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shared_library_init.c
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shared_library_init.c
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/*-------------------------------------------------------------------------
*
* shared_library_init.c
* Functionality related to the initialization of the Citus extension.
*
* Copyright (c) Citus Data, Inc.
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <limits.h>
#include <sys/stat.h>
#include <sys/types.h>
/* necessary to get alloca on illumos */
#ifdef __sun
#include <alloca.h>
#endif
#include "fmgr.h"
#include "miscadmin.h"
#include "safe_lib.h"
#include "catalog/pg_authid.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_extension.h"
#include "citus_version.h"
#include "commands/explain.h"
#include "commands/extension.h"
#include "common/string.h"
#include "executor/executor.h"
#include "distributed/backend_data.h"
#include "distributed/background_jobs.h"
#include "distributed/causal_clock.h"
#include "distributed/citus_depended_object.h"
#include "distributed/citus_nodefuncs.h"
#include "distributed/citus_safe_lib.h"
#include "distributed/commands.h"
#include "distributed/commands/multi_copy.h"
#include "distributed/commands/utility_hook.h"
#include "distributed/connection_management.h"
#include "distributed/cte_inline.h"
#include "distributed/distributed_deadlock_detection.h"
#include "distributed/errormessage.h"
#include "distributed/repartition_executor.h"
#include "distributed/intermediate_result_pruning.h"
#include "distributed/local_multi_copy.h"
#include "distributed/local_executor.h"
#include "distributed/local_distributed_join_planner.h"
#include "distributed/locally_reserved_shared_connections.h"
#include "distributed/log_utils.h"
#include "distributed/maintenanced.h"
#include "distributed/shard_cleaner.h"
#include "distributed/metadata_utility.h"
#include "distributed/coordinator_protocol.h"
#include "distributed/metadata_cache.h"
#include "distributed/metadata_sync.h"
#include "distributed/multi_physical_planner.h"
#include "distributed/multi_executor.h"
#include "distributed/multi_explain.h"
#include "distributed/multi_join_order.h"
#include "distributed/multi_logical_replication.h"
#include "distributed/multi_logical_optimizer.h"
#include "distributed/distributed_planner.h"
#include "distributed/combine_query_planner.h"
#include "distributed/multi_router_planner.h"
#include "distributed/multi_server_executor.h"
#include "distributed/pg_dist_partition.h"
#include "distributed/placement_connection.h"
#include "distributed/priority.h"
#include "distributed/query_stats.h"
#include "distributed/recursive_planning.h"
#include "distributed/reference_table_utils.h"
#include "distributed/relation_access_tracking.h"
#include "distributed/replication_origin_session_utils.h"
#include "distributed/run_from_same_connection.h"
#include "distributed/shard_cleaner.h"
#include "distributed/shard_transfer.h"
#include "distributed/shared_connection_stats.h"
#include "distributed/shardsplit_shared_memory.h"
#include "distributed/query_pushdown_planning.h"
#include "distributed/time_constants.h"
#include "distributed/query_stats.h"
#include "distributed/remote_commands.h"
#include "distributed/shard_rebalancer.h"
#include "distributed/shared_library_init.h"
#include "distributed/statistics_collection.h"
#include "distributed/subplan_execution.h"
#include "distributed/resource_lock.h"
#include "distributed/transaction_management.h"
#include "distributed/transaction_recovery.h"
#include "distributed/utils/citus_stat_tenants.h"
#include "distributed/utils/directory.h"
#include "distributed/worker_log_messages.h"
#include "distributed/worker_manager.h"
#include "distributed/worker_protocol.h"
#include "distributed/worker_shard_visibility.h"
#include "distributed/adaptive_executor.h"
#include "libpq/auth.h"
#include "port/atomics.h"
#include "postmaster/postmaster.h"
#include "replication/walsender.h"
#include "storage/ipc.h"
#include "optimizer/planner.h"
#include "optimizer/plancat.h"
#include "optimizer/paths.h"
#include "tcop/tcopprot.h"
#include "utils/guc.h"
#include "utils/guc_tables.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
#include "utils/varlena.h"
#include "columnar/columnar.h"
/* marks shared object as one loadable by the postgres version compiled against */
PG_MODULE_MAGIC;
ColumnarSupportsIndexAM_type extern_ColumnarSupportsIndexAM = NULL;
CompressionTypeStr_type extern_CompressionTypeStr = NULL;
IsColumnarTableAmTable_type extern_IsColumnarTableAmTable = NULL;
ReadColumnarOptions_type extern_ReadColumnarOptions = NULL;
/*
* Define "pass-through" functions so that a SQL function defined as one of
* these symbols in the citus module can use the definition in the columnar
* module.
