feature: added new method expire() that can change the TTL of the lock being held.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

Author: dndx

README.markdown

@@ -14,6 +14,7 @@ Table of Contents
     * [new](#new)
     * [lock](#lock)
     * [unlock](#unlock)
+    * [expire](#expire)
 * [For Multiple Lua Light Threads](#for-multiple-lua-light-threads)
 * [For Cache Locks](#for-cache-locks)
 * [Prerequisites](#prerequisites)
@@ -162,6 +163,22 @@ Returns `1` on success. Returns `nil` and a string describing the error otherwis
 
 If you call `unlock` when no lock is currently held, the error "unlocked" will be returned.
 
+expire
+------
+`syntax: ok, err = obj:expire(timeout)`
+
+Sets the TTL of the lock held by the current `resty.lock` object instance. This will reset the
+timeout of the lock to `timeout` seconds if it is given, otherwise the `timeout` provided while
+calling [new](#new) will be used.
+
+Note that the `timeout` supplied inside this function is independent from the `timeout` provided while
+calling [new](#new). Calling `expire()` will not change the `timeout` value specified inside [new](#new)
+and subsequent `expire(nil)` call will still use the `timeout` number from [new](#new).
+
+Returns `true` on success. Returns `nil` and a string describing the error otherwise.
+
+If you call `expire` when no lock is currently held, the error "unlocked" will be returned.
+
 [Back to TOC](#table-of-contents)
 
 For Multiple Lua Light Threads

lib/resty/lock.lua

@@ -135,6 +135,7 @@ function _M.lock(self, key)
     local ok, err = dict:add(key, true, exptime)
     if ok then
         cdata.key_id = ref_obj(key)
+        self.key = key
         return 0
     end
     if err ~= "exists" then
@@ -154,6 +155,7 @@ function _M.lock(self, key)
         local ok, err = dict:add(key, true, exptime)
         if ok then
             cdata.key_id = ref_obj(key)
+            self.key = key
             return elapsed
         end
 
@@ -193,4 +195,25 @@ function _M.unlock(self)
 end
 
 
+function _M.expire(self, time)
+    local dict = self.dict
+    local cdata = self.cdata
+    local key_id = tonumber(cdata.key_id)
+    if key_id <= 0 then
+        return nil, "unlocked"
+    end
+
+    if not time then
+        time = self.exptime
+    end
+
+    local ok, err =  dict:replace(self.key, true, time)
+    if not ok then
+        return nil, err
+    end
+
+    return true
+end
+
+
 return _M

t/sanity.t

@@ -468,3 +468,76 @@ lock 2: unlock: nil, unlocked
 --- no_error_log
 [error]
 
+
+
+=== TEST 13: expire()
+--- http_config eval: $::HttpConfig
+--- config
+    location = /t {
+        content_by_lua_block {
+            local lock = require "resty.lock"
+            for i = 1, 2 do
+                local lock1 = lock:new("cache_locks", { timeout = 0, exptime = 0.1 })
+                local lock2 = lock:new("cache_locks", { timeout = 0, exptime = 0.1 })
+
+                local exp, err = lock1:expire()
+                ngx.say("lock 1: expire: ", exp, ", ", err)
+
+                local elapsed, err = lock1:lock("foo")
+                ngx.say("lock 1: lock: ", elapsed, ", ", err)
+
+                ngx.sleep(0.06)
+
+                local exp, err = lock1:expire()
+                ngx.say("lock 1: expire: ", exp, ", ", err)
+
+                ngx.sleep(0.06)
+
+                local elapsed, err = lock2:lock("foo")
+                ngx.say("lock 2: lock: ", elapsed, ", ", err)
+
+                local exp, err = lock1:expire(0.2)
+                ngx.say("lock 1: expire: ", exp, ", ", err)
+
+                ngx.sleep(0.15)
+
+                local elapsed, err = lock2:lock("foo")
+                ngx.say("lock 2: lock: ", elapsed, ", ", err)
+
+                ngx.sleep(0.1)
+
+                local elapsed, err = lock2:lock("foo")
+                ngx.say("lock 2: lock: ", elapsed, ", ", err)
+
+                local ok, err = lock2:unlock()
+                ngx.say("lock 2: unlock: ", ok, ", ", err)
+
+                local exp, err = lock2:expire(0.2)
+                ngx.say("lock 2: expire: ", exp, ", ", err)
+            end
+        }
+    }
+--- request
+GET /t
+--- response_body
+lock 1: expire: nil, unlocked
+lock 1: lock: 0, nil
+lock 1: expire: true, nil
+lock 2: lock: nil, timeout
+lock 1: expire: true, nil
+lock 2: lock: nil, timeout
+lock 2: lock: 0, nil
+lock 2: unlock: 1, nil
+lock 2: expire: nil, unlocked
+lock 1: expire: nil, unlocked
+lock 1: lock: 0, nil
+lock 1: expire: true, nil
+lock 2: lock: nil, timeout
+lock 1: expire: true, nil
+lock 2: lock: nil, timeout
+lock 2: lock: 0, nil
+lock 2: unlock: 1, nil
+lock 2: expire: nil, unlocked
+
+--- no_error_log
+[error]