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Analysis of The fetcher capture model of nutch 1.0

Analysis of The fetcher capture model of nutch 1.0 ----------------------------- 1. Introduction 2. Capture Process Analysis 3. End ------------- 1. Introduction As a sub-project of Apache Lucene, nutch is mainly used to collect and index webpage data. It integrates Apache hadoop, Lucene, and other sub-projects. The following figure shows the general crawling process of the nutch: 1. Import the initial website inject to the crawldb for preparation. 2.

Reduce the Hadoop exception pull data failed (Error in shuffle in Fetcher)

Primary error message :error:org.apache.hadoop.mapreduce.task.reduce.shuffle$shuffleerror: Error in Shuffle in Fetcher#43workaround : Limit the shuffle memory usage of reduce hive:set mapreduce.reduce.shuffle.memory.limit.percent=0.1;MR:job.getConfiguration (). Setstrings ("Mapreduce.reduce.shuffle.memory.limit.percent", "0.1");principle Analysis : Reduce will initiate multiple fetch threads at map execution to a certain percentage to pull the outpu

Reading Process 3-Fetch

read the fetch code again, and found that this is a hard nut to crack, the focus of some materials on the Internet is also different, but in order to finish the nutch, you must cross this hurdle ...... Let's get started ~~~~ 1. the fetch entry is from the Fetcher of the crawl class. start with the fetch (segs [0], threads); statement. It uploads the segments and the number of crawled threads as parameters to the fetch function and enters the fetch fu

Python exception: Try, expect, finally

A little summary, otherwise always forget. [python] view plaincopyprint? 1. x = ' abc ' 2. def fetcher (obj, index): 3. return Obj[index] 4. 5. Fetcher (x, 4) Output: [Plain] view plaincopyprint? 1. File "test.py", line 6, in 2. Fetcher (x, 4) 3. File "test.py", line 4, in Fetcher 4. Return Obj[index] 5. Indexerror:s

Python try/except/finally, etc.

[code block] x = ' abc ' def fetcher (obj, index): return Obj[index] Fetcher (x, 4) Output: File "test.py", line 6, Fetcher (x, 4) File "test.py", line 4, in Fetcher return Obj[index] Indexerror:string index out of range First: Try not only catches exception

Kylin Build Cube Step 2 error (Kylin installed on slave node) __kylin

40:36 2016-08-14 22:47:17,782 INFO [pool-2-thread-1] ThreadPool. Defaultscheduler:106:job fetcher:0 running, 1 actual running, 1 ready, 7 others 2016-08-14 22:47:17,788 INFO [pool-3-thread-2] Manager. Executablemanager:274:job id:4ceac957-2e0a-4760-a8e1-2b34a473a1a5 from READY to RUNNING 2016-08-14 22:47:17,800 INFO [pool-3-thread-2] execution. Abstractexecutable:100:executing >>>>>>>>>>>>> Extract Fact Table Distinct Columns 2016-08-14 22:47:17,911 I

Article 3 MVC and observer models for Android Application Development

contextimpl cache. The view or controller object obtains the service management objects from the cache through the getsystemservice interface, interaction with the model. This method instantiates an object only once during packaging and registers it to the cache. Therefore, it can speed up obtaining system service management objects. Private Static final hashmap New hashmap Private Static void registerservice (string servicename, servicefetcher fetcher

Python try/except/finally

Illustrate the use of try/except/finally.If you do not use try/except/finally1 ' ABC ' 2 def fetcher (obj, index): 3 return Obj[index] 4 5 fetcher (x, 4)Output: " test.py " in 4) "test.py" in fetcher return obj[index]indexerror:string Index out of rangeUsing try/except/finally:First: Try not only catches exceptions, but also resumes execution1 def

[Distributed System Learning] 6.824 LEC2 RPC and thread notes

6.824 of the courses are usually prepared for you before class. Usually read a paper first, then ask you to ask a question, and then ask you to answer a question. Then class, and then decorate the lab.The preparation of the second lesson-crawlerThe second lesson is not a paper, it is to let you implement the crawler inside the Go tour. The original implementation in the Go tour is serial and may crawl to the same URL. ask you to parallel and go heavy.The simple idea is, in order to achieve paral

Detailed analysis of the workflow and file format of the nutch Crawler

Crawler of the nutchAndSearcherThe two parts are separated to ensure that the two parts can be deployed on the hardware platform. For example, crawler and searcher are placed on the two hosts respectively, this greatly improves flexibility and performance. I. general introduction: 1. Inject the seed URLs into the crawldb first.2. Loop: * Generate a subset of the URL generated from crawldb for crawling.* Fetch captures a small number of URLs to generate segments.* Parse analyzes the captured Segm

