Costbased Distributed Transaction Coordinator

1
Cost-based Distributed Transaction Coordinator
Jin Taiyong 08/22/2001
2
Architecture
Functionalities of Execute Element
Transaction Pool

• Execute the coordinated
• transactions

Transaction Scheduler
Database Distribution Manager
Load Information Manager

• Collect the load information of
• the executed transactions

Execute Element Manager
Adapter
Dispatcher

• Feedback the load information of
• the executed transactions to
• transaction coordinator

Dispatcher
Dispatcher
Dispatcher
Dispatcher
Dispatcher
Execute Element
Execute Element
Execute Element

• Transaction Placement Policy
• Decide how to coordinate the transaction
  when it is submitted to TC

• Transaction Scheduling Policy
• Decide which blocked transaction in
  Transaction Pool is executed
• at which site when a transaction is finished
  at an Execute Element

3
Transaction Type

• In actual applications, the number of the
  transaction types is limited.
• The transactions whose types are the same should
  have the same load characteristic
• The transaction type is decided by the designer
  of the application

4
Data Structure (1)

• Transaction Pool (TC_WaitTransactionList)
• Blocked Transaction( TC_WaitTran )
• Type int
• Priority int
• Param Size unsigned long
• Parameter char
• Next blocked tranaction TC_WaitTran

TC_WaitTransactionList
TC_WaitTran
5
Data Structure (2)

• Database Distribution Manager (DDM)
• DDMInfo_t
• Heap_number int
• Primary IP address unsigned long
• Heap Size unsigned long

DDMInfo_t
DDM
6
Data Structure (3)

• Cost Information Manager (CIM)
• CIMHeapInfo_t
• ddm_entry int
• Number of read pages int
• Number of written pages int
• CIMInfo_t
• Type int
• Throughput int
• Rollback int
• Cost Value CIMHeapInfo_tMAX_HEAP_NUM

CIMnfo_t
CIM
7
Data Structure (4)

• Execute Element Manager (EEM)
• EESocket
• handle int
• IP address unsigned long
• Port int
• Busy Flag int (1 The EE is executing a
  transaction 0 The EE is idle)
• Connect_flag int (1 The EE is connecting with
  TC 0 The EE is disconnected with TC)
• TC_EEManager
• Sockets EESocketMAX_EE_NUM
• Max MPL int ( The maximum number of the EEs
  whose Busy Flag is 1)
• Current MPL int

8
Data Structure (5)

• Execute Element (EE)
• Socket Handle int
• RPC Handle Client
• IP Address unsigned long
• Port int

9
When an EE is executed
TC

• TransactionEnd
• IP Address
• Port
• (RPC)

• TypeID
• Parameter
• (Socket)

EE_Open(ip_addr, port) (RPC)
Transaction Action Library
EE
10
Relationship between Transaction Load Information
and CDTC

• CDTC is based on the cost of transactions
  executed at Execute
• element
• The cost of transaction is different from the
  site where the
• transaction execute
• The cost of transaction is decided by the load
  information
• and the cost of the transaction could be
  calculated via the
• load information and the distribution status
  of database
• The load information of the transactions is
  collected while the
• EEs execute these transactions

11
Cost-based Approaches

• Cost-based Approach - 1
• Static approach(CTC-Static)
• Static Coordinator Description File (SCDF)
• T ? S
• T is the type ID of transaction
• S is the ip address of the host where the
• transaction t is executed.
• Transaction Placement Policy
• Select an idle EE for the submitted transaction
  according to SCDF
• Transaction Scheduling Policy
• Select the next transaction which is blocked also
  according to SCDF

12
Cost-based Approaches

• Cost-based Approach - 2
• Transaction Priority Oriented approach(CTC-TPOA)
• Transaction Placement Policy
• Look through all of the EEs to find an idle EE to
  execute the
• transaction submitted
• Transaction Scheduling Policy
• Look through all of the EEs to find an idle EE to
  execute the
• blocked transaction whose arrival time is the
  earliest.

13
Cost-based Approaches

• Cost-based Approaches -3
• Low-Cost Oriented approach(CTC-LCOA)
• Priority Value (PV)
• PV(t, s) Cost(t,s) Preemption Factor(t)
• Cost(t,s) is the cost for executing t at host s.
• If a transaction whose arrival time is later than
  that
• Of t is coordinated in prior to t, the Preemption
  Factor of t is increased by k
• Transaction Placement Policy
• It is the same with CTC-TPOA
• Transaction Scheduling Policy
• For the site where the EE has finished a
  transaction, look through all of the blocked
  transaction and coordinate the transaction whose
  PV is the lowest to the site

Distribution of Active EEs is fixed in CTC-LCOA
14
Relationship between Priority and cost-based
approaches

• Just in transaction scheduling policy, the
  priority is considered.
• In CTC-Static, the priority is not be considered
• In CTC-TPOA, just the priority is considered.
• In CTC-LCOA, not only the priority but also the
  cost is considered.