| name | value | description |
| hadoop.job.history.location | | If job tracker is static the history files are stored
in this single well known place. If No value is set here, by default,
it is in the local file system at ${hadoop.log.dir}/history.
|
| hadoop.job.history.user.location | | User can specify a location to store the history files of
a particular job. If nothing is specified, the logs are stored in
output directory. The files are stored in "_logs/history/" in the directory.
User can stop logging by giving the value "none".
|
| io.sort.factor | 10 | The number of streams to merge at once while sorting
files. This determines the number of open file handles. |
| io.sort.mb | 100 | The total amount of buffer memory to use while sorting
files, in megabytes. By default, gives each merge stream 1MB, which
should minimize seeks. |
| io.sort.record.percent | 0.05 | The percentage of io.sort.mb dedicated to tracking record
boundaries. Let this value be r, io.sort.mb be x. The maximum number
of records collected before the collection thread must block is equal
to (r * x) / 4 |
| io.sort.spill.percent | 0.80 | The soft limit in either the buffer or record collection
buffers. Once reached, a thread will begin to spill the contents to disk
in the background. Note that this does not imply any chunking of data to
the spill. A value less than 0.5 is not recommended. |
| io.map.index.skip | 0 | Number of index entries to skip between each entry.
Zero by default. Setting this to values larger than zero can
facilitate opening large map files using less memory. |
| mapred.job.tracker | local | The host and port that the MapReduce job tracker runs
at. If "local", then jobs are run in-process as a single map
and reduce task.
|
| mapred.job.tracker.http.address | 0.0.0.0:50030 |
The job tracker http server address and port the server will listen on.
If the port is 0 then the server will start on a free port.
|
| mapred.job.tracker.handler.count | 10 |
The number of server threads for the JobTracker. This should be roughly
4% of the number of tasktracker nodes.
|
| mapred.task.tracker.report.address | 127.0.0.1:0 | The interface and port that task tracker server listens on.
Since it is only connected to by the tasks, it uses the local interface.
EXPERT ONLY. Should only be changed if your host does not have the loopback
interface. |
| mapred.local.dir | ${hadoop.tmp.dir}/mapred/local | The local directory where MapReduce stores intermediate
data files. May be a comma-separated list of
directories on different devices in order to spread disk i/o.
Directories that do not exist are ignored.
|
| mapred.system.dir | ${hadoop.tmp.dir}/mapred/system | The shared directory where MapReduce stores control files.
|
| mapred.temp.dir | ${hadoop.tmp.dir}/mapred/temp | A shared directory for temporary files.
|
| mapred.local.dir.minspacestart | 0 | If the space in mapred.local.dir drops under this,
do not ask for more tasks.
Value in bytes.
|
| mapred.local.dir.minspacekill | 0 | If the space in mapred.local.dir drops under this,
do not ask more tasks until all the current ones have finished and
cleaned up. Also, to save the rest of the tasks we have running,
kill one of them, to clean up some space. Start with the reduce tasks,
then go with the ones that have finished the least.
Value in bytes.
|
| mapred.tasktracker.expiry.interval | 600000 | Expert: The time-interval, in miliseconds, after which
a tasktracker is declared 'lost' if it doesn't send heartbeats.
|
| mapred.tasktracker.instrumentation | org.apache.hadoop.mapred.TaskTrackerMetricsInst | Expert: The instrumentation class to associate with each TaskTracker.
|
| mapred.tasktracker.memory_calculator_plugin | |
Name of the class whose instance will be used to query memory information
on the tasktracker.
The class must be an instance of
org.apache.hadoop.util.MemoryCalculatorPlugin. If the value is null, the
tasktracker attempts to use a class appropriate to the platform.
Currently, the only platform supported is Linux.
|
| mapred.tasktracker.taskmemorymanager.monitoring-interval | 5000 | The interval, in milliseconds, for which the tasktracker waits
between two cycles of monitoring its tasks' memory usage. Used only if
tasks' memory management is enabled via mapred.tasktracker.tasks.maxmemory.
|
| mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill | 5000 | The time, in milliseconds, the tasktracker waits for sending a
SIGKILL to a process that has overrun memory limits, after it has been sent
a SIGTERM. Used only if tasks' memory management is enabled via
mapred.tasktracker.tasks.maxmemory. |
| mapred.map.tasks | 2 | The default number of map tasks per job.
Ignored when mapred.job.tracker is "local".
|
| mapred.reduce.tasks | 1 | The default number of reduce tasks per job. Typically set to 99%
of the cluster's reduce capacity, so that if a node fails the reduces can
still be executed in a single wave.