Python Try/except/finally__python

A little summary, otherwise always forget. x = ' abc ' def fetcher (obj, index): Return Obj[index] fetcher (x, 4) Output: File "test.py", line 6, in indexerror:string index out of range the first: Try not only catches exceptions, but also resumes execution Def catcher (): try: fetcher (x, 4) except: print "got Exception" p

"Original" Kafka Consumer source Code Analysis

group of associated objects, Where there is only one variable in object Shutdowncommand is used to identify the closing identity. When you see this identity in the queue, you need to end the iterative process. The Zookeeperconsumerconnector class is the core of this file. It implements the Consumerconnector trait, so it is also necessary to implement those abstract methods defined by the trait.Let's analyze some important fields of the class definition:1. Isshuttingdown: Used to identify whethe

Standard Crawler, a feast from the father of Python!

crawler until all finished. ""4with (yield from self.termination): 5 while self.todo or self.busy: 6 if self.todo: 7 url, max_redirect = Self.todo.popitem () 8 fetcher = Fetcher (URL, 9 Crawler=self,10 Max_redirect=max_redirect,11 Max_tries=self.max_tries,12) 13 self.busy[url] = Fetcher14 Fetcher.task = Asyncio. Task (Self.fetch (fetcher)) 15 else:16 yield from

GRAPHQL Service Development Guide _GRAPHQL

(" Purchasetime ")). FIeld (Field-> field.type (graphqldate). Name ("Finishtime"). field (field-> field.type (graphqldate). Name (" Timecreated ")). Build (); If Graphqlobjecttype field name and entity field type are the same, Graphql-java automatically does mapping. Querying queries with parameters Usually we create a node for the query, and all the clients using GRAPHQL to start the query with the node Public Graphqlobjecttype Getquerytype () {return newobject () . Name ("QueryType")

Goroutine and channel usage in Go

This is a creation in Article, where the information may have evolved or changed. As a go novice, the Go Guide was followed by the Go tutorial, and some goroutine related to channel issues were encountered when completing the web crawler exercises on the guide. The guide gives the original code at the beginning, the most important of which is the crawl function, the code is as follows: Crawl uses Fetcher to crawl pages recursively from a URL until t

else role in Python exceptions

First, the conceptAbnormal:Common Exception Statements:1. Try except Else2. Try Finally3. Raise4. Assert5. With ASSecond, the role of elseFirst, look at the exception and else in action:Except: Capturing exception items in a try, such as indexexception, SyntaxError, or the exception handler;ELSE: The statement in the else is executed only if there is no exception in the try;Here, I came up with two questions: 1. What is the time of the else use? 2. What is the difference between being and not be

The web crawler instance _golang the Go language implementation

This example describes the web crawler approach to the go implementation. Share to everyone for your reference. The specific analysis is as follows: This uses the Go Concurrency feature to execute the web crawler in parallel.Modify the Crawl function to crawl URLs in parallel and ensure that they are not duplicated. Copy Code code as follows: Package Main Import ( "FMT" ) Type Fetcher Interface { Fetch returns the body content of the

[Sorting] Analysis of Web Crawlers of nutch

the web page data stored in the existing webdb; The fetcher class runs during actual web page capturing. The files or folders generated by crawlers are generated by this class, nutch provides options-whether to parse the captured webpage. If this option is set to false, there will be no parseddata or parsedtext folders. Segments File Analysis Almost all files generated by the nutch crawler are key/value pairs. The difference is that the types a

Practical skills for crawling websites using python

time, I am so tired that the document does not exist. I have to read the source code to know how to complete it. If you want to support gzip/deflate and even some login extensions, you have to write a new HTTPClientFactory class for twisted, and so on. my frown is really big, so I gave up. If you have perseverance, please try it on your own. 2. design a simple multi-thread crawling class I still feel more comfortable in the python "local" stuff such as urllib. Think about it. if there is a

Go Linux Practice 4

This is a creation in Article, where the information may have evolved or changed. This is the most difficult go demo example of the current study ***************************************** If I could read it, you'd be apprenticeship, and my mission would be over. ***************************************** Package Main Import ("FMT") Type Fetcher Interface {Fetch (URL string) (body string, URLs []string, err Error)} Func Crawl (URL string, depth int,

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