*/
#define DEFINE_COLUMNAR_PASSTHROUGH_FUNC(funcname) \
static PGFunction CppConcat(extern_, funcname); \
PG_FUNCTION_INFO_V1(funcname); \
Datum funcname(PG_FUNCTION_ARGS) \
{ \
return CppConcat(extern_, funcname)(fcinfo); \
}
#define INIT_COLUMNAR_SYMBOL(typename, funcname) \
CppConcat(extern_, funcname) = \
(typename) (void *) lookup_external_function(handle, # funcname)
#define CDC_DECODER_DYNAMIC_LIB_PATH "$libdir/citus_decoders:$libdir"
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(columnar_handler)
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(alter_columnar_table_set)
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(alter_columnar_table_reset)
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(upgrade_columnar_storage)
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(downgrade_columnar_storage)
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(columnar_relation_storageid)
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(columnar_storage_info)
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(columnar_store_memory_stats)
DEFINE_COLUMNAR_PASSTHROUGH_FUNC(test_columnar_storage_write_new_page)
#define DUMMY_REAL_TIME_EXECUTOR_ENUM_VALUE 9999999
static char *CitusVersion = CITUS_VERSION;
static char *DeprecatedEmptyString = "";
static char *MitmfifoEmptyString = "";
static bool DeprecatedDeferShardDeleteOnMove = true;
static bool DeprecatedDeferShardDeleteOnSplit = true;
static bool DeprecatedReplicateReferenceTablesOnActivate = false;
/* deprecated GUC value that should not be used anywhere outside this file */
static int ReplicationModel = REPLICATION_MODEL_STREAMING;
/* we override the application_name assign_hook and keep a pointer to the old one */
static GucStringAssignHook OldApplicationNameAssignHook = NULL;
/*
* Flag to indicate when ApplicationNameAssignHook becomes responsible for
* updating the global pid.
*/
static bool FinishedStartupCitusBackend = false;
static object_access_hook_type PrevObjectAccessHook = NULL;
#if PG_VERSION_NUM >= PG_VERSION_15
static shmem_request_hook_type prev_shmem_request_hook = NULL;
#endif
void _PG_init(void);
#if PG_VERSION_NUM >= PG_VERSION_15
static void citus_shmem_request(void);
#endif
static void CitusObjectAccessHook(ObjectAccessType access, Oid classId, Oid objectId, int
subId, void *arg);
static void DoInitialCleanup(void);
static void ResizeStackToMaximumDepth(void);
static void multi_log_hook(ErrorData *edata);
static bool IsSequenceOverflowError(ErrorData *edata);
static void RegisterConnectionCleanup(void);
static void RegisterExternalClientBackendCounterDecrement(void);
static void CitusCleanupConnectionsAtExit(int code, Datum arg);
static void DecrementExternalClientBackendCounterAtExit(int code, Datum arg);
static void CreateRequiredDirectories(void);
static void RegisterCitusConfigVariables(void);
static void OverridePostgresConfigProperties(void);
static bool ErrorIfNotASuitableDeadlockFactor(double *newval, void **extra,
GucSource source);
static bool WarnIfDeprecatedExecutorUsed(int *newval, void **extra, GucSource source);
static bool WarnIfReplicationModelIsSet(int *newval, void **extra, GucSource source);
static bool NoticeIfSubqueryPushdownEnabled(bool *newval, void **extra, GucSource source);
static bool ShowShardsForAppNamePrefixesCheckHook(char **newval, void **extra,
GucSource source);
static void ShowShardsForAppNamePrefixesAssignHook(const char *newval, void *extra);
static void ApplicationNameAssignHook(const char *newval, void *extra);
static void CpuPriorityAssignHook(int newval, void *extra);
static bool NodeConninfoGucCheckHook(char **newval, void **extra, GucSource source);
static void NodeConninfoGucAssignHook(const char *newval, void *extra);
static const char * MaxSharedPoolSizeGucShowHook(void);
static const char * LocalPoolSizeGucShowHook(void);
static bool StatisticsCollectionGucCheckHook(bool *newval, void **extra, GucSource
