Chubby lock service

This project explores the design and implementation of “Chubby”, a distributed file system, designed by Google, that offers a lock service for loosely-coupled distributed systems

For an in-depth explanation of the project, please refer to the report

How to use

In order to successfully launch the project and its tests, make sure to have Docker, Gradle and Git installed.

Clone the project using

git clone https://github.com/MarcoFontana48/GoogleChubby.git

Once the project is downloaded, use the following command to set up 3 isolated chubby cells ’local’, ’cell1’, ’cell2’, to connect to:

docker stack deploy -c ./docker-compose0.yml local;
docker stack deploy -c ./docker-compose1.yml cell1;
docker stack deploy -c ./docker-compose2.yml cell2;
gradle etcd_setup

To connect to the cells using a custom gradle task, use the following command to access the ’local’ cell using an already registered user ’client0’ with password ’password’:

gradle run_client_0-local

Other tasks are already present to also connect to different cells using different clients, check file ’server/build.gradle.kts’

Once done, to delete all the containers previously created, use the command:

docker stack rm local; docker stack rm cell1; docker stack rm cell2

Usage example

how messages are formatted

Before showing some usage examples, it’s necessary to explain how the messages are formatted. Each message type is formatted the same way:

[date time] username-messageType:(handleType)path

i.e. a typical request from a client ’client0’ with an open handle on path ’/ls/local/test.txt’, that will be used to ’write’ content in it, is the following:

[2024-03-13 09:45:12] client0-request:(write)\ls\local\test.txt< read filecontent

and the response from the server:

[2024-03-13 09:45:12] chubby-response:(write)\ls\local\test.txt> hello world!

examples

The moment a client connects to a cell, a notification from the server, containing a message, will be sent

[2024-03-13 09:21:43] chubby-notification:\> acquired initial shared lock on root ’\’ node

This informs the client that an initial handle (read type) on root node has been successfully created.

In order to open a new handle use command ’open’; i.e. to open an handle on a ’test.txt’ file that will be used to write file content (on a cell named ’local’) the following command may be executed:

open /ls/local/test.txt write

It will now be shown the request that was sent to the server and the response that it’s sent back to the client:

[2024-03-13 09:31:30] client0-request:(read)\< open /ls/local/test.txt write

[2024-03-13 09:31:31] chubby-response:(write)\ls\local\test.txt> successfully opened node

This informs the client that the handle was successfully opened and that it now has an handle on the specified path ’/ls/local/test.txt’ of ’write’ type. The client may now write file content in it:

write filecontent hello world!

[2024-03-13 09:42:48] client0-request:(write)\ls\local\test.txt<write filecontent hello world!

[2024-03-13 09:42:48] chubby-response:(write)\ls\local\test.txt>node content updated successfully

To read the file content, use the read command:

read filecontent

[2024-03-13 09:45:12] client0-request:(write)\ls\local\test.txt<read filecontent

[2024-03-13 09:45:12] chubby-response:(write)\ls\local\test.txt>hello world!

If a command that cannot be executed with current handle is sent to the server, an error response will be received:

[2024-03-13 09:48:48] client0-request:(write)\ls\local\test.txt< write acl read new_read_acl_name

[2024-03-13 09:48:48] chubby-error:\ls\local\test.txt> it’s not possible to change acl names of current node with ’WRITE’ handle type, acquire ’CHANGE ACL’ handle type before proceeding

Once done, close the handle using ’close’ command, that automatically unlocks the node and creates a new handle (read type) on root node.

About event subscriptions, if ’client0’ opens a directory and activates the child node added subscription, those messages are going to be exchanged:

[2024-03-13 10:01:36] client0-request:(read)\< open \ls\local\test\dir change acl child node added

[2024-03-13 10:01:36] chubby-response:(change acl)\ls\local\test\dir> successfully opened node

If ’client1’ now creates a child node of ’test dir’ on the same cell:

[2024-03-13 10:02:03] client1-request:(read)\< open \ls\local\test\dir\test child dir change acl

[2024-03-13 10:02:04] chubby-response:(change acl)\ls\local\test\dir\test child dir> successfully opened node

’client0’ will receive the following notification:

[2024-03-13 10:02:03] chubby-notification:\ls\local\test\dir> number of child nodes from currently held node has increased

That informs the client that the number of child nodes has increased, and the directory from where the event took place: ’\ls\local\test\dir’.

Many other examples are provided from the tests that were made, please referto test classes for usage examples; also, once connected to a cell, the command’help’ may be executed for a detailed explanation of the possible commands that may be run.