|
|
@@ -5,17 +5,18 @@ Ruaft is a Rust version of [the Raft consensus protocol](https://raft.github.io/
|
|
|
## Raft
|
|
|
|
|
|
Raft is the algorithm behind the famous key-value store [etcd](https://github.com/etcd-io/etcd). It helps replicas of a
|
|
|
-distributed application to reach consensus on internal state. Raft maintains a log that consists of entries. Each entry
|
|
|
-carries one piece of data (commonly referred to as a "command") for the application. Once an entry is committed to the
|
|
|
-log, it will never be changed or removed across all replicas. Entries are appended to the end of the log linearly, which
|
|
|
-guarantees that the log never diverges.
|
|
|
+distributed application to reach consensus on internal state. Raft maintains an array of entries, collectively known as
|
|
|
+the log. Each entry carries one piece of data for the application. Once an entry is committed to the log, it will never
|
|
|
+be changed or removed. Entries are appended to the end of the log linearly, which guarantees that the log never diverges
|
|
|
+across replicas. The log as a whole, represents the internal state of the application. Replicas of the same application
|
|
|
+agree on the log entries, and thus agree on the internal state.
|
|
|
|
|
|
## APIs
|
|
|
|
|
|
Each application replica has a Raft instance that runs side by side with it. To add a log entry to the Raft log, the
|
|
|
-application calls `start()` with the data it wants to store. The log entry is not committed immediately. Instead, when
|
|
|
-the Raft instance is sure that the log entry is agreed upon, it calls the application back via an `apply_command`
|
|
|
-callback, which is supplied by the application.
|
|
|
+application calls `start()` with the data it wants to store (commonly referred to as a "command"). The log entry is not
|
|
|
+committed immediately. Instead, when the Raft instance is sure that the log entry is agreed upon, it calls the
|
|
|
+application back via an `apply_command` callback, which is supplied by the application.
|
|
|
|
|
|
Internally, Raft talks to other replicas of the same application via an RPC interface. From time to time, Raft saves its
|
|
|
log (and other data) to a permanent storage via a `persister`. The log can grow without bound. To save storage space,
|
|
|
@@ -28,9 +29,8 @@ callback, and a `request_snapshot` callback. More details of those callbacks can
|
|
|
|
|
|
### Raft RPCs
|
|
|
|
|
|
-Ruaft has three RPC handlers: `process_append_entries()`, `process_request_vote()` and
|
|
|
-`process_install_snapshot()`, serving requests from other Raft instances of the same application. These RPC handlers
|
|
|
-should be added to the RPC system that the application uses.
|
|
|
+Ruaft has three RPC handlers: `append_entries()`, `request_vote()` and `install_snapshot()`, serving requests from other
|
|
|
+Raft instances of the same application. These RPC handlers should be added to the RPC system that the application uses.
|
|
|
|
|
|
### Graceful shutdown
|
|
|
|
|
|
@@ -41,7 +41,7 @@ starvation.
|
|
|
|
|
|
## Code Quality
|
|
|
|
|
|
-The implementation is thoroughly tested. I copied (and translated) the tests from an obvious source. To avoid being
|
|
|
+The implementation is thoroughly tested. I copied (and translated) the test sets from an obvious source. To avoid being
|
|
|
indexed by a search engine, I will not name the source. The testing framework from the same source is also translated
|
|
|
from the original Go version. The code can be found at the [`labrpc`](https://github.com/ditsing/labrpc) repo.
|
|
|
|
Jing Yang