ZooKeeper Benchmark

Authors: Chen Liang, Andrew Ferguson, Rodrigo Fonseca

Please contact [email protected] with any questions or comments. Patches and additional features are more than welcome!

Introduction

This project provides a tool to benchmark the performance of ZooKeeper. It is designed to measure the per-request latency of a ZooKeeper ensemble for a predetermined length of time (e.g., sustained handling of create requests for 30 seconds). This tool can be used to build graphs such as Figure 8 in the paper "ZooKeeper: Wait-free coordination for Internet-scale systems", and differs from the ZooKeeper smoketest, which submits a fixed number of operations and records the time to complete all of them.

The benchmark exercises the ensemble's performance at handling znode reads, repeated writes to a single znode, znode creation, repeated writes to multiple znodes, and znode deletion. These tests can be performed with either synchronous or asynchronous operations. The benchmark connects to each server in the ZooKeeper ensemble using one thread per server.

In synchronous operation, each client makes a new request upon receiving the result of the previous one. In asynchronous operation, each client thread has a globally configurable target for the number of outstanding asynchronous requests. If the number of outstanding requests falls below a configurable lower bound, then new asynchronous requests are made to return to the target level.

During the benchmark, the current rate of request processing is recorded at a configurable intermediate interval to one file per operation: READ.dat, SETSINGLE.dat, CREATE.dat, SETMULTI.dat, and DELETE.dat. Additional output is recorded to the log file zk-benchmark.log, including the output of the ZooKeeper stat command after every test (srst is run before each test to reset the statistics). Some messages are also displayed on the console, all of which can be adjusted via the log4j.properties file.

Build and Usage Instructions

To compile the code, run:

mvn -DZooKeeperVersion=<version> package

where <version> is a ZooKeeper version such as 3.4.3, 3.5.0-pane, etc. The client code corresponding to the ZooKeeper version will be found using maven.

After this, run the benchmark using a configuration file:

java -cp target/lib/*:target/* edu.brown.cs.zkbenchmark.ZooKeeperBenchmark --conf benchmark.conf

The configuration file provides the list of servers to contact and parameters for the benchmark; please see the included example for more details. Many configuration parameters can also be set on the command line. A --help option lists the possible options:

Option (* = required)           Description                            
---------------------           -----------                            
* --conf                        configuration file (required)          
--help                          print this help statement              
--interval                      interval between rate measurements     
--lbound                        lowerbound for the number of operations
--ops                           total number of operations             
--sync                          sync or async test                     
--time                          time tests will run for (milliseconds)

In addition, we have included a script runBenchmark.sh which launches runs of the example benchmark configuration. It requires one argument, a name for the run. A path to a configuration file can be provided as an optional second argument. Finally, if the last argument is set to --gnuplot, the script plots the rate output files using the included gnuplot script, all.plot. A second gnuplot script, multi.plot, can be used to compare two runs named "pre" and "post".

Eclipse Development

As a simple Maven project, our benchmark can easily be developed using Eclipse. It is necessary to first set the M2_REPO variable for your workspace (This command only needs to be executed once per workspace):

mvn -Declipse.workspace=<path-to-eclipse-workspace> eclipse:configure-workspace

Next, install the libraries and create the Eclipse project files:

mvn -DZooKeeperVersion=<version> install -DskipTests
mvn -DZooKeeperVersion=<version> eclipse:eclipse

You can now import the project into Eclipse using, File > Import > Existing Projects into Workspace.

If you wish to view the source or JavaDocs of the benchmark's dependencies, you add -DdownloadSources=true or -DdownloadJavadocs=true when creating the Eclipse project files in the final step.

Internally, this project uses the Netflix Curator library to wrap the ZooKeeper client API.

Notes

1. In the benchmark, node creation and deletion tests are done by creating nodes in the first test, and then deleting them in the second. Since each test runs for a fixed amount of time, there are no guarantees about the number of nodes created in the first one. If there are more delete requests than create requests, the extra delete requests will not actually deleting anything. These requests are sent to, and processed by, the ZooKeeper server, which may affect the average per-request latency reported by the test. Examining the intermediately-reported request rates will provide more accurate information.

2. Read requests are handled by ZooKeeper more quickly than write requests. If the time interval and threshold are not chosen appropriately, it could happen that when the timer awakes, all requests have already been finished. In this case, the output of the read test doesn't reflect the actual rate of read requests the ensemble could support. As with the previous concern, examining the intermediately-reported request rates will provide better insight.

License

Ths ZooKeeper benchmark is provided under the 3-clause BSD license. See the file LICENSE for more details.