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I've been experiencing some issues with my Postgres database. It's a 4.2TB database.

Around 4 times per day for some reason the database stops responding for some seconds! But it's not every day.

We have a lot of inserts per day in 4 different tables including a table with 3.7 million rows (we can call this table X). The inserts are always executed with success, but sometimes when the problem starts, looking at pg_status_activity there are a lot of INSERT commands running and the slowest insert (in table X) takes around 2 minutes to finish!

Table X is a very simple table with 10 columns (integers, boolean and varchar columns), a primary key and one index in a integer column. There are no triggers or foreign keys.

Postgres is configured to accept 350 connections and we never reached this limit. We reviewed all postgres parameters without success.

Running iotop command we see that the process postgres: wal writer process reached 70% of IO during this problem. Looking at S.O there are no log errors and CPU and memory are ok!

Does anyone have idea what is happening?

Server

  • Cores: 96
  • RAM: 512
  • Storage: 7TB, RAID 0 in xfs
  • S.O: RHEL 7.3 - Kernel 3.10

SO Parameters

  • vm.overcommit_memory = 2
  • vm.overcommit_ratio = 100
  • vm.dirty_ratio = 15
  • vm.dirty_background_ratio = 10
  • kernel.shmmax = 412316860416
  • kernel.shmall = 98304

Postgres parameters

# -----------------------------
# PostgreSQL configuration file
# -----------------------------
#
# This file consists of lines of the form:
#
#   name = value
#
# (The "=" is optional.)  Whitespace may be used.  Comments are introduced with
# "#" anywhere on a line.  The complete list of parameter names and allowed
# values can be found in the PostgreSQL documentation.
#
# The commented-out settings shown in this file represent the default values.
# Re-commenting a setting is NOT sufficient to revert it to the default value;
# you need to reload the server.
#
# This file is read on server startup and when the server receives a SIGHUP
# signal.  If you edit the file on a running system, you have to SIGHUP the
# server for the changes to take effect, or use "pg_ctl reload".  Some
# parameters, which are marked below, require a server shutdown and restart to
# take effect.
#
# Any parameter can also be given as a command-line option to the server, e.g.,
# "postgres -c log_connections=on".  Some parameters can be changed at run time
# with the "SET" SQL command.
#
# Memory units:  kB = kilobytes        Time units:  ms  = milliseconds
#                MB = megabytes                     s   = seconds
#                GB = gigabytes                     min = minutes
#                                                   h   = hours
#                                                   d   = days


#------------------------------------------------------------------------------
# FILE LOCATIONS
#------------------------------------------------------------------------------

# The default values of these variables are driven from the -D command-line
# option or PGDATA environment variable, represented here as ConfigDir.

#data_directory = 'ConfigDir'           # use data in another directory
                                        # (change requires restart)
#hba_file = 'ConfigDir/pg_hba.conf'     # host-based authentication file
                                        # (change requires restart)
#ident_file = 'ConfigDir/pg_ident.conf' # ident configuration file
                                        # (change requires restart)

# If external_pid_file is not explicitly set, no extra PID file is written.
#external_pid_file = ''                 # write an extra PID file
                                        # (change requires restart)


#------------------------------------------------------------------------------
# CONNECTIONS AND AUTHENTICATION
#-------------------------------------------------  -----------------------------

# - Connection Settings -

listen_addresses = '*'          # what IP address(es) to listen on;
                                        # comma-separated list of addresses;
                                        # defaults to 'localhost'; use '*' for all
                                        # (change requires restart)
#port = 5432                            # (change requires restart)
max_connections = 350                   # (change requires restart)
superuser_reserved_connections = 3     # (change requires restart)
#unix_socket_directories = '/tmp'       # comma-separated list of directories
                                        # (change requires restart)
#unix_socket_group = ''                 # (change requires restart)
#unix_socket_permissions = 0777         # begin with 0 to use octal notation
                                        # (change requires restart)
#bonjour = off                          # advertise server via Bonjour
                                        # (change requires restart)
#bonjour_name = ''                      # defaults to the computer name
                                        # (change requires restart)

# - Security and Authentication -

#authentication_timeout = 1min          # 1s-600s
#ssl = off                              # (change requires restart)
#ssl_ciphers = 'DEFAULT:!LOW:!EXP:!MD5:@STRENGTH'       # allowed SSL ciphers
                                        # (change requires restart)
#ssl_renegotiation_limit = 0            # amount of data between renegotiations
#ssl_cert_file = 'server.crt'           # (change requires restart)
#ssl_key_file = 'server.key'            # (change requires restart)
#ssl_ca_file = ''                       # (change requires restart)
#ssl_crl_file = ''                      # (change requires restart)
#password_encryption = on
#db_user_namespace = off

