Add-on:Common plugin cache

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Common plugin cache
Author: TheCollective

Type: Services
Version: 2.5.4
Repo: XBMC.org (v12)
XBMC.org (v11)

Summary: Common caching api for xbmc plugins.

Contents

1 Installing

To install this add-on you must do so from the Add-on manager from within XBMC by going to:

  1. Settings
  2. Add-ons
  3. Get add-ons
  4. XBMC.org Add-ons
  5. Services
  6. Common plugin cache
  7. Install

2 Testing/Status

Integration and unittests are run continously by Jenkins

http://tc.tobiasussing.dk/jenkins/view/Cache%20Service/

3 Developers

This service works as an independant storage server to XBMC's implementation.

It provides proper thread safe locking and get set functions to store data.

Do note that important data should NOT be stored using this service as the sqlite database will be deleted on any corruption.

Development and support thread: http://forum.xbmc.org/showthread.php?t=116496

3.1 Setup

To use the cacheing service edit your addon.xml file like this.

 <requires>
   <import addon="xbmc.python" version="2.0"/>
   <import addon="script.common.plugin.cache" version="0.9.1"/> # Add this
 </requires>

And add the following to your py file.

 try:
   import StorageServer
 except:
   import storageserverdummy as StorageServer
 cache = StorageServer.StorageServer("tablename", 24) # (Your plugin name, Cache time in hours)

You can now access the caching service through the "cache" variable.

Remember to include a fallback storageserverdummy.py file(Copy it from the script.common.plugin.cache/lib/ directory)

3.2 Debugging

To enable debugging set the following values in default.py

dbg = True

Or you can change it after import with.

common.dbg = True

Note: Only the client communication will be debugged when setting this flag.

3.3 cacheFunction(self, funct = False, *args)

Caching function results for one day.

The function being cached must return a list or a dictionary.

A cache is only stored if the result returned is longer than 0 in length.

Returns what the provided function returns.

 def pi_count(self):
     def arccot(x, unity):
         sum = xpower = unity // x
         n = 3
         sign = -1
         while 1:
               xpower = xpower // (x*x)
               term = xpower // n
               if not term:
                       break
               sum += sign * term
               sign = -sign
               n += 2
         return sum
  
     digits = 40
     unity = 10**(digits + 10)
     pi = 4 * (4*arccot(5, unity) - arccot(239, unity))
     return pi // 10**10
 
 result = cache.cacheFunction(pi_count) # This will call the pi_count function, save the result in the cache, and return the result.
 time.sleep(300)
 result = cache.cacheFunction(pi_count) # This will return the cached result
 time.sleep(3600)
 result = cache.cacheFunction(pi_count) # This will again call pi_count since the result is now considered stale.

To pass arguments to the function, you just add them as additional arguments to cacheFunction.

 result = cache.cacheFunction(calc_add, 4, 4)
 second_result = cache.cacheFunction(another_function, 5, ret = "True", { "complicated": "true" } )

If you need to pass on another function as an argument, this must be done in in a dictionary like this: { "new_results_function": pi_count }.

Because functions are instances they have specific identifiers that will change on every run. When cacheFunction generates the hash for a call and its result it will not take into account params["new_results_function"]. This means:

  • One should NOT use params["new_results_function"] for anything OTHER than a function, since cacheFunction will then return false matches.
  • One should NOT pass on a function in any way other than params["new_results_function"], as cacheFunction will never find a match.
 def some_function(first, second, params = {} ):
   if params.has_key("new_results_function"):
     return params["new_results_function"](first, second)
   else:
     return 0

 result = cache.cacheFunction(some_function, 1, 3, params = { "new_results_function": calc_add } )

3.4 lock(self, str)

Try to aquire a lock

Returns bool

 cache.table_name = "PluginName"
 locked = cache.lock("lock_me") # Returns True
 if locked:
   print "Got lock"

 new_lock = cache.lock("lock_me") # Returns False
 if not new_lock:
   print "Couldn't aquire second lock.

3.5 unlock(self, str)

Try to unlock

Returns bool

 cache.table_name = "PluginName"
 lock = cache.lock("lock_me") # Returns True

 unlocked = cache.unlock("lock_me") # Returns True
 if unlocked:
   print "Discarded lock"

 new_unlocked = cache.unlock("lock_me") # Returns False
 if not new_unlocked:
   print "Couldn't discard lock."

3.6 delete(self, str)

Delete entities matching the str.

This functions accepts SQL wildcards.

Returns nothing

 cache.table_name = "PluginName"
 cache.set("mystring", "string")
 cache.set("myint", 1234)
 cache.set("mydict", repr({ "our": { "dictionary": [] } }) )
 cache.delete("my%")

 some_int = cache.get("myint")
 print some_int # prints ""

 some_string = cache.get("mystring")
 print some_string # prints ""

 some_dict = cache.get("mydict")
 print some_dict # prints ""

3.7 set(self, str, object )

Store a value

Returns nothing

 cache.table_name = "PluginName"
 cache.set("some_string", "string")
 cache.set("some_int", 1234)
 cache.set("some_dict", repr({ "our": { "dictionary": [] } }) )

3.8 setMulti(self, str, dict)

Store multiple values

Returns nothing

 cache.table_name = "PluginName"

 save_data = { "some_string": "string", "some_int": 1234, "some_dict": repr({ "our": { "dictionary": [] } }) }
 cache.setMulti("pre-", save_data)

3.9 get(self, str)

Get a value

Returns stored data.

 cache.table_name = "PluginName"
 cache.set("some_string", "string")
 cache.set("some_int", 1234)
 cache.set("some_dict", repr({ "our": { "dictionary": [] } }) )

 some_string = cache.get("some_string")
 print some_string # Prints "string"

 some_int = cache.get("some_int")
 print some_int # prints 1234

 some_dict = cache.get("some_dict")
 print eval(some_dict) # prints '{ "our": { "dictionary": [] } }'

3.10 getMulti(self, str, list)

Get multiple values

Retuns list of stored data elements.

 cache.table_name = "PluginName"

 save_data = { "some_string": "string", "some_int": 1234, "some_dict": repr({ "our": { "dictionary": [] } }) }
 cache.setMulti("pre-", save_data)

 get_list = [ "some_string", "some_int", "some_dict" ]
 result = cache.getMulti("pre-", get_list)
 print result[0] # Prints "string"
 print result[1] # Prints 1234
 print eval(result[2]) # Prints '{ "our": { "dictionary": [] } }'
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