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From ivakegg <...@git.apache.org>
Subject [GitHub] accumulo pull request #253: ACCUMULO-4086 Improve volume chooser fallback
Date Thu, 27 Jul 2017 21:42:15 GMT
Github user ivakegg commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/253#discussion_r129966848
  
    --- Diff: server/base/src/main/java/org/apache/accumulo/server/fs/PreferredVolumeChooser.java
---
    @@ -39,73 +40,139 @@
     
     /**
      * A {@link RandomVolumeChooser} that limits its choices from a given set of options
to the subset of those options preferred for a particular table. Defaults
    - * to selecting from all of the options presented. Can be customized via the table property
{@value #PREFERRED_VOLUMES_CUSTOM_KEY}, which should contain a comma
    + * to selecting from all of the options presented. Can be customized via the table property
table.custom.preferredVolumes, which should contain a comma
      * separated list of {@link Volume} URIs. Note that both the property name and the format
of its value are specific to this particular implementation.
      */
     public class PreferredVolumeChooser extends RandomVolumeChooser {
       private static final Logger log = LoggerFactory.getLogger(PreferredVolumeChooser.class);
     
    -  /**
    -   * This should match {@link Property#TABLE_ARBITRARY_PROP_PREFIX}
    -   */
    -  public static final String PREFERRED_VOLUMES_CUSTOM_KEY = "table.custom.preferredVolumes";
    -  // TODO ACCUMULO-3417 replace this with the ability to retrieve by String key.
    -  private static final Predicate<String> PREFERRED_VOLUMES_FILTER = key -> PREFERRED_VOLUMES_CUSTOM_KEY.equals(key);
    +  public static final String TABLE_PREFERRED_VOLUMES = Property.TABLE_ARBITRARY_PROP_PREFIX.getKey()
+ "preferred.volumes";
    +
    +  public static final String SCOPED_PREFERRED_VOLUMES(String scope) {
    +    return Property.GENERAL_ARBITRARY_PROP_PREFIX.getKey() + scope + ".preferred.volumes";
    +  }
    +
    +  public static final String DEFAULT_SCOPED_PREFERRED_VOLUMES = SCOPED_PREFERRED_VOLUMES("scoped");
     
       @SuppressWarnings("unchecked")
       private final Map<String,Set<String>> parsedPreferredVolumes = Collections.synchronizedMap(new
LRUMap(1000));
       // TODO has to be lazily initialized currently because of the reliance on HdfsZooInstance.
see ACCUMULO-3411
       private volatile ServerConfigurationFactory serverConfs;
     
       @Override
    -  public String choose(VolumeChooserEnvironment env, String[] options) {
    -    if (!env.hasTableId())
    +  public String choose(VolumeChooserEnvironment env, String[] options) throws AccumuloException
{
    +    if (!env.hasTableId() && !env.hasScope()) {
    +      // this should only happen during initialize
    +      log.warn("No table id or scope, so it's not possible to determine preferred volumes.
 Using all volumes.");
           return super.choose(env, options);
    +    }
     
    -    // Get the current table's properties, and find the preferred volumes property
    -    // This local variable is an intentional component of the single-check idiom.
    -    ServerConfigurationFactory localConf = serverConfs;
    -    if (localConf == null) {
    -      // If we're under contention when first getting here we'll throw away some initializations.
    -      localConf = new ServerConfigurationFactory(HdfsZooInstance.getInstance());
    -      serverConfs = localConf;
    +    // get the volumes property
    +    ServerConfigurationFactory localConf = loadConf();
    +    List<String> volumes;
    +    if (env.hasTableId()) {
    +      volumes = getPreferredVolumesForTable(env, localConf, options);
    +      // localConf.getTableConfiguration(env.getTableId()).get(PREFERRED_VOLUMES_CUSTOM_KEY);
    +    } else { // env.hasScope()
    +      volumes = getPreferredVolumesForNonTable(env, localConf, options);
    +      // localConf.getSystemConfiguration().get(PREFERRED_VOLUMES_SCOPED_KEY(env.getScope()));
         }
    -    TableConfiguration tableConf = localConf.getTableConfiguration(env.getTableId());
    -    final Map<String,String> props = new HashMap<>();
    -    tableConf.getProperties(props, PREFERRED_VOLUMES_FILTER);
    -    if (props.isEmpty()) {
    -      log.warn("No preferred volumes specified. Defaulting to randomly choosing from
instance volumes");
    -      return super.choose(env, options);
    +
    +    // Randomly choose the volume from the preferred volumes
    +    String choice = super.choose(env, volumes.toArray(EMPTY_STRING_ARRAY));
    +    if (log.isTraceEnabled()) {
    +      log.trace("Choice = " + choice);
         }
    -    String volumes = props.get(PREFERRED_VOLUMES_CUSTOM_KEY);
    +    return choice;
    +  }
     
    +  private List<String> getPreferredVolumesForTable(VolumeChooserEnvironment env,
ServerConfigurationFactory localConf, String[] options)
    +      throws AccumuloException {
         if (log.isTraceEnabled()) {
    -      log.trace("In custom chooser");
    -      log.trace("Volumes: " + volumes);
    -      log.trace("TableID: " + env.getTableId());
    +      log.trace("Looking up property " + TABLE_PREFERRED_VOLUMES + " for Table id: "
+ env.getTableId());
         }
    -    // If the preferred volumes property was specified, split the returned string by
the comma and add use it to filter the given options.
    -    Set<String> preferred = parsedPreferredVolumes.get(volumes);
    -    if (preferred == null) {
    -      preferred = new HashSet<>(Arrays.asList(StringUtils.split(volumes, ',')));
    -      parsedPreferredVolumes.put(volumes, preferred);
    +    final TableConfiguration tableConf = localConf.getTableConfiguration(env.getTableId());
    +    String volumes = tableConf.get(TABLE_PREFERRED_VOLUMES);
    +
    +    return getFilteredOptions(TABLE_PREFERRED_VOLUMES, volumes, options);
    +  }
    +
    +  private List<String> getPreferredVolumesForNonTable(VolumeChooserEnvironment
env, ServerConfigurationFactory localConf, String[] options)
    +      throws AccumuloException {
    +    String property = SCOPED_PREFERRED_VOLUMES(env.getScope());
    +
    +    if (log.isTraceEnabled()) {
    +      log.trace("Looking up property: " + property);
    +    }
    +
    +    AccumuloConfiguration systemConfiguration = localConf.getSystemConfiguration();
    +    String volumes = systemConfiguration.get(property);
    +
    +    // only if the custom property is not set to we fallback to the default scoped preferred
volumes
    +    if (null == volumes) {
    +      log.debug("Property not found: " + property + " using " + DEFAULT_SCOPED_PREFERRED_VOLUMES);
    +      property = DEFAULT_SCOPED_PREFERRED_VOLUMES;
    +      volumes = systemConfiguration.get(DEFAULT_SCOPED_PREFERRED_VOLUMES);
    --- End diff --
    
    If we want this to work like the table preferred volume where you can set a default in
the system configuration, the we would need to have scoped configurations like we have table
specific configurations.  I am not sure how to handle this in the same way.  We could get
rid of the default scope property but then we would be requiring users to set both the "logger"
and "init" scoped properties which seems wrong.  Realistically users will only set the default
one until we actually come up with other scopes.


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