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  • PostgreSQL的HA解决方案-1主从和备份(master/slave and backup)

     一.部署说明

    1.1 实施环境

    本文档实验环境如下:

    PGSQL主机: 192.168.1.45

    PGSQL备机: 192.168.1.50

    软件和系统版本

    Pgsql 版本: pgsql 9.2.4

    Linux 版本: Redhat 5.8

    1.2 文档说明

      本文档详细说明了PG的双机扩展,使pgsql数据库具备双机热备流复制功能。注意,双机热备中存在主从关系,这样才能保证数据的一直性,主机操作都可以,但从机只能用作查询。所以热备的意义在于分担主机的查询压力,备份主机数据,当主机出问题后,从机稍加修改就可以变为主机。

      为了试验减少不必要的麻烦,本系列试验中,各个主机之间的通信,都是设置为无密码访问,但对于实际生产,需要根据实际需要,配置密码,增强集群的安全性。

    二.配置步骤

      1.1 (主从一样)。编辑data/pg_hba.conf 访问控制文件。    

        在配置pgsql之前,首先要设置两台服务器使得postgres用户可以无密码相互访问。 配置过程一定要分清主从机。因为实验的两台虚拟机所在网段都是192.168.1.0/24.所以,新增如下:

    # TYPE  DATABASE        USER            ADDRESS                 METHOD
    
    # "local" is for Unix domain socket connections only
    local   all             all                                     trust
    # IPv4 local connections:
    host    all             all             127.0.0.1/32            trust
    host    all             all             192.168.1.0/24          trust
    # IPv6 local connections:
    host    all             all             ::1/128                 trust
    # Allow replication connections from localhost, by a user with the
    # replication privilege.
    #local   replication     postgres                                trust
    #host    replication     postgres        127.0.0.1/32            trust
    host    replication     postgres        192.168.1.0/24           trust
    #host    replication     postgres        ::1/128                 trust

      1.2 (主从一样)。编辑data/postgresql.conf 数据库配置文件。

        主从机的数据库postgresql.conf配置相同,主要是方便接下来的将主机的data文件直接备份还原到从机,并且也方便将来主从切换。请对照默认参数设置,设置相应参数,一些参数的设置,如

    max_connections = 100       #最大连接数的设置,当超过最大链接时,数据库拒绝访问。

    shared_buffers = 1280MB      #共享内存,主要是和服务器的硬件和实际的项目需求相关,理论上在硬件资源允许的情况下,此值越大越好。

    wal_level = hot_standby       #开启主从热备模式

    fsync = on              #异步数据同步

    full_page_writes = on

    checkpoint_segments = 32      #关于脏数据写回的
    archive_mode = on                    #打开归档模式

    archive_command ='cp %p /opt/bjca3/pgsql/data/archive/%f ' #将归档文件保存在data/archive目录下
    max_wal_senders = 2         #根据从机的个数设置,实验中只有一个从机,所以只设置为1

    wal_keep_segments = 250       

    hot_standby = on             #在配置中,并不是每个配置都起作用的,数据库会根据当前的主从机的属性,自动判断哪些是主机的配置,哪些是从机的配置,配置文档中也有说明。
    max_standby_archive_delay = 300s

    max_standby_streaming_delay = 300s

    wal_receiver_status_interval = 10s

    hot_standby_feedback = on 

    log_line_prefix = '[%t] '

        详细的配置及含义请看下边的配置文件。

    # -----------------------------
    # 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 = 'localhost'        # what IP address(es) to listen on;
    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)
    port = 5432                # (change requires restart)
    max_connections = 100            # (change requires restart)
    # Note:  Increasing max_connections costs ~400 bytes of shared memory per
    # connection slot, plus lock space (see max_locks_per_transaction).
    #superuser_reserved_connections = 3    # (change requires restart)
    #unix_socket_directory = ''        # (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 = 'ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH'    # allowed SSL ciphers
                        # (change requires restart)
    #ssl_renegotiation_limit = 512MB    # 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 = 0        # TCP_KEEPIDLE, in seconds;
                        # 0 selects the system default
    #tcp_keepalives_interval = 0        # TCP_KEEPINTVL, in seconds;
                        # 0 selects the system default
    #tcp_keepalives_count = 0        # TCP_KEEPCNT;
                        # 0 selects the system default
    
