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225 | </div> |
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226 | <h1> HDFS Synthetic Load Generator Guide </h1> |
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227 | <div id="minitoc-area"> |
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228 | <ul class="minitoc"> |
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229 | <li> |
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230 | <a href="#Description"> Description </a> |
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231 | </li> |
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232 | <li> |
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233 | <a href="#Synopsis"> Synopsis </a> |
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234 | </li> |
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235 | <li> |
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236 | <a href="#Test+Space+Population"> Test Space Population </a> |
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237 | <ul class="minitoc"> |
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238 | <li> |
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239 | <a href="#Structure+Generator"> Structure Generator </a> |
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240 | </li> |
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241 | <li> |
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242 | <a href="#Test+Space+Generator"> Test Space Generator </a> |
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243 | </li> |
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244 | </ul> |
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245 | </li> |
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246 | </ul> |
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247 | </div> |
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248 | |
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249 | <a name="N1000D"></a><a name="Description"></a> |
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250 | <h2 class="h3"> Description </h2> |
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251 | <div class="section"> |
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252 | <p> |
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253 | The synthetic load generator (SLG) is a tool for testing NameNode behavior |
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254 | under different client loads. The user can generate different mixes |
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255 | of read, write, and list requests by specifying the probabilities of |
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256 | read and write. The user controls the intensity of the load by adjusting |
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257 | parameters for the number of worker threads and the delay between |
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258 | operations. While load generators are running, the user can profile and |
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259 | monitor the running of the NameNode. When a load generator exits, it |
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260 | prints some NameNode statistics like the average execution time of each |
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261 | kind of operation and the NameNode throughput. |
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262 | </p> |
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263 | </div> |
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264 | |
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265 | <a name="N10017"></a><a name="Synopsis"></a> |
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266 | <h2 class="h3"> Synopsis </h2> |
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267 | <div class="section"> |
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268 | <p> |
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269 | |
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270 | <span class="codefrag">java LoadGenerator [options]</span> |
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271 | <br> |
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272 | |
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273 | </p> |
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274 | <p> |
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275 | Options include:<br> |
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276 | |
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277 | <span class="codefrag"> -readProbability <read probability></span> |
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278 | <br> |
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279 | |
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280 | <span class="codefrag"> the probability of the read operation; |
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281 | default is 0.3333. </span> |
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282 | <br> |
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283 | |
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284 | <span class="codefrag"> -writeProbability <write probability></span> |
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285 | <br> |
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286 | |
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287 | <span class="codefrag"> the probability of the write |
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288 | operations; default is 0.3333.</span> |
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289 | <br> |
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290 | |
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291 | <span class="codefrag"> -root <test space root></span> |
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292 | <br> |
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293 | |
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294 | <span class="codefrag"> the root of the test space; |
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295 | default is /testLoadSpace.</span> |
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296 | <br> |
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297 | |
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298 | <span class="codefrag"> -maxDelayBetweenOps |
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299 | <maxDelayBetweenOpsInMillis></span> |
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300 | <br> |
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301 | |
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302 | <span class="codefrag"> the maximum delay between two consecutive |
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303 | operations in a thread; default is 0 indicating no delay. |
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304 | </span> |
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305 | <br> |
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306 | |
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307 | <span class="codefrag"> -numOfThreads <numOfThreads></span> |
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308 | <br> |
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309 | |
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310 | <span class="codefrag"> the number of threads to spawn; |
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311 | default is 200.</span> |
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312 | <br> |
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313 | |
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314 | <span class="codefrag"> -elapsedTime <elapsedTimeInSecs></span> |
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315 | <br> |
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316 | |
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317 | <span class="codefrag"> the number of seconds that the program |
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318 | will run; A value of zero indicates that the program runs |
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319 | forever. The default value is 0.</span> |
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320 | <br> |
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321 | |
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322 | <span class="codefrag"> -startTime <startTimeInMillis></span> |
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323 | <br> |
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324 | |
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325 | <span class="codefrag"> the time that all worker threads |
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326 | start to run. By default it is 10 seconds after the main |
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327 | program starts running.This creates a barrier if more than |