source);
static void CitusAuthHook(Port *port, int status);
static bool IsSuperuser(char *userName);
static void AdjustDynamicLibraryPathForCdcDecoders(void);
static ClientAuthentication_hook_type original_client_auth_hook = NULL;
static emit_log_hook_type original_emit_log_hook = NULL;
/* *INDENT-OFF* */
/* GUC enum definitions */
static const struct config_enum_entry propagate_set_commands_options[] = {
{"none", PROPSETCMD_NONE, false},
{"local", PROPSETCMD_LOCAL, false},
{NULL, 0, false}
};
static const struct config_enum_entry stat_statements_track_options[] = {
{ "none", STAT_STATEMENTS_TRACK_NONE, false },
{ "all", STAT_STATEMENTS_TRACK_ALL, false },
{ NULL, 0, false }
};
static const struct config_enum_entry stat_tenants_track_options[] = {
{ "none", STAT_TENANTS_TRACK_NONE, false },
{ "all", STAT_TENANTS_TRACK_ALL, false },
{ NULL, 0, false }
};
static const struct config_enum_entry task_assignment_policy_options[] = {
{ "greedy", TASK_ASSIGNMENT_GREEDY, false },
{ "first-replica", TASK_ASSIGNMENT_FIRST_REPLICA, false },
{ "round-robin", TASK_ASSIGNMENT_ROUND_ROBIN, false },
{ NULL, 0, false }
};
static const struct config_enum_entry replication_model_options[] = {
{ "statement", REPLICATION_MODEL_COORDINATOR, false },
{ "streaming", REPLICATION_MODEL_STREAMING, false },
{ NULL, 0, false }
};
static const struct config_enum_entry task_executor_type_options[] = {
{ "adaptive", MULTI_EXECUTOR_ADAPTIVE, false },
{ "real-time", DUMMY_REAL_TIME_EXECUTOR_ENUM_VALUE, false }, /* keep it for backward comp. */
{ "task-tracker", MULTI_EXECUTOR_ADAPTIVE, false },
{ NULL, 0, false }
};
static const struct config_enum_entry use_secondary_nodes_options[] = {
{ "never", USE_SECONDARY_NODES_NEVER, false },
{ "always", USE_SECONDARY_NODES_ALWAYS, false },
{ NULL, 0, false }
};
static const struct config_enum_entry coordinator_aggregation_options[] = {
{ "disabled", COORDINATOR_AGGREGATION_DISABLED, false },
{ "row-gather", COORDINATOR_AGGREGATION_ROW_GATHER, false },
{ NULL, 0, false }
};
static const struct config_enum_entry log_level_options[] = {
{ "off", CITUS_LOG_LEVEL_OFF, false },
{ "debug5", DEBUG5, false},
{ "debug4", DEBUG4, false},
{ "debug3", DEBUG3, false},
{ "debug2", DEBUG2, false},
{ "debug1", DEBUG1, false},
{ "debug", DEBUG2, true},
{ "log", LOG, false},
{ "info", INFO, true},
{ "notice", NOTICE, false},
{ "warning", WARNING, false},
{ "error", ERROR, false},
{ NULL, 0, false}
};
static const struct config_enum_entry local_table_join_policies[] = {
{ "never", LOCAL_JOIN_POLICY_NEVER, false},
{ "prefer-local", LOCAL_JOIN_POLICY_PREFER_LOCAL, false},
{ "prefer-distributed", LOCAL_JOIN_POLICY_PREFER_DISTRIBUTED, false},
{ "auto", LOCAL_JOIN_POLICY_AUTO, false},
{ NULL, 0, false}
};
static const struct config_enum_entry multi_shard_modify_connection_options[] = {
{ "parallel", PARALLEL_CONNECTION, false },
{ "sequential", SEQUENTIAL_CONNECTION, false },
{ NULL, 0, false }
};
static const struct config_enum_entry explain_analyze_sort_method_options[] = {
{ "execution-time", EXPLAIN_ANALYZE_SORT_BY_TIME, false },
{ "taskId", EXPLAIN_ANALYZE_SORT_BY_TASK_ID, false },
{ NULL, 0, false }
};
static const struct config_enum_entry create_object_propagation_options[] = {
{"deferred", CREATE_OBJECT_PROPAGATION_DEFERRED, false},
{"automatic", CREATE_OBJECT_PROPAGATION_AUTOMATIC, false},
{"immediate", CREATE_OBJECT_PROPAGATION_IMMEDIATE, false},
{NULL, 0, false}
};
/*
* This used to choose CPU priorities for GUCs. For most other integer options
* we use the -1 value as inherit/default/unset. For CPU priorities this isn't
* possible, because they can actually have negative values. So we need a value
* outside of the range that's valid for priorities. But if this is only one
* more or less than the valid values, this can also be quite confusing for
* people that don't know the exact range of valid values.
