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package org.dcache.resilience.util;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.Sets;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Set;
import diskCacheV111.vehicles.PoolManagerPoolInformation;
import org.dcache.pool.migration.PoolSelectionStrategy;
import org.dcache.resilience.data.FileOperation;
import org.dcache.resilience.data.PoolInfoMap;
/**
* <p>Manages the selection of locations from the underlying pool map
* information. Encapsulates the logic involved in extracting
* sets of valid readable or writable pools in connection with
* the verify, copy and remove phases of the file operation.</p>
*/
public final class LocationSelector {
private static final Logger LOGGER = LoggerFactory.getLogger(
LocationSelector.class);
private PoolInfoMap poolInfoMap;
private PoolSelectionStrategy poolSelectionStrategy;
public String selectCopySource(FileOperation operation,
Set<String> locations) throws LocationSelectionException {
LOGGER.trace("selecting source for {}", operation);
if (locations.size() == 1) {
if (!operation.getTried().isEmpty()) {
throw new LocationSelectionException(String.format("Cannot find "
+ "a new source because only one exists: %s.",
locations));
}
return locations.iterator().next();
}
return selectSource(locations, operation.getTried());
}
public String selectCopyTarget(FileOperation operation, Integer gindex,
Collection<String> locations, Collection<String> tags)
throws LocationSelectionException {
LOGGER.trace("selecting target for {}", operation);
return selectCopyTarget(gindex, locations, operation.getTried(), tags);
}
public String selectRemoveTarget(FileOperation operation,
Collection<String> locations, Collection<String> tags)
throws LocationSelectionException {
LOGGER.trace("selecting target for {}", operation);
if (locations.size() == 1) {
String message = String.format("Remove replica was selected, but "
+ "the principal pool %s is the "
+ "only location; this is a bug.",
locations.iterator().next());
throw new LocationSelectionException(message);
}
return selectRemoveTarget(locations, tags);
}
public void setPoolInfoMap(PoolInfoMap poolInfoMap) {
this.poolInfoMap = poolInfoMap;
}
public void setPoolSelectionStrategy(PoolSelectionStrategy poolSelectionStrategy) {
this.poolSelectionStrategy = poolSelectionStrategy;
}
private Set<String> getEligibleCopyTargets(Integer gindex,
Collection<String> locations, Set<Integer> tried) {
Collection<Integer> pools = poolInfoMap.getPoolsOfGroup(gindex);
Set<Integer> writableMembers = poolInfoMap.getValidLocations(pools,
true);
Set<Integer> lindices = poolInfoMap.getPoolIndices(locations);
Set<Integer> valid = Sets.difference(writableMembers, lindices);
valid = Sets.difference(valid, tried);
return poolInfoMap.getPools(valid);
}
private Set<String> getEligibleRemoveTargets(Collection<String> locations) {
Collection<Integer> indices = poolInfoMap.getPoolIndices(locations);
indices = poolInfoMap.getValidLocations(indices, true);
return poolInfoMap.getPools(indices);
}
/**
* <p>Filters first the writable pools in the pool group which do
* not yet have a copy of this file, then applies any tag-induced
* partitioning on the basis of the tags of copies that already exist.
* From that list, it then chooses the pool using the
* configured poolSelectionStrategy.</p>
*/
@VisibleForTesting
String selectCopyTarget(Integer gindex,
Collection<String> locations, Set<Integer> tried,
Collection<String> oneCopyPer) throws LocationSelectionException {
/*
* Writable locations in the pool group without a copy of this file.
*/
Set<String> possible = getEligibleCopyTargets(gindex, locations, tried);
/*
* Filter by tag constraints.
*/
CopyLocationExtractor extractor = new CopyLocationExtractor(oneCopyPer,
poolInfoMap);
locations.stream().forEach(extractor::addSeenTagsFor);
Collection<String> candidates = extractor.getCandidateLocations(
possible);
if (candidates.isEmpty()) {
throw new LocationSelectionException(String.format("Cannot satisfy "
+ "copy request because there are no (further) "
+ "possible locations; candidates %s", candidates));
}
/*
* Get pool cost for the candidates, then select the one using
* the inject poolSelectionStrategy.
*/
List<PoolManagerPoolInformation> info = new ArrayList<>();
for (String c : candidates) {
/*
* throws InterruptedException
*/
info.add(poolInfoMap.getPoolManagerInfo(poolInfoMap.getPoolIndex(c)));
}
PoolManagerPoolInformation target = poolSelectionStrategy.select(info);
LOGGER.debug("Pool selection poolSelectionStrategy "
+ "selected {} as copy target.", target);
if (target == null) {
throw new LocationSelectionException(String.format("Cannot satisfy "
+ "copy request because the selection "
+ "algorithm returned no viable locations; "
+ "locations: %s; possible %s", locations, candidates));
}
return target.getName();
}
/**
* <p>Filters first the writable pools in the pool group which contain a
* copy of this file, then applies any tag-induced partitioning on
* the basis of the tags of copies that already exist to select a
* maximally constrained pool. If more than one pool has the same
* weight, one of them is chosen randomly.</p>
*/
@VisibleForTesting
String selectRemoveTarget(Collection<String> locations,
Collection<String> oneCopyPer) throws LocationSelectionException {
Set<String> possible = getEligibleRemoveTargets(locations);
RemoveLocationExtractor extractor = new RemoveLocationExtractor(
oneCopyPer, poolInfoMap);
List<String> maximallyConstrained = extractor.getCandidateLocations(
possible);
String target = RandomSelectionStrategy.SELECTOR.apply(maximallyConstrained);
if (target == null) {
throw new LocationSelectionException(String.format("Cannot satisfy "
+ "remove request because the selection algorithm "
+ "returned no viable locations: locations: %s; "
+ "possible: %s", locations, possible));
}
return target;
}
/**
* <p>Chooses a source randomly from among the readable locations which have
* not yet been tried.</p>
*/
@VisibleForTesting
String selectSource(Set<String> readable, Collection<Integer> tried)
throws LocationSelectionException {
Set<String> excluded = poolInfoMap.getPools(tried);
Set<String> possible = Sets.difference(readable, excluded);
if (possible.isEmpty()) {
throw new LocationSelectionException(String.format("Cannot find "
+ "a readable source because there "
+ "are no other viable locations; "
+ "readable: %s; tried: %s", readable, excluded));
}
return RandomSelectionStrategy.SELECTOR.apply(possible);
}
}