# Kerberos and GSSAPI
#krb_server_keyfile = ''
#krb_srvname = 'postgres'               # (Kerberos only)
#krb_caseins_users = off

# - TCP Keepalives -
# see "man 7 tcp" for details

tcp_keepalives_idle = 300                # TCP_KEEPIDLE, in seconds;
                                        # 0 selects the system default
tcp_keepalives_interval = 30            # TCP_KEEPINTVL, in seconds;
                                        # 0 selects the system default
tcp_keepalives_count = 2               # TCP_KEEPCNT;
                                        # 0 selects the system default


#------------------------------------------------------------------------------
# RESOURCE USAGE (except WAL)
#------------------------------------------------------------------------------

# - Memory -

shared_buffers = 64GB                  # min 128kB
                                        # (change requires restart)
temp_buffers = 500MB                     # min 800kB
#max_prepared_transactions = 0          # zero disables the feature
                                        # (change requires restart)
# Caution: it is not advisable to set max_prepared_transactions nonzero unless
# you actively intend to use prepared transactions.
work_mem = 2GB                         # min 64kB
maintenance_work_mem = 25GB            # min 1MB
max_stack_depth = 6MB                  # min 100kB

# - Disk -

#temp_file_limit = -1                   # limits per-session temp file space
                                        # in kB, or -1 for no limit

# - Kernel Resource Usage -

#max_files_per_process = 1000           # min 25
                                        # (change requires restart)
#shared_preload_libraries = ''          # (change requires restart)

# - Cost-Based Vacuum Delay -

#vacuum_cost_delay = 0                  # 0-100 milliseconds
#vacuum_cost_page_hit = 1               # 0-10000 credits
#vacuum_cost_page_miss = 10             # 0-10000 credits
#vacuum_cost_page_dirty = 20            # 0-10000 credits
#vacuum_cost_limit = 200                # 1-10000 credits

# - Background Writer -

#bgwriter_delay = 200ms                 # 10-10000ms between rounds
#bgwriter_lru_maxpages = 100            # 0-1000 max buffers written/round
#bgwriter_lru_multiplier = 2.0          # 0-10.0 multipler on buffers scanned/round

# - Asynchronous Behavior -

#effective_io_concurrency = 1           # 1-1000; 0 disables prefetching


#------------------------------------------------------------------------------
# WRITE AHEAD LOG
#------------------------------------------------------------------------------

# - Settings -

wal_level = minimal            # minimal, archive, or hot_standby
                                        # (change requires restart)
fsync = on                             # turns forced synchronization on or off
synchronous_commit = off                # synchronization level;
                                        # off, local, remote_write, or on
wal_sync_method = fsync                # the default is the first option
                                        # supported by the operating system:
                                        #   open_datasync
                                        #   fdatasync (default on Linux)
                                        #   fsync
                                        #   fsync_writethrough
                                        #   open_sync
#full_page_writes = on                  # recover from partial page writes
wal_buffers = -1                       # min 32kB, -1 sets based on shared_buffers
                                        # (change requires restart)
wal_writer_delay = 200ms               # 1-10000 milliseconds

commit_delay = 500                       # range 0-100000, in microseconds
#commit_siblings = 5                    # range 1-1000

# - Checkpoints -

checkpoint_segments = 100                # in logfile segments, min 1, 16MB each
checkpoint_timeout = 15min              # range 30s-1h
checkpoint_completion_target = 0.9     # checkpoint target duration, 0.0 - 1.0
#checkpoint_warning = 30s               # 0 disables


#------------------------------------------------------------------------------
# REPLICATION
#------------------------------------------------------------------------------

# - Sending Server(s) -

# Set these on the master and on any standby that will send replication data.

#max_wal_senders = 0            # max number of walsender processes
                                # (change requires restart)
#wal_keep_segments = 5000          # in logfile segments, 16MB each; 0 disables
#wal_sender_timeout = 60s       # in milliseconds; 0 disables

# - Master Server -

# These settings are ignored on a standby server.

#synchronous_standby_names = '' # standby servers that provide sync rep
                                # comma-separated list of application_name
                                # from standby(s); '*' = all
#vacuum_defer_cleanup_age = 0   # number of xacts by which cleanup is delayed