*
* So, instead we opt for using an enum that contains all valid priority values
* as strings, as well as the "inherit" string to indicate that the priority
* value should not be changed.
*/
static const struct config_enum_entry cpu_priority_options[] = {
{ "inherit", CPU_PRIORITY_INHERIT, false },
{ "-20", -20, false},
{ "-19", -19, false},
{ "-18", -18, false},
{ "-17", -17, false},
{ "-16", -16, false},
{ "-15", -15, false},
{ "-14", -14, false},
{ "-13", -13, false},
{ "-12", -12, false},
{ "-11", -11, false},
{ "-10", -10, false},
{ "-9", -9, false},
{ "-8", -8, false},
{ "-7", -7, false},
{ "-6", -6, false},
{ "-5", -5, false},
{ "-4", -4, false},
{ "-3", -3, false},
{ "-2", -2, false},
{ "-1", -1, false},
{ "0", 0, false},
{ "1", 1, false},
{ "2", 2, false},
{ "3", 3, false},
{ "4", 4, false},
{ "5", 5, false},
{ "6", 6, false},
{ "7", 7, false},
{ "8", 8, false},
{ "9", 9, false},
{ "10", 10, false},
{ "11", 11, false},
{ "12", 12, false},
{ "13", 13, false},
{ "14", 14, false},
{ "15", 15, false},
{ "16", 16, false},
{ "17", 17, false},
{ "18", 18, false},
{ "19", 19, false},
{ NULL, 0, false}
};
static const struct config_enum_entry metadata_sync_mode_options[] = {
{ "transactional", METADATA_SYNC_TRANSACTIONAL, false },
{ "nontransactional", METADATA_SYNC_NON_TRANSACTIONAL, false },
{ NULL, 0, false }
};
/* *INDENT-ON* */
/* shared library initialization function */
void
_PG_init(void)
{
if (!process_shared_preload_libraries_in_progress)
{
ereport(ERROR, (errmsg("Citus can only be loaded via shared_preload_libraries"),
errhint("Add citus to shared_preload_libraries configuration "
"variable in postgresql.conf in master and workers. Note "
"that citus should be at the beginning of "
"shared_preload_libraries.")));
}
/*
* Register contstraint_handler hooks of safestringlib first. This way
* loading the extension will error out if one of these constraints are hit
* during load.
*/
set_str_constraint_handler_s(ereport_constraint_handler);
set_mem_constraint_handler_s(ereport_constraint_handler);
/*
* Perform checks before registering any hooks, to avoid erroring out in a
* partial state.
*
* In many cases (e.g. planner and utility hook, to run inside
* pg_stat_statements et. al.) we have to be loaded before other hooks
* (thus as the innermost/last running hook) to be able to do our
* duties. For simplicity insist that all hooks are previously unused.
*/
if (planner_hook != NULL || ProcessUtility_hook != NULL ||
ExecutorStart_hook != NULL || ExecutorRun_hook != NULL ||
ExplainOneQuery_hook != NULL)
{
ereport(ERROR, (errmsg("Citus has to be loaded first"),
errhint("Place citus at the beginning of "
"shared_preload_libraries.")));
}
ResizeStackToMaximumDepth();
/*
* Extend the database directory structure before continuing with
* initialization - one of the later steps might require them to exist.
* If in a sub-process (windows / EXEC_BACKEND) this already has been
* done.
*/
if (!IsUnderPostmaster)
{
CreateRequiredDirectories();
}
InitConnParams();
/*
* Register Citus configuration variables. Do so before intercepting
* hooks or calling initialization functions, in case we want to do the
* latter in a configuration dependent manner.
*/
RegisterCitusConfigVariables();
/* make our additional node types known */
RegisterNodes();
/* make our custom scan nodes known */
RegisterCitusCustomScanMethods();
/* intercept planner */
planner_hook = distributed_planner;
/* register for planner hook */
set_rel_pathlist_hook = multi_relation_restriction_hook;
get_relation_info_hook = multi_get_relation_info_hook;
set_join_pathlist_hook = multi_join_restriction_hook;
ExecutorStart_hook = CitusExecutorStart;
ExecutorRun_hook = CitusExecutorRun;
ExplainOneQuery_hook = CitusExplainOneQuery;
prev_ExecutorEnd = ExecutorEnd_hook;
ExecutorEnd_hook = CitusAttributeToEnd;
/* register hook for error messages */
original_emit_log_hook = emit_log_hook;
emit_log_hook = multi_log_hook;
/*
* Register hook for counting client backends that
* are successfully authenticated.