Ignored when mapred.job.tracker is "local".
|
| mapred.jobtracker.restart.recover | false | "true" to enable (job) recovery upon restart,
"false" to start afresh
|
| mapred.jobtracker.job.history.block.size | 3145728 | The block size of the job history file. Since the job recovery
uses job history, its important to dump job history to disk as
soon as possible. Note that this is an expert level parameter.
The default value is set to 3 MB.
|
| mapred.jobtracker.taskScheduler | org.apache.hadoop.mapred.JobQueueTaskScheduler | The class responsible for scheduling the tasks. |
| mapred.jobtracker.taskScheduler.maxRunningTasksPerJob | | The maximum number of running tasks for a job before
it gets preempted. No limits if undefined.
|
| mapred.map.max.attempts | 4 | Expert: The maximum number of attempts per map task.
In other words, framework will try to execute a map task these many number
of times before giving up on it.
|
| mapred.reduce.max.attempts | 4 | Expert: The maximum number of attempts per reduce task.
In other words, framework will try to execute a reduce task these many number
of times before giving up on it.
|
| mapred.reduce.parallel.copies | 5 | The default number of parallel transfers run by reduce
during the copy(shuffle) phase.
|
| mapred.reduce.copy.backoff | 300 | The maximum amount of time (in seconds) a reducer spends on
fetching one map output before declaring it as failed.
|
| mapred.task.timeout | 600000 | The number of milliseconds before a task will be
terminated if it neither reads an input, writes an output, nor
updates its status string.
|
| mapred.tasktracker.map.tasks.maximum | 2 | The maximum number of map tasks that will be run
simultaneously by a task tracker.
|
| mapred.tasktracker.reduce.tasks.maximum | 2 | The maximum number of reduce tasks that will be run
simultaneously by a task tracker.
|
| mapred.jobtracker.completeuserjobs.maximum | 100 | The maximum number of complete jobs per user to keep around
before delegating them to the job history. |
| mapred.jobtracker.instrumentation | org.apache.hadoop.mapred.JobTrackerMetricsInst | Expert: The instrumentation class to associate with each JobTracker.
|
| mapred.child.java.opts | -Xmx200m | Java opts for the task tracker child processes.
The following symbol, if present, will be interpolated: @taskid@ is replaced
by current TaskID. Any other occurrences of '@' will go unchanged.
For example, to enable verbose gc logging to a file named for the taskid in
/tmp and to set the heap maximum to be a gigabyte, pass a 'value' of:
-Xmx1024m -verbose:gc -Xloggc:/tmp/@taskid@.gc
The configuration variable mapred.child.ulimit can be used to control the
maximum virtual memory of the child processes.
|
| mapred.child.ulimit | | The maximum virtual memory, in KB, of a process launched by the
Map-Reduce framework. This can be used to control both the Mapper/Reducer
tasks and applications using Hadoop Pipes, Hadoop Streaming etc.
By default it is left unspecified to let cluster admins control it via
limits.conf and other such relevant mechanisms.
Note: mapred.child.ulimit must be greater than or equal to the -Xmx passed to
JavaVM, else the VM might not start.
|
| mapred.child.tmp | ./tmp | To set the value of tmp directory for map and reduce tasks.
If the value is an absolute path, it is directly assigned. Otherwise, it is
prepended with task's working directory. The java tasks are executed with
option -Djava.io.tmpdir='the absolute path of the tmp dir'. Pipes and
streaming are set with environment variable,
TMPDIR='the absolute path of the tmp dir'
|
| mapred.inmem.merge.threshold | 1000 | The threshold, in terms of the number of files
for the in-memory merge process. When we accumulate threshold number of files
we initiate the in-memory merge and spill to disk. A value of 0 or less than
0 indicates we want to DON'T have any threshold and instead depend only on
the ramfs's memory consumption to trigger the merge.
|
| mapred.job.shuffle.merge.percent | 0.66 | The usage threshold at which an in-memory merge will be
initiated, expressed as a percentage of the total memory allocated to
storing in-memory map outputs, as defined by
mapred.job.shuffle.input.buffer.percent.
|
| mapred.job.shuffle.input.buffer.percent | 0.70 | The percentage of memory to be allocated from the maximum heap
size to storing map outputs during the shuffle.
|
| mapred.job.reduce.input.buffer.percent | 0.0 | The percentage of memory- relative to the maximum heap size- to
retain map outputs during the reduce. When the shuffle is concluded, any
remaining map outputs in memory must consume less than this threshold before
the reduce can begin.
|
| mapred.map.tasks.speculative.execution | true | If true, then multiple instances of some map tasks
may be executed in parallel. |
| mapred.reduce.tasks.speculative.execution | true | If true, then multiple instances of some reduce tasks
may be executed in parallel. |
| mapred.job.reuse.jvm.num.tasks | 1 | How many tasks to run per jvm. If set to -1, there is
no limit.
|
| mapred.min.split.size | 0 | The minimum size chunk that map input should be split
into. Note that some file formats may have minimum split sizes that
take priority over this setting. |
| mapred.jobtracker.maxtasks.per.job | -1 | The maximum number of tasks for a single job.