# - Standby Servers -

# These settings are ignored on a master server.

#hot_standby = on                      # "on" allows queries during recovery
                                        # (change requires restart)
#max_standby_archive_delay = 30s        # max delay before canceling queries
                                        # when reading WAL from archive;
                                        # -1 allows indefinite delay
#max_standby_streaming_delay = 30s      # max delay before canceling queries
                                        # when reading streaming WAL;
                                        # -1 allows indefinite delay
#wal_receiver_status_interval = 10s     # send replies at least this often
                                        # 0 disables
#hot_standby_feedback = off             # send info from standby to prevent
                                        # query conflicts
#wal_receiver_timeout = 60s             # time that receiver waits for
                                        # communication from master
                                        # in milliseconds; 0 disables


#------------------------------------------------------------------------------
# QUERY TUNING
#------------------------------------------------------------------------------

# - Planner Method Configuration -

enable_bitmapscan = on
enable_hashagg = on
enable_hashjoin = on
enable_indexscan = on
enable_indexonlyscan = on
enable_material = on
enable_mergejoin = on
enable_nestloop = on
enable_seqscan = on
enable_sort = on
enable_tidscan = on

# - Planner Cost Constants -

seq_page_cost = 1.0                    # measured on an arbitrary scale
random_page_cost = 2.0                 # same scale as above
#cpu_tuple_cost = 0.01                  # same scale as above
#cpu_index_tuple_cost = 0.005           # same scale as above
#cpu_operator_cost = 0.0025             # same scale as above
effective_cache_size = 50GB

# - Genetic Query Optimizer -

#geqo = on
#geqo_threshold = 12
#geqo_effort = 5                        # range 1-10
#geqo_pool_size = 0                     # selects default based on effort
#geqo_generations = 0                   # selects default based on effort
#geqo_selection_bias = 2.0              # range 1.5-2.0
#geqo_seed = 0.0                        # range 0.0-1.0

# - Other Planner Options -

default_statistics_target = 500        # range 1-10000
#constraint_exclusion = partition       # on, off, or partition
#cursor_tuple_fraction = 0.1            # range 0.0-1.0
#from_collapse_limit = 8
#join_collapse_limit = 8                # 1 disables collapsing of explicit
                                        # JOIN clauses


#------------------------------------------------------------------------------
# ERROR REPORTING AND LOGGING
#------------------------------------------------------------------------------

# - Where to Log -

#log_destination = 'stderr'             # Valid values are combinations of
                                        # stderr, csvlog, syslog, and eventlog,
                                        # depending on platform.  csvlog
                                        # requires logging_collector to be on.

# This is used when logging to stderr:
logging_collector = on                # Enable capturing of stderr and csvlog
                                        # into log files. Required to be on for
                                        # csvlogs.
                                        # (change requires restart)

# These are only used if logging_collector is on:
#log_directory = 'pg_log'               # directory where log files are written,
                                        # can be absolute or relative to PGDATA
#log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'        # log file name pattern,
                                        # can include strftime() escapes
#log_file_mode = 0600                   # creation mode for log files,
                                        # begin with 0 to use octal notation
#log_truncate_on_rotation = off         # If on, an existing log file with the
                                        # same name as the new log file will be
                                        # truncated rather than appended to.
                                        # But such truncation only occurs on
                                        # time-driven rotation, not on restarts
                                        # or size-driven rotation.  Default is
                                        # off, meaning append to existing files
                                        # in all cases.
log_rotation_age = 1h                  # Automatic rotation of logfiles will
                                        # happen after that time.  0 disables.
#log_rotation_size = 10MB               # Automatic rotation of logfiles will
                                        # happen after that much log output.
                                        # 0 disables.

# These are relevant when logging to syslog:
#syslog_facility = 'LOCAL0'
#syslog_ident = 'postgres'

# This is only relevant when logging to eventlog (win32):
#event_source = 'PostgreSQL'

# - When to Log -

#client_min_messages = notice           # values in order of decreasing detail:
                                        #   debug5
                                        #   debug4
                                        #   debug3
                                        #   debug2
                                        #   debug1
                                        #   log
                                        #   notice
                                        #   warning
                                        #   error

#log_min_messages = warning             # values in order of decreasing detail:
                                        #   debug5
                                        #   debug4
                                        #   debug3
                                        #   debug2
                                        #   debug1
                                        #   info
                                        #   notice
                                        #   warning
                                        #   error
                                        #   log
                                        #   fatal
                                        #   panic

