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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cassandra.locator;
import java.io.IOException;
import java.util.Set;
import com.google.common.annotations.VisibleForTesting;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.utils.Pair;
/**
* A snitch that assumes an EC2 region is a DC and an EC2 availability_zone
* is a rack. This information is available in the config for the node.
* Since CASSANDRA-16555, it is possible to choose version of AWS IMDS.
*
* By default, since CASSANDRA-16555, IMDSv2 is used.
*
* The version of IMDS is driven by property {@link Ec2MetadataServiceConnector#EC2_METADATA_TYPE_PROPERTY} and
* can be of value either 'v1' or 'v2'.
*
* It is possible to specify custom URL of IMDS by {@link Ec2MetadataServiceConnector#EC2_METADATA_URL_PROPERTY}.
* A user is not meant to change this under normal circumstances, it is suitable for testing only.
*
* IMDSv2 is secured by a token which needs to be fetched from IDMSv2 first, and it has to be passed in a header
* for the actual queries to IDMSv2. Ec2Snitch is doing this automatically. The only configuration parameter exposed
* to a user is {@link Ec2MetadataServiceConnector.V2Connector#AWS_EC2_METADATA_TOKEN_TTL_SECONDS_HEADER_PROPERTY}
* which is by default set to {@link Ec2MetadataServiceConnector.V2Connector#MAX_TOKEN_TIME_IN_SECONDS}. TTL has
* to be an integer from the range [30, 21600].
*/
public class Ec2Snitch extends AbstractCloudMetadataServiceSnitch
{
private static final String SNITCH_PROP_NAMING_SCHEME = "ec2_naming_scheme";
static final String EC2_NAMING_LEGACY = "legacy";
private static final String EC2_NAMING_STANDARD = "standard";
@VisibleForTesting
public static final String ZONE_NAME_QUERY = "/latest/meta-data/placement/availability-zone";
private final boolean usingLegacyNaming;
public Ec2Snitch() throws IOException, ConfigurationException
{
this(new SnitchProperties());
}
public Ec2Snitch(SnitchProperties props) throws IOException, ConfigurationException
{
this(Ec2MetadataServiceConnector.create(props));
}
Ec2Snitch(AbstractCloudMetadataServiceConnector connector) throws IOException
{
super(connector, getDcAndRack(connector));
usingLegacyNaming = isUsingLegacyNaming(connector.getProperties());
}
private static Pair getDcAndRack(AbstractCloudMetadataServiceConnector connector) throws IOException
{
String az = connector.apiCall(ZONE_NAME_QUERY);
// if using the full naming scheme, region name is created by removing letters from the
// end of the availability zone and zone is the full zone name
boolean usingLegacyNaming = isUsingLegacyNaming(connector.getProperties());
String region;
String localDc;
String localRack;
if (usingLegacyNaming)
{
// Split "us-east-1a" or "asia-1a" into "us-east"/"1a" and "asia"/"1a".
String[] splits = az.split("-");
localRack = splits[splits.length - 1];
// hack for CASSANDRA-4026
region = az.substring(0, az.length() - 1);
if (region.endsWith("1"))
region = az.substring(0, az.length() - 3);
}
else
{
// grab the region name, which is embedded in the availability zone name.
// thus an AZ of "us-east-1a" yields the region name "us-east-1"
region = az.replaceFirst("[a-z]+$","");
localRack = az;
}
localDc = region.concat(connector.getProperties().getDcSuffix());
return Pair.create(localDc, localRack);
}
private static boolean isUsingLegacyNaming(SnitchProperties props)
{
return props.get(SNITCH_PROP_NAMING_SCHEME, EC2_NAMING_STANDARD).equalsIgnoreCase(EC2_NAMING_LEGACY);
}
@Override
public boolean validate(Set datacenters, Set racks)
{
return validate(datacenters, racks, usingLegacyNaming);
}
@VisibleForTesting
static boolean validate(Set datacenters, Set racks, boolean usingLegacyNaming)
{
boolean valid = true;
for (String dc : datacenters)
{
// predicated on the late-2017 AWS naming 'convention' that all region names end with a digit.
// Unfortunately, life isn't that simple. Since we allow custom datacenter suffixes (CASSANDRA-5155),
// an operator could conceiveably make the suffix "a", and thus create a region name that looks just like
// one of the region's availability zones. (for example, "us-east-1a").
// Further, we can't make any assumptions of what that suffix might be by looking at this node's
// datacenterSuffix as conceivably their could be many different suffixes in play for a given region.
//
// It is impossible to distinguish standard and legacy names for datacenters in some cases
// as the format didn't change for some regions (us-west-2 for example).
// We can still identify as legacy the dc names without a number as a suffix like us-east"
boolean dcUsesLegacyFormat = dc.matches("^[a-z]+-[a-z]+$");
if (dcUsesLegacyFormat && !usingLegacyNaming)
{
valid = false;
break;
}
}
for (String rack : racks)
{
// predicated on late-2017 AWS naming 'convention' that AZs do not have a digit as the first char -
// we had that in our legacy AZ (rack) names. Thus we test to see if the rack is in the legacy format.
//
// NOTE: the allowed custom suffix only applies to datacenter (region) names, not availability zones.
boolean rackUsesLegacyFormat = rack.matches("[\\d][a-z]");
if (rackUsesLegacyFormat != usingLegacyNaming)
{
valid = false;
break;
}
}
if (!valid)
{
logger.error("This ec2-enabled snitch appears to be using the {} naming scheme for regions, " +
"but existing nodes in cluster are using the opposite: region(s) = {}, availability zone(s) = {}. " +
"Please check the {} property in the {} configuration file for more details.",
usingLegacyNaming ? "legacy" : "standard", datacenters, racks,
SNITCH_PROP_NAMING_SCHEME, SnitchProperties.RACKDC_PROPERTY_FILENAME);
}
return valid;
}
}