*/
original_client_auth_hook = ClientAuthentication_hook;
ClientAuthentication_hook = CitusAuthHook;
#if PG_VERSION_NUM >= PG_VERSION_15
prev_shmem_request_hook = shmem_request_hook;
shmem_request_hook = citus_shmem_request;
#endif
InitializeMaintenanceDaemon();
InitializeMaintenanceDaemonForMainDb();
/* initialize coordinated transaction management */
InitializeTransactionManagement();
InitializeBackendManagement();
InitializeConnectionManagement();
InitPlacementConnectionManagement();
InitRelationAccessHash();
InitializeCitusQueryStats();
InitializeSharedConnectionStats();
InitializeLocallyReservedSharedConnections();
InitializeClusterClockMem();
/*
* Adjust the Dynamic Library Path to prepend citus_decodes to the dynamic
* library path. This is needed to make sure that the citus decoders are
* loaded before the default decoders for CDC.
*/
if (EnableChangeDataCapture)
{
AdjustDynamicLibraryPathForCdcDecoders();
}
/* initialize shard split shared memory handle management */
InitializeShardSplitSMHandleManagement();
InitializeMultiTenantMonitorSMHandleManagement();
/* enable modification of pg_catalog tables during pg_upgrade */
if (IsBinaryUpgrade)
{
SetConfigOption("allow_system_table_mods", "true", PGC_POSTMASTER,
PGC_S_OVERRIDE);
}
/*
* In postmasters execution of _PG_init, IsUnderPostmaster will be false and
* we want to do the cleanup at that time only, otherwise there is a chance that
* there will be parallel queries and we might do a cleanup for things that are
* already in use. This is only needed in Windows.
*/
if (!IsUnderPostmaster)
{
DoInitialCleanup();
}
PrevObjectAccessHook = object_access_hook;
object_access_hook = CitusObjectAccessHook;
/* ensure columnar module is loaded at the right time */
load_file(COLUMNAR_MODULE_NAME, false);
/*
* Register utility hook. This must be done after loading columnar, so
* that the citus hook is called first, followed by the columnar hook,
* followed by standard_ProcessUtility. That allows citus to distribute
* ALTER TABLE commands before columnar strips out the columnar-specific
* options.
*/
PrevProcessUtility = (ProcessUtility_hook != NULL) ?
ProcessUtility_hook : standard_ProcessUtility;
ProcessUtility_hook = citus_ProcessUtility;
/*
* Acquire symbols for columnar functions that citus calls.
*/
void *handle = NULL;
/* use load_external_function() the first time to initialize the handle */
extern_ColumnarSupportsIndexAM = (ColumnarSupportsIndexAM_type) (void *)
load_external_function(COLUMNAR_MODULE_NAME,
"ColumnarSupportsIndexAM",
true, &handle);
CacheRegisterRelcacheCallback(InvalidateDistRelationCacheCallback,
(Datum) 0);
INIT_COLUMNAR_SYMBOL(CompressionTypeStr_type, CompressionTypeStr);
INIT_COLUMNAR_SYMBOL(IsColumnarTableAmTable_type, IsColumnarTableAmTable);
INIT_COLUMNAR_SYMBOL(ReadColumnarOptions_type, ReadColumnarOptions);
/* initialize symbols for "pass-through" functions */
INIT_COLUMNAR_SYMBOL(PGFunction, columnar_handler);
INIT_COLUMNAR_SYMBOL(PGFunction, alter_columnar_table_set);
INIT_COLUMNAR_SYMBOL(PGFunction, alter_columnar_table_reset);
INIT_COLUMNAR_SYMBOL(PGFunction, upgrade_columnar_storage);
INIT_COLUMNAR_SYMBOL(PGFunction, downgrade_columnar_storage);
INIT_COLUMNAR_SYMBOL(PGFunction, columnar_relation_storageid);
INIT_COLUMNAR_SYMBOL(PGFunction, columnar_storage_info);
INIT_COLUMNAR_SYMBOL(PGFunction, columnar_store_memory_stats);
INIT_COLUMNAR_SYMBOL(PGFunction, test_columnar_storage_write_new_page);
}
/*
* PrependCitusDecodersToDynamicLibrayPath prepends the $libdir/citus_decoders
* to the dynamic library path. This is needed to make sure that the citus
* decoders are loaded before the default decoders for CDC.