A value of -1 indicates that there is no maximum. |
| mapred.submit.replication | 10 | The replication level for submitted job files. This
should be around the square root of the number of nodes.
|
| mapred.tasktracker.dns.interface | default | The name of the Network Interface from which a task
tracker should report its IP address.
|
| mapred.tasktracker.dns.nameserver | default | The host name or IP address of the name server (DNS)
which a TaskTracker should use to determine the host name used by
the JobTracker for communication and display purposes.
|
| tasktracker.http.threads | 40 | The number of worker threads that for the http server. This is
used for map output fetching
|
| mapred.task.tracker.http.address | 0.0.0.0:50060 |
The task tracker http server address and port.
If the port is 0 then the server will start on a free port.
|
| keep.failed.task.files | false | Should the files for failed tasks be kept. This should only be
used on jobs that are failing, because the storage is never
reclaimed. It also prevents the map outputs from being erased
from the reduce directory as they are consumed. |
| mapred.output.compress | false | Should the job outputs be compressed?
|
| mapred.output.compression.type | RECORD | If the job outputs are to compressed as SequenceFiles, how should
they be compressed? Should be one of NONE, RECORD or BLOCK.
|
| mapred.output.compression.codec | org.apache.hadoop.io.compress.DefaultCodec | If the job outputs are compressed, how should they be compressed?
|
| mapred.compress.map.output | false | Should the outputs of the maps be compressed before being
sent across the network. Uses SequenceFile compression.
|
| mapred.map.output.compression.codec | org.apache.hadoop.io.compress.DefaultCodec | If the map outputs are compressed, how should they be
compressed?
|
| map.sort.class | org.apache.hadoop.util.QuickSort | The default sort class for sorting keys.
|
| mapred.userlog.limit.kb | 0 | The maximum size of user-logs of each task in KB. 0 disables the cap.
|
| mapred.userlog.retain.hours | 24 | The maximum time, in hours, for which the user-logs are to be
retained.
|
| mapred.hosts | | Names a file that contains the list of nodes that may
connect to the jobtracker. If the value is empty, all hosts are
permitted. |
| mapred.hosts.exclude | | Names a file that contains the list of hosts that
should be excluded by the jobtracker. If the value is empty, no
hosts are excluded. |
| mapred.max.tracker.blacklists | 4 | The number of blacklists for a taskTracker by various jobs
after which the task tracker could be blacklisted across
all jobs. The tracker will be given a tasks later
(after a day). The tracker will become a healthy
tracker after a restart.
|
| mapred.max.tracker.failures | 4 | The number of task-failures on a tasktracker of a given job
after which new tasks of that job aren't assigned to it.
|
| jobclient.output.filter | FAILED | The filter for controlling the output of the task's userlogs sent
to the console of the JobClient.
The permissible options are: NONE, KILLED, FAILED, SUCCEEDED and
ALL.
|
| mapred.job.tracker.persist.jobstatus.active | false | Indicates if persistency of job status information is
active or not.
|
| mapred.job.tracker.persist.jobstatus.hours | 0 | The number of hours job status information is persisted in DFS.
The job status information will be available after it drops of the memory
queue and between jobtracker restarts. With a zero value the job status
information is not persisted at all in DFS.
|
| mapred.job.tracker.persist.jobstatus.dir | /jobtracker/jobsInfo | The directory where the job status information is persisted
in a file system to be available after it drops of the memory queue and
between jobtracker restarts.
|
| mapred.task.profile | false | To set whether the system should collect profiler
information for some of the tasks in this job? The information is stored
in the user log directory. The value is "true" if task profiling
is enabled. |
| mapred.task.profile.maps | 0-2 | To set the ranges of map tasks to profile.
mapred.task.profile has to be set to true for the value to be accounted.
|
| mapred.task.profile.reduces | 0-2 | To set the ranges of reduce tasks to profile.
mapred.task.profile has to be set to true for the value to be accounted.
|
| mapred.line.input.format.linespermap | 1 | Number of lines per split in NLineInputFormat.
|
| mapred.skip.attempts.to.start.skipping | 2 | The number of Task attempts AFTER which skip mode
will be kicked off. When skip mode is kicked off, the
tasks reports the range of records which it will process
next, to the TaskTracker. So that on failures, TT knows which
ones are possibly the bad records. On further executions,
those are skipped.
|
| mapred.skip.map.auto.incr.proc.count | true | The flag which if set to true,
SkipBadRecords.COUNTER_MAP_PROCESSED_RECORDS is incremented
by MapRunner after invoking the map function. This value must be set to
false for applications which process the records asynchronously
or buffer the input records. For example streaming.
