经过一番努力，我最终设法在伪分布式节点中使用 hadoop，namenode 和 jobtracker 完美运行(在 http://localhost:50070 和 http://localhost:50030)
昨天我尝试重启我的 namenode、datanode 等:
$hadoop namenode -format
$start-all.sh
jps 给我以下输出:
17148 DataNode
17295 SecondaryNameNode
17419 JobTracker
17669 Jps
Namenode 似乎不再愿意启动了......Jobtracker 几秒钟后就死了。
标记我没有重新启动计算机并且我已经尝试了以下线程中给出的解决方案 Namenode not getting started但它没有帮助。
这是namenode的日志，有一堆错误。我完全不知道如何解决我的问题
2013-08-16 09:02:21,647 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: STARTUP_MSG:
/************************************************************
STARTUP_MSG: Starting NameNode
STARTUP_MSG: host = localhost.lan/192.168.1.94
STARTUP_MSG: args = []
STARTUP_MSG: version = 1.2.1
STARTUP_MSG: build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2 -r 1503152; compiled by 'mattf' on Mon Jul 22 15:23:09 PDT 2013
STARTUP_MSG: java = 1.7.0_25
************************************************************/
2013-08-16 09:02:21,839 INFO org.apache.hadoop.metrics2.impl.MetricsConfig: loaded properties from hadoop-metrics2.properties
2013-08-16 09:02:21,868 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source MetricsSystem,sub=Stats registered.
2013-08-16 09:02:21,871 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Scheduled snapshot period at 10 second(s).
2013-08-16 09:02:21,871 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: NameNode metrics system started
2013-08-16 09:02:22,098 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source ugi registered.
2013-08-16 09:02:22,103 WARN org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Source name ugi already exists!
2013-08-16 09:02:22,110 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source jvm registered.
2013-08-16 09:02:22,111 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source NameNode registered.
2013-08-16 09:02:22,140 INFO org.apache.hadoop.hdfs.util.GSet: Computing capacity for map BlocksMap
2013-08-16 09:02:22,140 INFO org.apache.hadoop.hdfs.util.GSet: VM type = 64-bit
2013-08-16 09:02:22,140 INFO org.apache.hadoop.hdfs.util.GSet: 2.0% max memory = 932118528
2013-08-16 09:02:22,140 INFO org.apache.hadoop.hdfs.util.GSet: capacity = 2^21 = 2097152 entries
2013-08-16 09:02:22,140 INFO org.apache.hadoop.hdfs.util.GSet: recommended=2097152, actual=2097152
2013-08-16 09:02:22,174 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: fsOwner=rlk
2013-08-16 09:02:22,174 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: supergroup=supergroup
2013-08-16 09:02:22,174 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: isPermissionEnabled=true
2013-08-16 09:02:22,189 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: dfs.block.invalidate.limit=100
2013-08-16 09:02:22,189 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: isAccessTokenEnabled=false accessKeyUpdateInterval=0 min(s), accessTokenLifetime=0 min(s)
2013-08-16 09:02:22,271 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Registered FSNamesystemStateMBean and NameNodeMXBean
2013-08-16 09:02:22,320 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: dfs.namenode.edits.toleration.length = 0
2013-08-16 09:02:22,321 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: Caching file names occuring more than 10 times
2013-08-16 09:02:22,363 INFO org.apache.hadoop.hdfs.server.common.Storage: Start loading image file /home/rlk/hduser/dfs/name/current/fsimage
2013-08-16 09:02:22,364 INFO org.apache.hadoop.hdfs.server.common.Storage: Number of files = 1
2013-08-16 09:02:22,372 INFO org.apache.hadoop.hdfs.server.common.Storage: Number of files under construction = 0
2013-08-16 09:02:22,375 INFO org.apache.hadoop.hdfs.server.common.Storage: Image file /home/rlk/hduser/dfs/name/current/fsimage of size 109 bytes loaded in 0 seconds.
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Start loading edits file /home/rlk/hduser/dfs/name/current/edits
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: EOF of /home/rlk/hduser/dfs/name/current/edits, reached end of edit log Number of transactions found: 0. Bytes read: 4
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Start checking end of edit log (/home/rlk/hduser/dfs/name/current/edits) ...
