Changeset 615 for trunk/server/doc/protocol.txt

Timestamp:

10/03/07 19:59:11 (2 years ago)

Author:

plindner

Message:

Incorporate "cas" operation developed by Dustin Sallings
<dustin@…> and implemented by Chris Goffinet
<goffinet@…>. This change allows you to do
atomic changes to an existing key.

Files:

• trunk/server/doc/protocol.txt (modified) (8 diffs)

trunk/server/doc/protocol.txt

@@ -54 +54 @@
 There are three types of commands. 
 
-Storage commands (there are three: "set", "add" and "replace") ask the
-server to store some data identified by a key. The client sends a
-command line, and then a data block; after that the client expects one
-line of response, which will indicate success or faulure.
-
-Retrieval commands (there is only one: "get") ask the server to
+Storage commands (there are four: "set", "add", "replace", and "cas")
+ask the server to store some data identified by a key. The client
+sends a command line, and then a data block; after that the client
+expects one line of response, which will indicate success or faulure.
+
+Retrieval commands (there are two: "get" and "gets") ask the server to
 retrieve data corresponding to a set of keys (one or more keys in one
 request). The client sends a command line, which includes all the
@@ -126 +126 @@
 First, the client sends a command line which looks like this:
 
-<command name> <key> <flags> <exptime> <bytes>\r\n
-
-- <command name> is "set", "add" or "replace"
+<command name> <key> <flags> <exptime> <bytes> [<unqiue>]\r\n
+
+- <command name> is "set", "add", "replace", or "cas"
 
   "set" means "store this data".  
@@ -137 +137 @@
   "replace" means "store this data, but only if the server *does*
   already hold data for this key".
+
+  "cas" is a check and set operation which means "store this data but
+  only if no one else has updated since I last fetched it."
 
 - <key> is the key under which the client asks to store the data
@@ -159 +162 @@
   it's followed by an empty data block).
 
+- <cas unique> is a unique 64-bit value of an existing entry.
+
 After this line, the client sends the data block:
 
@@ -176 +181 @@
 item is in a delete queue (see the "delete" command below).
 
+- "EXISTS\r\n" to indicate that the item you are trying to store with
+a "cas" command has been modified since you last fetched it.
 
 Retrieval command:
 ------------------
 
-The retrieval command looks like this:
+The retrieval commands "get" and "gets" operates like this:
 
 get <key>*\r\n
+gets <key>*\r\n
 
 - <key>* means one or more key strings separated by whitespace.
@@ -196 +204 @@
 Each item sent by the server looks like this:
 
-VALUE <key> <flags> <bytes>\r\n
+VALUE <key> <flags> <bytes> [<cas unique>]\r\n
 <data block>\r\n
 
@@ -205 +213 @@
 - <bytes> is the length of the data block to follow, *not* including
   its delimiting \r\n
+
+- <cas unique> is a unique 64-bit integer that uniquely identifies
+  this specific item.
 
 - <data block> is the data for this item.
@@ -213 +224 @@
 but deleted to make space for more items, or expired, or explicitly
 deleted by a client).
-