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/* ----------
* backend_status.h
* Definitions related to backend status reporting
*
* Copyright (c) 2001-2023, PostgreSQL Global Development Group
*
* src/include/utils/backend_status.h
* ----------
*/
#ifndef BACKEND_STATUS_H
#define BACKEND_STATUS_H
#include "datatype/timestamp.h"
#include "libpq/pqcomm.h"
#include "miscadmin.h" /* for BackendType */
#include "storage/backendid.h"
#include "utils/backend_progress.h"
/* ----------
* Backend states
* ----------
*/
typedef enum BackendState
{
STATE_UNDEFINED,
STATE_IDLE,
STATE_RUNNING,
STATE_IDLEINTRANSACTION,
STATE_FASTPATH,
STATE_IDLEINTRANSACTION_ABORTED,
STATE_DISABLED
} BackendState;
/* ----------
* Shared-memory data structures
* ----------
*/
/*
* PgBackendSSLStatus
*
* For each backend, we keep the SSL status in a separate struct, that
* is only filled in if SSL is enabled.
*
* All char arrays must be null-terminated.
*/
typedef struct PgBackendSSLStatus
{
/* Information about SSL connection */
int ssl_bits;
char ssl_version[NAMEDATALEN];
char ssl_cipher[NAMEDATALEN];
char ssl_client_dn[NAMEDATALEN];
/*
* serial number is max "20 octets" per RFC 5280, so this size should be
* fine
*/
char ssl_client_serial[NAMEDATALEN];
char ssl_issuer_dn[NAMEDATALEN];
} PgBackendSSLStatus;
/*
* PgBackendGSSStatus
*
* For each backend, we keep the GSS status in a separate struct, that
* is only filled in if GSS is enabled.
*
* All char arrays must be null-terminated.
*/
typedef struct PgBackendGSSStatus
{
/* Information about GSSAPI connection */
char gss_princ[NAMEDATALEN]; /* GSSAPI Principal used to auth */
bool gss_auth; /* If GSSAPI authentication was used */
bool gss_enc; /* If encryption is being used */
bool gss_delegation; /* If credentials delegated */
} PgBackendGSSStatus;
/* ----------
* PgBackendStatus
*
* Each live backend maintains a PgBackendStatus struct in shared memory
* showing its current activity. (The structs are allocated according to
* BackendId, but that is not critical.) Note that this is unrelated to the
* cumulative stats system (i.e. pgstat.c et al).
*
* Each auxiliary process also maintains a PgBackendStatus struct in shared
* memory.
* ----------
*/
typedef struct PgBackendStatus
{
/*
* To avoid locking overhead, we use the following protocol: a backend
* increments st_changecount before modifying its entry, and again after
* finishing a modification. A would-be reader should note the value of
* st_changecount, copy the entry into private memory, then check
* st_changecount again. If the value hasn't changed, and if it's even,
* the copy is valid; otherwise start over. This makes updates cheap
* while reads are potentially expensive, but that's the tradeoff we want.
*
* The above protocol needs memory barriers to ensure that the apparent
* order of execution is as it desires. Otherwise, for example, the CPU
* might rearrange the code so that st_changecount is incremented twice
* before the modification on a machine with weak memory ordering. Hence,
* use the macros defined below for manipulating st_changecount, rather
* than touching it directly.
*/
int st_changecount;
/* The entry is valid iff st_procpid > 0, unused if st_procpid == 0 */
int st_procpid;
/* Type of backends */
BackendType st_backendType;
/* Times when current backend, transaction, and activity started */
TimestampTz st_proc_start_timestamp;
TimestampTz st_xact_start_timestamp;
TimestampTz st_activity_start_timestamp;
TimestampTz st_state_start_timestamp;
/* Database OID, owning user's OID, connection client address */
Oid st_databaseid;
Oid st_userid;
SockAddr st_clientaddr;
char *st_clienthostname; /* MUST be null-terminated */
/* Information about SSL connection */
bool st_ssl;
PgBackendSSLStatus *st_sslstatus;
/* Information about GSSAPI connection */
bool st_gss;
PgBackendGSSStatus *st_gssstatus;
/* current state */
BackendState st_state;
/* application name; MUST be null-terminated */
char *st_appname;
/*
* Current command string; MUST be null-terminated. Note that this string
* possibly is truncated in the middle of a multi-byte character. As
* activity strings are stored more frequently than read, that allows to
* move the cost of correct truncation to the display side. Use
* pgstat_clip_activity() to truncate correctly.
*/
char *st_activity_raw;
/*
* Command progress reporting. Any command which wishes can advertise
* that it is running by setting st_progress_command,
* st_progress_command_target, and st_progress_param[].
* st_progress_command_target should be the OID of the relation which the
* command targets (we assume there's just one, as this is meant for
* utility commands), but the meaning of each element in the
* st_progress_param array is command-specific.
*/
ProgressCommandType st_progress_command;
Oid st_progress_command_target;
int64 st_progress_param[PGSTAT_NUM_PROGRESS_PARAM];
/* query identifier, optionally computed using post_parse_analyze_hook */
uint64 st_query_id;
} PgBackendStatus;
/*
* Macros to load and store st_changecount with appropriate memory barriers.