    
    #------------------------------------------------------------------------------
    # RESOURCE USAGE (except WAL)
    #------------------------------------------------------------------------------
    
    # - Memory -
    
    #shared_buffers = 32MB            # min 128kB
    shared_buffers = 256MB            # min 128kB
                        # (change requires restart)
    #temp_buffers = 8MB            # min 800kB
    #max_prepared_transactions = 0        # zero disables the feature
                        # (change requires restart)
    # Note:  Increasing max_prepared_transactions costs ~600 bytes of shared memory
    # per transaction slot, plus lock space (see max_locks_per_transaction).
    # It is not advisable to set max_prepared_transactions nonzero unless you
    # actively intend to use prepared transactions.
    #work_mem = 1MB                # min 64kB
    #maintenance_work_mem = 16MB        # min 1MB
    #max_stack_depth = 2MB            # 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 = 0ms        # 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
    wal_level = hot_standby            # minimal, archive, or hot_standby
                        # (change requires restart)
    #fsync = on                # turns forced synchronization on or off
    fsync = on                # turns forced synchronization on or off
    #synchronous_commit = on        # 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
    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 = 0            # range 0-100000, in microseconds
    #commit_siblings = 5            # range 1-1000
    
    # - Checkpoints -
    
    #checkpoint_segments = 3        # in logfile segments, min 1, 16MB each
    #checkpoint_timeout = 5min        # range 30s-1h
    #checkpoint_completion_target = 0.5    # checkpoint target duration, 0.0 - 1.0
    #checkpoint_warning = 30s        # 0 disables
    
    # - Archiving -
    
    #archive_mode = off        # allows archiving to be done
    archive_mode = on        # allows archiving to be done
                    # (change requires restart)
    #archive_command = ''        # command to use to archive a logfile segment
    archive_command = 'cp %p /usr/local/pgsql/data/archive/%f'        # command to use to archive a logfile segment
                    # placeholders: %p = path of file to archive
                    #               %f = file name only
                    # e.g. 'test ! -f /mnt/server/archivedir/%f && cp %p /mnt/server/archivedir/%f'
    #archive_timeout = 0        # force a logfile segment switch after this
                    # number of seconds; 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
    max_wal_senders = 1        # max number of walsender processes
                    # (change requires restart)
    #wal_keep_segments = 0        # in logfile segments, 16MB each; 0 disables
    wal_keep_segments = 250        # in logfile segments, 16MB each; 0 disables
    #replication_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
    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 = off            # "on" allows queries during recovery
    hot_standby = on            # "on" allows queries during recovery
                        # (change requires restart)
    #max_standby_archive_delay = 30s    # max delay before canceling queries
    max_standby_archive_delay = 300s    # max delay before canceling queries
                        # when reading WAL from archive;
                        # -1 allows indefinite delay
    #max_standby_streaming_delay = 30s    # max delay before canceling queries
    max_standby_streaming_delay = 300s    # max delay before canceling queries
                        # when reading streaming WAL;
                        # -1 allows indefinite delay
    #wal_receiver_status_interval = 10s    # send replies at least this often
    wal_receiver_status_interval = 10s    # send replies at least this often
                        # 0 disables
    #hot_standby_feedback = off        # send info from standby to prevent
    hot_standby_feedback = on        # send info from standby to prevent
                        # query conflicts
    
    
    #------------------------------------------------------------------------------
    # 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 = 4.0            # 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 = 128MB
    