In such cases applications should increment this counter on their own.
|
| mapred.skip.reduce.auto.incr.proc.count | true | The flag which if set to true,
SkipBadRecords.COUNTER_REDUCE_PROCESSED_GROUPS is incremented
by framework after invoking the reduce function. This value must be set to
false for applications which process the records asynchronously
or buffer the input records. For example streaming.
In such cases applications should increment this counter on their own.
|
| mapred.skip.out.dir | | If no value is specified here, the skipped records are
written to the output directory at _logs/skip.
User can stop writing skipped records by giving the value "none".
|
| mapred.skip.map.max.skip.records | 0 | The number of acceptable skip records surrounding the bad
record PER bad record in mapper. The number includes the bad record as well.
To turn the feature of detection/skipping of bad records off, set the
value to 0.
The framework tries to narrow down the skipped range by retrying
until this threshold is met OR all attempts get exhausted for this task.
Set the value to Long.MAX_VALUE to indicate that framework need not try to
narrow down. Whatever records(depends on application) get skipped are
acceptable.
|
| mapred.skip.reduce.max.skip.groups | 0 | The number of acceptable skip groups surrounding the bad
group PER bad group in reducer. The number includes the bad group as well.
To turn the feature of detection/skipping of bad groups off, set the
value to 0.
The framework tries to narrow down the skipped range by retrying
until this threshold is met OR all attempts get exhausted for this task.
Set the value to Long.MAX_VALUE to indicate that framework need not try to
narrow down. Whatever groups(depends on application) get skipped are
acceptable.
|
| job.end.retry.attempts | 0 | Indicates how many times hadoop should attempt to contact the
notification URL |
| job.end.retry.interval | 30000 | Indicates time in milliseconds between notification URL retry
calls |
| hadoop.rpc.socket.factory.class.JobSubmissionProtocol | | SocketFactory to use to connect to a Map/Reduce master
(JobTracker). If null or empty, then use hadoop.rpc.socket.class.default.
|
| mapred.task.cache.levels | 2 | This is the max level of the task cache. For example, if
the level is 2, the tasks cached are at the host level and at the rack
level.
|
| mapred.queue.names | default | Comma separated list of queues configured for this jobtracker.
Jobs are added to queues and schedulers can configure different
scheduling properties for the various queues. To configure a property
for a queue, the name of the queue must match the name specified in this
value. Queue properties that are common to all schedulers are configured
here with the naming convention, mapred.queue.$QUEUE-NAME.$PROPERTY-NAME,
for e.g. mapred.queue.default.submit-job-acl.
The number of queues configured in this parameter could depend on the
type of scheduler being used, as specified in
mapred.jobtracker.taskScheduler. For example, the JobQueueTaskScheduler
supports only a single queue, which is the default configured here.
Before adding more queues, ensure that the scheduler you've configured
supports multiple queues.
|
| mapred.acls.enabled | false | Specifies whether ACLs are enabled, and should be checked
for various operations.
|
| mapred.queue.default.acl-submit-job | * | Comma separated list of user and group names that are allowed
to submit jobs to the 'default' queue. The user list and the group list
are separated by a blank. For e.g. alice,bob group1,group2.
If set to the special value '*', it means all users are allowed to
submit jobs.
|
| mapred.queue.default.acl-administer-jobs | * | Comma separated list of user and group names that are allowed
to delete jobs or modify job's priority for jobs not owned by the current
user in the 'default' queue. The user list and the group list
are separated by a blank. For e.g. alice,bob group1,group2.
If set to the special value '*', it means all users are allowed to do
this operation.
|
| mapred.job.queue.name | default | Queue to which a job is submitted. This must match one of the
queues defined in mapred.queue.names for the system. Also, the ACL setup
for the queue must allow the current user to submit a job to the queue.
Before specifying a queue, ensure that the system is configured with
the queue, and access is allowed for submitting jobs to the queue.
|
| mapred.tasktracker.indexcache.mb | 10 | The maximum memory that a task tracker allows for the
index cache that is used when serving map outputs to reducers.
|
| mapred.merge.recordsBeforeProgress | 10000 | The number of records to process during merge before
sending a progress notification to the TaskTracker.
|
| mapred.reduce.slowstart.completed.maps | 0.05 | Fraction of the number of maps in the job which should be
complete before reduces are scheduled for the job.
|