Apache Hadoop Shell Rewrite
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This is a slightly updated draft of a talk I was planning on giving at Hadoop Summit in 2015. However the abstract was rejected. Rather than toss it, I'm going to share it with all of you on the (almost) 1 year anniversary of the first big commit of this feature! Keep in mind that this is (currently) locked away in trunk. If you ever want to see this see the light of day, bug your vendors....
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Apache Hadoop Shell Rewrite
- 1. Shell Script Rewrite Overview Allen Wittenauer
- 2. Twitter: @_a__w_ (1 a 2 w 1) Email: aw @ apache.org!
- 3. 3 What is the shell code?! ! ! bin/*! ! etc/hadoop/*sh! ! libexec/*! ! sbin/*! !
- 5. CUTTING, DOUG 1710 554 6239 2005 APACHE SOFTWARE FOUNDATION
- 7. 7
- 9. 9
- 10. 10
- 12. “[The scripts] finally got to you, didn’t they?”
- 13. 13 Primary Goals! Consistency! Code and Config Simplification! De-clash Parameters! Documentation! ! Secondary Goals! Backward Compatibility! “Lost” Ideas and Fixes!
- 15. 15 ! ! Tuesday, August 19, 2014 majority committed into trunk:! ! ! ! ! ! ... followed by many fixes & enhancements from the community
- 17. 17 Old:! ! hadoop -> hadoop-config.sh -> hadoop-env.sh! ! yarn -> yarn-config.sh -> yarn-env.sh! ! hdfs-> hdfs-config.sh -> hadoop-env.sh ! ! New:! ! hadoop -> hadoop-config.sh! -> hadoop-functions.sh! ! ! ! ! ! ! ! -> hadoop-env.sh! ! yarn -> yarn-config.sh! -> hadoop-config.sh -> (above)! ! ! ! ! ! ! -> yarn-env.sh! ! hdfs -> hdfs-config.sh! -> hadoop-config.sh -> (above)!
- 18. 18 Old:! ! yarn-env.sh:! JAVA_HOME=xyz ! hadoop-env.sh:! JAVA_HOME=xyz ! mapred-env.sh:! JAVA_HOME=xyz New:! ! hadoop-env.sh! JAVA_HOME=xyz ! OS X:! JAVA_HOME=$(/usr/libexec/java_home)
- 19. 19 Old:! ! xyz_OPT=“-‐Xmx4g” hdfs namenode java … -‐Xmx1000 … -‐Xmx4g … ! ! Command line size: ~2500 bytes! New:! ! xyz_OPT=“-‐Xmx4g” hdfs namenode java … -‐Xmx4g … ! ! Command line size: ~1750 bytes
- 20. 20 ! $ TOOL_PATH=blah:blah:blah hadoop distcp /old /new Error: could not find or load main class org.apache.hadoop.tools.DistCp! ! Old:! ! $ bash -‐x hadoop distcp /old /new + this=/home/aw/HADOOP/hadoop-‐3.0.0-‐SNAPSHOT/bin/hadoop +++ dirname -‐-‐ /home/aw/HADOOP/hadoop-‐3.0.0-‐SNAPSHOT/bin/hadoop ++ cd -‐P -‐-‐ /home/aw/HADOOP/hadoop-‐3.0.0-‐SNAPSHOT/bin ++ pwd -‐P + bin=/home/aw/HADOOP/hadoop-‐3.0.0-‐SNAPSHOT/bin + DEFAULT_LIBEXEC_DIR=/home/aw/HADOOP/hadoop-‐3.0.0-‐SNAPSHOT/bin/../libexec + HADOOP_LIBEXEC_DIR=/home/aw/HADOOP/hadoop-‐3.0.0-‐SNAPSHOT/bin/../libexec + [[ -‐f /home/aw/HADOOP/hadoop-‐3.0.0-‐SNAPSHOT/bin/../libexec/hadoop-‐ config.sh ]] … !
