redis: v↑ (2.8.23)

- update Redis software to latest upstream in 2.8.* series (which now
  supports IPv6 out of the box);

- update Redis instance template to the one from 2.8.23 and re-merge our
  templating changes to it (file/dir locations, port and binding, master
  password).

  The whole diff to pristine 2.8.23 redis conf is now this:

  diff --git a/.../redis-2.8.23/redis.conf b/slapos/recipe/redis/template/redis.conf.in
  index 870959f..2895539 100644
  --- a/.../redis-2.8.23/redis.conf
  +++ b/slapos/recipe/redis/template/redis.conf.in
  @@ -46 +46 @@ daemonize no
  -pidfile /var/run/redis.pid
  +pidfile %(pid_file)s
  @@ -50 +50 @@ pidfile /var/run/redis.pid
  -port 6379
  +port %(port)s
  @@ -69,0 +70 @@ tcp-backlog 511
  +bind %(ipv6)s
  @@ -108 +109 @@ loglevel notice
  -logfile ""
  +logfile %(log_file)s
  @@ -174 +175 @@ rdbcompression yes
  -# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
  +# hit to pay (around 10%%) when saving and loading RDB files, so you can disable it
  @@ -192 +193 @@ dbfilename dump.rdb
  -dir ./
  +dir %(server_dir)s
  @@ -217 +218 @@ dir ./
  -# masterauth <master-password>
  +%(master_passwd)s

NOTE There are test failures for almost all Redis versions when machine
have not small amount of CPUs:

    https://github.com/antirez/redis/issues/2715#issuecomment-151608948

Because the failure is in replication test, and so far we do not use
replication, and there is no feedback from upstream author to handle
this (for 7 days for my detailed report, and for ~ 3 months for this
issue in general), we can just disable replication test as a temporary
solution.  ( to handle remote patches with md5 hash easily the building
recipe is changed to slapos.recipe.cmmi )

NOTE Redis updated to 2.8 version because GitLab uses this series.
If/when we need more recent one we can add [redis30] in addition to
[redis28].

/reviewed-by @kazuhiko  (on !27 and on !26)
/cc @alain.takoudjou, @jerome

component/redis/0001-tests-Disable-replication-psync-for-now.patch

+From 4e23f7038ae9bdffeab84f1abb5aaf9552ab580e Mon Sep 17 00:00:00 2001
+From: Kirill Smelkov <kirr@nexedi.com>
+Date: Mon, 2 Nov 2015 20:22:33 +0300
+Subject: [PATCH] tests: Disable replication-psync for now
+
+This tests fails on multi-cpu machine for almost all know Redis version.
+A lot of people reported to upstream author and I too provided detailed
+feedback about how it fails and on which hardware and offered ssh access
+to debug:
+
+https://github.com/antirez/redis/issues/2715#issuecomment-151608948
+
+The issue there is already known for ~ 3 months with several people
+allowing to help, but so far it remains broken.
+
+Since we don't use Redis replication, for us it is ok to disable the
+test and move on.
+
+NOTE comments in tcl don't work inside lists (consruct inside { ... } )-
+that's why the entry was moved out.
+---
+ tests/test_helper.tcl | 4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+diff --git a/tests/test_helper.tcl b/tests/test_helper.tcl
+index d1ebde1..72e7022 100644
+--- a/tests/test_helper.tcl
++++ b/tests/test_helper.tcl
+@@ -11,6 +11,9 @@ source tests/support/tmpfile.tcl
+ source tests/support/test.tcl
+ source tests/support/util.tcl
+ 
++# fails on multi-cpu machines
++# https://github.com/antirez/redis/issues/2715#issuecomment-151608948
++#   integration/replication-psync
+ set ::all_tests {
+     unit/printver
+     unit/auth
+@@ -33,7 +36,6 @@ set ::all_tests {
+     integration/replication-2
+     integration/replication-3
+     integration/replication-4
+-    integration/replication-psync
+     integration/aof
+     integration/rdb
+     integration/convert-zipmap-hash-on-load
+-- 
+2.6.2.521.g3f87150
+

