Skip to content

Latest commit

 

History

History
90 lines (70 loc) · 3.05 KB

PROTOCOL.md

File metadata and controls

90 lines (70 loc) · 3.05 KB
Raw

The Bertha protocol

The Bertha server stores blobs of data. Blobs of data are accessed by their SHA-256 hashes: the key of a blob of data is its SHA-256 hash. All sizes send and received are 64 bit little endian unsigned integers.

Commands

After the TCP connection is established, the client sends a single octet. This is the command byte and is one of

  • 0 for LIST, lists the keys of the blobs
  • 1 for PUT, adds a blob
  • 2 for GET, retrieves a blob by its key
  • 3 for QUIT, quits the server
  • 4 for SPUT, adds a blob and give a hint of its size
  • 5 for SGET, retrieves a blob and its size by its key
  • 6 for SIZE, retreives the size of a blob by its key
  • 7 for STATS, retreives some statistical counters

LIST

Used to list all the keys.

  1. The server sends the keys of all blobs in a unspecified order. The keys are send as 32 byte binary words.
  2. The server closes the connection.

PUT

Used to add a new blob to the server.

  1. The client sends the blob to the server.
  2. The client shuts its socket down for writing.
  3. The server sends the key of the added blob.
  4. The server closes the connection.

GET

Used to retrieve a blob by its key

  1. The client sends the key to server.
  2. The server sends the blob if it exists. Otherwise the server closes the connection.
  3. The server closes the connection.

QUIT

Used to quit the server.

  1. The server closes the connection and shuts itself down.

SPUT

Similar to PUT. The client additionally sends the probable size of the blob. This allows the server to pre-allocate room for the blob.

  1. The client sends the probable size of the blob to the server as a little endian 64 bit unsigned integer.
  2. The client sends the blob to the server.
  3. The client shuts its socket down for writing.
  4. The server sends the key of the added blob.
  5. The server closes the connection.

SGET

Similar to GET. The server additionally sends the size of the blob.

  1. The client sends the key to server.
  2. The server sends the size of the blob as a little endian 64 bit unsigned integer, if the blob exists. Otherwise the server closes the connection.
  3. The server sends the blob.
  4. The server closes the connection.

SIZE

Used to retrieve the size of a blob by its key. Also useful to check whether a blob exists without having to execute LIST.

  1. The client sends the key to server.
  2. The server sends the size of the blob, if it exists.
  3. The server closes the connection.

STATS

Used to retrieve some counter.

  1. The server sends five little-endian 64bit unsigned integers:
    1. n_cycle: the number of non-trivial cycles in the mainloop;
    2. n_GET_sent: the total number of bytes sent for (S)GET requests;
    3. n_PUT_received: the total number of bytes received for (S)PUT requests;
    4. n_conns_accepted: the total number of connections accepted and
    5. n_conns_active: the number of currently active connections.
  2. The server closes the connection.