cacachehandl:erM:aaintains aacachefofadataoforsuseybyolowerelevelahandlers.(3)
NAME
netsnmpcachehandler - Maintains a cache of data for use by lower
level handlers.
Functions
netsnmpcache * netsnmpcachegethead (void)
get cache head
netsnmpcache * netsnmpcachefindbyoid (oid *rootoid, int
rootoidlen)
find existing cache
netsnmpcache * netsnmpcachecreate (int timeout, NetsnmpCacheLoad
*loadhook, NetsnmpCacheFree *freehook, oid *rootoid, int
rootoidlen)
returns a cache
unsigned int netsnmpcachetimerstart (netsnmpcache *cache)
starts the recurring cacheload callback
void netsnmpcachetimerstop (netsnmpcache *cache)
stops the recurring cacheload callback
netsnmpmibhandler * netsnmpcachehandlerget (netsnmpcache *cache)
returns a cache handler that can be injected into a given handler
chain.
netsnmpmibhandler * netsnmpgetcachehandler (int timeout,
NetsnmpCacheLoad *loadhook, NetsnmpCacheFree *freehook, oid
*rootoid, int rootoidlen)
returns a cache handler that can be injected into a given handler
chain.
int netsnmpcachehandlerregister (netsnmphandlerregistration
*reginfo, netsnmpcache *cache)
functionally the same as calling netsnmpregisterhandler() but
also injects a cache handler at the same time for you.
int netsnmpregistercachehandler (netsnmphandlerregistration
**reginfo,, int timeout,, NetsnmpCacheLoad **loadhook,,
NetsnmpCacheFree **freehook)
functionally the same as calling netsnmpregisterhandler() but
also injects a cache handler at the same time for you.
NETSNMPSTATICINLINE char ** buildcachename (const char **name)
void netsnmpcachereqinfoinsert (netsnmpcache **cache,,
netsnmpagentrequestinfo **reqinfo,, const char **name)
Insert the cache information for a given request (PDU).
netsnmpcache ** netsnmpcachereqinfoextract
(netsnmpagentrequestinfo **reqinfo,, const char **name)
Extract the cache information for a given request (PDU).
netsnmpcache ** netsnmpextractcacheinfo (netsnmpagentrequestinfo
**reqinfo)
Extract the cache information for a given request (PDU).
int netsnmpcachecheckexpired (netsnmpcache **cache)
Check if the cache timeout has passed.
int netsnmpcachecheckandreload (netsnmpcache **cache)
Reload the cache if required.
int netsnmpcacheisvalid (netsnmpagentrequestinfo **reqinfo,, const
char **name)
Is the cache valid for a given request?
int netsnmpiscachevalid (netsnmpagentrequestinfo **reqinfo)
for backwards compat
int netsnmpcachehelperhandler (netsnmpmibhandler **handler,,
netsnmphandlerregistration **reginfo,, netsnmpagentrequestinfo
**reqinfo,, netsnmprequestinfo **requests)
Implements the cache handler.
void releasecachedresources (unsigned int regNo,, void **clientargs)
run regularly to automatically release cached resources.
Detailed Description
This helper checks to see whether the data has been loaded 'recently'
(according to the timeout for that particular cache) and calls the
registered 'loadcache' routine if necessary. The lower handlers can
then work with this local cached data.
A timeout value of -1 will cause netsnmpcachecheckexpired() to
always return true, and thus the cache will be reloaded for every
request.
To minimze resource use by the agent, a periodic callback checks for
expired caches, and will call the freecache function for any expired
cache.
The loadcache route should return a negative number if the cache was
not successfully loaded. 0 or any positive number indicates successs.
Several flags can be set to affect the operations on the cache.
If NETSNMPCACHEDONTINVALIDATEONSET is set, the freecache method
will not be called after a set request has processed. It is assumed
that the lower mib handler using the cache has maintained cache
consistency.
If NETSNMPCACHEDONTFREBEFORELOAD is set, the freecache method
will not be called before the loadcache method is called. It is
assumed that the loadcache routine will properly deal with being
called with a valid cache.
