michael-o commented on a change in pull request #50: WAGON-537 Maven download
speed of large artifacts is slow
URL: https://github.com/apache/maven-wagon/pull/50#discussion_r225312303
##########
File path:
wagon-provider-api/src/main/java/org/apache/maven/wagon/AbstractWagon.java
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@@ -560,31 +564,78 @@ protected void transfer( Resource resource, InputStream
input, OutputStream outp
protected void transfer( Resource resource, InputStream input,
OutputStream output, int requestType, long maxSize )
throws IOException
{
- byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
+ byte[] buffer = bufferForTransferring( resource );
TransferEvent transferEvent = new TransferEvent( this, resource,
TransferEvent.TRANSFER_PROGRESS, requestType );
transferEvent.setTimestamp( System.currentTimeMillis() );
long remaining = maxSize;
while ( remaining > 0 )
{
- // let's safely cast to int because the min value will be lower
than the buffer size.
- int n = input.read( buffer, 0, (int) Math.min( buffer.length,
remaining ) );
+ // Read from the stream, block if necessary until either EOF or
buffer is filled.
+ // Filling the buffer has priority since downstream processors
will significantly degrade i/o
+ // performance if called to frequently (large data streams) as
they perform expensive tasks such as
+ // console output or data integrity checks.
+ int nextByte = input.read();
- if ( n == -1 )
+ if ( nextByte == -1 )
{
break;
}
- fireTransferProgress( transferEvent, buffer, n );
+ buffer[0] = ( byte ) nextByte;
+
+ // let's safely cast to int because the min value will be lower
than the buffer size.
+ int length = (int) min( buffer.length, remaining ),
+ read = 1;
+
+ for ( ; read < length ; ++read )
+ {
+ nextByte = input.read();
+ if ( nextByte == -1 )
+ {
+ break;
+ }
+ buffer[read] = ( byte ) nextByte;
+ }
+
+ fireTransferProgress( transferEvent, buffer, read );
- output.write( buffer, 0, n );
+ output.write( buffer, 0, read );
- remaining -= n;
+ remaining -= read;
}
output.flush();
}
+ /**
+ * Provide a buffer suitably sized for efficiently
+ * {@link #transfer(Resource, InputStream, OutputStream, int, long)
transferring}
+ * the given {@link Resource}. For larger files, larger buffers are
provided such that downstream
+ * {@link #fireTransferProgress(TransferEvent, byte[], int) listeners} are
not notified overly frequently.
+ * For instance, transferring gigabyte-sized resources would result in
millions of notifications when using
+ * only a few kilobytes of buffer, drastically slowing transfer since
transfer progress listeners and
+ * notifications are synchronous and may block, e.g. when writing download
progress status to console.
+ *
+ * @param resource must not be null.
+ * @return a byte buffer suitable for the {@link
Resource#getContentLength() content length} of the resource.
+ */
+ protected byte[] bufferForTransferring( Resource resource )
+ {
+ long contentLength = resource.getContentLength();
+
+ if ( contentLength <= 0 )
+ {
+ return new byte[DEFAULT_BUFFER_SIZE];
+ }
+
+ int numberOf4KbSegmentsFor100Chunks = ( ( int ) ( contentLength / ( 4
* 1024 * 100 ) ) );
Review comment:
Please use the `static final` for `4 * 1024` and also move the `100` to a
`static final`. Also add to the code why you have chosen `100`.
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