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328 | one load generator is running. |
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329 | </span> |
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330 | <br> |
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331 | |
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332 | <span class="codefrag"> -seed <seed></span> |
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333 | <br> |
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334 | |
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335 | <span class="codefrag"> the random generator seed for repeating |
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336 | requests to NameNode when running with a single thread; |
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337 | default is the current time.</span> |
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338 | <br> |
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339 | |
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340 | </p> |
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341 | <p> |
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342 | After command line argument parsing, the load generator traverses |
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343 | the test space and builds a table of all directories and another table |
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344 | of all files in the test space. It then waits until the start time to |
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345 | spawn the number of worker threads as specified by the user. Each |
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346 | thread sends a stream of requests to NameNode. At each iteration, |
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347 | it first decides if it is going to read a file, create a file, or |
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348 | list a directory following the read and write probabilities specified |
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349 | by the user. The listing probability is equal to |
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350 | <em>1-read probability-write probability</em>. When reading, |
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351 | it randomly picks a file in the test space and reads the entire file. |
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352 | When writing, it randomly picks a directory in the test space and |
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353 | creates a file there. To avoid two threads with the same load |
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354 | generator or from two different load generators create the same |
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355 | file, the file name consists of the current machine's host name |
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356 | and the thread id. The length of the file follows Gaussian |
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357 | distribution with an average size of 2 blocks and the standard |
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358 | deviation of 1. The new file is filled with byte 'a'. To avoid |
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359 | the test space to grow indefinitely, the file is deleted immediately |
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360 | after the file creation completes. While listing, it randomly |
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361 | picks a directory in the test space and lists its content. |
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362 | After an operation completes, the thread pauses for a random |
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363 | amount of time in the range of [0, maxDelayBetweenOps] if the |
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364 | specified maximum delay is not zero. All threads are stopped when |
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365 | the specified elapsed time is passed. Before exiting, the program |
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366 | prints the average execution for each kind of NameNode operations, |
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367 | and the number of requests served by the NameNode per second. |
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368 | </p> |
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369 | </div> |
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370 | |
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371 | <a name="N10070"></a><a name="Test+Space+Population"></a> |
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372 | <h2 class="h3"> Test Space Population </h2> |
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373 | <div class="section"> |
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374 | <p> |
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375 | The user needs to populate a test space before she runs a |
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376 | load generator. The structure generator generates a random |
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377 | test space structure and the data generator creates the files |
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378 | and directories of the test space in Hadoop distributed file system. |
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379 | </p> |
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380 | <a name="N10079"></a><a name="Structure+Generator"></a> |
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381 | <h3 class="h4"> Structure Generator </h3> |
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382 | <p> |
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383 | This tool generates a random namespace structure with the |
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384 | following constraints: |
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385 | </p> |
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386 | <ol> |
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387 | |
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388 | <li>The number of subdirectories that a directory can have is |
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389 | a random number in [minWidth, maxWidth].</li> |
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390 | |
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391 | <li>The maximum depth of each subdirectory is a random number |
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392 | [2*maxDepth/3, maxDepth].</li> |
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393 | |
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394 | <li>Files are randomly placed in leaf directories. The size of |
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395 | each file follows Gaussian distribution with an average size |
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396 | of 1 block and a standard deviation of 1.</li> |
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397 | |
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398 | </ol> |
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399 | <p> |
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400 | The generated namespace structure is described by two files in |
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401 | the output directory. Each line of the first file contains the |
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402 | full name of a leaf directory. Each line of the second file |
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403 | contains the full name of a file and its size, separated by a blank. |
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404 | </p> |
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405 | <p> |
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406 | The synopsis of the command is |
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407 | </p> |
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408 | <p> |
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409 | |
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410 | <span class="codefrag">java StructureGenerator [options]</span> |
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411 | |
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412 | </p> |
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413 | <p> |
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414 | Options include:<br> |
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415 | |
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416 | <span class="codefrag"> -maxDepth <maxDepth></span> |
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417 | <br> |
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418 | |