component/redis/buildout.cfg

@@ -6,9 +6,12 @@ parts =
 extends = ../tcl/buildout.cfg
 
 [redis]
-recipe = hexagonit.recipe.cmmi
-url = https://github.com/geoffgarside/redis/archive/ipv6.tar.gz
-md5sum = 0eb594bd4e8ee746a0e2ef67b28cb5d8
+<= redis28
+
+[redis28]
+recipe = slapos.recipe.cmmi
+url = http://download.redis.io/releases/redis-2.8.23.tar.gz
+md5sum = ac7f43f845d0eedb8ae3e5e217b34c61
 configure-command = true
 prefix = 
 make-options =
@@ -19,3 +22,6 @@ make-targets =
   test
 environment =
   PATH=${tcl:location}/bin:%(PATH)s
+patch-options = -p1
+patches =
+  ${:_profile_base_location_}/0001-tests-Disable-replication-psync-for-now.patch#1ed899443ed70fce02d9b95f5e7ca046

slapos/recipe/redis/template/redis.conf.in

-# Redis configuration file example
+# Redis configuration file example.
+#
+# Note that in order to read the configuration file, Redis must be
+# started with the file path as first argument:
+#
+# ./redis-server /path/to/redis.conf
 
 # Note on units: when memory size is needed, it is possible to specify
 # it in the usual form of 1k 5GB 4M and so forth:
@@ -12,6 +17,26 @@
 #
 # units are case insensitive so 1GB 1Gb 1gB are all the same.
 
+################################## INCLUDES ###################################
+
+# Include one or more other config files here.  This is useful if you
+# have a standard template that goes to all Redis servers but also need
+# to customize a few per-server settings.  Include files can include
+# other files, so use this wisely.
+#
+# Notice option "include" won't be rewritten by command "CONFIG REWRITE"
+# from admin or Redis Sentinel. Since Redis always uses the last processed
+# line as value of a configuration directive, you'd better put includes
+# at the beginning of this file to avoid overwriting config change at runtime.
+#
+# If instead you are interested in using includes to override configuration
+# options, it is better to use include as the last line.
+#
+# include /path/to/local.conf
+# include /path/to/other.conf
+
+################################ GENERAL  #####################################
+
 # By default Redis does not run as a daemon. Use 'yes' if you need it.
 # Note that Redis will write a pid file in /var/run/redis.pid when daemonized.
 daemonize no
@@ -22,35 +47,63 @@ pidfile %(pid_file)s
 
 # Accept connections on the specified port, default is 6379.
 # If port 0 is specified Redis will not listen on a TCP socket.
-port6 %(port)s
-port 0
+port %(port)s
+
+# TCP listen() backlog.
+#
+# In high requests-per-second environments you need an high backlog in order
+# to avoid slow clients connections issues. Note that the Linux kernel
+# will silently truncate it to the value of /proc/sys/net/core/somaxconn so
+# make sure to raise both the value of somaxconn and tcp_max_syn_backlog
+# in order to get the desired effect.
+tcp-backlog 511
 
-# If you want you can bind a single interface, if the bind option is not
-# specified all the interfaces will listen for incoming connections.
-# Bind can also be an IPv6 address
+# By default Redis listens for connections from all the network interfaces
+# available on the server. It is possible to listen to just one or multiple
+# interfaces using the "bind" configuration directive, followed by one or
+# more IP addresses.
+#
+# Examples:
+#
+# bind 192.168.1.100 10.0.0.1
 # bind 127.0.0.1
-# bind ::1
-bind6 %(ipv6)s
+bind %(ipv6)s
 
-# Specify the path for the unix socket that will be used to listen for
+# Specify the path for the Unix socket that will be used to listen for
 # incoming connections. There is no default, so Redis will not listen
 # on a unix socket when not specified.
 #
 # unixsocket /tmp/redis.sock
-# unixsocketperm 755
+# unixsocketperm 700
 
 # Close the connection after a client is idle for N seconds (0 to disable)
 timeout 0
 
-# Set server verbosity to 'debug'
-# it can be one of:
+# TCP keepalive.
+#
+# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
+# of communication. This is useful for two reasons:
+#
+# 1) Detect dead peers.
+# 2) Take the connection alive from the point of view of network
+#    equipment in the middle.
+#
+# On Linux, the specified value (in seconds) is the period used to send ACKs.
+# Note that to close the connection the double of the time is needed.
+# On other kernels the period depends on the kernel configuration.
+#
+# A reasonable value for this option is 60 seconds.
+tcp-keepalive 0
+
+# Specify the server verbosity level.
+# This can be one of:
 # debug (a lot of information, useful for development/testing)
 # verbose (many rarely useful info, but not a mess like the debug level)
 # notice (moderately verbose, what you want in production probably)
 # warning (only very important / critical messages are logged)
 loglevel notice
 
