Managing your application as a file system

Overview

"A database is a smart file system"-- Anonymous
"Your database/application is a file system"-- Chronicle Software.

Why mount your application as a file system?

The main benefits of using a file system are;

• It can give you another way to access your data which works in for any language.

• There is a lot of existing tools which work on files.

• It is a familiar way to arrange data.

What is Chronicle Engine?

Chronicle Engine lets you set up subscriptions and get notified of when things change, such as new maps or entries being added/deleted or changed. These subscriptions are also defined via the namespace.
You can think of the namespace much like a file path, where the file sits inside a directory. And the directory sits inside another directory. Typically you access a chronicle map via a Java programming interface. In chronicle-engine you could say something like
Map<String, String> map = tree1.acquireMap(“/root/data/mymap", String.class, String.class)
This command creates a Map<String, String> in a virtual directory called  /root/data/
Since this is a virtual directory, if you look on your file system you would not see this directory. For a certain class of problems just being able to access the map via Java is acceptable. However, if the map contained, for example your system configuration information, it’s sometimes desirable (of course with the appropriate access rights) to be able to mount this virtual file system as of though it was a true file system. As such, we've now provided NFS support for Chronicle Engine, because it's NFS, it lets you navigate the virtual file system, as though it was a true file system. You can edit and modify entries of your map as though they were files. The entries appear as files,  and the map is the directory of these files. Other users, Four example those using Java will see the entry changed, as though you changed it via the Java interface. Subscribers that register for changes will still get notified.

hat does this look like?

Chronicle Engine has a demo which has NFS enabled.  The configuration file is in YAML. engine.yaml  The section which configured NFS is

	# # Allow access via NFS to this engine.
	#
	nfs: !NfsCfg {
	enabled: true,
	debug: false, # log every NFS request.
	exports: {
	# export everything.
	"/": "*(rw,noacl,anonuid=1000,anongid=1000)",
	"/data": "*(rw,noacl,anonuid=1000,anongid=1000)"
	"/stocks": "*(rw,noacl,anonuid=1000,anongid=1000)"
	}
	} The configuration file is actually a deserialization of builders.  This means any component can be replaced even the file format itself without changing the calling code.   If you enable debug you can see every NFS call made to the virtual file system.