*/
static void
AdjustDynamicLibraryPathForCdcDecoders(void)
{
if (strcmp(Dynamic_library_path, "$libdir") == 0)
{
SetConfigOption("dynamic_library_path", CDC_DECODER_DYNAMIC_LIB_PATH,
PGC_POSTMASTER, PGC_S_OVERRIDE);
}
}
#if PG_VERSION_NUM >= PG_VERSION_15
/*
* Requests any additional shared memory required for citus.
*/
static void
citus_shmem_request(void)
{
if (prev_shmem_request_hook)
{
prev_shmem_request_hook();
}
RequestAddinShmemSpace(BackendManagementShmemSize());
RequestAddinShmemSpace(SharedConnectionStatsShmemSize());
RequestAddinShmemSpace(MaintenanceDaemonShmemSize());
RequestAddinShmemSpace(CitusQueryStatsSharedMemSize());
RequestAddinShmemSpace(LogicalClockShmemSize());
RequestNamedLWLockTranche(STATS_SHARED_MEM_NAME, 1);
}
#endif
/*
* DoInitialCleanup does cleanup at start time.
* Currently it:
* - Removes intermediate result directories ( in case there are any leftovers)
*/
static void
DoInitialCleanup(void)
{
CleanupJobCacheDirectory();
}
/*
* Stack size increase during high memory load may cause unexpected crashes.
* With this alloca call, we are increasing stack size explicitly, so that if
* it is not possible to increase stack size, we will get an OOM error instead
* of a crash.
*
* This function is called on backend startup. The allocated memory will
* automatically be released at the end of the function's scope. However, we'd
* have already expanded the stack and it wouldn't shrink back. So, in a sense,
* per backend we're securing max_stack_depth kB's of memory on the stack upfront.
*
* Not all the backends require max_stack_depth kB's on the stack, so we might end
* up with unnecessary allocations. However, the default value is 2MB, which seems
* an acceptable trade-off. Also, allocating memory upfront may perform better
* under some circumstances.
*/
static void
ResizeStackToMaximumDepth(void)
{
#ifndef WIN32
long max_stack_depth_bytes = max_stack_depth * 1024L;
/*
* Explanation of IGNORE-BANNED:
* alloca is safe to use here since we limit the allocated size. We cannot
* use malloc as a replacement, since we actually want to grow the stack
* here.
*/
volatile char *stack_resizer = alloca(max_stack_depth_bytes); /* IGNORE-BANNED */
/*
* Different architectures might have different directions while
* growing the stack. So, touch both ends.
*/
stack_resizer[0] = 0;
stack_resizer[max_stack_depth_bytes - 1] = 0;
/*
* Passing the address to external function also prevents the function
* from being optimized away, and the debug elog can also help with
* diagnosis if needed.
*/
elog(DEBUG5, "entry stack is at %p, increased to %p, the top and bottom values of "
"the stack is %d and %d", &stack_resizer[0],
&stack_resizer[max_stack_depth_bytes - 1],
stack_resizer[max_stack_depth_bytes - 1], stack_resizer[0]);
#endif
}
/*
* multi_log_hook intercepts postgres log commands. We use this to override
* postgres error messages when they're not specific enough for the users.
*/
static void
multi_log_hook(ErrorData *edata)
{
/*
* Show the user a meaningful error message when a backend is cancelled
* by the distributed deadlock detection. Also reset the state for this,
* since the next cancelation of the backend might have another reason.
*
* We also want to provide a useful hint for sequence overflow errors
* because they're likely to be caused by the way Citus handles smallint/int
* based sequences on worker nodes. Note that we add the hint without checking
* whether we're on a worker node or the sequence was used on a distributed
* table because catalog might not be available at this point. And given
* that this hint might be shown for regular Postgres tables too, we inject
* the hint only when EnableUnsupportedFeatureMessages is set to true.
* Otherwise, vanilla tests would fail.
