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marschalldhoard
marschall
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dhoard
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Use bulk string writes for text formats (#1273)
Further optimize `TextFormatUtil#writeEscapedLabelValue`. We're seeing `TextFormatUtil#writeEscapedLabelValue` show up in our production traces due to the single `char` writes to `OutputStreamWriter`. We're using `OpenMetricsTextFormatWriter`. #1241 and #1248 should take care of most of these issues but there still remains some optimization potential left. `BufferedWriter#write(int)` has some minimal overhead in terms of locking. If we assume that rarely any characters need to be escaped and instead optimize to write as large of a part of the String as possible in one method call. Before --------- ``` Benchmark Mode Cnt Score Error Units TextFormatUtilBenchmark.openMetricsWriteToByteArray thrpt 25 438485.372 ± 4270.355 ops/s TextFormatUtilBenchmark.openMetricsWriteToNull thrpt 25 440105.281 ± 2891.572 ops/s TextFormatUtilBenchmark.prometheusWriteToByteArray thrpt 25 467213.001 ± 878.780 ops/s TextFormatUtilBenchmark.prometheusWriteToNull thrpt 25 472931.759 ± 976.028 ops/s ``` After ------- ``` Benchmark Mode Cnt Score Error Units TextFormatUtilBenchmark.openMetricsWriteToByteArray thrpt 25 462852.243 ± 5071.696 ops/s TextFormatUtilBenchmark.openMetricsWriteToNull thrpt 25 469910.681 ± 1670.430 ops/s TextFormatUtilBenchmark.prometheusWriteToByteArray thrpt 25 482362.506 ± 2051.684 ops/s TextFormatUtilBenchmark.prometheusWriteToNull thrpt 25 487707.557 ± 3344.881 ops/s ``` About a 5% to 6% gain for `OpenMetricsTextFormatWriter` and around 3% for `PrometheusTextFormatWriter`. Note that this benchmark is actually for `OpenMetricsTextFormatWriter` and `PrometheusTextFormatWriter` since `TextFormatUtil` is not public and can therefore not be benchmarked directly. The relative gains in `#writeEscapedLabelValue` are higher because the benchmark runs the full text format writers. I also added a test for `TextFormatUtil#writeEscapedLabelValue` since the code is now more complicated. --------- Signed-off-by: Philippe Marschall <[email protected]> Co-authored-by: Doug Hoard <[email protected]>
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‎benchmarks/pom.xml‎

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@@ -42,20 +42,13 @@
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<version>${jmh.version}</version>
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</dependency>
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<dependency>
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<groupId>org.openjdk.jmh</groupId>
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<artifactId>jmh-generator-annprocess</artifactId>
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<version>${jmh.version}</version>
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</dependency>
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<!--
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<dependency>
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<groupId>javax.annotation</groupId>
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<artifactId>javax.annotation-api</artifactId>
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<version>1.3.2</version>
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<groupId>io.prometheus</groupId>
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<artifactId>prometheus-metrics-core</artifactId>
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<version>${project.version}</version>
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</dependency>
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-->
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<dependency>
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<groupId>io.prometheus</groupId>
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<artifactId>prometheus-metrics-core</artifactId>
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<artifactId>prometheus-metrics-exposition-textformats</artifactId>
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<version>${project.version}</version>
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</dependency>
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<dependency>

‎benchmarks/src/main/java/io/prometheus/metrics/benchmarks/TextFormatUtilBenchmark.java‎

