postgresql.conf のログ出力設定について

Question

postgresql.confのログ出力設定についての質問です。

postgresql.conf にエラーの出力方式を記載できますが、
関連する箇所（log_destinationなど）が全てコメントアウトされていた場合、
ログは出力されるのでしょうか？

デフォルトでは'stderr'が設定されていると記載がありますが、
postgresql.confにもともと'stderr'が書かれているという意味にも捉えられますし（まあないと思いますが）、
実際にはどうなのかわかりません。
https://www.postgresql.jp/document/8.4/html/runtime-config-logging.html

具体的なコードは以下のような感じです。

#------------------------------------------------------------------------------
# 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 = off		# Enable capturing of stderr and csvlog
					# into log files. Required to be on for
					# csvlogs.
					# (change requires restart)
～省略～

#log_timezone = unknown			# actually, defaults to TZ environment
					# setting


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

ご存知の方いらっしゃれば教えてください。

Answer 1

以下のような、logから始まる行を#でコメントアウトしたコンフィグを用意して、試してみました。

[root@localhost ~]# cat /var/lib/pgsql/data/postgresql.conf | grep log
# "postgres -c log_connections=on".  Some parameters can be changed at run time
#wal_level = minimal                    # minimal, replica, or logical
#wal_log_hints = off                    # also do full page writes of non-critical updates
#archive_command = ''           # command to use to archive a logfile segment
#archive_timeout = 0            # force a logfile segment switch after this
#wal_keep_segments = 0          # in logfile segments, 16MB each; 0 disables
# 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:
#log_ging_collector = on                        # Enable capturing of stderr and csvlog
                                        # into log files. Required to be on for
                                        # csvlogs.
# These are only used if logging_collector is on:
#log_directory = 'pg_log'               # directory where log files are written,
#log_filename = 'postgresql-%a.log'     # log file name pattern,
#log_file_mode = 0600                   # creation mode for log files,
#log_truncate_on_rotation = on          # If on, an existing log file with the
                                        # same name as the new log file will be
#log_rotation_age = 1d                  # Automatic rotation of logfiles will
#log_rotation_size = 0                  # Automatic rotation of logfiles will
                                        # happen after that much log output.
# These are relevant when logging to syslog:
#syslog_facility = 'LOCAL0'
#syslog_ident = 'postgres'
#syslog_sequence_numbers = on
#syslog_split_messages = on
# This is only relevant when logging to eventlog (win32):
                                        #   log
#log_min_messages = warning             # values in order of decreasing detail:
                                        #   log
#log_min_error_statement = error        # values in order of decreasing detail:
                                        #   log
#log_min_duration_statement = -1        # -1 is disabled, 0 logs all statements
                                        # and their durations, > 0 logs only
#log_checkpoints = off
#log_connections = off
#log_disconnections = off
#log_duration = off
#log_error_verbosity = default          # terse, default, or verbose messages
#log_hostname = off
#log_line_prefix = '< %m > '                    # special values:
#log_lock_waits = off                   # log lock waits >= deadlock_timeout
#log_statement = 'none'                 # none, ddl, mod, all
#log_replication_commands = off
#log_temp_files = -1                    # log temporary files equal or larger
                                        # -1 disables, 0 logs all temp files
#log_timezone = 'Japan'
#log_parser_stats = off
#log_planner_stats = off
#log_executor_stats = off
#log_statement_stats = off
#log_autovacuum_min_duration = -1       # -1 disables, 0 logs all actions and
                                        # their durations, > 0 logs only
default_text_search_config = 'pg_catalog.english'