- 21. 21 New:! ! $ TOOL_PATH=blah:blah:blah hadoop -‐-‐debug distcp /tmp/ /1 DEBUG: HADOOP_CONF_DIR=/home/aw/HADOOP/conf DEBUG: Initial CLASSPATH=/home/aw/HADOOP/conf … DEBUG: Append CLASSPATH: /home/aw/HADOOP/ hadoop-‐3.0.0-‐SNAPSHOT/share/hadoop/mapreduce/* DEBUG: Injecting TOOL_PATH into CLASSPATH DEBUG: Rejected CLASSPATH: blah:blah:blah (does not exist) … !
- 25. 25 Old:! ! hadoop thisisnotacommand ! ! == stack trace! New:! hadoop thisisnotacommand ! ! == hadoop help
- 26. 26 Old:! ! sbin/hadoop-‐daemon.sh start namenode sbin/yarn-‐daemon.sh start resourcemanager ! New:! ! bin/hdfs -‐-‐daemon start namenode bin/yarn -‐-‐daemon start resourcemanager ! ! + common daemon start/stop/status routines
- 27. 27 hdfs namenode vs hadoop-‐daemon.sh namenode ! Old:!! ! - effectively different code paths! ! - no pid vs pid! ! ! - wait for socket for failure! New:! ! - same code path ! ! - hadoop-‐daemon.sh cmd => hdfs -‐-‐daemon cmd ! ! ! - both generate pid! ! - hdfs -‐-‐daemon status namenode
- 28. 28 Old:! ! “mkdir: cannot create <dir>”! ! “chown: cannot change permission of <dir>”! ! ! New:! ! “WARNING: <dir> does not exist. Creating.”! ! “ERROR: Unable to create <dir>. Aborting.”! ! “ERROR: Cannot write to <dir>.”
- 29. 29 Old:! ! (foo) > (foo).out rm (foo).out = Open file handle! ! New:! (foo) >> (foo).out rm (foo).out ! ! = Closed file handle! ! ! = rotatable .out files!
- 30. 30 Old:! ! sbin/*-‐daemons.sh -‐> slaves.sh blah! ! (several hundred ssh processes later)! ! *crash*! ! ! New:! ! sbin/*-‐daemons.sh -> hadoop-‐functions.sh ! slaves.sh -> hadoop-‐functions.sh ! pdsh or (if enabled) xargs -‐P! ! *real work gets done*
- 31. 31 Old:! egrep -‐c ‘^#’ hadoop-‐branch-‐2/…/*-‐env.sh ! ! ! hadoop-env.sh: 59! ! ! ! mapred-env.sh: 21! ! ! ! yarn-env.sh: 60! New:! ! egrep -‐c ‘^#’ hadoop-‐trunk/…/*-‐env.sh ! ! ! hadoop-env.sh: 333! ! ! ! mapred-env.sh: 40! ! ! ! yarn-env.sh: 112! ! ! ! + hadoop-layout.sh.example : 77! ! ! ! + hadoop-user-functions.sh.example: 109
- 32. But wait! There’s more!
- 33. 33 ! ! HADOOP_namenode_USER=hdfs ! ! ! hdfs namenode only works as hdfs! ! ! Fun: HADOOP_fs_USER=aw! ! ! ! hadoop fs only works as aw! ! ! hadoop -‐-‐loglevel WARN ! ! ! ! => WARN,whatever! ! hadoop -‐-‐loglevel DEBUG -‐-‐daemon start => start daemon in DEBUG mode!
- 34. 34 ! Old:! ! HADOOP_HEAPSIZE=15234 <-‐-‐-‐ M only JAVA_HEAP_MAX="hahahah you set something in HADOOP_HEAPSIZE" ! New:! ! HADOOP_HEAPSIZE_MAX=15g HADOOP_HEAPSIZE_MIN=10g <-‐-‐-‐ units! JAVA_HEAP_MAX removed => no Xmx settings == Java default
- 35. 35 ! Old:! ! Lots of different yet same variables for settings ! New:! ! Deprecated ~60 variables ${HDFS|YARN|KMS|HTTPFS|*}_{foo} => HADOOP_{foo}
- 36. 36 ! Old:! ! "I wonder what's in HADOOP_CLIENT_OPTS?"! ! "I want to override just this one thing in *-env.sh."! ! New:! ! ${HOME}/.hadooprc
- 37. 37 ! shellprofile.d! ! ! bash snippets to easily inject:! ! ! classpath! ! ! JNI! ! ! Java command line options! ! ! ... and more!
