Github user aledsage commented on a diff in the pull request:
https://github.com/apache/brooklyn-server/pull/731#discussion_r122727924
--- Diff:
utils/common/src/main/java/org/apache/brooklyn/util/stream/LoggingOutputStream.java
---
@@ -0,0 +1,134 @@
+/*
+ * 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.brooklyn.util.stream;
+
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.slf4j.Logger;
+
+/**
+ * Wraps another output stream, intercepting the writes to log it.
+ */
+public class LoggingOutputStream extends FilterOutputStream {
+
+ private static final OutputStream NOOP_OUTPUT_STREAM = new
FilterOutputStream(null) {
+ @Override public void write(int b) throws IOException {
+ }
+ @Override public void flush() throws IOException {
+ }
+ @Override public void close() throws IOException {
+ }
+ };
+
+ public static Builder builder() {
+ return new Builder();
+ }
+
+ public static class Builder {
+ OutputStream out;
+ Logger log;
+ String logPrefix;
+
+ public Builder outputStream(OutputStream val) {
+ this.out = val;
+ return this;
+ }
+ public Builder logger(Logger val) {
+ this.log = val;
+ return this;
+ }
+ public Builder logPrefix(String val) {
+ this.logPrefix = val;
+ return this;
+ }
+ public LoggingOutputStream build() {
+ return new LoggingOutputStream(this);
+ }
+ }
+
+ protected final Logger log;
+ protected final String logPrefix;
+ private final AtomicBoolean running = new AtomicBoolean(true);
+ private final StringBuilder lineSoFar = new StringBuilder(16);
+
+ private LoggingOutputStream(Builder builder) {
+ super(builder.out != null ? builder.out : NOOP_OUTPUT_STREAM);
+ log = builder.log;
+ logPrefix = (builder.logPrefix != null) ? builder.logPrefix : "";
+ }
+
+ @Override
+ public void write(int b) throws IOException {
+ if (running.get() && b >= 0) onChar(b);
+ out.write(b);
+ }
+
+ @Override
+ public void flush() throws IOException {
+ try {
+ if (lineSoFar.length() > 0) {
+ onLine(lineSoFar.toString());
+ lineSoFar.setLength(0);
--- End diff --
Is your concern about leaking that the `lineSoFar` might now have a very
large internal array in `StringBuilder.value`, which won't be GC'ed until the
`LoggingOutputStream` is GC'ed?
I could add a call to `StringBuilder.trimToSize()` as well (which would set
it to size 0, rather than our initial size of 16). That would be less efficient
(causing array-copy to grow again), but probably not noticeably so. Maybe I'll
compromise and say that if the size was `>= 1024` then I'll `trimToSize`.
Note that this code was copy-pasted from `StreamGobbler`.
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