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package io.prometheus.metrics.benchmarks;
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import io.prometheus.metrics.expositionformats.ExpositionFormatWriter;
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import io.prometheus.metrics.expositionformats.OpenMetricsTextFormatWriter;
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import io.prometheus.metrics.expositionformats.PrometheusTextFormatWriter;
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import io.prometheus.metrics.model.snapshots.GaugeSnapshot;
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import io.prometheus.metrics.model.snapshots.GaugeSnapshot.GaugeDataPointSnapshot;
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import io.prometheus.metrics.model.snapshots.Labels;
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import io.prometheus.metrics.model.snapshots.MetricSnapshot;
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import io.prometheus.metrics.model.snapshots.MetricSnapshots;
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import io.prometheus.metrics.model.snapshots.SummarySnapshot;
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import io.prometheus.metrics.model.snapshots.SummarySnapshot.SummaryDataPointSnapshot;
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import io.prometheus.metrics.model.snapshots.Unit;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.io.OutputStream;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.State;
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public class TextFormatUtilBenchmark {
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private static final MetricSnapshots SNAPSHOTS;
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static {
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MetricSnapshot gaugeSnapshot =
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GaugeSnapshot.builder()
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.name("gauge_snapshot_name")
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.dataPoint(
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GaugeDataPointSnapshot.builder()
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.labels(Labels.of("name", "value"))
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.scrapeTimestampMillis(1000L)
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.value(123.45d)
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.build())
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.build();
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MetricSnapshot summaryDataPointSnapshot =
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SummarySnapshot.builder()
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.name("summary_snapshot_name_bytes")
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.dataPoint(
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SummaryDataPointSnapshot.builder()
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.count(5)
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.labels(Labels.of("name", "value"))
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.sum(123456d)
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.build())
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.unit(Unit.BYTES)
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.build();
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SNAPSHOTS = MetricSnapshots.of(gaugeSnapshot, summaryDataPointSnapshot);
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}
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private static final ExpositionFormatWriter OPEN_METRICS_TEXT_FORMAT_WRITER =
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new OpenMetricsTextFormatWriter(false, false);
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private static final ExpositionFormatWriter PROMETHEUS_TEXT_FORMAT_WRITER =
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new PrometheusTextFormatWriter(false);
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@State(Scope.Benchmark)
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public static class WriterState {
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final ByteArrayOutputStream byteArrayOutputStream;
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public WriterState() {
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this.byteArrayOutputStream = new ByteArrayOutputStream();
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}
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}
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@Benchmark
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public OutputStream openMetricsWriteToByteArray(WriterState writerState) throws IOException {
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// avoid growing the array
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ByteArrayOutputStream byteArrayOutputStream = writerState.byteArrayOutputStream;
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byteArrayOutputStream.reset();
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OPEN_METRICS_TEXT_FORMAT_WRITER.write(byteArrayOutputStream, SNAPSHOTS);
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return byteArrayOutputStream;
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}
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@Benchmark
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public OutputStream openMetricsWriteToNull() throws IOException {
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OutputStream nullOutputStream = NullOutputStream.INSTANCE;
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OPEN_METRICS_TEXT_FORMAT_WRITER.write(nullOutputStream, SNAPSHOTS);
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return nullOutputStream;
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}
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@Benchmark
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public OutputStream prometheusWriteToByteArray(WriterState writerState) throws IOException {
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// avoid growing the array
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ByteArrayOutputStream byteArrayOutputStream = writerState.byteArrayOutputStream;
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byteArrayOutputStream.reset();
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PROMETHEUS_TEXT_FORMAT_WRITER.write(byteArrayOutputStream, SNAPSHOTS);
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return byteArrayOutputStream;
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}
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@Benchmark
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public OutputStream prometheusWriteToNull() throws IOException {
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OutputStream nullOutputStream = NullOutputStream.INSTANCE;
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PROMETHEUS_TEXT_FORMAT_WRITER.write(nullOutputStream, SNAPSHOTS);
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return nullOutputStream;
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}
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static final class NullOutputStream extends OutputStream {
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static final OutputStream INSTANCE = new NullOutputStream();
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private NullOutputStream() {
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super();
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}
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@Override
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public void write(int b) {}
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@Override
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public void write(byte[] b) {}
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@Override
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public void write(byte[] b, int off, int len) {}
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@Override
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public void flush() {}
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@Override
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public void close() {}
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}
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}

‎prometheus-metrics-exposition-textformats/src/main/java/io/prometheus/metrics/expositionformats/TextFormatUtil.java‎

Lines changed: 39 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -35,21 +35,53 @@ static void writeTimestamp(Writer writer, long timestampMs) throws IOException {
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}
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static void writeEscapedLabelValue(Writer writer, String s) throws IOException {
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for (int i = 0; i < s.length(); i++) {
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char c = s.charAt(i);
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// optimize for the common case where no escaping is needed
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int start = 0;
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// #indexOf is a vectorized intrinsic
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int backslashIndex = s.indexOf('\\', start);
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int quoteIndex = s.indexOf('\"', start);
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int newlineIndex = s.indexOf('\n', start);
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int allEscapesIndex = backslashIndex & quoteIndex & newlineIndex;
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while (allEscapesIndex != -1) {
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int escapeStart = Integer.MAX_VALUE;
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if (backslashIndex != -1) {
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escapeStart = backslashIndex;
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}
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if (quoteIndex != -1) {
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escapeStart = Math.min(escapeStart, quoteIndex);
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}
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if (newlineIndex != -1) {
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escapeStart = Math.min(escapeStart, newlineIndex);
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}
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// bulk write up to the first character that needs to be escaped
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if (escapeStart > start) {
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writer.write(s, start, escapeStart - start);
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}
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char c = s.charAt(escapeStart);
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start = escapeStart + 1;
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switch (c) {
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case '\\':
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writer.append("\\\\");
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writer.write("\\\\");
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backslashIndex = s.indexOf('\\', start);
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break;
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case '\"':
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writer.append("\\\"");
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writer.write("\\\"");
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quoteIndex = s.indexOf('\"', start);
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break;
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case '\n':
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writer.append("\\n");
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writer.write("\\n");
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newlineIndex = s.indexOf('\n', start);
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break;
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default:
51-
writer.append(c);
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}
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allEscapesIndex = backslashIndex & quoteIndex & newlineIndex;
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}
81+
// up until the end nothing needs to be escaped anymore
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int remaining = s.length() - start;
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if (remaining > 0) {
84+
writer.write(s, start, remaining);
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}
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}
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‎prometheus-metrics-exposition-textformats/src/test/java/io/prometheus/metrics/expositionformats/TextFormatUtilTest.java‎

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package io.prometheus.metrics.expositionformats;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import java.io.IOException;
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import java.io.StringWriter;
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import org.junit.jupiter.api.Test;
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class TextFormatUtilTest {
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@Test
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void writeEscapedLabelValue() throws IOException {
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assertEquals("aa\\\\bb\\\"cc\\ndd\\nee\\\\ff\\\"gg", escape("aa\\bb\"cc\ndd\nee\\ff\"gg"));
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assertEquals("\\\\", escape("\\"));
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assertEquals("\\\\\\\\", escape("\\\\"));
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assertEquals("text", escape("text"));
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}
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private static String escape(String s) throws IOException {
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StringWriter writer = new StringWriter();
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TextFormatUtil.writeEscapedLabelValue(writer, s);
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return writer.toString();
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}
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}

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