Sebastiano Vigna created HTTPCLIENT-1461:
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Summary: GZIP decoding is very slow
Key: HTTPCLIENT-1461
URL: https://issues.apache.org/jira/browse/HTTPCLIENT-1461
Project: HttpComponents HttpClient
Issue Type: Bug
Components: HttpClient
Affects Versions: 4.3.2
Reporter: Sebastiano Vigna
Priority: Critical
In 4.3.1, LazyDecompressingInputStream was introduced. However,
LazyDecompressingInputStream subclasses InputStream without overriding the
multi-byte read() method, and the inherited method does a byte-by-byte read.
This is trace showing what happens:
java.util.zip.Inflater.inflateBytes(Inflater.java:Unknown line)
java.util.zip.Inflater.inflate(Inflater.java:259)
java.util.zip.InflaterInputStream.read(InflaterInputStream.java:152)
java.util.zip.GZIPInputStream.read(GZIPInputStream.java:116)
java.util.zip.InflaterInputStream.read(InflaterInputStream.java:122)
org.apache.http.client.entity.LazyDecompressingInputStream.read(LazyDecompressingInputStream.java:56)
java.io.InputStream.read(InputStream.java:179)
it.unimi.di.law.warc.util.InspectableCachedHttpEntity.copyContent(InspectableCachedHttpEntity.java:67)
copyContent() would love to read(byte[],int,int) in a buffer, but since
LazyDecompressingInputStream doesn't override it it invokes instead the
read-byte-by-byte inherited method in InputStream, which in turn now calls for
each byte the one-byte read() method from LazyDecompressingInputStream, which
invokes the one-byte read method from InflaterInputStream, which does a
multi-byte, length-one read from GZIPInputStream, which unleashes a similar
call on InflaterInputStream, which unfortunately makes a similar read using the
native inflateBytes() method.
Thus, for each byte there is a native-method call. The result is a 10-50x
increase in CPU usage, which turns into a 10x-50x decrease in speed if, as in
our case, you have 7000 threads downloading in parallel.
Overriding read(byte[],int,int) in LazyDecompressingInputStream will solve the
problem:
@Override
public int read(byte[] b, int off, int len) throws IOException {
initWrapper();
return wrapperStream.read(b, off, len);
}
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