サービスをreloadして、showコマンドで見てみると、以下の内容で起動します。

[root@localhost ~]# /usr/pgsql-9.6/bin/psql -h localhost -d SAG3 -U sa -c 'SHOW ALL' | grep log
 application_name                    | psql                                  | Sets the application name to be reported in statistics and logs.
 archive_timeout                     | 0                                     | Forces a switch to the next xlog file if a new file has not been started within N seconds.
 default_text_search_config          | pg_catalog.english                    | Sets default text search configuration.
 event_source                        | PostgreSQL                            | Sets the application name used to identify PostgreSQL messages in the event log.
 log_autovacuum_min_duration         | -1                                    | Sets the minimum execution time above which autovacuum actions will be logged.
 log_checkpoints                     | off                                   | Logs each checkpoint.
 log_connections                     | off                                   | Logs each successful connection.
 log_destination                     | stderr                                | Sets the destination for server log output.
 log_directory                       | pg_log                                | Sets the destination directory for log files.
 log_disconnections                  | off                                   | Logs end of a session, including duration.
 log_duration                        | off                                   | Logs the duration of each completed SQL statement.
 log_error_verbosity                 | default                               | Sets the verbosity of logged messages.
 log_executor_stats                  | off                                   | Writes executor performance statistics to the server log.
 log_file_mode                       | 0600                                  | Sets the file permissions for log files.
 log_filename                        | postgresql-%Y-%m-%d_%H%M%S.log        | Sets the file name pattern for log files.
 log_hostname                        | off                                   | Logs the host name in the connection logs.
 log_line_prefix                     |                                       | Controls information prefixed to each log line.
 log_lock_waits                      | off                                   | Logs long lock waits.
 log_min_duration_statement          | -1                                    | Sets the minimum execution time above which statements will be logged.
 log_min_error_statement             | error                                 | Causes all statements generating error at or above this level to be logged.
 log_min_messages                    | warning                               | Sets the message levels that are logged.
 log_parser_stats                    | off                                   | Writes parser performance statistics to the server log.
 log_planner_stats                   | off                                   | Writes planner performance statistics to the server log.
 log_replication_commands            | off                                   | Logs each replication command.
 log_rotation_age                    | 1d                                    | Automatic log file rotation will occur after N minutes.
 log_rotation_size                   | 10MB                                  | Automatic log file rotation will occur after N kilobytes.
 log_statement                       | none                                  | Sets the type of statements logged.
 log_statement_stats                 | off                                   | Writes cumulative performance statistics to the server log.
 log_temp_files                      | -1                                    | Log the use of temporary files larger than this number of kilobytes.
 log_timezone                        | GMT                                   | Sets the time zone to use in log messages.
 log_truncate_on_rotation            | off                                   | Truncate existing log files of same name during log rotation.
 logging_collector                   | on                                    | Start a subprocess to capture stderr output and/or csvlogs into log files.
 syslog_facility                     | local0                                | Sets the syslog "facility" to be used when syslog enabled.
 syslog_ident                        | postgres                              | Sets the program name used to identify PostgreSQL messages in syslog.
 syslog_sequence_numbers             | on                                    | Add sequence number to syslog messages to avoid duplicate suppression.
 syslog_split_messages               | on                                    | Split messages sent to syslog by lines and to fit into 1024 bytes.
 trace_recovery_messages             | log                                   | Enables logging of recovery-related debugging information.
 wal_block_size                      | 8192                                  | Shows the block size in the write ahead log.
 wal_log_hints                       | off                                   | Writes full pages to WAL when first modified after a checkpoint, even for a non-critical modifications.
 wal_segment_size                    | 16MB                                  | Shows the number of pages per write ahead log segment.

この状態で、もう1回サービスをreloadすると、
pg_logディレクトリの下に、以下のようなファイルが出来ます。

[root@localhost ~]# ll /var/lib/pgsql/data/pg_log/
合計 12
-rw------- 1 postgres postgres 1140 11月 15 14:04 2017 postgresql-2017-11-15_045852.log
-rw------- 1 postgres postgres 4130 11月 15 13:58 2017 postgresql-Wed.log
[root@localhost ~]#

yumでインストールして配置されるpostgresql.confのログ出力内容とは、異なる内容で出てきますね。

postgresql-Wed.logの内容は、yumでインストールしたpostgresql.confの内容で動かすと作成されるログファイルです。

logの内容をすべてコメントアウトした場合は、postgresql-2017-11-15_045852.logという名前でログファイルができました。

というわけで、logに関する内容をすべてコメントアウトしても、ログは出ます。

Comments

[mi-c3]

試していただきありがとうございます！
そのような挙動になるのですね。
非常に助かりました！