com.bigdata.rdf.sail.webapp.lbs

Interface AbstractHostLBSPolicy.InitParams

All Superinterfaces:

AbstractLBSPolicy.InitParams

All Known Subinterfaces:

CountersLBSPolicy.InitParams, GangliaLBSPolicy.InitParams

Enclosing class:

AbstractHostLBSPolicy

public static interface AbstractHostLBSPolicy.InitParams
extends AbstractLBSPolicy.InitParams

See Also:

for how these init-param values can be set in web.xml and via environment variables.

Field Summary

Fields

Modifier and Type	Field and Description
static String	DEFAULT_HOST_DISCOVERY_DELAY
static String	DEFAULT_HOST_DISCOVERY_INITIAL_DELAY
static String	DEFAULT_LOCAL_FORWARD_THRESHOLD
static String	HOST_DISCOVERY_DELAY The delay in milliseconds between scheduled tasks that update the in-memory snapshots of the performance metrics for the joined services (default "10000").
static String	HOST_DISCOVERY_INITIAL_DELAY The initial delay in milliseconds before the first scheduled task that updates the in-memory snapshots of the performance metrics for the joined services (default "10000").
static String	HOST_SCORING_RULE The IHostScoringRule that will be used to score the IHostMetrics.
static String	LOCAL_FORWARD_THRESHOLD Read requests are forwarded to the local service if the availability on that service is greater than or equal to the configured threshold when considering the normalized workload of the hosts.

Field Detail

HOST_SCORING_RULE

static final String HOST_SCORING_RULE

The IHostScoringRule that will be used to score the IHostMetrics. The IHostMetrics are obtained periodically from the from some source (specified by a concrete derived class).

The purpose of the IHostScoringRule is to compute a single workload number based on those host metrics. The resulting scores are then normalized. Load balancing decisions are made based on those normalized scores.

Note: The default policy is specific to the concrete instance of the outer class.

See Also:

Constant Field Values

LOCAL_FORWARD_THRESHOLD

static final String LOCAL_FORWARD_THRESHOLD

Read requests are forwarded to the local service if the availability on that service is greater than or equal to the configured threshold when considering the normalized workload of the hosts. The value must be in [0:1] and represents a normalized availability threshold for the hosts having services that are joined with the met quorum. This may be set to ONE (1.0) to disable this bias. The default is "1.0".

This bias is designed for use when an external round-robin policy is distributing the requests evenly across the services. In this case, the round-robin smooths out most of the workload and the IHALoadBalancerPolicy takes over only when there is a severe workload imbalance (as defined by the value of this parameter).

For example, if you have 3 hosts and they are equally available, then their normalized availability scores will be .3333. If the score for a given host is close to this normalized availability, then a local forward is a reasonable choice. TODO In fact, we could automatically compute and use a reasonable value based on the quorum size as ceil((1/replicationFactor)-.01). With this approach, the local forward bias is automatic. However, we still only want to do this if there is a round-robin over the services. Otherwise we will slam this host whenever its load gets below the threshold while not assigning any work to the other hosts until the next update of the HostTable.

See Also:

Constant Field Values

DEFAULT_LOCAL_FORWARD_THRESHOLD

static final String DEFAULT_LOCAL_FORWARD_THRESHOLD

See Also:

Constant Field Values

HOST_DISCOVERY_INITIAL_DELAY

static final String HOST_DISCOVERY_INITIAL_DELAY

The initial delay in milliseconds before the first scheduled task that updates the in-memory snapshots of the performance metrics for the joined services (default "10000").

See Also:

Constant Field Values

DEFAULT_HOST_DISCOVERY_INITIAL_DELAY

static final String DEFAULT_HOST_DISCOVERY_INITIAL_DELAY

See Also:

Constant Field Values

HOST_DISCOVERY_DELAY

static final String HOST_DISCOVERY_DELAY

The delay in milliseconds between scheduled tasks that update the in-memory snapshots of the performance metrics for the joined services (default "10000").

See Also:

Constant Field Values

DEFAULT_HOST_DISCOVERY_DELAY

static final String DEFAULT_HOST_DISCOVERY_DELAY

See Also:

Constant Field Values