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0b1fe1413e
postgres/src/include/utils/guc_hooks.h
Nathan Bossart 0b1fe1413e Remove check hooks for GUCs that contribute to MaxBackends. 
Each of max_connections, max_worker_processes,
autovacuum_max_workers, and max_wal_senders has a GUC check hook
that verifies the sum of those GUCs does not exceed a hard-coded
limit (see the comment for MAX_BACKENDS in postmaster.h).  In
general, the hooks effectively guard against egregious
misconfigurations.

However, this approach has some problems.  Since these check hooks
are called as each GUC is assigned its user-specified value, only
one of the hooks will be called with all the relevant GUCs set.  If
one or more of the user-specified values are less than the initial
values of the GUCs' underlying variables, false positives can
occur.

Furthermore, the error message emitted when one of the check hooks
fails is not tremendously helpful.  For example, the command

	$ pg_ctl -D . start -o "-c max_connections=262100 -c max_wal_senders=10000"

fails with the following error:

	FATAL:  invalid value for parameter "max_wal_senders": 10000

Fortunately, there is an extra copy of this check in
InitializeMaxBackends() that we can rely on, so this commit removes
the aforementioned GUC check hooks in favor of that one.  It also
enhances the error message to clearly show the values of the
relevant GUCs and the hard-coded limit their sum may not exceed.
The downside of this change is that server startup progresses
further before failing due to such misconfigurations (thus taking
longer), but these failures are expected to be rare, so we don't
anticipate any real harm in practice.

Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/ZnMr2k-Nk5vj7T7H%40nathan
2024-07-05 14:42:55 -05:00