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419 | <span class="codefrag"> maximum depth of the directory tree; |
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420 | default is 5.</span> |
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421 | <br> |
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422 | |
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423 | <span class="codefrag"> -minWidth <minWidth></span> |
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424 | <br> |
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425 | |
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426 | <span class="codefrag"> minimum number of subdirectories per |
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427 | directories; default is 1.</span> |
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428 | <br> |
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429 | |
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430 | <span class="codefrag"> -maxWidth <maxWidth></span> |
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431 | <br> |
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432 | |
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433 | <span class="codefrag"> maximum number of subdirectories per |
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434 | directories; default is 5.</span> |
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435 | <br> |
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436 | |
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437 | <span class="codefrag"> -numOfFiles <#OfFiles></span> |
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438 | <br> |
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439 | |
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440 | <span class="codefrag"> the total number of files in the test |
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441 | space; default is 10.</span> |
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442 | <br> |
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443 | |
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444 | <span class="codefrag"> -avgFileSize <avgFileSizeInBlocks></span> |
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445 | <br> |
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446 | |
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447 | <span class="codefrag"> average size of blocks; default is 1. |
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448 | </span> |
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449 | <br> |
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450 | |
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451 | <span class="codefrag"> -outDir <outDir></span> |
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452 | <br> |
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453 | |
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454 | <span class="codefrag"> output directory; default is the |
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455 | current directory. </span> |
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456 | <br> |
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457 | |
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458 | <span class="codefrag"> -seed <seed></span> |
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459 | <br> |
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460 | |
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461 | <span class="codefrag"> random number generator seed; |
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462 | default is the current time.</span> |
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463 | <br> |
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464 | |
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465 | </p> |
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466 | <a name="N100D8"></a><a name="Test+Space+Generator"></a> |
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467 | <h3 class="h4"> Test Space Generator </h3> |
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468 | <p> |
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469 | This tool reads the directory structure and file structure from |
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470 | the input directory and creates the namespace in Hadoop distributed |
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471 | file system. All files are filled with byte 'a'. |
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472 | </p> |
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473 | <p> |
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474 | The synopsis of the command is |
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475 | </p> |
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476 | <p> |
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477 | |
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478 | <span class="codefrag">java DataGenerator [options]</span> |
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479 | |
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480 | </p> |
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481 | <p> |
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482 | Options include:<br> |
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483 | |
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484 | <span class="codefrag"> -inDir <inDir></span> |
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485 | <br> |
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486 | |
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487 | <span class="codefrag"> input directory name where directory/file |
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488 | structures are stored; default is the current directory. |
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489 | </span> |
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490 | <br> |
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491 | |
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492 | <span class="codefrag"> -root <test space root></span> |
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493 | <br> |
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494 | |
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495 | <span class="codefrag"> the name of the root directory which the |
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496 | new namespace is going to be placed under; |
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497 | default is "/testLoadSpace".</span> |
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498 | <br> |
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499 | |
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500 | </p> |
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501 | </div> |
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502 | |
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503 | </div> |
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504 | <!--+ |
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505 | |end content |
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506 | +--> |
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507 | <div class="clearboth"> </div> |
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508 | </div> |
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509 | <div id="footer"> |
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510 | <!--+ |
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511 | |start bottomstrip |
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512 | +--> |
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513 | <div class="lastmodified"> |
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514 | <script type="text/javascript"><!-- |
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515 | document.write("Last Published: " + document.lastModified); |
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516 | // --></script> |
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517 | </div> |
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518 | <div class="copyright"> |
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519 | Copyright © |
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520 | 2008 <a href="http://www.apache.org/licenses/">The Apache Software Foundation.</a> |
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521 | </div> |
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522 | <!--+ |
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523 | |end bottomstrip |
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524 | +--> |
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525 | </div> |
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526 | </body> |
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527 | </html> |
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