- Text files are represented as Strings and stored in memory
- Master is responsible for splitting the data and scheduling the map/reduce tasks to workers
- Workers are represented as threads, they are run using CompletableFuture api
- When map task is finished, the combine function will be run on the result
- When Master will notice that all map tasks have finished, it will take all resulted distinct keys and pass them as an argument to reduce tasks
- When reduce tasks are finished, result is printed and the executor is closed
It is easy to define new user programs, check example package.
In memory data:
"file1.txt" -> "This is the first file \ncontent. " "file2.txt" -> "And this is the second file content. " "file3.txt" -> "More text in \nthird file" "file4.txt" -> "And some random text here" "file5.txt" -> "Why not \none more" "file6.txt" -> "Lululu tengo manzana"
Distributed Grep (search for "And"):
New map task for key: file5.txt
New map task for key: file4.txt
New map task for key: file3.txt
New map task for key: file6.txt
New map task for key: file1.txt
New map task for key: file2.txt
Combine task for: file2.txt
Combine task for: file4.txt
Writing: IntermediateResult{key=file2.txt, value=And this is the second file content. }
Writing: IntermediateResult{key=file4.txt, value=And some random text here}
New reduce task for: file4.txt
New reduce task for: file2.txt
Results:
file4.txt - And some random text here
file2.txt - And this is the second file content.
Word count:
New map task for key: file5.txt
New map task for key: file4.txt
New map task for key: file3.txt
New map task for key: file6.txt
New map task for key: file1.txt
New map task for key: file2.txt
Combine task for: not
Combine task for: here
Combine task for: the
Combine task for: manzana
Combine task for: the
Combine task for: More
Writing: IntermediateResult{key=More, value=1}
Writing: IntermediateResult{key=the, value=1}
Writing: IntermediateResult{key=here, value=1}
Writing: IntermediateResult{key=the, value=1}
Writing: IntermediateResult{key=not, value=1}
Writing: IntermediateResult{key=manzana, value=1}
Combine task for: file
Combine task for: random
Writing: IntermediateResult{key=file, value=1}
Writing: IntermediateResult{key=random, value=1}
Combine task for: file
Combine task for: tengo
Combine task for: file
Combine task for: more
Writing: IntermediateResult{key=tengo, value=1}
Writing: IntermediateResult{key=file, value=1}
Combine task for: some
Combine task for: third
Writing: IntermediateResult{key=some, value=1}
Combine task for: This
Combine task for: Lululu
Writing: IntermediateResult{key=Lululu, value=1}
Writing: IntermediateResult{key=more, value=1}
Writing: IntermediateResult{key=file, value=1}
Combine task for: one
Writing: IntermediateResult{key=one, value=1}
Writing: IntermediateResult{key=This, value=1}
Combine task for: And
Writing: IntermediateResult{key=And, value=1}
Writing: IntermediateResult{key=third, value=1}
Combine task for: in
Combine task for: text
Writing: IntermediateResult{key=in, value=1}
Combine task for: content.
Combine task for: Why
Writing: IntermediateResult{key=content., value=1}
Writing: IntermediateResult{key=Why, value=1}
Combine task for: And
Writing: IntermediateResult{key=And, value=1}
Combine task for: this
Combine task for: is
Combine task for: text
Writing: IntermediateResult{key=text, value=1}
Writing: IntermediateResult{key=text, value=1}
Writing: IntermediateResult{key=is, value=1}
Writing: IntermediateResult{key=this, value=1}
Combine task for: first
Combine task for: content.
Writing: IntermediateResult{key=first, value=1}
Writing: IntermediateResult{key=content., value=1}
Combine task for: is
Writing: IntermediateResult{key=is, value=1}
Combine task for: second
Writing: IntermediateResult{key=second, value=1}
New reduce task for: not
New reduce task for: more
New reduce task for: one
New reduce task for: the
New reduce task for: file
New reduce task for: This
New reduce task for: content.
New reduce task for: first
New reduce task for: Lululu
New reduce task for: More
New reduce task for: in
New reduce task for: text
New reduce task for: Why
New reduce task for: random
New reduce task for: here
New reduce task for: third
New reduce task for: tengo
New reduce task for: manzana
New reduce task for: is
New reduce task for: second
New reduce task for: this
New reduce task for: And
New reduce task for: some
Results:
not - 1
more - 1
one - 1
Why - 1
the - 2
file - 3
This - 1
content. - 2
is - 2
first - 1
manzana - 1
tengo - 1
Lululu - 1
More - 1
third - 1
in - 1
text - 2
here - 1
random - 1
some - 1
And - 2
this - 1
second - 1
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