*/
bool clearState = true;
if (edata->elevel == ERROR && edata->sqlerrcode == ERRCODE_QUERY_CANCELED &&
MyBackendGotCancelledDueToDeadlock(clearState))
{
edata->sqlerrcode = ERRCODE_T_R_DEADLOCK_DETECTED;
/*
* This hook is called by EmitErrorReport() when emitting the ereport
* either to frontend or to the server logs. And some callers of
* EmitErrorReport() (e.g.: errfinish()) seems to assume that string
* fields of given ErrorData object needs to be freed. For this reason,
* we copy the message into heap here.
*/
edata->message = pstrdup("canceling the transaction since it was "
"involved in a distributed deadlock");
}
else if (EnableUnsupportedFeatureMessages &&
IsSequenceOverflowError(edata))
{
edata->detail = pstrdup("nextval(sequence) calls in worker nodes "
"are not supported for column defaults of "
"type int or smallint");
edata->hint = pstrdup("If the command was issued from a worker node, "
"try issuing it from the coordinator node "
"instead.");
}
if (original_emit_log_hook)
{
original_emit_log_hook(edata);
}
}
/*
* IsSequenceOverflowError returns true if the given error is a sequence
* overflow error.
*/
static bool
IsSequenceOverflowError(ErrorData *edata)
{
static const char *sequenceOverflowedMsgPrefix =
"nextval: reached maximum value of sequence";
static const int sequenceOverflowedMsgPrefixLen = 42;
return edata->elevel == ERROR &&
edata->sqlerrcode == ERRCODE_SEQUENCE_GENERATOR_LIMIT_EXCEEDED &&
edata->message != NULL &&
strncmp(edata->message, sequenceOverflowedMsgPrefix,
sequenceOverflowedMsgPrefixLen) == 0;
}
/*
* StartupCitusBackend initializes per-backend infrastructure, and is called
* the first time citus is used in a database.
*
* NB: All code here has to be able to cope with this routine being called
* multiple times in the same backend. This will e.g. happen when the
* extension is created, upgraded or dropped. Due to the way we detect the
* extension being dropped this can also happen when autovacuum runs ANALYZE on
* pg_dist_partition, see InvalidateDistRelationCacheCallback for details.
*/
void
StartupCitusBackend(void)
{
InitializeMaintenanceDaemonBackend();
/*
* For query backends this will be a no-op, because InitializeBackendData
* is already called from the CitusAuthHook. But for background workers we
* still need to initialize the backend data.
*/
InitializeBackendData(application_name);
/*
* If this is an external connection or a background workers this will
* generate the global PID for this connection. For internal connections
* this is a no-op, since InitializeBackendData will already have extracted
* the gpid from the application_name.
*/
AssignGlobalPID(application_name);
SetBackendDataDatabaseId();
RegisterConnectionCleanup();
FinishedStartupCitusBackend = true;
}
/*
* GetCurrentClientMinMessageLevelName returns the name of the
* the GUC client_min_messages for its specified value.
*/
const char *
GetClientMinMessageLevelNameForValue(int minMessageLevel)
{
struct config_enum record = { 0 };
record.options = log_level_options;
const char *clientMinMessageLevelName = config_enum_lookup_by_value(&record,
minMessageLevel);
return clientMinMessageLevelName;
}
/*
* RegisterConnectionCleanup cleans up any resources left at the end of the
* session. We prefer to cleanup before shared memory exit to make sure that
* this session properly releases anything hold in the shared memory.
*/
static void
RegisterConnectionCleanup(void)
{
static bool registeredCleanup = false;
if (registeredCleanup == false)
{
before_shmem_exit(CitusCleanupConnectionsAtExit, 0);
registeredCleanup = true;
}
}
/*
* RegisterExternalClientBackendCounterDecrement is called when the backend terminates.
* For all client backends, we register a callback that will undo
*/
static void
RegisterExternalClientBackendCounterDecrement(void)
{
static bool registeredCleanup = false;
if (registeredCleanup == false)
{
before_shmem_exit(DecrementExternalClientBackendCounterAtExit, 0);
registeredCleanup = true;
}
}
/*
* CitusCleanupConnectionsAtExit is called before_shmem_exit() of the
* backend for the purposes of any clean-up needed.
*/
static void
CitusCleanupConnectionsAtExit(int code, Datum arg)
{
/* properly close all the cached connections */
ShutdownAllConnections();
/*
* Make sure that we give the shared connections back to the shared
* pool if any. This operation is a no-op if the reserved connections
* are already given away.
