bsddb3 locking questions

[Eric S. Johansson]

man, I'm in really bad form replying to myself twice but I'me solved the 
problem at least in a simple form.

Eric S. Johansson wrote:
> Eric S. Johansson wrote:
>> are there any simple examples of how to do record locking with bsddb3?

#!/usr/bin/python

from bsddb import db                   # the Berkeley db data base
import sys, os, time

# some helpers fcns

def countdown(id, count):
     limit = 0
     while limit < count:
         print id, limit,
         limit = limit+1

# fork into 2 instances and collide
pid = os.fork()

# Part 1: Create database and insert 4 elements
#
filename = 'fruit'

# Get an instance of BerkeleyDB
db_env = db.DBEnv()
db_env.set_lk_detect(db.DB_LOCK_YOUNGEST)
db_env.open("/tmp/bsddb3",db.DB_INIT_LOCK|db.DB_CREATE| db.DB_INIT_MPOOL)

# force a collision
time.sleep(2)

an_id = db_env.lock_id()

print pid, an_id

fruitDB = db.DB(db_env)
# Create a database in file "fruit" with a Hash access method
# 	There are also, B+tree and Recno access methods
fruitDB.open(filename, None, db.DB_HASH, db.DB_CREATE)

# Print version information
print '\t', pid, db.DB_VERSION_STRING

while(1):
     try:
         lock = db_env.lock_get(an_id, "anytid", db.DB_LOCK_WRITE, 
db.DB_LOCK_NOWAIT)
         break
     except Exception,error:
         #print error
         pass

print pid, "here"

# force another one
time.sleep(2)

# Insert new elements in database
fruitDB.put("apple","red")
fruitDB.put("orange","orange")
fruitDB.put("banana","yellow")
fruitDB.put("tomato","red")

db_env.lock_put(lock)
print pid, "there"

# Close database
fruitDB.close()

# Part 2: Open database and write its contents out
#
fruitDB = db.DB(db_env)
# Open database
#	Access method: Hash
#	set isolation level to "dirty read (read uncommited)"
fruitDB.open(filename, None, db.DB_HASH, db.DB_DIRTY_READ)

# get database cursor and print out database content
cursor = fruitDB.cursor()
rec = cursor.first()
while rec:
         print rec
         rec = cursor.next()
fruitDB.close()

----------

still unanswered, under what conditions do you change the second 
argument of lock_get?  Is that a simple lock identifier within the 
context of the lock ID so that you can lock different records?  Anyway, 
this locking is close enough for what I need to do.

---eric