Managing Ramcache Entries with Pycontrol

A DevCentral user posted a question in the forums asking for verification of an attribute on the RamCacheKey structure. The maximum_responses attribute should be a long integer. With his C# code, the maximum_responses returned from his iControl call is always double the setting. I fired up pycontrol to see if this was a bug, and in my pycontrol code, I received the expected responses. While he’s taking a look at his code and the .Net library he’s using, I took an interest in the ramcache methods as I have not messed with the Ramcache module much. In this article, I’ll build out a pycontrol script that will enable users to query/evict ramcache entries.

The Interface

The iControl interface for querying/evicting Ramcache entries is RAMCacheInformation. The methods I’ll handle in the script are:

• get_ramcache_entry
• get_ramcache_entry_exact_match
• evict_ramcache_entry_v2
• evict_all_ramcache_entries

There are two more methods defined:

• get_version – All interfaces have this method, not important to Ramcache function
• get_ramcache_entry – Deprecated in favor of _v2 above.

Preparing the BIG-IP

Beginning in v11, the ramcache configuration was removed from the http profile and moved into its own under Local Traffic->Profiles->Services->Web Acceleration. I created a profile called lcache with a parent profile of optimized-caching, increasing the cache size to 25 MB and decreasing the max age to 3600 seconds for testing. I left all the other settings default.

Apply this profile to an http virtual and a pool member with some content and I’m ready to move to the iControl work.

Building the Script

Because there are multiple actions in this interface I want to address, I’ll use command line options to control the script flow:

• Host – (-H) Required
• Username (-u) Required
• Get Entries (-g) Profile Required 
• Get Exact Entry (-x) Profile, Host and URI required (as a white-space separated list in quotes. Ex. “lcache 10.10.20.60 /images/img1.png”
• Evict Entry (-E) Profile, Host and partial URI required
• Evict Exact Entry (-X)  Profile, Host and URI required
• Evict All Entries (-A) No arguments necessary, empties the ramcache

With that plan in place, I can configure the parser options, shown in the following code snippet:

  1:  from optparse import OptionParser

  2:   

  3:  parser = OptionParser()

  4:  parser.add_option("-H", "--host", action="store", type="string", dest="host")

  5:  parser.add_option("-u", "--user", action="store", type="string", dest="uname")

  6:  parser.add_option("-g", "--get", action="store", type="string", dest="get", help="Supply profile name")

  7:  parser.add_option("-x", "--get_exact", action="store", type="string", dest="get_exact", help="Supply profile name, host, and URI")

  8:  parser.add_option("-E", "--evict", action="store", type="string", dest="evict_entry")

  9:  parser.add_option("-X", "--evict_exact", action="store", type="string", dest="evict_exact")

 10:  parser.add_option("-A", "--evict_all", action="store_false", default=False, dest="evict_all")

 11:  (options, args) = parser.parse_args()

 12: 

 13:  if (options.host is None) or (options.uname is None):

 14:   print "\n\tHost (-H) and username (-u) must be supplied, exiting..."

 15:   sys.exit()

Now that the options are in place, we need to act based on the options provided

  1:  if options.get is not None:

  2:   rce = getRAMCacheEntries(rc, options.get)

  3:   print rce

  4: 

  5:  elif options.get_exact is not None:

  6:   rce = getRAMCacheExactEntry(rc, options.get_exact)

  7:   print rce

  8: 

  9:  elif options.evict_entry is not None:

 10:   rce = evictRAMCacheEntry(rc, options.evict_entry)

 11:   print rce

 12: 

 13:  elif options.evict_exact is not None:

 14:   rce = evictRAMCacheExactEntry(rc, options.evict_exact)

 15:   print rce

 16: 

 17:  elif options.evict_all is not None:

 18:   rce = evictRAMCacheAllEntries(rc)

 19:   print rce

 20: 

 21:  else:

 22:   print "No options selected!"

 23:   sys.exit()

In this code, I’m checking for the options and if none are set, I’m exiting. For each option, I’m calling a function to operate on that particular action. I’m passing the iControl object (see code below) and the argument list (“profile host uri”) as necessary to each function.

