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// Copyright (c) Keith D Gregory
//
// Licensed 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 com.kdgregory.logging.aws.common;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
import com.amazonaws.util.EC2MetadataUtils;
import com.kdgregory.logging.aws.internal.Utils;
/**
* Handles the standard substitution variables. You create a new instance whenever
* performing substitutions; instances are not thread-safe.
*/
public class Substitutions
{
// we precompute all substitution values and cache them for future use; we don't
// expect to be called in any sort of tight loop
private String date;
private String timestamp;
private String hourlyTimestamp;
private String startupTimestamp;
private String pid;
private String hostname;
private String sequence;
public Substitutions(Date currentDate, int sequence)
{
RuntimeMXBean runtimeMx = ManagementFactory.getRuntimeMXBean();
String vmName = runtimeMx.getName();
pid = (vmName.indexOf('@') > 0)
? vmName.substring(0, vmName.indexOf('@'))
: "unknown";
hostname = (vmName.indexOf('@') > 0)
? vmName.substring(vmName.indexOf('@') + 1, vmName.length())
: "unknown";
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMdd");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
date = dateFormat.format(currentDate);
SimpleDateFormat timestampFormat = new SimpleDateFormat("yyyyMMddHHmmss");
timestampFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
timestamp = timestampFormat.format(currentDate);
hourlyTimestamp = timestamp.substring(0, 10) + "0000"; // yeah, it's a hack
startupTimestamp = timestampFormat.format(new Date(runtimeMx.getStartTime()));
this.sequence = String.valueOf(sequence);
}
/**
* Applies all substitutions. This is not particularly performant, but it
* won't be called frequently. If passed null returns it.
*/
public String perform(String input)
{
if (input == null)
return null;
String output = input;
do
{
input = output;
output = substitute("{date}", date,
substitute("{timestamp}", timestamp,
substitute("{hourlyTimestamp}", hourlyTimestamp,
substitute("{startupTimestamp}", startupTimestamp,
substitute("{pid}", pid,
substitute("{hostname}", hostname,
substitute("{sequence}", sequence,
substituteAwsAccountId(
substituteEC2InstanceId(
substituteEC2Region(
substituteSysprop(
substituteEnvar(
input))))))))))));
}
while (! output.equals(input));
return output;
}
/**
* Performs simple subsitutions, where the tag fully describes the substitution.
*/
private String substitute(String tag, String value, String input)
{
if (input == null)
return "";
if (value == null)
return input;
int index = input.indexOf(tag);
if (index < 0)
return input;
return input.substring(0, index) + value + input.substring(index + tag.length(), input.length());
}
/**
* Substitutes the AWS account ID. This makes a call to AWS.
*/
private String substituteAwsAccountId(String input)
{
String tag = "{aws:accountId}";
int index = input.indexOf(tag);
if (index < 0)
return input;
String accountId = Utils.retrieveAWSAccountId();
return (accountId != null)
? substitute(tag, accountId, input)
: input;
}
/**
* Substitutes the EC2 instance ID. If not running on EC2 we won't be able
* to retrieve instance metadata (and it takes a long time to learn that,
* waiting for a timeout) so this isn't handled as a "simple" substitution.
*/
private String substituteEC2InstanceId(String input)
{
String tag = "{ec2:instanceId}";
int index = input.indexOf(tag);
if (index < 0)
{
tag = "{instanceId}";
index = input.indexOf(tag);
if (index < 0)
return input;
}
String instanceId = EC2MetadataUtils.getInstanceId();
if ((instanceId == null) || (instanceId.length() == 0))
return input;
return substitute(tag, instanceId, input);
}
/**
* Substitutes the EC2 regsion. If not running on EC2 we won't be able
* to retrieve instance metadata (and it takes a long time to learn that,
* waiting for a timeout) so this isn't handled as a "simple" substitution.
*/
private String substituteEC2Region(String input)
{
String tag = "{ec2:region}";
int index = input.indexOf(tag);
if (index < 0)
return input;
String region = EC2MetadataUtils.getEC2InstanceRegion();
if ((region == null) || (region.length() == 0))
return input;
return substitute(tag, region, input);
}
/**
* Substitutes system properties, where the property depends on the tag.
*/
private String substituteSysprop(String input)
{
String propName = extractPropName("sysprop", input);
if (propName == null)
return input;
return substitute("{" + "sysprop" + ":" + propName + "}", System.getProperty(propName), input);
}
/**
* Substitutes environment variables, where the variable depends on the tag.
*/
private String substituteEnvar(String input)
{
String propName = extractPropName("env", input);
if (propName == null)
return input;
return substitute("{" + "env" + ":" + propName + "}", System.getenv(propName), input);
}
/**
* Extracts the property name for a colon-delimited tag, null if unable to
* do so.
*/
private String extractPropName(String tagType, String input)
{
String tagForm = "{" + tagType + ":";
int index1 = input.indexOf(tagForm);
if (index1 < 0)
return null;
int index2 = input.indexOf("}", index1);
if (index2 < 0)
return null;
return input.substring(index1 + tagForm.length(), index2);
}
}
