· Feb 9, 2017

Atelier & GIT work principles across multiple servers


Trying out Atelier , and need to understand what working principles are best to follow.

Scenario I have a local Cache Instance for development that is linked to a GIT repository for Namespace "ABC"

I have got a local working directory /workingdir/ABC 

I have checked out branch "a"

So at this point I need to connect to a dev server that has this Namespace "ABC" but currently the  branch that is on this server is "b"


Do I create a new workspace and new project for this connection to the dev server.
And also an addisional GIT project with different local workspace /folders.

What is good practice to handle this.

Also if I connect to a instance, and previously when I worked on that project I had checked out branch "a" . In the mean time I disconnected another developer connected and he checked out branch "b" and synced the source with the instance.

What will the behavior be when I connect again , will my Atelier/Git now that that source on the server is now branch "b"

, or how is this handled?




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You can have multiple projects in your workspace and thats the way to go.

Below is an overview of the synchronization strategy. You will see if that someone changes files on the server underneath you then conflicts will occur. With Atelier you need to focus on the fact that the source on the client is the 'source of truth' the server is where you run your code. Your workflow should be sourcecontrol -> client -> server.

Synchronization Services for the New Development Paradigm 

This document describes the current approach to client/server synchronization.

Documents may be edited on the client independently of a connection to a Caché server. However, when a connection is established with a server for the purposes of saving, compiling and running code, then the client and server must agree with respect to the version of documents that are being operated upon.

Each document that exists on a server has a hash value associated with it. Each time the document changes, the hash value also changes. The hash value represents the server's version of the document. It's important to keep in mind that there is only ever ONE current version of a document on a server. The hash value is an opaque value, as far as the user is concerned it's just a 'cookie'.

All that is necessary when a client pushes a document to the server, is for the client to specify (via the hash) the version of the document it is replacing on the server. If the current server hash and the hash passed to the server from the client are equal then there is a MATCH on version and the server can go ahead and SAVE the document. If the hashes don't MATCH then there is a CONFLICT and the document will NOT be saved on the server.


The key idea here is that you cannot successfully push a document from a client to a server unless you identify by version the server document you are replacing. The hashes allow you to do that.


In the case of creating a new file, the client will not know the server hash. In this case it just passes the empty string to the server as the server hash value.

If the server does not have that document (that is, it is new to the server too) then the hashes will MATCH, the operation will succeed and the server will return a new document hash.

If the server already has the document, then there is a CONFLICT, the operation will not succeed.

Conflicts have to be resolved before a document can be modified on the server. How the conflict is actually resolved really does not matter (one could pull the server version, merge the diffs or do whatever). What is important is that when the resolution on the client has been done, the client must update its cached server hash to reflect the current server version. This means that when the client passes that hash value back to the server on the next save, the versions will match and the modification will go ahead.

In the case of deleting a file, the client must once again specify the server hash (if it has it). A MATCH on the server will result in the document being deleted, a MISMATCH will result in a CONFLICT.

All this is predicated on the client's ability to cache the hashes according to client source file, server address, server namespace and server document. How the data is stored is not important, what is important is that the hashes must be cached and passed to the server when a document modification is requested.

It's also important that the hash cache is persisted in some sort of client database. If not, then the synchronization of sources would have to be redone each time an interaction with a server is initiated.

The relationship between client and server sources is shown in this diagram