  1:  b = pc.BIGIP(

  2:   hostname = options.host,

  3:   username = options.uname,

  4:   password = upass,

  5:   fromurl = True,

  6:   wsdls = ['LocalLB.RAMCacheInformation']

  7:  )

  8: 

  9:  rc = b.LocalLB.RAMCacheInformation

For all the functions except the one to handle evicting all ramcache entries, I need to create an object for the RamCacheKey structure. This is done in pycontrol with the typefactory. Once the structure is created, I just need to add the appropriate attributes as defined in the API: profile_name, host_name, uri, and maximum_responses. The first three are strings, the last is a long integer. So the code is very similar in each function:

  1:  rc_key=obj.typefactory.create('LocalLB.RAMCacheInformation.RAMCacheKey')

  2: 

  3:  key_attr = rc_info.split(' ')

  4:  rc_key.profile_name = key_attr[0]

  5:  rc_key.host_name = ''

  6:  rc_key.uri = ''

  7:  rc_key.maximum_responses = 100L

I split the arguments to get each attribute isolated, then assign as appropriate. For a general get, I only need the profile name so I set the host and uri to an empty string. I chose 100 as a max response just to pick something. Now that the structure is defined, I can make an iControl call, in this case, to get all ramcache entries, then I return those values from the function to the variable making the function call above.

  1:  rc_entry = obj.get_ramcache_entry(keys=[rc_key])

  2:  return rc_entry

So if I put all this together, I can issue this command at the command line, with the data below returned:

C:\Users\jrahm\PycharmProjects\pyControl_Scripts>python ramcache_manager.py -H 10.10.20.5 -u admin -g lcache
Please enter the password for user admin
Password:
[[(LocalLB.RAMCacheInformation.RAMCacheEntry){
   profile_name = "lcache"
   host_name = "10.10.20.60"
   uri = "/images/gnome-64.png"
   vary_type = "RAM_CACHE_VARY_NONE"
   vary_count = 1
   hits = 0
   received = 1326237864
   last_sent = 1326237864
   expiration = 1326241060
   size = 4677
 }, (LocalLB.RAMCacheInformation.RAMCacheEntry){
   profile_name = "lcache"
   host_name = "10.10.20.60"
   uri = "/images/ad_remoteauth_ssh_1.png"
   vary_type = "RAM_CACHE_VARY_NONE"
   vary_count = 1
   hits = 0
   received = 1326237873
   last_sent = 1326237873
   expiration = 1326241069
   size = 16304
 }, (LocalLB.RAMCacheInformation.RAMCacheEntry){
   profile_name = "lcache"
   host_name = "10.10.20.60"
   uri = "/images/ad_descr.png"
   vary_type = "RAM_CACHE_VARY_NONE"
   vary_count = 1
   hits = 0
   received = 1326237818
   last_sent = 1326237818
   expiration = 1326241014
   size = 17942
 }]]

Now, if I want to evict one of those, I can change my options a little and try again, then do another query:

C:\Users\jrahm\PycharmProjects\pyControl_Scripts>python ramcache_manager.py -H 10.10.20.5 -u admin -E "lcache 10.10.20.60 /images/ad_descr.png"
Please enter the password for user admin
Password:
None

C:\Users\jrahm\PycharmProjects\pyControl_Scripts>python ramcache_manager.py -H 10.10.20.5 -u admin -g lcache
Please enter the password for user admin
Password:
[[(LocalLB.RAMCacheInformation.RAMCacheEntry){
   profile_name = "lcache"
   host_name = "10.10.20.60"
   uri = "/images/gnome-64.png"
   vary_type = "RAM_CACHE_VARY_NONE"
   vary_count = 1
   hits = 0
   received = 1326237864
   last_sent = 1326237864
   expiration = 1326241060
   size = 4677
 }, (LocalLB.RAMCacheInformation.RAMCacheEntry){
   profile_name = "lcache"
   host_name = "10.10.20.60"
   uri = "/images/ad_remoteauth_ssh_1.png"
   vary_type = "RAM_CACHE_VARY_NONE"
   vary_count = 1
   hits = 0
   received = 1326237873
   last_sent = 1326237873
   expiration = 1326241069
   size = 16304
 }]]

You can see that the entry is now gone. And finally, If I evict all:

C:\Users\jrahm\PycharmProjects\pyControl_Scripts>python ramcache_manager.py -H 10.10.20.5 -u admin -A
Please enter the password for user admin
Password:
None

C:\Users\jrahm\PycharmProjects\pyControl_Scripts>python ramcache_manager.py -H 10.10.20.5 -u admin -g lcache
Please enter the password for user admin
Password:
[[]]

Conclusion

There is access to great power via the iControl interface of your BIG-IP. With just a few lines of code, you can manage the ramcache from the CLI. For the full script, please check out the RAMCache Manager wiki page in the iControl codeshare. Happy Coding!