Re: overhead of ZEO connection

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On 05/06/2016 09:33 AM, Sanjay Rao wrote:

> In this post I want to understand the overhead of creating database 
> connections in a zope application what is overhead of creating a new 
> connection to ZEO ?
> 
> which one is recommended ?
> 
> - Create a connection - Use this connection for each transaction 
> commit (one transaction commit could be bounded into one function) - 
> Close connection when application terminates
> 
> OR
> 
> - Create one separate connection for each transaction commit - Commit 
> transaction - Close connection .....

You definitely don't want to *destroy* the connection at transaction
boundaries:  each connection holds a cache (in RAM) of objects retrieved
from the database.  The `ZODB.DB.DB` object, which holds onto the
storage, also maintains a connection pool.  The usual pattern would be:

- ------------------------- %< -------------------------
# At startup
from ZODB.DB import DB
from ZEO.ClientStorage impport ClientStorage

storage = ClientStoraget((192.168.1.200, 9876))
db = DB(storage)

# Whenever you need a connection
conn = db.open()  # checks it out of the pool
root = conn.root()

# Use the root object to do work
try:
    do_something_with(root)
except Exception:
    transaction.abort()
    raise
else:
    transaction.commit()

conn.close()  # return 'conn' to the pool
- ------------------------- %< -------------------------

Zope follows this pattern for each HTTP request it serves.  Hope that helps,


Tres.
- -- 
===================================================================
Tres Seaver          +1 540-429-0999          [email protected]
Palladion Software   "Excellence by Design"    http://palladion.com
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