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Checked the bytes after the end of edit log (/home/rlk/hduser/dfs/name/current/edits):
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Padding position = -1 (-1 means padding not found)
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Edit log length = 4
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Read length = 4
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Corruption length = 0
2013-08-16 09:02:22,376 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Toleration length = 0 (= dfs.namenode.edits.toleration.length)
2013-08-16 09:02:22,382 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Summary: |---------- Read=4 ----------|-- Corrupt=0 --|-- Pad=0 --|
2013-08-16 09:02:22,382 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Edits file /home/rlk/hduser/dfs/name/current/edits of size 4 edits # 0 loaded in 0 seconds.
2013-08-16 09:02:22,387 INFO org.apache.hadoop.hdfs.server.common.Storage: Image file /home/rlk/hduser/dfs/name/current/fsimage of size 109 bytes saved in 0 seconds.
2013-08-16 09:02:22,553 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: closing edit log: position=4, editlog=/home/rlk/hduser/dfs/name/current/edits
2013-08-16 09:02:22,553 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: close success: truncate to 4, editlog=/home/rlk/hduser/dfs/name/current/edits
2013-08-16 09:02:22,933 INFO org.apache.hadoop.hdfs.server.namenode.NameCache: initialized with 0 entries 0 lookups
2013-08-16 09:02:22,933 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Finished loading FSImage in 776 msecs
2013-08-16 09:02:22,935 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: dfs.safemode.threshold.pct = 0.9990000128746033
2013-08-16 09:02:22,935 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: dfs.namenode.safemode.min.datanodes = 0
2013-08-16 09:02:22,935 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: dfs.safemode.extension = 30000
2013-08-16 09:02:22,935 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Number of blocks excluded by safe block count: 0 total blocks: 0 and thus the safe blocks: 0
2013-08-16 09:02:22,956 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Total number of blocks = 0
2013-08-16 09:02:22,956 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Number of invalid blocks = 0
2013-08-16 09:02:22,956 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Number of under-replicated blocks = 0
2013-08-16 09:02:22,956 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Number of over-replicated blocks = 0
2013-08-16 09:02:22,956 INFO org.apache.hadoop.hdfs.StateChange: STATE* Safe mode termination scan for invalid, over- and under-replicated blocks completed in 21 msec
2013-08-16 09:02:22,956 INFO org.apache.hadoop.hdfs.StateChange: STATE* Leaving safe mode after 0 secs
2013-08-16 09:02:22,956 INFO org.apache.hadoop.hdfs.StateChange: STATE* Network topology has 0 racks and 0 datanodes
2013-08-16 09:02:22,962 INFO org.apache.hadoop.hdfs.StateChange: STATE* UnderReplicatedBlocks has 0 blocks
2013-08-16 09:02:22,972 INFO org.apache.hadoop.util.HostsFileReader: Refreshing hosts (include/exclude) list
2013-08-16 09:02:22,974 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: ReplicateQueue QueueProcessingStatistics: First cycle completed 0 blocks in 1 msec
2013-08-16 09:02:22,974 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: ReplicateQueue QueueProcessingStatistics: Queue flush completed 0 blocks in 1 msec processing time, 1 msec clock time, 1 cycles
2013-08-16 09:02:22,974 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: InvalidateQueue QueueProcessingStatistics: First cycle completed 0 blocks in 0 msec
2013-08-16 09:02:22,974 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: InvalidateQueue QueueProcessingStatistics: Queue flush completed 0 blocks in 0 msec processing time, 0 msec clock time, 1 cycles
2013-08-16 09:02:22,983 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source FSNamesystemMetrics registered.
2013-08-16 09:02:23,026 INFO org.apache.hadoop.ipc.Server: Starting SocketReader
2013-08-16 09:02:23,029 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source RpcDetailedActivityForPort8020 registered.
2013-08-16 09:02:23,030 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source RpcActivityForPort8020 registered.
