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| <h1> HDFS Utilities: Synthetic Load Generator User Guide </h1> |
| <div id="minitoc-area"> |
| <ul class="minitoc"> |
| <li> |
| <a href="#Description"> Description </a> |
| </li> |
| <li> |
| <a href="#Synopsis"> Synopsis </a> |
| </li> |
| <li> |
| <a href="#Test+Space+Population"> Test Space Population </a> |
| <ul class="minitoc"> |
| <li> |
| <a href="#Structure+Generator"> Structure Generator </a> |
| </li> |
| <li> |
| <a href="#Test+Space+Generator"> Test Space Generator </a> |
| </li> |
| </ul> |
| </li> |
| </ul> |
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| |
| <a name="N1000D"></a><a name="Description"></a> |
| <h2 class="h3"> Description </h2> |
| <div class="section"> |
| <p> |
| The synthetic load generator is a tool for testing NameNode behavior |
| under different client loads. The user can generate different mixes |
| of read, write, and list requests by specifying the probabilities of |
| read and write. The user controls the intensity of the load by adjusting |
| parameters for the number of worker threads and the delay between |
| operations. While load generators are running, the user can profile and |
| monitor the running of the NameNode. When a load generator exits, it |
| prints some NameNode statistics like the average execution time of each |
| kind of operation and the NameNode throughput. |
| </p> |
| </div> |
| |
| <a name="N10017"></a><a name="Synopsis"></a> |
| <h2 class="h3"> Synopsis </h2> |
| <div class="section"> |
| <p> |
| |
| <span class="codefrag">java LoadGenerator [options]</span> |
| <br> |
| |
| </p> |
| <p> |
| Options include:<br> |
| |
| <span class="codefrag"> -readProbability <read probability></span> |
| <br> |
| |
| <span class="codefrag"> the probability of the read operation; |
| default is 0.3333. </span> |
| <br> |
| |
| <span class="codefrag"> -writeProbability <write probability></span> |
| <br> |
| |
| <span class="codefrag"> the probability of the write |
| operations; default is 0.3333.</span> |
| <br> |
| |
| <span class="codefrag"> -root <test space root></span> |
| <br> |
| |
| <span class="codefrag"> the root of the test space; |
| default is /testLoadSpace.</span> |
| <br> |
| |
| <span class="codefrag"> -maxDelayBetweenOps |
| <maxDelayBetweenOpsInMillis></span> |
| <br> |
| |
| <span class="codefrag"> the maximum delay between two consecutive |
| operations in a thread; default is 0 indicating no delay. |
| </span> |
| <br> |
| |
| <span class="codefrag"> -numOfThreads <numOfThreads></span> |
| <br> |
| |
| <span class="codefrag"> the number of threads to spawn; |
| default is 200.</span> |
| <br> |
| |
| <span class="codefrag"> -elapsedTime <elapsedTimeInSecs></span> |
| <br> |
| |
| <span class="codefrag"> the number of seconds that the program |
| will run; A value of zero indicates that the program runs |
| forever. The default value is 0.</span> |
| <br> |
| |
| <span class="codefrag"> -startTime <startTimeInMillis></span> |
| <br> |
| |
| <span class="codefrag"> the time that all worker threads |
| start to run. By default it is 10 seconds after the main |
| program starts running.This creates a barrier if more than |
| one load generator is running. |
| </span> |
| <br> |
| |
| <span class="codefrag"> -seed <seed></span> |
| <br> |
| |
| <span class="codefrag"> the random generator seed for repeating |
| requests to NameNode when running with a single thread; |
| default is the current time.</span> |
| <br> |
| |
| </p> |
| <p> |
| After command line argument parsing, the load generator traverses |
| the test space and builds a table of all directories and another table |
| of all files in the test space. It then waits until the start time to |
| spawn the number of worker threads as specified by the user. Each |
| thread sends a stream of requests to NameNode. At each iteration, |
| it first decides if it is going to read a file, create a file, or |
| list a directory following the read and write probabilities specified |
| by the user. The listing probability is equal to |
| <em>1-read probability-write probability</em>. When reading, |
| it randomly picks a file in the test space and reads the entire file. |
| When writing, it randomly picks a directory in the test space and |
| creates a file there. To avoid two threads with the same load |
| generator or from two different load generators create the same |
| file, the file name consists of the current machine's host name |
| and the thread id. The length of the file follows Gaussian |
