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Simplified API for accessing JDBC data sources.
/*
* Copyright 2014 The Board of Trustees of The Leland Stanford Junior University.
*
* 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.github.susom.database;
import java.util.ArrayList;
import java.util.List;
/**
* This class provides explicit instrumentation functionality.
*
* @author garricko
*/
public class Metric {
private final boolean enabled;
private boolean done;
private long startNanos;
private long lastCheckpointNanos;
private List checkpoints;
private static class Checkpoint {
String description;
long durationNanos;
private final Object[] args;
Checkpoint(String description, long durationNanos, Object... args) {
this.description = description;
this.durationNanos = durationNanos;
this.args = args;
}
}
/**
* Create a metric tracking object and start the nanosecond timer. Times
* are obtained using {@code System.nanoTime()}. The canonical way to use
* this looks something like this:
*
*
*
* Metric metric = new Metric(log.isDebugEnabled);
* ...
* metric.checkpoint("received");
* ...
* metric.checkpoint("processed");
* ...
* metric.done("sent");
* ...
* if (log.isDebugEnabled()) {
* log.debug("Processed: " + metric.getMessage());
* }
*
*
* @param enabled {@code true} if timings will be taken, {@code false} to
* optimize out the time tracking
*/
public Metric(boolean enabled) {
this.enabled = enabled;
if (enabled) {
checkpoints = new ArrayList<>();
startNanos = System.nanoTime();
lastCheckpointNanos = startNanos;
}
}
/**
* Find out how many milliseconds have elapsed since this timer was started.
*
* @return the number of milliseconds elapsed, or -1 if {@code false} was
* passed in the constructor
*/
public long elapsedMillis() {
if (!enabled) {
return -1;
}
return (System.nanoTime() - startNanos) / 1000000;
}
/**
* Find out how many nanoseconds have elapsed since this timer was started.
*
* @return the number of nanoseconds elapsed, or -1 if {@code false} was
* passed in the constructor
*/
public long elapsedNanos() {
if (!enabled) {
return -1;
}
return (System.nanoTime() - startNanos);
}
/**
* Set a mark for timing. It is strongly recommended to use a short,
* simple alphanumeric description. For example, "sent" or "didThat".
* With this version you can provide additional arguments, such as
* byte counts, which will be appended comma-separated within brackets.
* For example, {@code checkpoint("sent", 25, 3)} will result in a
* description "sent[25,3]". The string evaluation and concatenation is
* lazy, and won't be done if this metric is disabled.
*
* @param description a label for this mark; may not be null; spaces
* and tabs will be converted to underscores
* @param args additional information to append to the description; will
* print "null" if null; evaluated with String.valueOf() lazily
* and sanitized of most non-alphanumeric characters
*/
public void checkpoint(String description, Object... args) {
if (enabled) {
long currentCheckpointNanos = System.nanoTime();
checkpoints.add(new Checkpoint(noTabsOrSpaces(description), currentCheckpointNanos - lastCheckpointNanos, args));
lastCheckpointNanos = currentCheckpointNanos;
}
}
/**
* Set a final mark for timing and stop the timer. Once you call this
* method, subsequent calls have no effect.
*
* @param description a label for this mark; may not be null; spaces
* and tabs will be converted to underscores
* @return time in nanoseconds from the start of this metric, or -1
* if {@code false} was passed in the constructor
*/
public long done(String description, Object... args) {
checkpoint(description, args);
return done();
}
/**
* Indicate we are done (stop the timer). Once you call this
* method, subsequent calls have no effect.
*
* @return time in nanoseconds from the start of this metric, or -1
* if {@code false} was passed in the constructor
*/
public long done() {
if (enabled) {
if (!done) {
lastCheckpointNanos = System.nanoTime();
done = true;
}
return lastCheckpointNanos - startNanos;
}
return -1;
}
/**
* Construct and return a message based on the timing and checkpoints. This
* will look like "123.456ms(checkpoint1=100.228ms,checkpoint2=23.228ms)"
* without the quotes. There will be no spaces or tabs in the output.
*
* This will automatically call the done() method to stop the timer if
* you haven't already done so.
*
* @return a string with timing information, or {@code "metricsDisabled"}
* if {@code false} was passed in the constructor.
* @see #printMessage(StringBuilder)
*/
public String getMessage() {
if (enabled) {
StringBuilder buf = new StringBuilder();
printMessage(buf);
return buf.toString();
}
return "metricsDisabled";
}
/**
* Construct and print a message based on the timing and checkpoints. This
* will look like "123.456ms(checkpoint1=100.228ms,checkpoint2=23.228ms)"
* without the quotes. There will be no spaces or tabs in the output. A
* value of {@code "metricsDisabled"} will be printed if {@code false} was
* passed in the constructor.
*
* This will automatically call the done() method to stop the timer if
* you haven't already done so.
*
* @param buf the message will be printed to this builder
* @see #getMessage()
*/
public void printMessage(StringBuilder buf) {
if (enabled) {
done();
writeNanos(buf, lastCheckpointNanos - startNanos);
if (!checkpoints.isEmpty()) {
buf.append("(");
boolean first = true;
for (Checkpoint checkpoint : checkpoints) {
if (first) {
first = false;
} else {
buf.append(',');
}
buf.append(checkpoint.description);
if (checkpoint.args != null && checkpoint.args.length > 0) {
buf.append('[');
boolean firstArg = true;
for (Object o : checkpoint.args) {
if (firstArg) {
firstArg = false;
} else {
buf.append(',');
}
buf.append(sanitizeArg(String.valueOf(o)));
}
buf.append(']');
}
buf.append('=');
writeNanos(buf, checkpoint.durationNanos);
}
buf.append(')');
}
} else {
buf.append("metricsDisabled");
}
}
private void writeNanos(StringBuilder buf, long nanos) {
if (nanos < 0) {
buf.append("-");
nanos = -nanos;
}
String nanosStr = Long.toString(nanos);
if (nanosStr.length() > 6) {
buf.append(nanosStr.substring(0, nanosStr.length() - 6));
buf.append('.');
buf.append(nanosStr.substring(nanosStr.length() - 6, nanosStr.length() - 3));
} else {
buf.append("0.0000000".substring(0, 8 - Math.max(nanosStr.length(), 4)));
if (nanosStr.length() > 3) {
buf.append(nanosStr.substring(0, nanosStr.length() - 3));
}
}
buf.append("ms");
}
private String noTabsOrSpaces(String s) {
return s.replace(' ', '_').replace('\t', '_');
}
private String sanitizeArg(String s) {
return s.replaceAll("[^\\p{Alnum}_.\\-\\+]", "*");
}
}
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