code migaration

code migration

process of moving executable code from one machine to another in a distributed system to improve performance, efficiency, or flexibility; avoids pre-installing software and increases dynamic configuration.

load distribution

ensuring that servers in a data center are sufficiently _ (e.g., to prevent waste of energy); minimizing communication by ensuring that computations are close to where the data is (think of mobile computing).

flexibility

moving code to a client when needed

client-server

the client sends a request to a server. The server processes the request locally and sends back the result; code stays put, only data moves between client and server.

remote evaluation

the client sends code to the server to be executed there; useful when the server has more data or resources.; code moves from client to server.

code on demand

the server sends code to the client, where it's executed, often used when clients need dynamic behavior or updates; code moves from server to client.

mobile agents

(code + execution state + data) moves from host to host, executing parts of its task at each; code and state move between systems.

code segment

contains the actual code

data segment

contains the state

execution state

contains the context of the thread executing the object’s code

weak mobility

move only code and data segment (and reboot execution)

code shipping

push

code fetching

pull

strong mobility

move component, including execution state

migration

move the entire object from one machine to the other

cloning

start a _, and set it in the same execution state.

pre-copy strategy

low downtime, high performance, medium complexity, widely used in practice

stop-and-copy strategy

high downtime, low complexity, simple but disruptive

post-copy strategy

low downtime; variable performance, high complexity, fast start but riskier