-# Specify the log file name. Also 'stdout' can be used to force
+# Specify the log file name. Also the empty string can be used to force
 # Redis to log on the standard output. Note that if you use standard
 # output for logging but daemonize, logs will be sent to /dev/null
 logfile %(log_file)s
@@ -70,7 +123,7 @@ logfile %(log_file)s
 # dbid is a number between 0 and 'databases'-1
 databases 16
 
-################################ SNAPSHOTTING  #################################
+################################ SNAPSHOTTING  ################################
 #
 # Save the DB on disk:
 #
@@ -84,7 +137,7 @@ databases 16
 #   after 300 sec (5 min) if at least 10 keys changed
 #   after 60 sec if at least 10000 keys changed
 #
-#   Note: you can disable saving at all commenting all the "save" lines.
+#   Note: you can disable saving completely by commenting out all "save" lines.
 #
 #   It is also possible to remove all the previously configured save
 #   points by adding a save directive with a single empty string argument
@@ -98,16 +151,16 @@ save 60 10000
 
 # By default Redis will stop accepting writes if RDB snapshots are enabled
 # (at least one save point) and the latest background save failed.
-# This will make the user aware (in an hard way) that data is not persisting
+# This will make the user aware (in a hard way) that data is not persisting
 # on disk properly, otherwise chances are that no one will notice and some
-# distater will happen.
+# disaster will happen.
 #
 # If the background saving process will start working again Redis will
 # automatically allow writes again.
 #
 # However if you have setup your proper monitoring of the Redis server
 # and persistence, you may want to disable this feature so that Redis will
-# continue to work as usually even if there are problems with disk,
+# continue to work as usual even if there are problems with disk,
 # permissions, and so forth.
 stop-writes-on-bgsave-error yes
 
@@ -117,7 +170,7 @@ stop-writes-on-bgsave-error yes
 # the dataset will likely be bigger if you have compressible values or keys.
 rdbcompression yes
 
-# Since verison 5 of RDB a CRC64 checksum is placed at the end of the file.
+# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
 # This makes the format more resistant to corruption but there is a performance
 # hit to pay (around 10%%) when saving and loading RDB files, so you can disable it
 # for maximum performances.
@@ -134,7 +187,7 @@ dbfilename dump.rdb
 # The DB will be written inside this directory, with the filename specified
 # above using the 'dbfilename' configuration directive.
 #
-# Also the Append Only File will be created inside this directory.
+# The Append Only File will also be created inside this directory.
 #
 # Note that you must specify a directory here, not a file name.
 dir %(server_dir)s
@@ -142,9 +195,18 @@ dir %(server_dir)s
 ################################# REPLICATION #################################
 
 # Master-Slave replication. Use slaveof to make a Redis instance a copy of
-# another Redis server. Note that the configuration is local to the slave
-# so for example it is possible to configure the slave to save the DB with a
-# different interval, or to listen to another port, and so on.
+# another Redis server. A few things to understand ASAP about Redis replication.
+#
+# 1) Redis replication is asynchronous, but you can configure a master to
+#    stop accepting writes if it appears to be not connected with at least
+#    a given number of slaves.
+# 2) Redis slaves are able to perform a partial resynchronization with the
+#    master if the replication link is lost for a relatively small amount of
+#    time. You may want to configure the replication backlog size (see the next
+#    sections of this file) with a sensible value depending on your needs.
+# 3) Replication is automatic and does not need user intervention. After a
+#    network partition slaves automatically try to reconnect to masters
+#    and resynchronize with them.
 #
 # slaveof <masterip> <masterport>
 
@@ -155,14 +217,14 @@ dir %(server_dir)s
 #
 %(master_passwd)s
 
-# When a slave lost the connection with the master, or when the replication
+# When a slave loses its connection with the master, or when the replication
 # is still in progress, the slave can act in two different ways:
 #
 # 1) if slave-serve-stale-data is set to 'yes' (the default) the slave will
 #    still reply to client requests, possibly with out of date data, or the
 #    data set may just be empty if this is the first synchronization.
 #
-# 2) if slave-serve-stale data is set to 'no' the slave will reply with
+# 2) if slave-serve-stale-data is set to 'no' the slave will reply with
 #    an error "SYNC with master in progress" to all the kind of commands
 #    but to INFO and SLAVEOF.
 #
@@ -179,19 +241,65 @@ slave-serve-stale-data yes
 # Note: read only slaves are not designed to be exposed to untrusted clients
 # on the internet. It's just a protection layer against misuse of the instance.
 # Still a read only slave exports by default all the administrative commands
-# such as CONFIG, DEBUG, and so forth. To a limited extend you can improve
+# such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
 # security of read only slaves using 'rename-command' to shadow all the
 # administrative / dangerous commands.
 slave-read-only yes
 