#log_min_error_statement = error        # values in order of decreasing detail:
                                        #   debug5
                                        #   debug4
                                        #   debug3
                                        #   debug2
                                        #   debug1
                                        #   info
                                        #   notice
                                        #   warning
                                        #   error
                                        #   log
                                        #   fatal
                                        #   panic (effectively off)

log_min_duration_statement = 100        # -1 is disabled, 0 logs all statements
                                        # and their durations, > 0 logs only
                                        # statements running at least this number
                                        # of milliseconds


# - What to Log -

#debug_print_parse = off
#debug_print_rewritten = off
#debug_print_plan = off
#debug_pretty_print = on
log_checkpoints = on
#log_connections = off
#log_disconnections = off
#log_duration = off
#log_error_verbosity = default          # terse, default, or verbose messages
log_hostname = on
log_line_prefix = '%t:%r:%u@%d:[%p]:' # special values:
                                        #   %a = application name
                                        #   %u = user name
                                        #   %d = database name
                                        #   %r = remote host and port
                                        #   %h = remote host
                                        #   %p = process ID
                                        #   %t = timestamp without milliseconds
                                        #   %m = timestamp with milliseconds
                                        #   %i = command tag
                                        #   %e = SQL state
                                        #   %c = session ID
                                        #   %l = session line number
                                        #   %s = session start timestamp
                                        #   %v = virtual transaction ID
                                        #   %x = transaction ID (0 if none)
                                        #   %q = stop here in non-session
                                        #        processes
                                        #   %% = '%'
                                        # e.g. ' '
#log_lock_waits = off                   # log lock waits >= deadlock_timeout
#log_statement = 'none'                 # none, ddl, mod, all
#log_temp_files = -1                    # log temporary files equal or larger
                                        # than the specified size in kilobytes;
                                        # -1 disables, 0 logs all temp files
log_timezone = 'UTC'


#------------------------------------------------------------------------------
# RUNTIME STATISTICS
#------------------------------------------------------------------------------

# - Query/Index Statistics Collector -

#track_activities = on
track_counts = on
#track_io_timing = off
#track_functions = none                 # none, pl, all
#track_activity_query_size = 1024       # (change requires restart)
#update_process_title = on
#stats_temp_directory = 'pg_stat_tmp'


# - Statistics Monitoring -

#log_parser_stats = off
#log_planner_stats = off
#log_executor_stats = off
#log_statement_stats = off


#------------------------------------------------------------------------------
# AUTOVACUUM PARAMETERS
#------------------------------------------------------------------------------

autovacuum = on                        # Enable autovacuum subprocess?  'on'
                                        # requires track_counts to also be on.
#log_autovacuum_min_duration = -1       # -1 disables, 0 logs all actions and
                                        # their durations, > 0 logs only
                                        # actions running at least this number
                                        # of milliseconds.
autovacuum_max_workers = 3             # max number of autovacuum subprocesses
                                        # (change requires restart)
autovacuum_naptime = 1min              # time between autovacuum runs
autovacuum_vacuum_threshold = 50       # min number of row updates before
                                        # vacuum
autovacuum_analyze_threshold = 50      # min number of row updates before
                                        # analyze
autovacuum_vacuum_scale_factor = 0.2   # fraction of table size before vacuum
autovacuum_analyze_scale_factor = 0.1  # fraction of table size before analyze
#autovacuum_freeze_max_age = 200000000  # maximum XID age before forced vacuum
                                        # (change requires restart)
#autovacuum_multixact_freeze_max_age = 400000000        # maximum Multixact age
                                        # before forced vacuum
                                        # (change requires restart)
autovacuum_vacuum_cost_delay = 20ms    # default vacuum cost delay for
                                        # autovacuum, in milliseconds;
                                        # -1 means use vacuum_cost_delay
autovacuum_vacuum_cost_limit = -1      # default vacuum cost limit for
                                        # autovacuum, -1 means use
                                        # vacuum_cost_limit


#------------------------------------------------------------------------------
# CLIENT CONNECTION DEFAULTS
#------------------------------------------------------------------------------

# - Statement Behavior -

#search_path = '"$user",public'         # schema names
#default_tablespace = ''                # a tablespace name, '' uses the default
#temp_tablespaces = ''                  # a list of tablespace names, '' uses
                                        # only default tablespace
#check_function_bodies = on
#default_transaction_isolation = 'read committed'
#default_transaction_read_only = off
#default_transaction_deferrable = off
#session_replication_role = 'origin'
#statement_timeout = 0                  # in milliseconds, 0 is disabled
#lock_timeout = 0                       # in milliseconds, 0 is disabled
#vacuum_freeze_min_age = 50000000
#vacuum_freeze_table_age = 150000000
#vacuum_multixact_freeze_min_age = 5000000
#vacuum_multixact_freeze_table_age = 150000000
#bytea_output = 'hex'                   # hex, escape
#xmlbinary = 'base64'
#xmloption = 'content'
#gin_fuzzy_search_limit = 0