If NETSNMPCACHEDONTFREXPIRED is set, the freecache method will
not be called with the cache expires. The expired flag will be set, but
the valid flag will not be cleared. It is assumed that the loadcache
routine will properly deal with being called with a valid cache.
If NETSNMPCACHEPRELOAD is set when a the cache handler is created,
the cache load routine will be called immediately.
If NETSNMPCACHEDONTAUTORELEASE is set, the periodic callback that
checks for expired caches will skip the cache. The cache will only be
checked for expiration when a request triggers the cache handler. This
is useful if the cache has it's own periodic callback to keep the cache
fresh.
If NETSNMPCACHEAUTORELOAD is set, a timer will be set up to reload
the cache when it expires. This is useful for keeping the cache fresh,
even in the absence of incoming snmp requests.
Here are some suggestions for some common situations.
Cached File: If your table is based on a file that may periodically
change, you can test the modification date to see if the file has
changed since the last cache load. To get the cache helper to call the
load function for every request, set the timeout to -1, which will
cause the cache to always report that it is expired. This means that
you will want to prevent the agent from flushing the cache when it has
expired, and you will have to flush it manually if you detect that the
file has changed. To accomplish this, set the following flags:
NETSNMPCACHEDONTFREXPIRED NETSNMPCACHEDONTAUTORELEASE
Constant (periodic) reload: If you want the cache kept up to date
regularly, even if no requests for the table are received, you can have
your cache load routine called periodically. This is very useful if you
need to monitor the data for changes (eg a LastChanged object). You
will need to prevent the agent from flushing the cache when it expires.
Set the cache timeout to the frequency, in seconds, that you wish to
reload your cache, and set the following flags:
NETSNMPCACHEDONTFREXPIRED NETSNMPCACHEDONTAUTORELEASE
NETSNMPCACHEAUTORELOAD
Function Documentation
int netsnmpcachecheckandreload (netsnmpcache ** cache)
Reload the cache if required. Definition at line 383 of file
cachehandler.c.
References netsnmpcachecheckexpired().
Referenced by netsnmpcachehelperhandler().
int netsnmpcachecheckexpired (netsnmpcache ** cache)
Check if the cache timeout has passed. Sets and return the expired
flag. Definition at line 368 of file cachehandler.c.
References atimeready().
Referenced by netsnmpcachecheckandreload(), and
releasecachedresources().
netsnmpcache** netsnmpcachecreate (int timeout,, NetsnmpCacheLoad **
loadhook,, NetsnmpCacheFree ** freehook,, oid ** rootoid,, int
rootoidlen)
returns a cache Definition at line 140 of file cachehandler.c.
References snmplog(), and SNMPMALOCTYPEDEF.
Referenced by netsnmpgetcachehandler().
netsnmpcache** netsnmpcachefindbyoid (oid ** rootoid,, int rootoidlen)
find existing cache Definition at line 124 of file cachehandler.c.
References netsnmpoidequals().
netsnmpcache** netsnmpcachegethead (void)
get cache head Definition at line 116 of file cachehandler.c.
netsnmpmibhandler** netsnmpcachehandlerget (netsnmpcache ** cache)
returns a cache handler that can be injected into a given handler
chain. Definition at line 245 of file cachehandler.c.
References netsnmpmibhandlers::flags, netsnmpmibhandlers::myvoid,
netsnmpcachetimerstart(), netsnmpcreatehandler(), and
netsnmpmibhandler.
Referenced by netsnmpcachehandlerregister(), and
netsnmpgetcachehandler().
int netsnmpcachehandlerregister (netsnmphandlerregistration ** reginfo,,
netsnmpcache ** cache)
functionally the same as calling netsnmpregisterhandler() but also
injects a cache handler at the same time for you. Definition at line
293 of file cachehandler.c.
References netsnmpcachehandlerget(), netsnmpinjecthandler(),
netsnmpmibhandler, and netsnmpregisterhandler().
int netsnmpcachehelperhandler (netsnmpmibhandler ** handler,,
netsnmphandlerregistration ** reginfo,, netsnmpagentrequestinfo **
reqinfo,, netsnmprequestinfo ** requests)
Implements the cache handler. next handler called automatically -
'AUTONEXT'
next handler called automatically - 'AUTONEXT'
next handler called automatically - 'AUTONEXT' Definition at line 418
of file cachehandler.c.