+# Replication SYNC strategy: disk or socket.
+#
+# -------------------------------------------------------
+# WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY
+# -------------------------------------------------------
+#
+# New slaves and reconnecting slaves that are not able to continue the replication
+# process just receiving differences, need to do what is called a "full
+# synchronization". An RDB file is transmitted from the master to the slaves.
+# The transmission can happen in two different ways:
+#
+# 1) Disk-backed: The Redis master creates a new process that writes the RDB
+#                 file on disk. Later the file is transferred by the parent
+#                 process to the slaves incrementally.
+# 2) Diskless: The Redis master creates a new process that directly writes the
+#              RDB file to slave sockets, without touching the disk at all.
+#
+# With disk-backed replication, while the RDB file is generated, more slaves
+# can be queued and served with the RDB file as soon as the current child producing
+# the RDB file finishes its work. With diskless replication instead once
+# the transfer starts, new slaves arriving will be queued and a new transfer
+# will start when the current one terminates.
+#
+# When diskless replication is used, the master waits a configurable amount of
+# time (in seconds) before starting the transfer in the hope that multiple slaves
+# will arrive and the transfer can be parallelized.
+#
+# With slow disks and fast (large bandwidth) networks, diskless replication
+# works better.
+repl-diskless-sync no
+
+# When diskless replication is enabled, it is possible to configure the delay
+# the server waits in order to spawn the child that trnasfers the RDB via socket
+# to the slaves.
+#
+# This is important since once the transfer starts, it is not possible to serve
+# new slaves arriving, that will be queued for the next RDB transfer, so the server
+# waits a delay in order to let more slaves arrive.
+#
+# The delay is specified in seconds, and by default is 5 seconds. To disable
+# it entirely just set it to 0 seconds and the transfer will start ASAP.
+repl-diskless-sync-delay 5
+
 # Slaves send PINGs to server in a predefined interval. It's possible to change
 # this interval with the repl_ping_slave_period option. The default value is 10
 # seconds.
 #
 # repl-ping-slave-period 10
 
-# The following option sets a timeout for both Bulk transfer I/O timeout and
-# master data or ping response timeout. The default value is 60 seconds.
+# The following option sets the replication timeout for:
+#
+# 1) Bulk transfer I/O during SYNC, from the point of view of slave.
+# 2) Master timeout from the point of view of slaves (data, pings).
+# 3) Slave timeout from the point of view of masters (REPLCONF ACK pings).
 #
 # It is important to make sure that this value is greater than the value
 # specified for repl-ping-slave-period otherwise a timeout will be detected
@@ -199,6 +307,80 @@ slave-read-only yes
 #
 # repl-timeout 60
 