# - Locale and Formatting -

datestyle = 'iso, mdy'
#intervalstyle = 'postgres'
timezone = 'UTC'
#timezone_abbreviations = 'Default'     # Select the set of available time zone
                                        # abbreviations.  Currently, there are
                                        #   Default
                                        #   Australia (historical usage)
                                        #   India
                                        # You can create your own file in
                                        # share/timezonesets/.
#extra_float_digits = 0                 # min -15, max 3
#client_encoding = sql_ascii            # actually, defaults to database
                                        # encoding

# These settings are initialized by initdb, but they can be changed.
lc_messages = 'C'                     # locale for system error message
                                        # strings
lc_monetary = 'en_US'                     # locale for monetary formatting
lc_numeric = 'en_US'                      # locale for number formatting
lc_time = 'en_US'                         # locale for time formatting

# default configuration for text search
default_text_search_config = 'pg_catalog.simple'

# - Other Defaults -

#dynamic_library_path = '$libdir'
#local_preload_libraries = ''


#------------------------------------------------------------------------------
# LOCK MANAGEMENT
#------------------------------------------------------------------------------

#deadlock_timeout = 1s
#max_locks_per_transaction = 64         # min 10
                                        # (change requires restart)
#max_pred_locks_per_transaction = 64    # min 10
                                        # (change requires restart)


#------------------------------------------------------------------------------
# VERSION/PLATFORM COMPATIBILITY
#------------------------------------------------------------------------------

# - Previous PostgreSQL Versions -

#array_nulls = on
#backslash_quote = safe_encoding        # on, off, or safe_encoding
#default_with_oids = off
#escape_string_warning = on
#lo_compat_privileges = off
#quote_all_identifiers = off
#sql_inheritance = on
#standard_conforming_strings = on
#synchronize_seqscans = on

# - Other Platforms and Clients -

#transform_null_equals = off


#------------------------------------------------------------------------------
# ERROR HANDLING
#------------------------------------------------------------------------------

#exit_on_error = off                    # terminate session on any error?
#restart_after_crash = on               # reinitialize after backend crash?


#------------------------------------------------------------------------------
# CONFIG FILE INCLUDES
#------------------------------------------------------------------------------

# These options allow settings to be loaded from files other than the
# default postgresql.conf.

#include_dir = 'conf.d'                 # include files ending in '.conf' from
                                        # directory 'conf.d'
#include_if_exists = 'exists.conf'      # include file only if it exists
#include = 'special.conf'               # include file


#------------------------------------------------------------------------------
# CUSTOMIZED OPTIONS
#------------------------------------------------------------------------------

# Add settings for extensions here

closed as off-topic by Evan Carroll, hot2use, mustaccio, RDFozz, McNets Nov 2 '17 at 11:43

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Too localized - this could be because your code has a typo, basic error, or is not relevant to most of our audience. Consider revising your question so that it appeals to a broader audience. As it stands, the question is unlikely to help other users (regarding typo questions, see this meta question for background)." – Evan Carroll, hot2use, mustaccio, RDFozz, McNets
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    Is there a reason shared_buffers is set to 64GB? Have you tried it at 4 or 8GB? – bma Apr 5 '17 at 14:46
  • 1
    What does iotop look like while this is running? – CalZ Apr 5 '17 at 16:40
  • You're not mentioning pg_locks at all, make sure nothing opperating on that table is waiting for a lock for 2 minutes. SELECT * FROM pg_locks WHERE NOT granted; – Evan Carroll Apr 5 '17 at 17:39
  • hey guys thanks for reply we found the problem....a corrupted table! – Leonardo Carbone Apr 7 '17 at 12:58
  • Is that "RAM: 512" in gigs? – Basil Bourque Jun 13 '17 at 2:32
0

it's not many time to inserted per day(4times). okay you found the problem now, but anyway slow inserting operation can caused by few reasons:

  1. lock session
  2. bad query for inserting (if you use select sub-query to get data to inserted)
  3. you mentioned "postgres: wal writer process reached 70%", postgresql make sure your data that you're inserting is committed to disk so that why it takes the time. try to set you session to AUTOCOMMITE to off.

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