- 39. Power Users Rejoice:! Function Overrides
- 40. 40 Default *.out log rotation:! ! function hadoop_rotate_log { local log=$1; local num=${2:-‐5}; ! if [[ -‐f "${log}" ]]; then # rotate logs while [[ ${num} -‐gt 1 ]]; do let prev=${num}-‐1 if [[ -‐f "${log}.${prev}" ]]; then mv "${log}.${prev}" "${log}.${num}" fi num=${prev} done mv "${log}" "${log}.${num}" fi } namenode.out.1 -‐> namenode.out.2 namenode.out -‐> namenode.out.1
- 41. 41 Put a replacement rotate function w/gzip support in hadoop-user-functions.sh!! ! function hadoop_rotate_log { local log=$1; local num=${2:-‐5}; ! if [[ -‐f "${log}" ]]; then while [[ ${num} -‐gt 1 ]]; do let prev=${num}-‐1 if [[ -‐f "${log}.${prev}.gz" ]]; then mv "${log}.${prev}.gz" "${log}.${num}.gz" fi num=${prev} done mv "${log}" "${log}.${num}" gzip -‐9 "${log}.${num}" fi } namenode.out.1.gz -‐> namenode.out.2.gz namenode.out -‐> namenode.out.1 gzip -‐9 namenode.out.1 -‐> namenode.out.1.gz
- 42. What if we wanted to log every daemon start in syslog?
- 43. 43 Default daemon starter:! ! function hadoop_start_daemon { local command=$1 local class=$2 shift 2 ! hadoop_debug "Final CLASSPATH: ${CLASSPATH}" hadoop_debug "Final HADOOP_OPTS: ${HADOOP_OPTS}" ! export CLASSPATH exec "${JAVA}" "-‐Dproc_${command}" ${HADOOP_OPTS} "$ {class}" "$@" }
- 44. 44 Put a replacement start function in hadoop-user-functions.sh!! ! function hadoop_start_daemon { local command=$1 local class=$2 shift 2 ! hadoop_debug "Final CLASSPATH: ${CLASSPATH}" hadoop_debug "Final HADOOP_OPTS: ${HADOOP_OPTS}" ! export CLASSPATH logger -‐i -‐p local0.notice -‐t hadoop "Started ${COMMAND}" exec "${JAVA}" "-‐Dproc_${command}" ${HADOOP_OPTS} "$ {class}" "$@" }
- 45. Secure Daemons
- 46. What if we could start them as non-root?
- 47. 47 Setup:! ! sudoers (either /etc/sudoers or in LDAP):! ! hdfs ALL=(root:root) NOPASSWD: /usr/bin/jsvc! ! hadoop-env.sh:! ! HADOOP_SECURE_COMMAND=/usr/sbin/sudo
- 48. 48 # hadoop-user-functions.sh: (partial code below)! function hadoop_start_secure_daemon { … jsvc="${JSVC_HOME}/jsvc" ! if [[ “${USER}” -‐ne "${HADOOP_SECURE_USER}" ]]; then hadoop_error "You must be ${HADOOP_SECURE_USER} in order to start a secure ${daemonname}" exit 1 fi … exec /usr/sbin/sudo "${jsvc}" "-‐Dproc_${daemonname}" -‐outfile "${daemonoutfile}" -‐errfile "${daemonerrfile}" -‐pidfile "${daemonpidfile}" -‐nodetach -‐home "${JAVA_HOME}" —user "${HADOOP_SECURE_USER}" -‐cp "${CLASSPATH}" ${HADOOP_OPTS} "${class}" "$@" }
- 49. 49 $ hdfs datanode! sudo launches jsvc as root! jsvc launches secure datanode! ! ! In order to get -‐-‐daemon start to work, one other function needs to get replaced*, but that’s a SMOP, now that you know how!! ! ! * - hadoop_start_secure_daemon_wrapper assumes it is running as root!
- 50. 50 Lots more, but out of time... e.g.:! ! ! Internals for contributors! ! Unit tests! ! API documentation! ! Other projects in the works! ! ...! ! ! Reminder: This is in trunk. Ask vendors their plans!
- 52. Altiscale copyright 2015. All rights reserved.52