+# Disable TCP_NODELAY on the slave socket after SYNC?
+#
+# If you select "yes" Redis will use a smaller number of TCP packets and
+# less bandwidth to send data to slaves. But this can add a delay for
+# the data to appear on the slave side, up to 40 milliseconds with
+# Linux kernels using a default configuration.
+#
+# If you select "no" the delay for data to appear on the slave side will
+# be reduced but more bandwidth will be used for replication.
+#
+# By default we optimize for low latency, but in very high traffic conditions
+# or when the master and slaves are many hops away, turning this to "yes" may
+# be a good idea.
+repl-disable-tcp-nodelay no
+
+# Set the replication backlog size. The backlog is a buffer that accumulates
+# slave data when slaves are disconnected for some time, so that when a slave
+# wants to reconnect again, often a full resync is not needed, but a partial
+# resync is enough, just passing the portion of data the slave missed while
+# disconnected.
+#
+# The bigger the replication backlog, the longer the time the slave can be
+# disconnected and later be able to perform a partial resynchronization.
+#
+# The backlog is only allocated once there is at least a slave connected.
+#
+# repl-backlog-size 1mb
+
+# After a master has no longer connected slaves for some time, the backlog
+# will be freed. The following option configures the amount of seconds that
+# need to elapse, starting from the time the last slave disconnected, for
+# the backlog buffer to be freed.
+#
+# A value of 0 means to never release the backlog.
+#
+# repl-backlog-ttl 3600
+
+# The slave priority is an integer number published by Redis in the INFO output.
+# It is used by Redis Sentinel in order to select a slave to promote into a
+# master if the master is no longer working correctly.
+#
+# A slave with a low priority number is considered better for promotion, so
+# for instance if there are three slaves with priority 10, 100, 25 Sentinel will
+# pick the one with priority 10, that is the lowest.
+#
+# However a special priority of 0 marks the slave as not able to perform the
+# role of master, so a slave with priority of 0 will never be selected by
+# Redis Sentinel for promotion.
+#
+# By default the priority is 100.
+slave-priority 100
+
+# It is possible for a master to stop accepting writes if there are less than
+# N slaves connected, having a lag less or equal than M seconds.
+#
+# The N slaves need to be in "online" state.
+#
+# The lag in seconds, that must be <= the specified value, is calculated from
+# the last ping received from the slave, that is usually sent every second.
+#
+# This option does not GUARANTEE that N replicas will accept the write, but
+# will limit the window of exposure for lost writes in case not enough slaves
+# are available, to the specified number of seconds.
+#
+# For example to require at least 3 slaves with a lag <= 10 seconds use:
+#
+# min-slaves-to-write 3
+# min-slaves-max-lag 10
+#
+# Setting one or the other to 0 disables the feature.
+#
+# By default min-slaves-to-write is set to 0 (feature disabled) and
+# min-slaves-max-lag is set to 10.
+
 ################################## SECURITY ###################################
 
 # Require clients to issue AUTH <PASSWORD> before processing any other
@@ -218,23 +400,26 @@ slave-read-only yes
 #
 # It is possible to change the name of dangerous commands in a shared
 # environment. For instance the CONFIG command may be renamed into something
-# of hard to guess so that it will be still available for internal-use
-# tools but not available for general clients.
+# hard to guess so that it will still be available for internal-use tools
+# but not available for general clients.
 #
 # Example:
 #
 # rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
 #
-# It is also possible to completely kill a command renaming it into
+# It is also possible to completely kill a command by renaming it into
 # an empty string:
 #
 # rename-command CONFIG ""
+#
+# Please note that changing the name of commands that are logged into the
+# AOF file or transmitted to slaves may cause problems.
 
 ################################### LIMITS ####################################
 
 # Set the max number of connected clients at the same time. By default
 # this limit is set to 10000 clients, however if the Redis server is not
-# able ot configure the process file limit to allow for the specified limit
+# able to configure the process file limit to allow for the specified limit
 # the max number of allowed clients is set to the current file limit
 # minus 32 (as Redis reserves a few file descriptors for internal uses).
 #
@@ -245,7 +430,7 @@ slave-read-only yes
 
 # Don't use more memory than the specified amount of bytes.
 # When the memory limit is reached Redis will try to remove keys
-# accordingly to the eviction policy selected (see maxmemmory-policy).
+# according to the eviction policy selected (see maxmemory-policy).
 #
 # If Redis can't remove keys according to the policy, or if the policy is
 # set to 'noeviction', Redis will start to reply with errors to commands
@@ -253,7 +438,7 @@ slave-read-only yes
 # to reply to read-only commands like GET.
 #
 # This option is usually useful when using Redis as an LRU cache, or to set
-# an hard memory limit for an instance (using the 'noeviction' policy).
+# a hard memory limit for an instance (using the 'noeviction' policy).
 #
 # WARNING: If you have slaves attached to an instance with maxmemory on,
 # the size of the output buffers needed to feed the slaves are subtracted
@@ -269,19 +454,19 @@ slave-read-only yes
 # maxmemory <bytes>
 
 # MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
-# is reached? You can select among five behavior:
+# is reached. You can select among five behaviors:
 #
 # volatile-lru -> remove the key with an expire set using an LRU algorithm
-# allkeys-lru -> remove any key accordingly to the LRU algorithm
+# allkeys-lru -> remove any key according to the LRU algorithm
 # volatile-random -> remove a random key with an expire set
 # allkeys-random -> remove a random key, any key
 # volatile-ttl -> remove the key with the nearest expire time (minor TTL)
 # noeviction -> don't expire at all, just return an error on write operations
 #
-# Note: with all the kind of policies, Redis will return an error on write
-#       operations, when there are not suitable keys for eviction.
+# Note: with any of the above policies, Redis will return an error on write
+#       operations, when there are no suitable keys for eviction.
 #
-#       At the date of writing this commands are: set setnx setex append
+#       At the date of writing these commands are: set setnx setex append
 #       incr decr rpush lpush rpushx lpushx linsert lset rpoplpush sadd
 #       sinter sinterstore sunion sunionstore sdiff sdiffstore zadd zincrby
 #       zunionstore zinterstore hset hsetnx hmset hincrby incrby decrby
@@ -322,19 +507,20 @@ slave-read-only yes
 appendonly no
 
 # The name of the append only file (default: "appendonly.aof")
-# appendfilename appendonly.aof
+
+appendfilename "appendonly.aof"
 
 # The fsync() call tells the Operating System to actually write data on disk
-# instead to wait for more data in the output buffer. Some OS will really flush
+# instead of waiting for more data in the output buffer. Some OS will really flush
 # data on disk, some other OS will just try to do it ASAP.
 #
 # Redis supports three different modes:
 #
 # no: don't fsync, just let the OS flush the data when it wants. Faster.
-# always: fsync after every write to the append only log . Slow, Safest.
+# always: fsync after every write to the append only log. Slow, Safest.
 # everysec: fsync only one time every second. Compromise.
 #
-# The default is "everysec" that's usually the right compromise between
+# The default is "everysec", as that's usually the right compromise between
 # speed and data safety. It's up to you to understand if you can relax this to
 # "no" that will let the operating system flush the output buffer when
 # it wants, for better performances (but if you can live with the idea of
@@ -362,21 +548,22 @@ appendfsync everysec
 # that will prevent fsync() from being called in the main process while a
 # BGSAVE or BGREWRITEAOF is in progress.
 #
-# This means that while another child is saving the durability of Redis is
-# the same as "appendfsync none", that in practical terms means that it is
-# possible to lost up to 30 seconds of log in the worst scenario (with the
+# This means that while another child is saving, the durability of Redis is
+# the same as "appendfsync none". In practical terms, this means that it is
+# possible to lose up to 30 seconds of log in the worst scenario (with the
 # default Linux settings).
 #
 # If you have latency problems turn this to "yes". Otherwise leave it as
 # "no" that is the safest pick from the point of view of durability.
+
 no-appendfsync-on-rewrite no
 
 # Automatic rewrite of the append only file.
 # Redis is able to automatically rewrite the log file implicitly calling
-# BGREWRITEAOF when the AOF log size will growth by the specified percentage.
+# BGREWRITEAOF when the AOF log size grows by the specified percentage.
 #
 # This is how it works: Redis remembers the size of the AOF file after the
-# latest rewrite (or if no rewrite happened since the restart, the size of
+# latest rewrite (if no rewrite has happened since the restart, the size of
 # the AOF at startup is used).
 #
 # This base size is compared to the current size. If the current size is
@@ -391,6 +578,30 @@ no-appendfsync-on-rewrite no
 auto-aof-rewrite-percentage 100
 auto-aof-rewrite-min-size 64mb
 
+# An AOF file may be found to be truncated at the end during the Redis
+# startup process, when the AOF data gets loaded back into memory.
+# This may happen when the system where Redis is running
+# crashes, especially when an ext4 filesystem is mounted without the
+# data=ordered option (however this can't happen when Redis itself
+# crashes or aborts but the operating system still works correctly).
+#
+# Redis can either exit with an error when this happens, or load as much
+# data as possible (the default now) and start if the AOF file is found
+# to be truncated at the end. The following option controls this behavior.
+#
+# If aof-load-truncated is set to yes, a truncated AOF file is loaded and
+# the Redis server starts emitting a log to inform the user of the event.
+# Otherwise if the option is set to no, the server aborts with an error
+# and refuses to start. When the option is set to no, the user requires
+# to fix the AOF file using the "redis-check-aof" utility before to restart
+# the server.
+#
+# Note that if the AOF file will be found to be corrupted in the middle
+# the server will still exit with an error. This option only applies when
+# Redis will try to read more data from the AOF file but not enough bytes
+# will be found.
+aof-load-truncated yes
+
 ################################ LUA SCRIPTING  ###############################
 
