Class ARCWriter

java.lang.Object

org.archive.io.WriterPoolMember

org.archive.io.arc.ARCWriter

All Implemented Interfaces:

Closeable, AutoCloseable

public class ARCWriter
extends WriterPoolMember
implements Closeable

Write ARC files. Assumption is that the caller is managing access to this ARCWriter ensuring only one thread of control accessing this ARC file instance at any one time.

ARC files are described here: Arc File Format. This class does version 1 of the ARC file format. It also writes version 1.1 which is version 1 with data stuffed into the body of the first arc record in the file, the arc file meta record itself.

An ARC file is three lines of meta data followed by an optional 'body' and then a couple of '\n' and then: record, '\n', record, '\n', record, etc. If we are writing compressed ARC files, then each of the ARC file records is individually gzipped and concatenated together to make up a single ARC file. In GZIP terms, each ARC record is a GZIP member of a total gzip'd file.

The GZIPping of the ARC file meta data is exceptional. It is GZIPped w/ an extra GZIP header, a special Internet Archive (IA) extra header field (e.g. FEXTRA is set in the GZIP header FLG field and an extra field is appended to the GZIP header). The extra field has little in it but its presence denotes this GZIP as an Internet Archive gzipped ARC. See RFC1952 to learn about the GZIP header structure.

This class then does its GZIPping in the following fashion. Each GZIP member is written w/ a new instance of GZIPOutputStream -- actually ARCWriterGZIPOututStream so we can get access to the underlying stream. The underlying stream stays open across GZIPoutputStream instantiations. For the 'special' GZIPing of the ARC file meta data, we cheat by catching the GZIPOutputStream output into a byte array, manipulating it adding the IA GZIP header, before writing to the stream.

I tried writing a resettable GZIPOutputStream and could make it work w/ the SUN JDK but the IBM JDK threw NPE inside in the deflate.reset -- its zlib native call doesn't seem to like the notion of resetting -- so I gave up on it.

Because of such as the above and troubles with GZIPInputStream, we should write our own GZIP*Streams, ones that resettable and consious of gzip members.

This class will write until we hit >= maxSize. The check is done at record boundary. Records do not span ARC files. We will then close current file and open another and then continue writing.

TESTING: Here is how to test that produced ARC files are good using the alexa ARC c-tools:

 % av_procarc hx20040109230030-0.arc.gz | av_ziparc > \
     /tmp/hx20040109230030-0.dat.gz
 % av_ripdat /tmp/hx20040109230030-0.dat.gz > /tmp/hx20040109230030-0.cdx
 

Examine the produced cdx file to make sure it makes sense. Search for 'no-type 0'. If found, then we're opening a gzip record w/o data to write. This is bad.

You can also do gzip -t FILENAME and it will tell you if the ARC makes sense to GZIP.

While being written, ARCs have a '.open' suffix appended.

Author:

stack

Field Summary

Fields inherited from class org.archive.io.WriterPoolMember

countOut, currentBasename, currentTimestamp, DEFAULT_PREFIX, DEFAULT_TEMPLATE, f, out, roundRobinIndex, scratchbuffer, serialNoFormatter, serialNoFormatterSymbols, settings, UTF8

Constructor Summary

Constructors

Constructor	Description
ARCWriter(AtomicInteger serialNo, PrintStream out, File arc, WriterPoolSettings settings)	Constructor.
ARCWriter(AtomicInteger serialNo, WriterPoolSettings settings)	Constructor.

Method Summary

Modifier and Type	Method	Description
protected String	createFile()	Create a new file.
String	createMetaline(String uri, String hostIP, String timeStamp, String mimetype, String recordLength)
String	getMetadataHeaderLinesTwoAndThree(String version)
protected String	getMetaLine(String uri, String contentType, String hostIP, long fetchBeginTimeStamp, long recordLength)
protected String	validateMetaLine(String metaLineStr)	Test that the metadata line is valid before writing.
void	write(String uri, String contentType, String hostIP, long fetchBeginTimeStamp, long recordLength, ByteArrayOutputStream baos)	Deprecated. use input-stream version directly instead
void	write(String uri, String contentType, String hostIP, long fetchBeginTimeStamp, long recordLength, InputStream in)
void	write(String uri, String contentType, String hostIP, long fetchBeginTimeStamp, long recordLength, InputStream in, boolean enforceLength)	Write a record with the given metadata/content.

Methods inherited from class org.archive.io.WriterPoolMember

checkSize, checkWriteable, close, copyFrom, createFile, flush, generateNewBasename, getBaseFilename, getFile, getNextDirectory, getOutputStream, getPosition, isCompressed, isOversize, postWriteRecordTasks, preWriteRecordTasks, write, write, write

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.io.Closeable

close

Constructor Details

ARCWriter

public ARCWriter(AtomicInteger serialNo,
 PrintStream out,
 File arc,
 WriterPoolSettings settings)
          throws IOException

Constructor. Takes a stream. Use with caution. There is no upperbound check on size. Will just keep writing.

Parameters:

serialNo - used to generate unique file name sequences

out - Where to write.

arc - File the out is connected to. 2

Throws:

IOException

ARCWriter

public ARCWriter(AtomicInteger serialNo,
 WriterPoolSettings settings)

Constructor.

Parameters:

serialNo - used to generate unique file name sequences

settings - all creation parameters

Method Details

createFile

protected String createFile()
                     throws IOException

Description copied from class: WriterPoolMember

Create a new file. Rotates off the current Writer and creates a new in its place to take subsequent writes. Usually called from WriterPoolMember.checkSize().

Overrides:

createFile in class WriterPoolMember

Returns:

Name of file created.

Throws:

IOException

getMetadataHeaderLinesTwoAndThree

public String getMetadataHeaderLinesTwoAndThree(String version)

write

public void write(String uri,
 String contentType,
 String hostIP,
 long fetchBeginTimeStamp,
 long recordLength,
 ByteArrayOutputStream baos)
           throws IOException

Deprecated.

use input-stream version directly instead

Throws:

IOException

write

public void write(String uri,
 String contentType,
 String hostIP,
 long fetchBeginTimeStamp,
 long recordLength,
 InputStream in)
           throws IOException

Throws:

IOException

write

public void write(String uri,
 String contentType,
 String hostIP,
 long fetchBeginTimeStamp,
 long recordLength,
 InputStream in,
 boolean enforceLength)
           throws IOException

Write a record with the given metadata/content.

Parameters:

uri - URI for metadata-line

contentType - MIME content-type for metadata-line

hostIP - IP for metadata-line

fetchBeginTimeStamp - timestamp for metadata-line

recordLength - length for metadata-line; also may be enforced

in - source InputStream for record content

enforceLength - whether to enforce the declared length; should be true unless intentionally writing bad records for testing

Throws:

IOException

getMetaLine

protected String getMetaLine(String uri,
 String contentType,
 String hostIP,
 long fetchBeginTimeStamp,
 long recordLength)
                      throws IOException

Parameters:

uri -

contentType -

hostIP -

fetchBeginTimeStamp -

recordLength -

Returns:

Metadata line for an ARCRecord made of passed components.

Throws:

IOException

createMetaline

public String createMetaline(String uri,
 String hostIP,
 String timeStamp,
 String mimetype,
 String recordLength)

validateMetaLine

protected String validateMetaLine(String metaLineStr)
                           throws IOException

Test that the metadata line is valid before writing.

Parameters:

metaLineStr -

Returns:

The passed in metaline.

Throws:

IOException