Re: Shared SO's and Load Balancing

Thanks, Tom. I understand this issue a lot better now.
Dale
On Wed, 21 Jan 1998 23:28:33 +0000, Tom O'Rourke wrote:
Dale,
You are right in that it many times does not make sense to load balance
services that are multi-threaded.
But, when a TOOL service object is partitioned with a DBSession service
object, the TOOL service acts as if it is single-threaded regardless of if
it is SHARED or not (while the partition is accessing the database). This
means that the entire partition will be blocked (single-threaded) while the
TOOL service object is using the DBSession to access a database.
Forte blocks the partition to protect the integrity of the data being
passed back and forth to the database because the database vendors have yet
to provide a thread safe call interface to the RDBMS. This is changing as
we speak and Forte is in the process of making the appropriate adjustments.
So, this is the case where it makes complete sense to load balance a
service that is not marked as being SHARED and why it can be a tremendous
performance advantage to use Forte load balancing. As we all know, this
architecture (TOOL EVSO partitioned with DBSession UVSO) is one that is
widely used and proven to produce high performing applications.
The point you bring up is a good one and that is often misunderstood. A
load balanced SO will behave as if it is single threaded (or SHARED).
FYI, we have just added a new feature in release 3.F. Performance-based
load balancing. Check it out.
Tom
At 07:38 PM 1/21/98, Dale V. Georg wrote:
On Wed, 21 Jan 1998 17:24:33 -0000, Richard Stobart wrote:
Dale,
If SHARED is true in a Service Object then the Service Object is not
re-entrant (because many clients are sharing its variables and therefore is
not multitasked (Funny logical naming if you ask me)). I got a lot of replies correcting me on what SHARED means! I do know
what SHARED means, I just phrased it backwards in my post. Excuse me
while I smack myself upside the head. :)
All replicates of a
load balanced partition are not re-entrant and thus equivalent to SHARED =
true. The advantage of load balancing is that the replicates can be
distributed over machines and thus the load is balanced. What I fail to understand is this: If you have a non-SHARED SO all by
itself in a partition which is not load-balanced, it will be
re-rentrant and multiple users can call it at the same time. But as
soon as you load-balance it, all of a sudden it behaves as if it were
SHARED. Why? I don't understand the technical limitations that impose
this, nor do I understand the advantage. For example, let's say that I
have 50 concurrent users of the SO I described above. It's in a
non-load-balanced partition, so all 50 users can access it at the same
time without any problem. Now let's say my server is a little
stressed, so I decide I want to load-balance my SO and have two
replicates, one on the original server and one on a second server. But
now that I've load-balanced it, the partitions act as if they're SHARED
and my 50 concurrent users are going to be lining up in queues and
suffering from horrible response times. How is this advantageous?
================================================
Dale V. Georg
Systems Analyst
Indus Consultancy Services
[email protected]
================================================
================================================
Dale V. Georg
Systems Analyst
Indus Consultancy Services
[email protected]
================================================

Thanks, Tom. I understand this issue a lot better now.
Dale
On Wed, 21 Jan 1998 23:28:33 +0000, Tom O'Rourke wrote:
Dale,
You are right in that it many times does not make sense to load balance
services that are multi-threaded.
But, when a TOOL service object is partitioned with a DBSession service
object, the TOOL service acts as if it is single-threaded regardless of if
it is SHARED or not (while the partition is accessing the database). This
means that the entire partition will be blocked (single-threaded) while the
TOOL service object is using the DBSession to access a database.
Forte blocks the partition to protect the integrity of the data being
passed back and forth to the database because the database vendors have yet
to provide a thread safe call interface to the RDBMS. This is changing as
we speak and Forte is in the process of making the appropriate adjustments.
So, this is the case where it makes complete sense to load balance a
service that is not marked as being SHARED and why it can be a tremendous
performance advantage to use Forte load balancing. As we all know, this
architecture (TOOL EVSO partitioned with DBSession UVSO) is one that is
widely used and proven to produce high performing applications.
The point you bring up is a good one and that is often misunderstood. A
load balanced SO will behave as if it is single threaded (or SHARED).
FYI, we have just added a new feature in release 3.F. Performance-based
load balancing. Check it out.
Tom
At 07:38 PM 1/21/98, Dale V. Georg wrote:
On Wed, 21 Jan 1998 17:24:33 -0000, Richard Stobart wrote:
Dale,
If SHARED is true in a Service Object then the Service Object is not
re-entrant (because many clients are sharing its variables and therefore is
not multitasked (Funny logical naming if you ask me)). I got a lot of replies correcting me on what SHARED means! I do know
what SHARED means, I just phrased it backwards in my post. Excuse me
while I smack myself upside the head. :)
All replicates of a
load balanced partition are not re-entrant and thus equivalent to SHARED =
true. The advantage of load balancing is that the replicates can be
distributed over machines and thus the load is balanced. What I fail to understand is this: If you have a non-SHARED SO all by
itself in a partition which is not load-balanced, it will be
re-rentrant and multiple users can call it at the same time. But as
soon as you load-balance it, all of a sudden it behaves as if it were
SHARED. Why? I don't understand the technical limitations that impose
this, nor do I understand the advantage. For example, let's say that I
have 50 concurrent users of the SO I described above. It's in a
non-load-balanced partition, so all 50 users can access it at the same
time without any problem. Now let's say my server is a little
stressed, so I decide I want to load-balance my SO and have two
replicates, one on the original server and one on a second server. But
now that I've load-balanced it, the partitions act as if they're SHARED
and my 50 concurrent users are going to be lining up in queues and
suffering from horrible response times. How is this advantageous?
================================================
Dale V. Georg
Systems Analyst
Indus Consultancy Services
[email protected]
================================================
================================================
Dale V. Georg
Systems Analyst
Indus Consultancy Services
[email protected]
================================================