References netsnmpmibhandlers::flags,
netsnmphandlerregistrations::handlerName,
netsnmpagentrequestinfos::mode, netsnmpmibhandlers::myvoid,
netsnmpcachecheckandreload(), netsnmpcacheisvalid(),
netsnmpcachereqinfoinsert(), netsnmphandlerregistration,
netsnmpsetallrequestserror(),
netsnmphandlerregistrations::rootoid,
netsnmphandlerregistrations::rootoidlen, and snmplog().
int netsnmpcacheisvalid (netsnmpagentrequestinfo ** reqinfo,, const
char ** name)
Is the cache valid for a given request? Definition at line 400 of file
cachehandler.c.
References netsnmpcachereqinfoextract().
Referenced by netsnmpcachehelperhandler(), and
netsnmpiscachevalid().
netsnmpcache** netsnmpcachereqinfoextract (netsnmpagentrequestinfo **
reqinfo,, const char ** name)
Extract the cache information for a given request (PDU). Definition at
line 348 of file cachehandler.c.
References SNMPFRE.
Referenced by netsnmpcacheisvalid(), and
netsnmpextractcacheinfo().
void netsnmpcachereqinfoinsert (netsnmpcache ** cache,,
netsnmpagentrequestinfo ** reqinfo,, const char ** name)
Insert the cache information for a given request (PDU). Definition at
line 331 of file cachehandler.c.
References netsnmpcreatedatalist(), and SNMPFRE.
Referenced by netsnmpcachehelperhandler().
unsigned int netsnmpcachetimerstart (netsnmpcache ** cache)
starts the recurring cacheload callback Definition at line 195 of file
cachehandler.c.
References snmpalarmregister(), and snmplog().
Referenced by netsnmpcachehandlerget().
void netsnmpcachetimerstop (netsnmpcache ** cache)
stops the recurring cacheload callback Definition at line 225 of file
cachehandler.c.
References snmpalarmunregister(), and snmplog().
netsnmpcache** netsnmpextractcacheinfo (netsnmpagentrequestinfo **
reqinfo)
Extract the cache information for a given request (PDU). Definition at
line 360 of file cachehandler.c.
References netsnmpcachereqinfoextract().
netsnmpmibhandler** netsnmpgetcachehandler (int timeout,,
NetsnmpCacheLoad ** loadhook,, NetsnmpCacheFree ** freehook,, oid **
rootoid,, int rootoidlen)
returns a cache handler that can be injected into a given handler
chain. Definition at line 274 of file cachehandler.c.
References netsnmpmibhandlers::myvoid, netsnmpcachecreate(),
netsnmpcachehandlerget(), and netsnmpmibhandler.
Referenced by netsnmpregistercachehandler().
int netsnmpiscachevalid (netsnmpagentrequestinfo ** reqinfo)
for backwards compat netsnmpcacheisvalid() is preferred. Definition
at line 411 of file cachehandler.c.
References netsnmpcacheisvalid().
int netsnmpregistercachehandler (netsnmphandlerregistration ** reginfo,,
int timeout,, NetsnmpCacheLoad ** loadhook,, NetsnmpCacheFree **
freehook)
functionally the same as calling netsnmpregisterhandler() but also
injects a cache handler at the same time for you. Definition at line
306 of file cachehandler.c.
References netsnmpgetcachehandler(), netsnmpinjecthandler(),
netsnmpmibhandler, netsnmpregisterhandler(),
netsnmphandlerregistrations::rootoid, and
netsnmphandlerregistrations::rootoidlen.
void releasecachedresources (unsigned int regNo,, void ** clientargs)
run regularly to automatically release cached resources. xxx - method
to prevent cache from expiring while a request is being processed (e.g.
delegated request). proposal: set a flag, which would be cleared when
request finished (which could be acomplished by a dummy data list item
in agent req info & custom free function). Definition at line 575 of
file cachehandler.c.
References netsnmpcachecheckexpired(), releasecachedresources(),
and snmpalarmregister().
Referenced by releasecachedresources().
necachehandler: Maintains a cache2ofJdata00for use by lower level handlers.(3)
|