    # - 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 = 100    # 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
    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
    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,
    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,
    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 = 1d            # 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 = -1    # -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 = 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 = '[%t]'        # 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. '<%u%%%d> '
    #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 = 'PRC'
    
    
    #------------------------------------------------------------------------------
    # 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_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
    #vacuum_freeze_min_age = 50000000
    #vacuum_freeze_table_age = 150000000
    #bytea_output = 'hex'            # hex, escape
    #xmlbinary = 'base64'
    #xmloption = 'content'
    
    # - Locale and Formatting -
    
    datestyle = 'iso, mdy'
    #intervalstyle = 'postgres'
    timezone = 'PRC'
    #timezone_abbreviations = 'Default'     # Select the set of available time zone
                        # abbreviations.  Currently, there are
                        #   Default
                        #   Australia
                        #   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 = 'C'            # locale for monetary formatting
    lc_numeric = 'C'            # locale for number formatting
    lc_time = 'C'                # locale for time formatting
    
    # default configuration for text search
    default_text_search_config = 'pg_catalog.english'
    
    # - Other Defaults -
    
    #dynamic_library_path = '$libdir'
    #local_preload_libraries = ''
    
    
    #------------------------------------------------------------------------------
    # LOCK MANAGEMENT
    #------------------------------------------------------------------------------
    
    #deadlock_timeout = 1s
    #max_locks_per_transaction = 64        # min 10
                        # (change requires restart)
    # Note:  Each lock table slot uses ~270 bytes of shared memory, and there are
    # max_locks_per_transaction * (max_connections + max_prepared_transactions)
    # lock table slots.
    #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?
    
    
    #------------------------------------------------------------------------------
    # CUSTOMIZED OPTIONS
    #------------------------------------------------------------------------------
    
    # Add settings for extensions here
    View Code

      1.3 此时主从数据库的配置是相同的,所以可以将主库直接备份,然后还原至从库。其实对于从库,配置本身很简单,只是因为考虑到接下来的主从切换麻烦,所以讲主从配置成一样的。

    此时可以使用PG自带的pg_basebackup工具,对主机进行远程基础备份。

      在从机中执行:pg_basebackup -F p -D $PGDATA -x -v -h db1 -w

      将主机的数据库远程备份并恢复到从机中。其中db1是我添加在系统hosts里的,对于不想添加的,可以直接使用Ip地址。其实hosts中的文件就是给出不同IP的别名,方便使用。其他参数请--help.

      1.4 备份还原到从机后,需要添加另外一个配置文件:recovery.conf,此时才把主机与从机区分开来。在PGHOME目录下的share文件夹中有实例文件,将之拷贝过来,修改即可。

        执行cp /usr/local/pgsql/share/recovery.conf.sample /usr/local/pgsql/data/recovery.conf. 

        主要配置:

    standby_mode = 'on'          #开启从机模式

    trigger_file = '/usr/local/pgsql/data/pg.trigger'#注意路径是可以自定义的,但是当主机失效,从机变为主机是,为产生该文件,但当重新恢复为从机自己写的shell脚本要删除该文件,注意权限问题。

    primary_conninfo = 'host=db1'

      1.5 此时可以启动从机的数据库了。此时会报如下错误:

    FATAL:  data directory "/usr/local/pgsql/data" has group or world access
    DETAIL:  Permissions should be u=rwx (0700).