Similar Messages

  • Shared SO's and Load Balancing

    On Wed, 21 Jan 1998 17:24:33 -0000, Richard Stobart wrote:
    Dale,
    If SHARED is true in a Service Object then the Service Object is not
    re-entrant (because many clients are sharing its variables and therefore is
    not multitasked (Funny logical naming if you ask me)). I got a lot of replies correcting me on what SHARED means! I do know
    what SHARED means, I just phrased it backwards in my post. Excuse me
    while I smack myself upside the head. :)
    All replicates of a
    load balanced partition are not re-entrant and thus equivalent to SHARED =
    true. The advantage of load balancing is that the replicates can be
    distributed over machines and thus the load is balanced. What I fail to understand is this: If you have a non-SHARED SO all by
    itself in a partition which is not load-balanced, it will be
    re-rentrant and multiple users can call it at the same time. But as
    soon as you load-balance it, all of a sudden it behaves as if it were
    SHARED. Why? I don't understand the technical limitations that impose
    this, nor do I understand the advantage. For example, let's say that I
    have 50 concurrent users of the SO I described above. It's in a
    non-load-balanced partition, so all 50 users can access it at the same
    time without any problem. Now let's say my server is a little
    stressed, so I decide I want to load-balance my SO and have two
    replicates, one on the original server and one on a second server. But
    now that I've load-balanced it, the partitions act as if they're SHARED
    and my 50 concurrent users are going to be lining up in queues and
    suffering from horrible response times. How is this advantageous?
    ================================================
    Dale V. Georg
    Systems Analyst
    Indus Consultancy Services
    [email protected]
    ================================================

    Dale,
    The argument for load balancing services falls into two basic categories:
    1. The service is blocking. That is, it is either not thread safe, not
    signal tolerant, or not re-entrant. Most database libraries are the most
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    Load balancing vs. multi-threading is a pretty hot topic among all of the
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    At 07:38 PM 1/21/98, Dale V. Georg wrote:
    On Wed, 21 Jan 1998 17:24:33 -0000, Richard Stobart wrote:
    Dale,
    If SHARED is true in a Service Object then the Service Object is not
    re-entrant (because many clients are sharing its variables and therefore is
    not multitasked (Funny logical naming if you ask me)). I got a lot of replies correcting me on what SHARED means! I do know
    what SHARED means, I just phrased it backwards in my post. Excuse me
    while I smack myself upside the head. :)
    All replicates of a
    load balanced partition are not re-entrant and thus equivalent to SHARED =
    true. The advantage of load balancing is that the replicates can be
    distributed over machines and thus the load is balanced. What I fail to understand is this: If you have a non-SHARED SO all by
    itself in a partition which is not load-balanced, it will be
    re-rentrant and multiple users can call it at the same time. But as
    soon as you load-balance it, all of a sudden it behaves as if it were
    SHARED. Why? I don't understand the technical limitations that impose
    this, nor do I understand the advantage. For example, let's say that I
    have 50 concurrent users of the SO I described above. It's in a
    non-load-balanced partition, so all 50 users can access it at the same
    time without any problem. Now let's say my server is a little
    stressed, so I decide I want to load-balance my SO and have two
    replicates, one on the original server and one on a second server. But
    now that I've load-balanced it, the partitions act as if they're SHARED
    and my 50 concurrent users are going to be lining up in queues and
    suffering from horrible response times. How is this advantageous?
    ================================================
    Dale V. Georg
    Systems Analyst
    Indus Consultancy Services
    [email protected]
    ================================================
    ============================================
    Don Nelson
    Regional Consulting Manager - Rocky Mountain Region
    Forte Software, Inc.
    Denver, CO
    Phone: 303-265-7709
    Corporate voice mail: 510-986-3810
    aka: [email protected]
    ============================================
    "We tigers prefer to inflict excitement on others." - Hobbes

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