Install

Requirements

• Dune >= 1.6
• OCaml version 4.05.0 (exactly for now)

Instructions

To run OCaml ZFS and TxForest, make sure you have all dependencies ('core', 'async', 'ppx_deriving', and 'dune') by running

opam install dune core async ppx_deriving

Then, run:

make

./executables/zfs_server.exe .

Now you are ready to run TxForest or a simple client. To explore the built-in virtual filesystem, in one or more other terminals run:

./executables/zfs_client.exe

And type help to get a list of commands.

TxForest

The concept of TxForest is similar to Forest and Incremental Forest. Refer to those papers for details and a high level overview of the project.

Differences between TxForest and Incremental Forest are listed below, as is a link to the code of Incremental Forest.

Examples

Simple

This is a very simple example with 3 available transactions. Run it as follows:

./executables/simple.exe -id [0-3] -name "[a-d]" -trans [0-2]

Transaction description:

• Transaction 0 takes no further arguments and prints a description of the filestore
• Transaction 1 takes an 'id' and looks up the file with that id
• Transaction 2 takes a name (a,b,c, or d) and looks up the file with that name

Shelter

This is a much larger example with 14 transactions (1-14). Run:

./executables/shelter.exe -help

To see the interface.

Differences from Incremental Forest

See forest/examples/shelter.ml for an example of using the TxForest API (which is specified in forest/forest.mli).

• There are no delays or cursors as these are embedded in the Zipper. That is, as users walk through the zipper, data is automatically loaded as necessary.

• Several specifications are not yet available or unnecessary, including:

  • s option (N/A)
  • s where e (N/A)
  • link (N/A)
  • <s> (No longer necessary)

• The interface and representation types are entirely different. See forest/forest.mli for both. The 'fetch_result' type is the representation type of each existing specification. In essence, this comes from the fact that only local data is made available to the user.

• A constructed specification should be used in one of two ways:

  • let open Core.Result.Let_syntax in
    let%map zipper = mk_zipper specification path in
    let t = my_transaction zipper in
    finish t

    With the 'mk_zipper' operation, which takes a specification and a filesystem path and instantiates the specification at the path. This constructs a Forest zipper which can then be traversed and manipulated with the TxForest API. The 'finish' operation will try to commit the transaction.

  • run_txn ~f:my_transaction specification path ()

    With the 'run_txn' function, which uses a specification, path, and a transaction (function on Forest zippers) to start a new transaction, run the transaction function given, then attempt to commit. It will then redo these steps until the commit succeeds.

• ZFS does not currently connect to a real filesystem and instead uses an internal virtual FS. To add additional folders, extend the 'FS.init' function in src/lib/ZFSUtils.ml. Start by adding a child to 'root' with your main folder as an empty directory, then add whatever else you want:

    add_child root main_folder_name empty_dir;
    add_child (Filename.concat root main_folder_name) some_file (FFile contents);
    add_child (Filename.concat root main_folder_name) some_folder empty_dir;

  etc