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/*-------------------------------------------------------------------------
*
* guc_hooks.h
* Declarations of per-variable callback functions used by GUC.
*
* These functions are scattered throughout the system, but we
* declare them all here to avoid having to propagate guc.h into
* a lot of unrelated header files.
*
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
*
* src/include/utils/guc_hooks.h
*
*-------------------------------------------------------------------------
*/
#ifndef GUC_HOOKS_H
#define GUC_HOOKS_H 1
#include "utils/guc.h"
/*
* See guc.h for the typedefs that these hook functions should match
* (GucBoolCheckHook and so on).
*
* Please keep the declarations in order by GUC variable name.
*/
extern bool check_application_name(char **newval, void **extra,
GucSource source);
extern void assign_application_name(const char *newval, void *extra);
extern const char *show_archive_command(void);
extern bool check_autovacuum_work_mem(int *newval, void **extra,
GucSource source);
extern bool check_vacuum_buffer_usage_limit(int *newval, void **extra,
GucSource source);
extern bool check_backtrace_functions(char **newval, void **extra,
GucSource source);
extern void assign_backtrace_functions(const char *newval, void *extra);
extern bool check_bonjour(bool *newval, void **extra, GucSource source);
extern bool check_canonical_path(char **newval, void **extra, GucSource source);
extern void assign_checkpoint_completion_target(double newval, void *extra);
extern bool check_client_connection_check_interval(int *newval, void **extra,
GucSource source);
extern bool check_client_encoding(char **newval, void **extra, GucSource source);
extern void assign_client_encoding(const char *newval, void *extra);
extern bool check_cluster_name(char **newval, void **extra, GucSource source);
extern bool check_commit_ts_buffers(int *newval, void **extra,
GucSource source);
extern const char *show_data_directory_mode(void);
extern bool check_datestyle(char **newval, void **extra, GucSource source);
extern void assign_datestyle(const char *newval, void *extra);
extern bool check_debug_io_direct(char **newval, void **extra, GucSource source);
extern void assign_debug_io_direct(const char *newval, void *extra);
extern bool check_default_table_access_method(char **newval, void **extra,
GucSource source);
extern bool check_default_tablespace(char **newval, void **extra,
GucSource source);
extern bool check_default_text_search_config(char **newval, void **extra, GucSource source);
extern void assign_default_text_search_config(const char *newval, void *extra);
extern bool check_default_with_oids(bool *newval, void **extra,
GucSource source);
extern bool check_effective_io_concurrency(int *newval, void **extra,
GucSource source);
extern bool check_huge_page_size(int *newval, void **extra, GucSource source);
extern const char *show_in_hot_standby(void);
extern bool check_locale_messages(char **newval, void **extra, GucSource source);
extern void assign_locale_messages(const char *newval, void *extra);
extern bool check_locale_monetary(char **newval, void **extra, GucSource source);
extern void assign_locale_monetary(const char *newval, void *extra);
extern bool check_locale_numeric(char **newval, void **extra, GucSource source);
extern void assign_locale_numeric(const char *newval, void *extra);
extern bool check_locale_time(char **newval, void **extra, GucSource source);
extern void assign_locale_time(const char *newval, void *extra);
extern bool check_log_destination(char **newval, void **extra,
GucSource source);
extern void assign_log_destination(const char *newval, void *extra);
extern const char *show_log_file_mode(void);
extern bool check_log_stats(bool *newval, void **extra, GucSource source);
extern bool check_log_timezone(char **newval, void **extra, GucSource source);
extern void assign_log_timezone(const char *newval, void *extra);
extern const char *show_log_timezone(void);
extern bool check_maintenance_io_concurrency(int *newval, void **extra,
GucSource source);
extern void assign_maintenance_io_concurrency(int newval, void *extra);
extern bool check_max_slot_wal_keep_size(int *newval, void **extra,
GucSource source);
extern void assign_max_wal_size(int newval, void *extra);
extern bool check_max_stack_depth(int *newval, void **extra, GucSource source);
extern void assign_max_stack_depth(int newval, void *extra);
extern bool check_multixact_member_buffers(int *newval, void **extra,
GucSource source);
extern bool check_multixact_offset_buffers(int *newval, void **extra,
GucSource source);
extern bool check_notify_buffers(int *newval, void **extra, GucSource source);
extern bool check_primary_slot_name(char **newval, void **extra,
GucSource source);
extern bool check_random_seed(double *newval, void **extra, GucSource source);
extern void assign_random_seed(double newval, void *extra);
extern const char *show_random_seed(void);
extern bool check_recovery_prefetch(int *new_value, void **extra,
GucSource source);
extern void assign_recovery_prefetch(int new_value, void *extra);
extern bool check_recovery_target(char **newval, void **extra,
GucSource source);
extern void assign_recovery_target(const char *newval, void *extra);
extern bool check_recovery_target_lsn(char **newval, void **extra,
GucSource source);
extern void assign_recovery_target_lsn(const char *newval, void *extra);
extern bool check_recovery_target_name(char **newval, void **extra,
GucSource source);
extern void assign_recovery_target_name(const char *newval, void *extra);
extern bool check_recovery_target_time(char **newval, void **extra,
GucSource source);
extern void assign_recovery_target_time(const char *newval, void *extra);
extern bool check_recovery_target_timeline(char **newval, void **extra,
GucSource source);
extern void assign_recovery_target_timeline(const char *newval, void *extra);
extern bool check_recovery_target_xid(char **newval, void **extra,
GucSource source);
extern void assign_recovery_target_xid(const char *newval, void *extra);
extern bool check_role(char **newval, void **extra, GucSource source);
extern void assign_role(const char *newval, void *extra);
extern const char *show_role(void);
extern bool check_search_path(char **newval, void **extra, GucSource source);
extern void assign_search_path(const char *newval, void *extra);
extern bool check_serial_buffers(int *newval, void **extra, GucSource source);
extern bool check_session_authorization(char **newval, void **extra, GucSource source);
extern void assign_session_authorization(const char *newval, void *extra);
extern void assign_session_replication_role(int newval, void *extra);
extern void assign_stats_fetch_consistency(int newval, void *extra);
extern bool check_ssl(bool *newval, void **extra, GucSource source);
extern bool check_stage_log_stats(bool *newval, void **extra, GucSource source);
extern bool check_subtrans_buffers(int *newval, void **extra,
GucSource source);
extern bool check_synchronous_standby_names(char **newval, void **extra,
GucSource source);
extern void assign_synchronous_standby_names(const char *newval, void *extra);
extern void assign_synchronous_commit(int newval, void *extra);
extern void assign_syslog_facility(int newval, void *extra);
extern void assign_syslog_ident(const char *newval, void *extra);
extern void assign_tcp_keepalives_count(int newval, void *extra);
extern const char *show_tcp_keepalives_count(void);
extern void assign_tcp_keepalives_idle(int newval, void *extra);
extern const char *show_tcp_keepalives_idle(void);
extern void assign_tcp_keepalives_interval(int newval, void *extra);
extern const char *show_tcp_keepalives_interval(void);
extern void assign_tcp_user_timeout(int newval, void *extra);
extern const char *show_tcp_user_timeout(void);
extern bool check_temp_buffers(int *newval, void **extra, GucSource source);
extern bool check_temp_tablespaces(char **newval, void **extra,
GucSource source);
extern void assign_temp_tablespaces(const char *newval, void *extra);
extern bool check_timezone(char **newval, void **extra, GucSource source);
extern void assign_timezone(const char *newval, void *extra);
extern const char *show_timezone(void);
extern bool check_timezone_abbreviations(char **newval, void **extra,
GucSource source);
extern void assign_timezone_abbreviations(const char *newval, void *extra);
extern bool check_transaction_buffers(int *newval, void **extra, GucSource source);
extern bool check_transaction_deferrable(bool *newval, void **extra, GucSource source);
extern bool check_transaction_isolation(int *newval, void **extra, GucSource source);
extern bool check_transaction_read_only(bool *newval, void **extra, GucSource source);
extern void assign_transaction_timeout(int newval, void *extra);
extern const char *show_unix_socket_permissions(void);
extern bool check_wal_buffers(int *newval, void **extra, GucSource source);
extern bool check_wal_consistency_checking(char **newval, void **extra,
GucSource source);
extern void assign_wal_consistency_checking(const char *newval, void *extra);
extern bool check_wal_segment_size(int *newval, void **extra, GucSource source);
extern void assign_wal_sync_method(int new_wal_sync_method, void *extra);
extern bool check_synchronized_standby_slots(char **newval, void **extra,
GucSource source);
extern void assign_synchronized_standby_slots(const char *newval, void *extra);
#endif /* GUC_HOOKS_H */
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