2013-08-16 09:02:23,037 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: Namenode up at: localhost.localdomain/127.0.0.1:8020
2013-08-16 09:02:23,195 INFO org.mortbay.log: Logging to org.slf4j.impl.Log4jLoggerAdapter(org.mortbay.log) via org.mortbay.log.Slf4jLog
2013-08-16 09:02:23,306 INFO org.apache.hadoop.http.HttpServer: Added global filtersafety (class=org.apache.hadoop.http.HttpServer$QuotingInputFilter)
2013-08-16 09:02:23,318 INFO org.apache.hadoop.http.HttpServer: dfs.webhdfs.enabled = false
2013-08-16 09:02:23,329 INFO org.apache.hadoop.http.HttpServer: Port returned by webServer.getConnectors()[0].getLocalPort() before open() is -1. Opening the listener on 50070
2013-08-16 09:02:23,331 INFO org.apache.hadoop.http.HttpServer: listener.getLocalPort() returned 50070 webServer.getConnectors()[0].getLocalPort() returned 50070
2013-08-16 09:02:23,331 INFO org.apache.hadoop.http.HttpServer: Jetty bound to port 50070
2013-08-16 09:02:23,331 INFO org.mortbay.log: jetty-6.1.26
2013-08-16 09:02:23,386 INFO org.mortbay.log: Extract jar:file:/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.25-2.3.12.3.fc19.x86_64/jre/lib/ext/hadoop-core-1.2.1.jar!/webapps/hdfs to /tmp/Jetty_0_0_0_0_50070_hdfs____w2cu08/webapp
2013-08-16 09:02:25,171 WARN org.mortbay.log: failed jsp: java.lang.NoClassDefFoundError: javax/servlet/jsp/JspFactory
2013-08-16 09:02:25,215 WARN org.mortbay.log: failed org.mortbay.jetty.webapp.WebAppContext@12305d34{/,jar:file:/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.25-2.3.12.3.fc19.x86_64/jre/lib/ext/hadoop-core-1.2.1.jar!/webapps/hdfs}: java.lang.NoClassDefFoundError: javax/servlet/jsp/JspFactory
2013-08-16 09:02:25,225 WARN org.mortbay.log: failed ContextHandlerCollection@25370a40: java.lang.NoClassDefFoundError: javax/servlet/jsp/JspFactory
2013-08-16 09:02:25,226 ERROR org.mortbay.log: Error starting handlers
java.lang.NoClassDefFoundError: javax/servlet/jsp/JspFactory
at org.apache.jasper.servlet.JspServlet.init(JspServlet.java:99)
at org.mortbay.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:440)
at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:263)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:736)
at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1282)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:518)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:499)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerCollection.doStart(HandlerCollection.java:152)
at org.mortbay.jetty.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:156)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
at org.mortbay.jetty.Server.doStart(Server.java:224)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.apache.hadoop.http.HttpServer.start(HttpServer.java:638)
at org.apache.hadoop.hdfs.server.namenode.NameNode$1.run(NameNode.java:517)
at org.apache.hadoop.hdfs.server.namenode.NameNode$1.run(NameNode.java:395)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
at org.apache.hadoop.hdfs.server.namenode.NameNode.startHttpServer(NameNode.java:395)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:337)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:569)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1479)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1488)
Caused by: java.lang.ClassNotFoundException: javax.servlet.jsp.JspFactory
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 27 more
2013-08-16 09:02:25,307 INFO org.mortbay.log: Started SelectChannelConnector@0.0.0.0:50070
2013-08-16 09:02:25,307 ERROR org.apache.hadoop.security.UserGroupInformation: PriviledgedActionException as:rlk cause:java.io.IOException: Problem in starting http server. Server handlers failed