      所以,此时要修改data的权限为700.修改之后启动,就没问题了。此时查看启动日志:data/pg_log中的日志如下:

    LOG:  creating missing WAL directory "pg_xlog/archive_status"
    LOG:  entering standby mode
    LOG:  redo starts at 0/4000020
    LOG:  consistent recovery state reached at 0/40000C8
    LOG:  database system is ready to accept read only connections
    LOG:  streaming replication successfully connected to primary

      说明,此时从机已经开启了从机模式,只读模式等待连接,并且已经连接到主机的数据库。

      1.6验证数据同步。

        ①在主库中创建表,查看从库中是否有同样的数据表即可。

        ②当然也可以主机中在psql中执行:select * from pg_stat_replication;

    pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | state | sent_location | write_locat
    ion | flush_location | replay_location | sync_priority | sync_state
    -------+----------+----------+------------------+--------------+-----------------+-------------+-------------------------------+-----------+---------------+------------
    ----+----------------+-----------------+---------------+------------
    22877 | 10 | postgres | walreceiver | 192.168.1.50 | | 47967 | 2015-09-18 16:09:13.711784+08 | streaming | 0/5016334 | 0/5016334
    | 0/5016334 | 0/5016334 | 1 | sync

        ③在主机中运行命令:top -c -u postgres

    12707 postgres 15 0 4612 1368 1108 S 0.0 0.1 0:00.09 bash
    13190 postgres 18 0 4992 1256 1072 T 0.0 0.1 0:00.02 vi pg_hba.conf
    17668 postgres 15 0 281m 16m 15m S 0.0 1.6 0:00.03 /usr/local/pgsql/bin/postgres -D /usr/local/pgsql/data
    17669 postgres 18 0 9124 660 356 S 0.0 0.1 0:00.00 postgres: logger process
    17671 postgres 16 0 281m 3164 2808 S 0.0 0.3 0:00.34 postgres: checkpointer process
    17672 postgres 15 0 281m 2544 2208 S 0.0 0.2 0:00.01 postgres: writer process
    17673 postgres 15 0 281m 840 504 S 0.0 0.1 0:00.00 postgres: wal writer process
    17674 postgres 18 0 282m 1680 984 S 0.0 0.2 0:00.00 postgres: autovacuum launcher process
    17675 postgres 18 0 9168 688 356 S 0.0 0.1 0:00.00 postgres: archiver process last was 000000010000000000000004
    17676 postgres 16 0 9168 796 424 S 0.0 0.1 0:00.03 postgres: stats collector process
    22877 postgres 18 0 282m 2176 1360 S 0.0 0.2 0:00.00 postgres: wal sender process postgres 192.168.1.50(47967) streaming 0/5016334
    25439 postgres 15 0 2432 1068 816 R 0.0 0.1 0:00.19 top -c -u postgres

        ④在从机中运行命令:top -c -u postgres

    PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    12446 postgres 15 0 4612 1384 1120 S 0.0 0.1 0:00.08 bash
    19711 postgres 15 0 4612 1376 1116 S 0.0 0.1 0:00.02 bash
    20040 postgres 15 0 4612 1360 1124 S 0.0 0.1 0:00.01 bash
    20152 postgres 15 0 4612 1388 1124 S 0.0 0.1 0:00.05 bash
    21809 postgres 18 0 281m 16m 15m S 0.0 1.6 0:00.05 /usr/local/pgsql/bin/postgres -D /usr/local/pgsql/data
    21810 postgres 22 0 9120 652 352 S 0.0 0.1 0:00.00 postgres: logger process
    21811 postgres 15 0 282m 1784 1420 S 0.0 0.2 0:00.00 postgres: startup process recovering 000000010000000000
    21812 postgres 16 0 281m 2988 2640 S 0.0 0.3 0:00.00 postgres: checkpointer process
    21813 postgres 15 0 281m 2532 2200 S 0.0 0.2 0:00.00 postgres: writer process
    21814 postgres 16 0 9164 780 408 S 0.0 0.1 0:00.00 postgres: stats collector process
    21815 postgres 15 0 282m 1768 1244 S 0.0 0.2 0:00.28 postgres: wal receiver process streaming 0/50163B8
    24569 postgres 15 0 2432 1072 816 R 0.0 0.1 0:00.14 top -c -u postgres

      都可以证明已经正常启动。

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  • 原文地址:https://www.cnblogs.com/cz-blog/p/4818976.html
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