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README.md

Stresso

Build Status

An example application designed to stress Apache Fluo. This Fluo application computes the number of unique integers through the process of building a bitwise trie. New numbers are added to the trie as leaf nodes. Observers watch all nodes in the trie to create parents and percolate counts up to the root nodes such that each node in the trie keeps track of the number of leaf nodes below it. The count at the root nodes should equal the total number of leaf nodes. This makes it easy to verify if the test ran correctly. The test stresses Apache Fluo in that multiple transactions can operate on the same data as counts are percolated up the trie.

Concepts and definitions

This test has the following set of configurable parameters.

  • nodeSize : The number of bits chopped off the end each time a number is percolated up. Must choose a nodeSize such that 64 % nodeSize == 0
  • stopLevel : The number of levels in the tree is a function of the nodeSize. The deepest possible level is 64 / nodeSize. Levels are decremented going up the tree. Setting the stop level determines how far up to percolate. The lower the stop level, the more root nodes there are. Having more root nodes means less collisions, but all roots need to be scanned to get the count of unique numbers. Having ~64k root nodes is a good choice.
  • max : Random numbers are generated modulo the max.

Setting the stop level such that you have ~64k root nodes is dependent on the max and nodeSize. For example assume we choose a max of 1012 and a node size of 8. The following table shows information about each level in the tree using this configuration. So for a max of 1012 choosing a stop level of 5 would result in 59,604 root nodes. With this many root nodes there would not be many collisions and scanning 59,604 nodes to compute the unique number of intergers is a quick operation.

Level Max Node Number of possible Nodes
0 0xXXXXXXXXXXXXXXXX 1
1 0x00XXXXXXXXXXXXXX 1
2 0x0000XXXXXXXXXXXX 1
3 0x000000XXXXXXXXXX 1
4 0x000000E8XXXXXXXX 232
5 0x000000E8D4XXXXXX 59,604
6 0x000000E8D4A5XXXX 15,258,789
7 0x000000E8D4A510XX 3,906,250,000
8 0x000000E8D4A51000 1,000,000,000,000

In the table above, X indicates nibbles that are always zeroed out for every node at that level. You can easily view nodes at a level using a row prefix with the fluo scan command. For example fluo scan -p 05 shows all nodes at level 5.

For small scale test a max of 109 and a stop level of 6 is a good choice.

Building Stresso

mvn package 

This will create a jar and shaded jar in target:

$ ls target/stresso-*
target/stresso-0.0.1-SNAPSHOT.jar  target/stresso-0.0.1-SNAPSHOT-shaded.jar

Run Stresso using MiniFluo

There are several integration tests that run Stresso on a MiniFluo instance. These tests can be run using mvn verify.

Run Stresso on cluster

The bin directory contains a set of scripts to help run this test on a cluster. These scripts make the following assumpitions.

  • FLUO_HOME environment variable is set. If not set, then set it in conf/env.sh.
  • Hadoop yarn command is on path.
  • Hadoop hadoop command is on path.
  • Accumulo accumulo command is on path.

Before running any of the scipts, copy conf/env.sh.example to conf/env.sh, then inspect and modify the file.

Next, execute the run-test.sh script. This script will create a new Apache Fluo app called stresso (which can be changed by FLUO_APP_NAME in your env.sh). It will modify the application's fluo.properties, copy the stresso jar to the lib/ directory of the app and set the following in fluo.properties:

fluo.observer.0=stresso.trie.NodeObserver
fluo.app.trie.nodeSize=X
fluo.app.trie.stopLevel=Y

The run-test.sh script will then initialize and start the Stresso application.
It will load a lot of data directly into Accumulo without transactions and then incrementally load smaller amounts of data using transactions. After incrementally loading some data, it computes the expected number of unique integers using map reduce. It then prints the number of unique integers computed by Apache Fluo.

Additional Scripts

The script generate.sh starts a map reduce job to generate random integers.

generate.sh <num files> <num per file> <max> <out dir>

where:

num files = Number of files to generate (and number of map task)
numPerMap = Number of random numbers to generate per file
max       = Generate random numbers between 0 and max
out dir   = Output directory

The script split.sh pre-splits the Accumulo table used by Apache Fluo. Consider running this command before loading data.

split.sh <num tablets> <max>

where:

num tablets = Num tablets to create for lowest level of tree.  Will create less tablets for higher levels based on the max.

After generating random numbers, load them into Apache Fluo with one of the following commands. The script init.sh intializes any empty table using map reduce. This simulates the case where a user has a lot of initial data to load into Fluo. This command should only be run when the table is empty because it writes directly to the Fluo table w/o using transactions.

init.sh <input dir> <tmp dir> <num reducers>

where:

input dir    = A directory with file created by stresso.trie.Generate
node size    = Size of node in bits which must be a divisor of 32/64
tmp dir      = This command runs two map reduce jobs and needs an intermediate directory to store data.
num reducers = Number of reduce task map reuduce job should run

Run the load.sh script on a table with existing data. It starts a map reduce job that executes load transactions. Loading the same directory multiple times should not result in incorrect counts.

load.sh <input dir>

After loading data, run the print.sh script to check the status of the computation of the number of unique integers within Apache Fluo. This command will print two numbers, the sum of the root nodes and number of root nodes. If there are outstanding notification to process, this count may not be accurate.

print.sh

In order to know how many unique numbers are expected, run the unique.sh script. This scrpt runs a map reduce job that calculates the number of unique integers. This script can take a list of directories created by multiple runs of generate.sh

unique.sh <num reducers> <input dir>{ <input dir>}

As transactions execute they leave a trail of history behind. The nodes in the lower levels of the tree are updated by many transactions and therefore have a long history trail. A long transactional history can slow down transactions. Forcing a compaction in Accumulo will clean up this history. However compacting the entire table is expensive. To avoid this expense, compact only the lower levels of the tree. The following command will compact levels of the tree with a maximum number of nodes less than the specified cutoff.

compact-ll.sh <max> <cutoff>

where:

cutoff    = Any level of the tree with a maximum number of nodes that is less than this cutoff will be compacted.