Java ReadPreference.primary方法代碼示例

import com.mongodb.ReadPreference; //導入方法依賴的package包/類
/**
 * Prepares {@link ReadPreference} from given {@link ReadPreferenceEnum}
 *
 * @param readPreferenceEnum    Read preference enum value provided in config
 * @return  Read preference for mongo client options
 */
public static ReadPreference readPreference(ReadPreferenceEnum readPreferenceEnum) {
    switch (readPreferenceEnum) {
        case NEAREST:
            return ReadPreference.nearest();

        case PRIMARY:
            return ReadPreference.primary();

        case SECONDARY:
            return ReadPreference.secondary();

        case PRIMARY_PREFERRED:
            return ReadPreference.primaryPreferred();

        case SECONDARY_PREFERRED:
            return ReadPreference.secondaryPreferred();

        default:
            return null;
    }
}
 

import com.mongodb.ReadPreference; //導入方法依賴的package包/類
private MongoBlob getBlob(String id, long lastMod) {
    DBObject query = getBlobQuery(id, lastMod);

    // try the secondary first
    // TODO add a configuration option for whether to try reading from secondary
    ReadPreference pref = ReadPreference.secondaryPreferred();
    DBObject fields = new BasicDBObject();
    fields.put(MongoBlob.KEY_DATA, 1);
    MongoBlob blob = (MongoBlob) getBlobCollection().findOne(query, fields, pref);
    if (blob == null) {
        // not found in the secondary: try the primary
        pref = ReadPreference.primary();
        blob = (MongoBlob) getBlobCollection().findOne(query, fields, pref);
    }
    return blob;
}
 

import com.mongodb.ReadPreference; //導入方法依賴的package包/類
<T extends Document> ReadPreference getMongoReadPreference(Collection<T> collection,
                                                           String parentId,
                                                           DocumentReadPreference preference) {
    switch(preference){
        case PRIMARY:
            return ReadPreference.primary();
        case PREFER_PRIMARY :
            return ReadPreference.primaryPreferred();
        case PREFER_SECONDARY :
            return getConfiguredReadPreference(collection);
        case PREFER_SECONDARY_IF_OLD_ENOUGH:
            if(collection != Collection.NODES){
                return ReadPreference.primary();
            }

            //Default to primary preferred such that in case primary is being elected
            //we can still read from secondary
            //TODO REVIEW Would that be safe
            ReadPreference readPreference = ReadPreference.primaryPreferred();
            if (parentId != null) {
                long replicationSafeLimit = getTime() - maxReplicationLagMillis;
                NodeDocument cachedDoc = (NodeDocument) getIfCached(collection, parentId);
                if (cachedDoc != null && !cachedDoc.hasBeenModifiedSince(replicationSafeLimit)) {

                    //If parent has been modified loooong time back then there children
                    //would also have not be modified. In that case we can read from secondary
                    readPreference = getConfiguredReadPreference(collection);
                }
            }
            return readPreference;
        default:
            throw new IllegalArgumentException("Unsupported usage " + preference);
    }
}
 

import com.mongodb.ReadPreference; //導入方法依賴的package包/類
public static ReadPreference parse(String value) {
    value = value.trim();
    int paren = value.indexOf('(');
    String pref;
    List<TagSet> tags;
    if (paren != -1) {
        pref = value.substring(0, paren).trim();
        String argsStr = value.substring(paren + 1).trim();
        if (!argsStr.endsWith(")")) {
            throw new InvalidReadPreference(value);
        }
        tags = parseArgs(argsStr.substring(0, argsStr.length() - 1));
    } else {
        pref = value;
        tags = null;
    }
    switch (pref) {
        case READ_PREFERENCE_NEAREST:
            if (tags == null) {
                return ReadPreference.nearest();
            } else {
                return ReadPreference.nearest(tags);
            }
        case READ_PREFERENCE_PRIMARY:
            return ReadPreference.primary();
        case READ_PREFERENCE_PRIMARY_PREFERRED:
            if (tags == null) {
                return ReadPreference.primaryPreferred();
            } else {
                return ReadPreference.primaryPreferred(tags);
            }
        case READ_PREFERENCE_SECONDARY:
            if (tags == null) {
                return ReadPreference.secondary();
            } else {
                return ReadPreference.secondary(tags);
            }
        case READ_PREFERENCE_SECONDARY_PREFERRED:
            if (tags == null) {
                return ReadPreference.secondaryPreferred();
            } else {
                return ReadPreference.secondaryPreferred(tags);
            }
        default:
            throw new InvalidReadPreference(value);
    }
}
 

import com.mongodb.ReadPreference; //導入方法依賴的package包/類
ReadPreference getTaggableReadPreference()
  {
      ReadPreference readPref = getQueryReadPreference();
      if( readPref == ReadPreference.primary() )
          return readPref;    // primary read preference mode does not apply tags
      
      DBObject tagObjects = getReadPreferenceTagsAsParsedObject();
      
      if( tagObjects == null )
          return readPref;    // no tags in read preference

List<TagSet> tagsList = new ArrayList<TagSet>( );
if ( tagObjects instanceof BasicDBList )
{
	BasicDBList tagObjectList = (BasicDBList) tagObjects;
	for ( Object obj : tagObjectList )
	{
		if ( obj instanceof DBObject )
		{
			tagsList.add( toTags( (DBObject) obj ) );
		}
		else
		{ // ignore elements that are not DBObject
			logInvalidTagValue( obj );
		}
	}
}
else
{
	tagsList.add( toTags( tagObjects ) );
}
if ( tagsList.size( ) == 0 )
{
	return readPref;
}
      
      try
      {
          return ReadPreference.valueOf( readPref.getName( ), tagsList );
      }
      catch( RuntimeException ex )
      {
          // log and ignore tags
          getLogger().info( ex.getLocalizedMessage() );
      }
      return readPref;
  }