| distribution with an average size of 2 blocks and the standard |
| deviation of 1. The new file is filled with byte 'a'. To avoid |
| the test space to grow indefinitely, the file is deleted immediately |
| after the file creation completes. While listing, it randomly |
| picks a directory in the test space and lists its content. |
| After an operation completes, the thread pauses for a random |
| amount of time in the range of [0, maxDelayBetweenOps] if the |
| specified maximum delay is not zero. All threads are stopped when |
| the specified elapsed time is passed. Before exiting, the program |
| prints the average execution for each kind of NameNode operations, |
| and the number of requests served by the NameNode per second. |
| </p> |
| </div> |
| |
| <a name="N10070"></a><a name="Test+Space+Population"></a> |
| <h2 class="h3"> Test Space Population </h2> |
| <div class="section"> |
| <p> |
| The user needs to populate a test space before she runs a |
| load generator. The structure generator generates a random |
| test space structure and the data generator creates the files |
| and directories of the test space in Hadoop distributed file system. |
| </p> |
| <a name="N10079"></a><a name="Structure+Generator"></a> |
| <h3 class="h4"> Structure Generator </h3> |
| <p> |
| This tool generates a random namespace structure with the |
| following constraints: |
| </p> |
| <ol> |
| |
| <li>The number of subdirectories that a directory can have is |
| a random number in [minWidth, maxWidth].</li> |
| |
| <li>The maximum depth of each subdirectory is a random number |
| [2*maxDepth/3, maxDepth].</li> |
| |
| <li>Files are randomly placed in leaf directories. The size of |
| each file follows Gaussian distribution with an average size |
| of 1 block and a standard deviation of 1.</li> |
| |
| </ol> |
| <p> |
| The generated namespace structure is described by two files in |
| the output directory. Each line of the first file contains the |
| full name of a leaf directory. Each line of the second file |
| contains the full name of a file and its size, separated by a blank. |
| </p> |
| <p> |
| The synopsis of the command is |
| </p> |
| <p> |
| |
| <span class="codefrag">java StructureGenerator [options]</span> |
| |
| </p> |
| <p> |
| Options include:<br> |
| |
| <span class="codefrag"> -maxDepth <maxDepth></span> |
| <br> |
| |
| <span class="codefrag"> maximum depth of the directory tree; |
| default is 5.</span> |
| <br> |
| |
| <span class="codefrag"> -minWidth <minWidth></span> |
| <br> |
| |
| <span class="codefrag"> minimum number of subdirectories per |
| directories; default is 1.</span> |
| <br> |
| |
| <span class="codefrag"> -maxWidth <maxWidth></span> |
| <br> |
| |
| <span class="codefrag"> maximum number of subdirectories per |
| directories; default is 5.</span> |
| <br> |
| |
| <span class="codefrag"> -numOfFiles <#OfFiles></span> |
| <br> |
| |
| <span class="codefrag"> the total number of files in the test |
| space; default is 10.</span> |
| <br> |
| |
| <span class="codefrag"> -avgFileSize <avgFileSizeInBlocks></span> |
| <br> |
| |
| <span class="codefrag"> average size of blocks; default is 1. |
| </span> |
| <br> |
| |
| <span class="codefrag"> -outDir <outDir></span> |
| <br> |
| |
| <span class="codefrag"> output directory; default is the |
| current directory. </span> |
| <br> |
| |
| <span class="codefrag"> -seed <seed></span> |
| <br> |
| |
| <span class="codefrag"> random number generator seed; |
| default is the current time.</span> |
| <br> |
| |
| </p> |
| <a name="N100D8"></a><a name="Test+Space+Generator"></a> |
| <h3 class="h4"> Test Space Generator </h3> |
| <p> |
| This tool reads the directory structure and file structure from |
| the input directory and creates the namespace in Hadoop distributed |
| file system. All files are filled with byte 'a'. |
| </p> |
| <p> |
| The synopsis of the command is |
| </p> |
| <p> |
| |
| <span class="codefrag">java DataGenerator [options]</span> |
| |
| </p> |
| <p> |
| Options include:<br> |
| |
| <span class="codefrag"> -inDir <inDir></span> |
| <br> |
| |
| <span class="codefrag"> input directory name where directory/file |
| structures are stored; default is the current directory. |
| </span> |
| <br> |
| |
| <span class="codefrag"> -root <test space root></span> |
| <br> |
| |
| <span class="codefrag"> the name of the root directory which the |
| new namespace is going to be placed under; |
| default is "/testLoadSpace".</span> |
| <br> |
| |
| </p> |
| </div> |
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