org.eclipse.jgit.internal.ketch

Class KetchSystem

java.lang.Object

org.eclipse.jgit.internal.ketch.KetchSystem

public class KetchSystem
extends Object

Ketch system-wide configuration.

This class provides useful defaults for testing and small proof of concepts. Full scale installations are expected to subclass and override methods to provide consistent configuration across all managed repositories.

Servers should configure their own ScheduledExecutorService.

Constructor Summary

Constructors

Constructor and Description
KetchSystem() Create a default system with a thread pool of 1 thread per CPU.
KetchSystem(ScheduledExecutorService executor, String txnNamespace) Create a Ketch system with the provided executor service.

Method Summary

Methods

Modifier and Type	Method and Description
KetchLeader	createLeader(Repository repo) Construct the KetchLeader instance of a repository.
protected List<KetchReplica>	createReplicas(KetchLeader leader, Repository repo) Get the collection of replicas for a repository.
static ScheduledExecutorService	defaultExecutor()
ScheduledExecutorService	getExecutor()
String	getTxnAccepted()
String	getTxnCommitted()
String	getTxnNamespace() Get the namespace used for the RefTree graph and transaction management.
String	getTxnStage()
PersonIdent	newCommitter()
String	newLeaderTag() Construct a random tag to identify a candidate during leader election.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

KetchSystem

public KetchSystem()

Create a default system with a thread pool of 1 thread per CPU.

KetchSystem

public KetchSystem(ScheduledExecutorService executor,
           String txnNamespace)

Create a Ketch system with the provided executor service.

Parameters:

executor - thread pool to run background operations.

txnNamespace - reference namespace for the RefTree graph and associated transaction state. Must begin with "refs/" and end with '/', for example "refs/txn/".

Method Detail

defaultExecutor

public static ScheduledExecutorService defaultExecutor()

Returns:

default executor, one thread per available processor.

getExecutor

public ScheduledExecutorService getExecutor()

Returns:

executor to perform background operations.

getTxnNamespace

public String getTxnNamespace()

Get the namespace used for the RefTree graph and transaction management.

Returns:

reference namespace such as "refs/txn/".

getTxnAccepted

public String getTxnAccepted()

Returns:

name of the accepted RefTree graph.

getTxnCommitted

public String getTxnCommitted()

Returns:

name of the committed RefTree graph.

getTxnStage

public String getTxnStage()

Returns:

prefix for staged objects, e.g. "refs/txn/stage/".

newCommitter

public PersonIdent newCommitter()

Returns:

identity line for the committer header of a RefTreeGraph.

newLeaderTag

@Nullable
public String newLeaderTag()

Construct a random tag to identify a candidate during leader election.

Multiple processes trying to elect themselves leaders at exactly the same time (rounded to seconds) using the same newCommitter() identity strings, for the same term, may generate the same ObjectId for the election commit and falsely assume they have both won.

Candidates add this tag to their election ballot commit to disambiguate the election. The tag only needs to be unique for a given triplet of newCommitter(), system time (rounded to seconds), and term. If every replica in the system uses a unique newCommitter (such as including the host name after the "@" in the email address) the tag could be the empty string.

The default implementation generates a few bytes of random data.

Returns:

unique tag; null or empty string if newCommitter() is sufficiently unique to identify the leader.

createLeader

public KetchLeader createLeader(Repository repo)
                         throws URISyntaxException

Construct the KetchLeader instance of a repository.

Parameters:

repo - local repository stored by the leader.

Returns:

leader instance.

Throws:

URISyntaxException - a follower configuration contains an unsupported URI.

createReplicas

protected List<KetchReplica> createReplicas(KetchLeader leader,
                                Repository repo)
                                     throws URISyntaxException

Get the collection of replicas for a repository.

The collection of replicas must include the local repository.

Parameters:

leader - the leader driving these replicas.

repo - repository to get the replicas of.

Returns:

collection of replicas for the specified repository.

Throws:

URISyntaxException - a configured URI is invalid.