2013-08-16 09:02:25,308 INFO org.mortbay.log: Stopped SelectChannelConnector@0.0.0.0:50070
2013-08-16 09:02:25,308 ERROR org.mortbay.log: EXCEPTION
java.lang.NullPointerException
at org.apache.jasper.servlet.JspServlet.destroy(JspServlet.java:282)
at org.mortbay.jetty.servlet.ServletHolder.destroyInstance(ServletHolder.java:318)
at org.mortbay.jetty.servlet.ServletHolder.doStop(ServletHolder.java:289)
at org.mortbay.component.AbstractLifeCycle.stop(AbstractLifeCycle.java:76)
at org.mortbay.jetty.servlet.ServletHandler.doStop(ServletHandler.java:185)
at org.mortbay.component.AbstractLifeCycle.stop(AbstractLifeCycle.java:76)
at org.mortbay.jetty.handler.HandlerWrapper.doStop(HandlerWrapper.java:142)
at org.mortbay.component.AbstractLifeCycle.stop(AbstractLifeCycle.java:76)
at org.mortbay.jetty.handler.HandlerWrapper.doStop(HandlerWrapper.java:142)
at org.mortbay.jetty.servlet.SessionHandler.doStop(SessionHandler.java:125)
at org.mortbay.component.AbstractLifeCycle.stop(AbstractLifeCycle.java:76)
at org.mortbay.jetty.handler.HandlerWrapper.doStop(HandlerWrapper.java:142)
at org.mortbay.jetty.handler.ContextHandler.doStop(ContextHandler.java:592)
at org.mortbay.jetty.webapp.WebAppContext.doStop(WebAppContext.java:537)
at org.mortbay.component.AbstractLifeCycle.stop(AbstractLifeCycle.java:76)
at org.mortbay.jetty.handler.HandlerCollection.doStop(HandlerCollection.java:169)
at org.mortbay.component.AbstractLifeCycle.stop(AbstractLifeCycle.java:76)
at org.mortbay.jetty.handler.HandlerWrapper.doStop(HandlerWrapper.java:142)
at org.mortbay.jetty.Server.doStop(Server.java:283)
at org.mortbay.component.AbstractLifeCycle.stop(AbstractLifeCycle.java:76)
at org.apache.hadoop.http.HttpServer.stop(HttpServer.java:688)
at org.apache.hadoop.hdfs.server.namenode.NameNode.stop(NameNode.java:604)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:571)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1479)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1488)
2013-08-16 09:02:25,336 WARN org.apache.hadoop.hdfs.server.namenode.FSNamesystem: ReplicationMonitor thread received InterruptedExceptionjava.lang.InterruptedException: sleep interrupted
2013-08-16 09:02:25,337 INFO org.apache.hadoop.hdfs.server.namenode.DecommissionManager: Interrupted Monitor
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at org.apache.hadoop.hdfs.server.namenode.DecommissionManager$Monitor.run(DecommissionManager.java:65)
at java.lang.Thread.run(Thread.java:724)
2013-08-16 09:02:25,339 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: Number of transactions: 0 Total time for transactions(ms): 0 Number of transactions batched in Syncs: 0 Number of syncs: 0 SyncTimes(ms): 0
2013-08-16 09:02:25,375 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: closing edit log: position=4, editlog=/home/rlk/hduser/dfs/name/current/edits
2013-08-16 09:02:25,375 INFO org.apache.hadoop.hdfs.server.namenode.FSEditLog: close success: truncate to 4, editlog=/home/rlk/hduser/dfs/name/current/edits
2013-08-16 09:02:25,403 INFO org.apache.hadoop.ipc.Server: Stopping server on 8020
2013-08-16 09:02:25,411 INFO org.apache.hadoop.ipc.metrics.RpcInstrumentation: shut down
2013-08-16 09:02:25,412 ERROR org.apache.hadoop.hdfs.server.namenode.NameNode: java.io.IOException: Problem in starting http server. Server handlers failed
at org.apache.hadoop.http.HttpServer.start(HttpServer.java:662)
at org.apache.hadoop.hdfs.server.namenode.NameNode$1.run(NameNode.java:517)
at org.apache.hadoop.hdfs.server.namenode.NameNode$1.run(NameNode.java:395)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
