| Title: 1.3 - DirectoryService |
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| # 1.3 - DirectoryService |
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| The _DirectoryService_ is the core of the server. This is where we process incoming requests and ask the backend for data. |
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| It has an entry point, the _OperationManager_, which is in charge of pushing the requests into the _Interceptors_ chain, and to protect the server against concurrent modifications. |
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| Then the request is going through every _Interceptor_ being registered for this operation. When we have gone through all the _Interceptors_, we have reached the _PartitionNexus_, which is the connection with the backends. |
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| We now just have to determinate which type of _Backend_ we should address, and this is done using the _Dn_. The request is then transmitted to the _Backend_, which returns the result. |
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| The result bubbles up through the _Interceptors_ as we unfold the stack stack, up to the _OperationManager_ and to the caller. |
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| ## Environment |
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| The _DirectoryService_ knows about its execution environment : it has a _schemaManager_ instance, it knows about the _Interceptors_ chain, it stores a map of all the pending requests (it's necessary as one may abandon some request), it holds the existing _Sessions_. |
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| In other word, the _DirectoryService_ is not only the part of the server executing the logic, it also holds the current state of every clients. |
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