 # Max execution time of a Lua script in milliseconds.
@@ -399,35 +610,16 @@ auto-aof-rewrite-min-size 64mb
 # still in execution after the maximum allowed time and will start to
 # reply to queries with an error.
 #
-# When a long running script exceed the maximum execution time only the
+# When a long running script exceeds the maximum execution time only the
 # SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
 # used to stop a script that did not yet called write commands. The second
-# is the only way to shut down the server in the case a write commands was
-# already issue by the script but the user don't want to wait for the natural
+# is the only way to shut down the server in the case a write command was
+# already issued by the script but the user doesn't want to wait for the natural
 # termination of the script.
 #
 # Set it to 0 or a negative value for unlimited execution without warnings.
 lua-time-limit 5000
 
-################################ REDIS CLUSTER  ###############################
-#
-# Normal Redis instances can't be part of a Redis Cluster, only nodes that are
-# started as cluster nodes can. In order to start a Redis instance as a
-# cluster node enable the cluster support uncommenting the following:
-#
-# cluster-enabled yes
-
-# Every cluster node has a cluster configuration file. This file is not
-# intended to be edited by hand. It is created and updated by Redis nodes.
-# Every Redis Cluster node requires a different cluster configuration file.
-# Make sure that instances running in the same system does not have
-# overlapping cluster configuration file names.
-#
-# cluster-config-file nodes-6379.conf
-
-# In order to setup your cluster make sure to read the documentation
-# available at http://redis.io web site.
-
 ################################## SLOW LOG ###################################
 
 # The Redis Slow Log is a system to log queries that exceeded a specified
@@ -452,6 +644,73 @@ slowlog-log-slower-than 10000
 # You can reclaim memory used by the slow log with SLOWLOG RESET.
 slowlog-max-len 128
 
+################################ LATENCY MONITOR ##############################
+
+# The Redis latency monitoring subsystem samples different operations
+# at runtime in order to collect data related to possible sources of
+# latency of a Redis instance.
+#
+# Via the LATENCY command this information is available to the user that can
+# print graphs and obtain reports.
+#
+# The system only logs operations that were performed in a time equal or
+# greater than the amount of milliseconds specified via the
+# latency-monitor-threshold configuration directive. When its value is set
+# to zero, the latency monitor is turned off.
+#
+# By default latency monitoring is disabled since it is mostly not needed
+# if you don't have latency issues, and collecting data has a performance
+# impact, that while very small, can be measured under big load. Latency
+# monitoring can easily be enalbed at runtime using the command
+# "CONFIG SET latency-monitor-threshold <milliseconds>" if needed.
+latency-monitor-threshold 0
+
+############################# Event notification ##############################
+
+# Redis can notify Pub/Sub clients about events happening in the key space.
+# This feature is documented at http://redis.io/topics/notifications
+#
+# For instance if keyspace events notification is enabled, and a client
+# performs a DEL operation on key "foo" stored in the Database 0, two
+# messages will be published via Pub/Sub:
+#
+# PUBLISH __keyspace@0__:foo del
+# PUBLISH __keyevent@0__:del foo
+#
+# It is possible to select the events that Redis will notify among a set
+# of classes. Every class is identified by a single character:
+#
+#  K     Keyspace events, published with __keyspace@<db>__ prefix.
+#  E     Keyevent events, published with __keyevent@<db>__ prefix.
+#  g     Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
+#  $     String commands
+#  l     List commands
+#  s     Set commands
+#  h     Hash commands
+#  z     Sorted set commands
+#  x     Expired events (events generated every time a key expires)
+#  e     Evicted events (events generated when a key is evicted for maxmemory)
+#  A     Alias for g$lshzxe, so that the "AKE" string means all the events.
+#
+#  The "notify-keyspace-events" takes as argument a string that is composed
+#  of zero or multiple characters. The empty string means that notifications
+#  are disabled.
+#
+#  Example: to enable list and generic events, from the point of view of the
+#           event name, use:
+#
+#  notify-keyspace-events Elg
+#
+#  Example 2: to get the stream of the expired keys subscribing to channel
+#             name __keyevent@0__:expired use:
+#
+#  notify-keyspace-events Ex
+#
+#  By default all notifications are disabled because most users don't need
+#  this feature and the feature has some overhead. Note that if you don't
+#  specify at least one of K or E, no events will be delivered.
+notify-keyspace-events ""
+
 ############################### ADVANCED CONFIG ###############################
 