*
* Use PGSTAT_BEGIN_WRITE_ACTIVITY() before, and PGSTAT_END_WRITE_ACTIVITY()
* after, modifying the current process's PgBackendStatus data. Note that,
* since there is no mechanism for cleaning up st_changecount after an error,
* THESE MACROS FORM A CRITICAL SECTION. Any error between them will be
* promoted to PANIC, causing a database restart to clean up shared memory!
* Hence, keep the critical section as short and straight-line as possible.
* Aside from being safer, that minimizes the window in which readers will
* have to loop.
*
* Reader logic should follow this sketch:
*
* for (;;)
* {
* int before_ct, after_ct;
*
* pgstat_begin_read_activity(beentry, before_ct);
* ... copy beentry data to local memory ...
* pgstat_end_read_activity(beentry, after_ct);
* if (pgstat_read_activity_complete(before_ct, after_ct))
* break;
* CHECK_FOR_INTERRUPTS();
* }
*
* For extra safety, we generally use volatile beentry pointers, although
* the memory barriers should theoretically be sufficient.
*/
#define PGSTAT_BEGIN_WRITE_ACTIVITY(beentry) \
do { \
START_CRIT_SECTION(); \
(beentry)->st_changecount++; \
pg_write_barrier(); \
} while (0)
#define PGSTAT_END_WRITE_ACTIVITY(beentry) \
do { \
pg_write_barrier(); \
(beentry)->st_changecount++; \
Assert(((beentry)->st_changecount & 1) == 0); \
END_CRIT_SECTION(); \
} while (0)
#define pgstat_begin_read_activity(beentry, before_changecount) \
do { \
(before_changecount) = (beentry)->st_changecount; \
pg_read_barrier(); \
} while (0)
#define pgstat_end_read_activity(beentry, after_changecount) \
do { \
pg_read_barrier(); \
(after_changecount) = (beentry)->st_changecount; \
} while (0)
#define pgstat_read_activity_complete(before_changecount, after_changecount) \
((before_changecount) == (after_changecount) && \
((before_changecount) & 1) == 0)
/* ----------
* LocalPgBackendStatus
*
* When we build the backend status array, we use LocalPgBackendStatus to be
* able to add new values to the struct when needed without adding new fields
* to the shared memory. It contains the backend status as a first member.
* ----------
*/
typedef struct LocalPgBackendStatus
{
/*
* Local version of the backend status entry.
*/
PgBackendStatus backendStatus;
/*
* The backend ID. For auxiliary processes, this will be set to a value
* greater than MaxBackends (since auxiliary processes do not have proper
* backend IDs).
*/
BackendId backend_id;
/*
* The xid of the current transaction if available, InvalidTransactionId
* if not.
*/
TransactionId backend_xid;
/*
* The xmin of the current session if available, InvalidTransactionId if
* not.
*/
TransactionId backend_xmin;
/*
* Number of cached subtransactions in the current session.
*/
int backend_subxact_count;
/*
* The number of subtransactions in the current session which exceeded the
* cached subtransaction limit.
*/
bool backend_subxact_overflowed;
} LocalPgBackendStatus;
/* ----------
* GUC parameters
* ----------
*/
extern PGDLLIMPORT bool pgstat_track_activities;
extern PGDLLIMPORT int pgstat_track_activity_query_size;
/* ----------
* Other global variables
* ----------
*/
extern PGDLLIMPORT PgBackendStatus *MyBEEntry;
/* ----------
* Functions called from postmaster
* ----------
*/
extern Size BackendStatusShmemSize(void);
extern void CreateSharedBackendStatus(void);
/* ----------
* Functions called from backends
* ----------
*/
/* Initialization functions */
extern void pgstat_beinit(void);
extern void pgstat_bestart(void);
extern void pgstat_clear_backend_activity_snapshot(void);
/* Activity reporting functions */
extern void pgstat_report_activity(BackendState state, const char *cmd_str);
extern void pgstat_report_query_id(uint64 query_id, bool force);
extern void pgstat_report_tempfile(size_t filesize);
extern void pgstat_report_appname(const char *appname);
extern void pgstat_report_xact_timestamp(TimestampTz tstamp);
extern const char *pgstat_get_backend_current_activity(int pid, bool checkUser);
extern const char *pgstat_get_crashed_backend_activity(int pid, char *buffer,
int buflen);
extern uint64 pgstat_get_my_query_id(void);
/* ----------
* Support functions for the SQL-callable functions to
* generate the pgstat* views.
* ----------
*/
extern int pgstat_fetch_stat_numbackends(void);
extern PgBackendStatus *pgstat_get_beentry_by_backend_id(BackendId beid);
extern LocalPgBackendStatus *pgstat_get_local_beentry_by_backend_id(BackendId beid);
extern LocalPgBackendStatus *pgstat_get_local_beentry_by_index(int idx);
extern char *pgstat_clip_activity(const char *raw_activity);
#endif /* BACKEND_STATUS_H */