be used by manifests and types.
The initial manifest, which should be used for mappings of hosts to types, is executed. This stage creates objects in a cconfig database that contains the objects as defined in the manifest for the specific host. In this stage, no conflicts may occur, i.e. no object of the same type with the same id may be created.
Every object is checked whether its type has explorers and if so, these are transfered to the target host and executed. The results are transfered back and can be used in the following stages to decide what changes need to be made on the target to implement the desired state.
Every object is checked whether its type has a executable manifest. The manifest script may generate and change the created objects. In other words, one type can reuse other types.
For instance the object apache/www.test.ch is of type apache, which may contain a manifest script, which creates new objects of type __file.
The newly created objects are merged back into the existing tree. No conflicts may occur during the merge. A conflict would mean that two different objects try to create the same object, which indicates a broken configuration.
In this stage for every created object its type is checked for executable gencode scripts. The gencode scripts generate the code to be executed on the target on stdout. If the gencode executables fail, they must print diagnostic messages on stderr and exit non-zero.
For every object the resulting code from the previous stage is transferred to the target host and executed there to apply the configuration changes.
If, and only if, all the stages complete without an errors, the configuration will be applied to the target. Each stage can also be run individually, though dependencies for each stage must be fulfilled and thus the stages must be run in correct order.