*/
DeallocateReservedConnections();
/* we don't want any monitoring view/udf to show already exited backends */
SetActiveMyBackend(false);
UnSetGlobalPID();
}
/*
* DecrementExternalClientBackendCounterAtExit is called before_shmem_exit() of the
* backend for the purposes decrementing
*/
static void
DecrementExternalClientBackendCounterAtExit(int code, Datum arg)
{
DecrementExternalClientBackendCounter();
}
/*
* CreateRequiredDirectories - Create directories required for Citus to
* function.
*
* These used to be created by initdb, but that's not possible anymore.
*/
static void
CreateRequiredDirectories(void)
{
const char *subdirs[] = {
"pg_foreign_file",
"pg_foreign_file/cached",
("base/" PG_JOB_CACHE_DIR)
};
for (int dirNo = 0; dirNo < lengthof(subdirs); dirNo++)
{
int ret = mkdir(subdirs[dirNo], S_IRWXU);
if (ret != 0 && errno != EEXIST)
{
ereport(ERROR, (errcode_for_file_access(),
errmsg("could not create directory \"%s\": %m",
subdirs[dirNo])));
}
}
}
/* Register Citus configuration variables. */
static void
RegisterCitusConfigVariables(void)
{
DefineCustomBoolVariable(
"citus.all_modifications_commutative",
gettext_noop("Bypasses commutativity checks when enabled"),
NULL,
&AllModificationsCommutative,
false,
PGC_USERSET,
GUC_STANDARD,
NULL, NULL, NULL);
DefineCustomBoolVariable(
"citus.allow_modifications_from_workers_to_replicated_tables",
gettext_noop("Enables modifications from workers to replicated "
"tables such as reference tables or hash "
"distributed tables with replication factor "
"greater than 1."),
gettext_noop("Allowing modifications from the worker nodes "
"requires extra locking which might decrease "
"the throughput. Disabling this GUC skips the "
"extra locking and prevents modifications from "
"worker nodes."),
&AllowModificationsFromWorkersToReplicatedTables,
true,
PGC_USERSET,
GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE,
NULL, NULL, NULL);
DefineCustomBoolVariable(
"citus.allow_nested_distributed_execution",
gettext_noop("Enables distributed execution within a task "
"of another distributed execution."),
gettext_noop("Nested distributed execution can happen when Citus "
"pushes down a call to a user-defined function within "
"a distributed query, and the function contains another "
"distributed query. In this scenario, Citus makes no "
"guarantess with regards to correctness and it is therefore "
"disallowed by default. This setting can be used to allow "
"nested distributed execution."),
&AllowNestedDistributedExecution,
false,
PGC_USERSET,
GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE,
NULL, NULL, NULL);
DefineCustomBoolVariable(
"citus.allow_unsafe_constraints",
gettext_noop("Enables unique constraints and exclusion constraints "
"that do not include a distribution column."),
gettext_noop("To enforce global uniqueness, Citus normally requires "
"that unique constraints and exclusion constraints contain "
"the distribution column. If the tuple does not include the "
"distribution column, Citus cannot ensure that the same value "
"is not present in another shard. However, in some cases the "
"index creator knows that uniqueness within the shard implies "
"global uniqueness (e.g. when indexing an expression derived "
"from the distribution column) and adding the distribution column "
"separately may not be desirable. This setting can then be used "
"to disable the check."),
&AllowUnsafeConstraints,
false,
PGC_USERSET,
GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE,
NULL, NULL, NULL);
DefineCustomBoolVariable(
"citus.allow_unsafe_locks_from_workers",
gettext_noop("Enables acquiring a distributed lock from a worker "
"when the coordinator is not in the metadata"),
gettext_noop("Set to false by default. If set to true, enables "
"acquiring a distributed lock from a worker "
"when the coordinator is not in the metadata. "
"This type of lock is unsafe because the worker will not be "
"able to lock the coordinator; the coordinator will be able to "
"intialize distributed operations on the resources locked "
"by the worker. This can lead to concurrent operations from the "
"coordinator and distributed deadlocks since the coordinator "
"and the workers would not acquire locks across the same nodes "
"in the same order."),
&EnableAcquiringUnsafeLockFromWorkers,
false,
PGC_USERSET,
GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE,
NULL, NULL, NULL);
DefineCustomIntVariable(
"citus.background_task_queue_interval",
gettext_noop("Time to wait between checks for scheduled background tasks."),
NULL,
&BackgroundTaskQueueCheckInterval,
5000, -1, 7 * 24 * 3600 * 1000,