Borland Load Distribution Submission

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BorlandLoad DistributionSubmission

• Dave Stringer
• dstringer_at_borland.com
• mars/2004-10-08

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Borland submission to the Load Distribution RFP

• Specifications and Products
• The Load Distribution Problem
• Extending the Naming Service
• Future Enhancements

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Specifications and Products

• Load distribution is part of many ORB products
• it has been part of VisiBroker for 10 years
• Load distribution is used by many ORB customers
• they havent been requesting this specification
• they expect any new specifications to protect
  their investment or vendors to protect it
• Specifications should be based on real technology
• Proof of concept !!

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Object Interactions in CORBA
NS
C
S
REF
1. Bind Name to Object Reference
2. Resolve Name for Object Reference
3. Bind Reference to Object
4. Invoke Operation on Object
. . . Invoke again
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The Load Distribution Problem

• Load Balancing who is responsible for achieving
  balance?
• heterogeneous systems measuring load
• stability of feed-back systems
• Skewed Distributions
• abnormal versus uniform units of work
• long lived clients
• When to take the load distribution decision
• at discovery, at binding or at invocation?
• how do applications influence the decision?
• Fail-over and Fault Tolerance
• not part of the RFP, should it be part of the
  solution?
• Load Re-distribution
• recovering a group member gives a skewed
  distribution

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Naming Contexts and Object Clusters

• Object Clusters are bound in Naming Contexts
• just like ordinary Naming Contexts
• Object Clusters are transparent
• resolving the clusters name gives a bound object
  reference
• bindings within Object Clusters are not directly
  accessible
• The Name of an Object Cluster needs to have two
  meanings
• the name of the cluster and the name of a member

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Object Cluster in Name Service
S1
NS
C
S2
REF 2
1. Bind Name to Object Reference
and to another
2. Resolve Name for Object Reference
3. Bind Reference to Object
4. Invoke Operation on Object
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Explicit Clusters

• // Client.java
• . . .
• Object obj rootCtx.resolve(My_Server)
• Srvr sa SrvrHelper.narrow(obj)
• . . .
• obj rootCtx.resolve(My_Server)
• Srvr sb SrvrHelper.narrow(obj)
• . . .
• if (sa._is_equivalent(sb))
• System.out.println(
• distribution failed)

• // Server.java
• . . .
• Cluster cluster clusterMgr.create_cluster("RR")
  
• rootCtx.bind(My_Server", cluster)
• . . .
• Srvr s1 aPOA.create_reference( srvrRepId)
• cluster.bind(First_Member", s1)
• . . .
• Srvr s2 aPOA.create_reference( srvrRepId)
• cluster.bind(Second_Member",s2)

// Server.java . . . Cluster cluster
clusterMgr.create_cluster("RR")
rootCtx.bind(My_Server", cluster) . . . Srvr
s1 aPOA.create_reference( srvrRepId) cluster.bi
nd(First_Member", s1) . . . Srvr s2
aPOA.create_reference( srvrRepId) cluster.bind(S
econd_Member",s2)
// Client.java . . . Object obj
rootCtx.resolve(My_Server) Srvr sa
SrvrHelper.narrow(obj) . . . obj
rootCtx.resolve(My_Server) Srvr sb
SrvrHelper.narrow(obj) . . . if
(sa._is_equivalent(sb)) System.out.println(
distribution failed)
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Implicit Clusters

• // Client.java
• . . .
• Object obj rootCtx.resolve(My_Server)
• Srvr sa SrvrHelper.narrow(obj)
• . . .
• obj rootCtx.resolve(My_Server)
• Srvr sb SrvrHelper.narrow(obj)
• . . .
• if (sa._is_equivalent(sb))
• System.out.println(
• distribution failed)

• // Server.java
• . . .
• Srvr s1 aPOA.create_reference( srvrRepId)
• rootCtx.bind(My_Server", s1)
• . . .
• Srvr s2 aPOA.create_reference( srvrRepId)
• rootCtx.bind(My_Server", s2)
• // AlreadyBound will not be thrown

// Server.java . . . Srvr s1 aPOA.create_referen
ce( srvrRepId) rootCtx.bind(My_Server", s1) .
. . Srvr s2 aPOA.create_reference(
srvrRepId) rootCtx.bind(My_Server", s2) //
AlreadyBound will not be thrown
// Client.java . . . Object obj
rootCtx.resolve(My_Server) Srvr sa
SrvrHelper.narrow(obj) . . . obj
rootCtx.resolve(My_Server) Srvr sb
SrvrHelper.narrow(obj) . . . if
(sa._is_equivalent(sb)) System.out.println(
distribution failed)
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Cluster Interface

• Interface Cluster
• Object select()
• // cf. resolving the cluster name at the
  parent context
• void bind(in CosNamingNameComponent n, in
  Object o)
• void rebind( . . . )
• Object resolve(in CosNamingNameComponent n)
• void unbind( . . . )
• void destroy()
• void list(in unsigned long how_many, out . .
  . bl, out . . . bi)

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ClusterManager Interface

• Interface ClusterManager
• Cluster create_cluster(in string algorithm)
• Cluster find_cluster(in CosNamingNamingContex
  t ctx,
• in CosNamingName n)
• Cluster find_cluster_str(in CosNamingNamingCo
  ntext ctx,
• in string n)
• ClusterList clusters()

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2 more (supporting) Interfaces

• Interface NamingContextExtExtended
• void unbind_from_cluster(in CosNamingName
  cn,
• in Object srvrRef)
• boolean is_ncluster_type(in CosNamingName n,
  
• out Object c)
• Interface NamingContextFactory
• CosNamingNamingContextExt create_context()
• oneway void shutdown()
• ClusterManager get_cluster_manager()

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Future Enhancements

• Consolidate interfaces into the CosNaming
  interfaces
• Cluster as an alternate implementation of
  NamingContext
• NamingCluster derived from NamingContext
• Clusters that combine Object References
• Obviates need to declare fail-over alternates at
  POA
• Federate NamingContexts to Clusters
• Improve scalability of Load Distribution
• Review outstanding RFP requirements
• . . .

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Thank You