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Parallel-diff Project (POC)

Fetching

git clone https://github.com/Money-Honey/parallel-diff.git

Building

Run next command:

  1. cd parallel-diff/
  2. ./gradlew clean build During the build tests will be run. There is test which run a diff between files from the task.

jar file will be accessible by the path build/libs/parallel-diff-1.0-SNAPSHOT.jar

Running

Just a copy the jar parallel-diff-1.0-SNAPSHOT.jar into the other (empty) directory and then run it, or specify path to this jar:

Example: java -jar parallel-diff-1.0-SNAPSHOT.jar -i1 aus-28-2002 -i2 aws-28-2002 -o out.txt

aus-28-2002 and aws-28-2002 files are expected to be in the same directory. -i1 and -i2 are required options and consumes relative paths to the files to diff. -o is optional and will be defaulted.

The working example is from the parallel-diff dir is (build project first): java -jar build/libs/parallel-diff-1.0-SNAPSHOT.jar -i1 src/main/resources/aus-28-2002 -i2 src/main/resources/aws-28-2002 -o out.txt

Verifying

diff directory will be created with diff chunks. out.txt or defaulted eventsDiff.txt will be created with merged chunks.

Also it's possible to check the logs from the console output or $HOME file with detailed statistic and metrics. Example: 2019-03-25 01:33:00 INFO DiffService:91 - Total diff result: DiffReport(leftSkippedRows=225, rightSkippedRows=222, timeElapsed=10744, metrics=DiffMetrics(newLeftRowsAmount=65, newRightRowsAmount=2, differentEventsRowsAmount=1480, sameLines=498903)). Within Threads: 7. Approximate diff time: 1534 Where Within Threads: 7 means that 7 workers were used in parallel and Approximate diff time: 1534 means that it took 1534ms

Tested on MacOs with i7 processor

The beginning plan

    /*
     * make a diffEvents in parallel what involves tricky manipulations by splitting files
     * 1) get first, last keys from files
     * 2) find start_key, stop_key as higher and lower for both files
     * 3) split the range (start_key - stop_key) by (num of processors - 1) * 10 for example
     *  to split there is some algorithm implementation from hbase core to receive start/stop keys for each split
     * 4) split both input files by dividing their sizes by (num of processors - 1) * 10 for example
     *  it's a rough slip which should be continued by seeking to start or end of line (all records are splited by \n).
     * 5) Create parallel task to evaluate the diffEvents
     *  by going through the range splits and find splits from both files which fit the range.
     * 5.1) It's important to have file model with type A, B or Left, Right to understand which exactly strategy should be applied
     *  - if the is no slip from the left -> all records from the right are new and vice versa
     * 6) During the diffEvents task we always need to skip all records which don't belong to the range split
     *  (some records close to start and close to the end)
     * 7) During the reading files using `RandomAccessFile` class it's expected to make the diffEvents in the memory
     *  buffer and upon the buffer overflows the buffer should be flushed to the disk
     *  It's important to save files with split's name like (1,2,3,4,5).txt.
     *  Then these files i think might be able to be joined without reading with O(f) not O(n)
     *  where n (number of records inside the diffs) and f (number of files to be joined)
     * 8) Check if ForkJoin algorithm and RecursiveTask might be able to be used.
     *
     *  _FILE_A______________VIRTUAL_
     * |____1___|         |_____1____|          _FILE_B_
     * |___13___|         |____10____|         |___45___|
     * |___25___|         |____20____|         |___54___|
     * |___37___|         |____30____|         |___58___|
     * |___49___|         |____40____|         |___62___|
     * |___51___|         |____50____|         |___67___|
     * |___55___|         |____60____|         |___71___|
     * |___61___|         |____70____|         |___75___|
     * |___78___|         |____80____|         |___78___|
     * |___87___|         |____90____|         |___91___|
     *                    |____99____|_________|___99___|
     *
     * Next pairs will be created for virtual splits range:
     * 1.  1-10:  A(1-13)                       : 1-10 records will be flushed as NEW. 10-13 will be skipped
     * 2.  10-20: A(1-13) + (13-25)             : 1-10 records will be skipped. 10-20 marked as as NEW. 20-25 will be skipped
     * 3.  20-30: A(13-25) + (25-37)            : 13-20 records will be skipped. 20-30 marked as as NEW. 30-37 will be skipped
     * 4.  30-40: A(25-37) + (37-49)            : 25-30 records will be skipped. 30-40 marked as as NEW. 40-49 will be skipped
     * Interesting starts here :)
     * 5.  40-50: A(37-49) + (49-51) + B(45-54) : 37-40 records will be skipped. 40-50 will be compared. 50-51(A) and 50-54(B) will be skipped
     * 6.  50-60: A(49-61)           + B(45-62) : 49-50(A) + 45-50(B) will be skipped. 50-60 will be compared. 60-61(A) and 60-62(B) will be skipped
     * 7.  60-70: A(55-78)           + B(58-71) : 55-60(A) + 58-60(B) will be skipped. 60-70 will be compared. 70-78(A) and 70-71(B) will be skipped
     * 8.  70-80: A(61-87)           + B(67-91) : 61-70(A) + 67-70(B) will be skipped. 70-80 will be compared. 80-87(A) and 70-91(B) will be skipped
     * 9.  80-90: A(78-87)           + B(78-91) : 78-80(A) + 78-80(B) will be skipped. 80-90 will be compared. 90-91(B) will be skipped
     * 10. 90-99:                      B(78-99) : 90-99(B) will be marked as NEW.
     *
     *
     * Hence, looks this algorithm should work in parallel as well
     * */

    /*
     * Finally both approaches should be measured by time, and results with diffs should be compared
     * */