Re: [pysnmp-users] varbind persistence in my trap object?

[Ilya E. <il...@gl...>]

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Pete,

In fact both approaches should work exactly the same. The only difference
is the point where you pass encoded oids&vals to trap object.

> trap = v2c.TRAP()
> encoded_oids = []
> encoded_vals = []
> [add the encoded oids and vals]
> host.send(trap.encode(encoded_oids=encoded_oids, encoded_vals=encoded_vals))

So, what is the problem with the above?

> This is what I first tried, but was never able to get working because
> each time a trap was fired, the trap contained all of the varbinds
> from the previous trap (i.e. they kept appending):
> 
> def add_varbind(trap, oid, val):
>    trap['encoded_oids'].append(oid)
>    trap['encoded_vals'].append(val)
> 
> trap = v2c.TRAP()
> [add the encoded oids and vals using 'add_varbind(trap, oid, val)' function]
> encoded_trap = trap.encode()
> host.send(encoded_trap)
> 
> This never worked; yet I am not sure why because I create myself a new
> trap object each time a trap is fired and I stuff it with the
> appropriate values.  Clearly, I am using the API wrong.  I searched
> for a method to clear the object state (trap.clear() didn't work).

That's probably because you're doing append() to var-bind list. Try
assignment (=) instead.

> My questions are:
> 
> 1) Should I just abandon the second approach?  Or am I just using the
>    API incorrectly in this case?

I do not see much difference in these approaches. The bottom line is to
have a single persistent trap object stuffed with new oids&vals on each
trap.

> 2) In both examples above, the 'host' object (created from
>    role.manager()) is created once in the lifetime of the program.  Is
>    it safe to use this object multiple times for each trap that I
>    send? 

Yes, to the extent of slight performance penalty (objects and socket
creation etc.).

BTW, I suggest you trying pysnmp-3.x (its native API) instead of 
pysnmp-2.x as it's hopefully has a more clear design and implementation.

Hope this helps,
ilya