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我很难弄清楚如何将hadoop流式映射还原的二进制输出用作另一个hadoop流式映射还原的输入。使用二进制数据级联hadoop流式映射还原
echo.py：
import sys
while True:
buffer = sys.stdin.read(1024)
if not buffer:
break
sys.stdout.write(buffer)
sys.stdout.flush()
$ XXD input.txt中
0000000: 6b31 0976 310a 6b32 0976 320a 6b33 0976 k1.v1.k2.v2.k3.v
0000010: 330a 6b34 0976 340a 3.k4.v4.
用下面的命令，我期待得到一个output.seq.txt文件，它看起来像input.txt中但这并未发生。为什么？
./hadoop/bin/hadoop dfs -rmr /samples/output.seq ;\
./hadoop/bin/hadoop jar ./hadoop/contrib/streaming/hadoop-streaming-1.0.3.jar \
-D 'stream.map.input=typedbytes' \
-D 'stream.map.output=typedbytes' \
-D 'stream.reduce.input=typedbytes' \
-D 'stream.reduce.output=typedbytes' \
-D 'mapred.job.name=echo.py (1/2)' \
-mapper 'python -m echo map 0 262144000' \
-reducer 'python -m echo red 0 262144000' \
-file echo.py \
-inputformat 'org.apache.hadoop.mapred.KeyValueTextInputFormat' \
-input /samples/input.txt \
-outputformat 'org.apache.hadoop.mapred.SequenceFileOutputFormat' \
-output /samples/output.seq ;\
./hadoop/bin/hadoop dfs -cat /samples/output.seq/part-0000 > output.seq
$ XXD output.seq
0000000: 5345 5106 2f6f 7267 2e61 7061 6368 652e SEQ./org.apache.
0000010: 6861 646f 6f70 2e74 7970 6564 6279 7465 hadoop.typedbyte
0000020: 732e 5479 7065 6442 7974 6573 5772 6974 s.TypedBytesWrit
0000030: 6162 6c65 2f6f 7267 2e61 7061 6368 652e able/org.apache.
0000040: 6861 646f 6f70 2e74 7970 6564 6279 7465 hadoop.typedbyte
0000050: 732e 5479 7065 6442 7974 6573 5772 6974 s.TypedBytesWrit
0000060: 6162 6c65 0000 0000 0000 41e2 785b 996d able......A.x[.m
0000070: f015 772c 9c66 10d4 13e7 0000 0012 0000 ..w,.f..........
0000080: 0009 0000 0005 0700 0000 0000 0000 0507 ................
0000090: 0000 0000 0000 0016 0000 000b 0000 0007 ................
00000a0: 0700 0000 026b 3100 0000 0707 0000 0002 .....k1.........
00000b0: 7631 0000 0016 0000 000b 0000 0007 0700 v1..............
00000c0: 0000 026b 3200 0000 0707 0000 0002 7632 ...k2.........v2
00000d0: 0000 0016 0000 000b 0000 0007 0700 0000 ................
00000e0: 026b 3300 0000 0707 0000 0002 7633 0000 .k3.........v3..
00000f0: 0016 0000 000b 0000 0007 0700 0000 026b ...............k
0000100: 3400 0000 0707 0000 0002 7634 4.........v4
然后
./hadoop/bin/hadoop dfs -rmr /samples/output.seq.txt ;\
./hadoop/bin/hadoop jar ./hadoop/contrib/streaming/hadoop-streaming-1.0.3.jar \
-D 'stream.map.input=typedbytes' \
-D 'stream.map.output=typedbytes' \
-D 'stream.reduce.input=typedbytes' \
-D 'stream.reduce.output=typedbytes' \
-D 'mapred.job.name=echo.py (2/2)' \
-mapper 'python -m echo map 0 262144000' \
-reducer 'python -m echo red 0 262144000' \
-file echo.py \
-inputformat 'org.apache.hadoop.mapred.SequenceFileInputFormat' \
-input /samples/output.seq/part-00000 \
-outputformat 'org.apache.hadoop.mapred.TextOutputFormat' \
-output /samples/output.seq.txt ;\
./hadoop/bin/hadoop dfs -cat /samples/output.seq.txt/part-0000 > output.seq.txt
$ XXD output.seq.txt
0000000: 5345 5106 2f6f 7267 2e61 7061 6368 652e SEQ./org.apache.
0000010: 6861 646f 6f70 2e74 7970 6564 6279 7465 hadoop.typedbyte
0000020: 732e 5479 7065 6442 7974 6573 5772 6974 s.TypedBytesWrit
0000030: 6162 6c65 2f6f 7267 2e61 7061 6368 652e able/org.apache.
0000040: 6861 646f 6f70 2e74 7970 6564 6279 7465 hadoop.typedbyte
0000050: 732e 5479 7065 6442 7974 6573 5772 6974 s.TypedBytesWrit
0000060: 6162 6c65 0000 0000 0000 41ef bfbd 785b able......A...x[
0000070: efbf bd6d efbf bd15 772c efbf bd66 10ef ...m....w,...f..
0000080: bfbd 13ef bfbd 0000 0012 0000 0009 0000 ................
0000090: 0005 0700 0000 0000 0000 0507 0000 0000 ................
00000a0: 0000 0016 0000 000b 0000 0007 0700 0000 ................
00000b0: 026b 3100 0000 0707 0000 0002 7631 0000 .k1.........v1..
00000c0: 0016 0000 000b 0000 0007 0700 0000 026b ...............k
00000d0: 3200 0000 0707 0000 0002 7632 0000 0016 2.........v2....
00000e0: 0000 000b 0000 0007 0700 0000 026b 3300 .............k3.
00000f0: 0000 0707 0000 0002 7633 0000 0016 0000 ........v3......
0000100: 000b 0000 0007 0700 0000 026b 3400 0000 ...........k4...
0000110: 0707 0000 0002 7634 0a ......v4.
（方问题：上面的命令取〜30-60完成每个。为什么他们很慢！？）