Class TabletBalancer
- java.lang.Object
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- org.apache.accumulo.server.master.balancer.TabletBalancer
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- Direct Known Subclasses:
ChaoticLoadBalancer
,DefaultLoadBalancer
,GroupBalancer
,TableLoadBalancer
public abstract class TabletBalancer extends Object
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Nested Class Summary
Nested Classes Modifier and Type Class Description protected static class
TabletBalancer.BalancerProblem
A deferred call descendent TabletBalancers use to log why they can't continue.protected static class
TabletBalancer.NoTservers
If a TabletBalancer requires active tservers, it should use this problem to indicate when there are none.protected static class
TabletBalancer.OutstandingMigrations
If a TabletBalancer only balances when there are no outstanding migrations, it should use this problem to indicate when they exist.
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Field Summary
Fields Modifier and Type Field Description protected ServerConfigurationFactory
configuration
protected AccumuloServerContext
context
protected static long
TIME_BETWEEN_BALANCER_WARNINGS
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Constructor Summary
Constructors Constructor Description TabletBalancer()
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Deprecated Methods Modifier and Type Method Description abstract long
balance(SortedMap<TServerInstance,TabletServerStatus> current, Set<KeyExtent> migrations, List<TabletMigration> migrationsOut)
Ask the balancer if any migrations are necessary.static List<TabletMigration>
checkMigrationSanity(Set<TServerInstance> current, List<TabletMigration> migrations)
Utility to ensure that the migrations from balance() are consistent: Tablet objects are not null Source and destination tablet servers are not null and currentprotected void
constraintNotMet(TabletBalancer.BalancerProblem cause)
Warn that a Balancer can't work because of some external restriction.abstract void
getAssignments(SortedMap<TServerInstance,TabletServerStatus> current, Map<KeyExtent,TServerInstance> unassigned, Map<KeyExtent,TServerInstance> assignments)
Assign tablets to tablet servers.List<TabletStats>
getOnlineTabletsForTable(TServerInstance tserver, String tableId)
Fetch the tablets for the given table by asking the tablet server.void
init(ServerConfiguration conf)
Deprecated.since 1.7.3 and 1.8.1; overriding this has no effect; subclasses should overrideinit(ServerConfigurationFactory)
instead.void
init(ServerConfigurationFactory conf)
Initialize the TabletBalancer.protected void
resetBalancerErrors()
Resets logging about problems meeting an external constraint on balancing.
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Field Detail
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configuration
protected ServerConfigurationFactory configuration
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context
protected AccumuloServerContext context
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TIME_BETWEEN_BALANCER_WARNINGS
protected static final long TIME_BETWEEN_BALANCER_WARNINGS
- See Also:
- Constant Field Values
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Method Detail
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init
public void init(ServerConfigurationFactory conf)
Initialize the TabletBalancer. This gives the balancer the opportunity to read the configuration.
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init
@Deprecated public void init(ServerConfiguration conf)
Deprecated.since 1.7.3 and 1.8.1; overriding this has no effect; subclasses should overrideinit(ServerConfigurationFactory)
instead.
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getAssignments
public abstract void getAssignments(SortedMap<TServerInstance,TabletServerStatus> current, Map<KeyExtent,TServerInstance> unassigned, Map<KeyExtent,TServerInstance> assignments)
Assign tablets to tablet servers. This method is called whenever the master finds tablets that are unassigned.- Parameters:
current
- The current table-summary state of all the online tablet servers. Read-only. The TabletServerStatus for each server may be null if the tablet server has not yet responded to a recent request for status.unassigned
- A map from unassigned tablet to the last known tablet server. Read-only.assignments
- A map from tablet to assigned server. Write-only.
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balance
public abstract long balance(SortedMap<TServerInstance,TabletServerStatus> current, Set<KeyExtent> migrations, List<TabletMigration> migrationsOut)
Ask the balancer if any migrations are necessary. If the balancer is going to self-abort due to some environmental constraint (e.g. it requires some minimum number of tservers, or a maximum number of outstanding migrations), it should issue a log message to alert operators. The message should be at WARN normally and at ERROR if the balancer knows that the problem can not self correct. It should not issue these messages more than once a minute.- Parameters:
current
- The current table-summary state of all the online tablet servers. Read-only.migrations
- the current set of migrations. Read-only.migrationsOut
- new migrations to perform; should not contain tablets in the current set of migrations. Write-only.- Returns:
- the time, in milliseconds, to wait before re-balancing. This method will not be called when there are unassigned tablets.
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constraintNotMet
protected void constraintNotMet(TabletBalancer.BalancerProblem cause)
Warn that a Balancer can't work because of some external restriction. Will not call the provided logging handler more often than TIME_BETWEEN_BALANCER_WARNINGS
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resetBalancerErrors
protected void resetBalancerErrors()
Resets logging about problems meeting an external constraint on balancing.
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getOnlineTabletsForTable
public List<TabletStats> getOnlineTabletsForTable(TServerInstance tserver, String tableId) throws ThriftSecurityException, org.apache.thrift.TException
Fetch the tablets for the given table by asking the tablet server. Useful if your balance strategy needs details at the tablet level to decide what tablets to move.- Parameters:
tserver
- The tablet server to ask.tableId
- The table id- Returns:
- a list of tablet statistics
- Throws:
ThriftSecurityException
- tablet server disapproves of your internal System password.org.apache.thrift.TException
- any other problem
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checkMigrationSanity
public static List<TabletMigration> checkMigrationSanity(Set<TServerInstance> current, List<TabletMigration> migrations)
Utility to ensure that the migrations from balance() are consistent:- Tablet objects are not null
- Source and destination tablet servers are not null and current
- Returns:
- A list of TabletMigration object that passed sanity checks.
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