at org.apache.hadoop.hdfs.server.namenode.NameNode.startHttpServer(NameNode.java:395)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:337)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:569)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1479)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1488)
2013-08-16 09:02:25,413 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at localhost.lan/192.168.1.94
************************************************************/
我也给你我的hadoop配置(我使用的是hadoop-1.2.1):
核心网站.xml :
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!-- core-site.xml -->
<configuration>
<property>
<name>hadoop.tmp.dir</name>
<value>/home/rlk/hduser</value>
</property>
<property>
<name>fs.default.name</name>
<value>hdfs://localhost/</value>
</property>
</configuration>
hdfs-site.xml :
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!-- hdfs-site.xml -->
<configuration>
<property>
<name>dfs.replication</name>
<value>1</value>
</property>
</configuration>
mapred-site.xml :
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!-- mapred-site.xml -->
<configuration>
<property>
<name>mapred.job.tracker</name>
<value>localhost:8021</value>
</property>
</configuration>
最佳答案
我找到了解决方案:这是一些 jar 冲突。我在 hadoop-x.y.z/ 和 hadoop-x.y.z/lib 以及 path-to-java/jre/lib/ext/ 中都有重复的 jar 文件。
我刚刚删除了前者，一切又恢复正常了。
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1.1.1 YARN的介绍 为克服Hadoop1.0中HDFS和MapReduce存在的各种问题⽽提出的，针对Hadoop1.0中的MapReduce在扩展性和多框架⽀持⽅⾯的不⾜，提出了全新的资源管理框架YARN. ApacheYARN（YetanotherResourceNegotiator的缩写）是Hadoop集群的资源管理系统，负责为计算程序提供服务器计算资源，相当于⼀个分布式的操作系统平台，⽽MapReduce等计算程序则相当于运⾏于操作系统之上的应⽤程序。 YARN被引⼊Hadoop2,最初是为了改善MapReduce的实现，但是因为具有⾜够的通⽤性，同样可以⽀持其他的分布式计算模
我想为名字验证编写一个正则表达式。正则表达式应包括所有字母(拉丁/法语/德语字符等)。但是我想从中排除数字并允许-。所以基本上它是\w(减)数(加)-。请帮忙。 最佳答案 ^[\p{L}-]+$\p{L}匹配anykindofletterfromanylanguage. 关于ruby-on-rails-rails中的正则表达式匹配[\w]和"-"但不匹配数字，我们在StackOverflow上找到一个类似的问题： https://stackoverflow.c
我想用Capistrano启动sidekiq。下面是代码namespace:sidekiqdotask:startdorun"cd#{current_path}&&bundleexecsidekiq-c10-eproduction-Llog/sidekiq.log&"pcapture("psaux|grepsidekiq|awk'{print$2}'|sed-n1p").strip!endend它执行成功但sidekiq仍然没有在服务器上启动。输出:$capsidekiq:starttriggeringloadcallbacks*2014-06-0315:03:01executing`
我有一个正在升级到Rails3的Rails2.3.5应用程序。我做了所有我需要做的升级以及当我使用启动Rails服务器时要做的事情railsserver它给了我这个PleaseswitchtoRuby1.9'sstandardCSVlibrary.It'sFasterCSVplussupportforRuby1.9'sm17nencodingengine.我正在使用ruby-1.9.2-p0并安装了fastercsv(1.5.3)gem。在puts语句的帮助下，我能够追踪到错误发生的位置。我发现执行在这一行停止了Bundler.require(:default,Rails.env)if
电脑启动出现显示器黑屏是一个相当常见的问题。如果您遇到了这个问题，不要惊慌，因为它有很多可能的原因，可以采取一些简单的措施来解决它。在本文中，小编将介绍下面4种常见的电脑启动后显示器黑屏的原因，排查这些原因，快速解决！ 演示机型：联想Ideapad700-15ISK-ISE系统版本：Windows10一、显示器问题如果出现电脑启动后显示器黑屏的情况。那么首先您需要检查一下显示器是否正常工作。您可以通过更换另一个显示器或将当前显示器连接到另一台计算机来检查显示器是否存在问题。如果问题仍然存在，那么您可以排除显示器故障的可能性。 二、显卡问题如果您的电脑配备了独立显卡，那么显卡故障也可能是导致电脑
plsql连接Oracle超时，完犊子了肯定是服务器断电了。得马上检查Oracle服务器状态1、检查数据库是否启动su-oracle切换到Oracle用户，输入sqlplus/assysdba显示连接状态。如果末尾显示的状态是Connectedtoanidleinstance.证明未启动2、启动数据库startup启动数据库，末尾出现Databaseopened说明数据库启动成功3、查看数据库监听是否正常先quit;断开Oracle连接，使用lsnrctlstatus查看监听状态，如果出现TNS-开头的Nolistener、Connectionrefused等错误，说明监听未启动4、启动数据库
当Rails启动时，它会预加载所有依赖项(gems)，这会导致启动时间非常缓慢。在我正在处理的一个中型项目中，Rails的启动时间为10-15秒，具体取决于机器。虽然这在生产中不是问题，但在开发中却是一个巨大的痛苦。特别是在工作TDD/BDD时。有加速测试的解决方案(如spork)，但它们会引入自己的问题。我的问题是:为什么不在每个代码文件中要求所需的依赖项，而不是在启动时预加载所有内容？手动要求的缺点是什么？额外的代码行？ 最佳答案 Rails不是PHP。一些资源是自动加载的，但是您可能需要的所有资源都在启动/初始化时加载，因为最
我有一个作为守护程序运行的Sinatra应用程序，使用Apache端口转发在端口80和端口7655之间进行调解。这在过去一直运行良好。今天，不太好。我不明白为什么。问题:sudorubymy_process.rb返回:/var/lib/gems/1.9.1/gems/eventmachine-1.0.0/lib/eventmachine.rb:526:in`start_tcp_server':noacceptor(portisinuseorrequiresrootprivileges)(RuntimeError)尝试过:更新所有系统包，更新所有gem。没有帮助(除了来自eventm