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:
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!