 # Hashes are encoded using a memory efficient data structure when they have a
@@ -467,7 +726,7 @@ list-max-ziplist-entries 512
 list-max-ziplist-value 64
 
 # Sets have a special encoding in just one case: when a set is composed
-# of just strings that happens to be integers in radix 10 in the range
+# of just strings that happen to be integers in radix 10 in the range
 # of 64 bit signed integers.
 # The following configuration setting sets the limit in the size of the
 # set in order to use this special memory saving encoding.
@@ -479,20 +738,34 @@ set-max-intset-entries 512
 zset-max-ziplist-entries 128
 zset-max-ziplist-value 64
 
+# HyperLogLog sparse representation bytes limit. The limit includes the
+# 16 bytes header. When an HyperLogLog using the sparse representation crosses
+# this limit, it is converted into the dense representation.
+#
+# A value greater than 16000 is totally useless, since at that point the
+# dense representation is more memory efficient.
+#
+# The suggested value is ~ 3000 in order to have the benefits of
+# the space efficient encoding without slowing down too much PFADD,
+# which is O(N) with the sparse encoding. The value can be raised to
+# ~ 10000 when CPU is not a concern, but space is, and the data set is
+# composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
+hll-sparse-max-bytes 3000
+
 # Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in
 # order to help rehashing the main Redis hash table (the one mapping top-level
 # keys to values). The hash table implementation Redis uses (see dict.c)
-# performs a lazy rehashing: the more operation you run into an hash table
+# performs a lazy rehashing: the more operation you run into a hash table
 # that is rehashing, the more rehashing "steps" are performed, so if the
 # server is idle the rehashing is never complete and some more memory is used
 # by the hash table.
 #
 # The default is to use this millisecond 10 times every second in order to
-# active rehashing the main dictionaries, freeing memory when possible.
+# actively rehash the main dictionaries, freeing memory when possible.
 #
 # If unsure:
 # use "activerehashing no" if you have hard latency requirements and it is
-# not a good thing in your environment that Redis can reply form time to time
+# not a good thing in your environment that Redis can reply from time to time
 # to queries with 2 milliseconds delay.
 #
 # use "activerehashing yes" if you don't have such hard requirements but
@@ -506,9 +779,9 @@ activerehashing yes
 #
 # The limit can be set differently for the three different classes of clients:
 #
-# normal -> normal clients
-# slave  -> slave clients and MONITOR clients
-# pubsub -> clients subcribed to at least one pubsub channel or pattern
+# normal -> normal clients including MONITOR clients
+# slave  -> slave clients
+# pubsub -> clients subscribed to at least one pubsub channel or pattern
 #
 # The syntax of every client-output-buffer-limit directive is the following:
 #
@@ -531,17 +804,30 @@ activerehashing yes
 # Instead there is a default limit for pubsub and slave clients, since
 # subscribers and slaves receive data in a push fashion.
 #
-# Both the hard or the soft limit can be disabled just setting it to zero.
+# Both the hard or the soft limit can be disabled by setting them to zero.
 client-output-buffer-limit normal 0 0 0
 client-output-buffer-limit slave 256mb 64mb 60
 client-output-buffer-limit pubsub 32mb 8mb 60
 
-################################## INCLUDES ###################################
-
-# Include one or more other config files here.  This is useful if you
-# have a standard template that goes to all Redis server but also need
-# to customize a few per-server settings.  Include files can include
-# other files, so use this wisely.
+# Redis calls an internal function to perform many background tasks, like
+# closing connections of clients in timeout, purging expired keys that are
+# never requested, and so forth.
 #
-# include /path/to/local.conf
-# include /path/to/other.conf
+# Not all tasks are performed with the same frequency, but Redis checks for
+# tasks to perform according to the specified "hz" value.
\ No newline at end of file
+#
+# By default "hz" is set to 10. Raising the value will use more CPU when
+# Redis is idle, but at the same time will make Redis more responsive when
+# there are many keys expiring at the same time, and timeouts may be
+# handled with more precision.
+#
+# The range is between 1 and 500, however a value over 100 is usually not
+# a good idea. Most users should use the default of 10 and raise this up to
+# 100 only in environments where very low latency is required.
+hz 10
+
+# When a child rewrites the AOF file, if the following option is enabled
+# the file will be fsync-ed every 32 MB of data generated. This is useful
+# in order to commit the file to the disk more incrementally and avoid
+# big latency spikes.
+aof-rewrite-incremental-fsync yes