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Diffstat (limited to 'src/backend/replication/logical/logical.c')
| -rw-r--r-- | src/backend/replication/logical/logical.c | 920 |
1 files changed, 920 insertions, 0 deletions
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c new file mode 100644 index 00000000000..4fb0974f297 --- /dev/null +++ b/src/backend/replication/logical/logical.c @@ -0,0 +1,920 @@ +/*------------------------------------------------------------------------- + * logical.c + * PostgreSQL logical decoding coordination + * + * Copyright (c) 2012-2014, PostgreSQL Global Development Group + * + * IDENTIFICATION + * src/backend/replication/logical/logical.c + * + * NOTES + * This file coordinates interaction between the various modules that + * together providethe logical decoding, primarily by providing so + * called LogicalDecodingContexts. The goal is to encapsulate most of the + * internal complexity for consumers of logical decoding, so they can + * create and consume a changestream with a low amount of code. + * + * The idea is that a consumer provides three callbacks, one to read WAL, + * one to prepare a data write, and a final one for actually writing since + * their implementation depends on the type of consumer. Check + * logicalfunc.c for an example implementations of a fairly simple consumer + * and a implementation of a WAL reading callback that's suitable for + * simpler consumers. + *------------------------------------------------------------------------- + */ + +#include "postgres.h" + +#include <unistd.h> +#include <sys/stat.h> + +#include "miscadmin.h" + +#include "access/xact.h" + +#include "replication/decode.h" +#include "replication/logical.h" +#include "replication/reorderbuffer.h" +#include "replication/snapbuild.h" + +#include "storage/proc.h" +#include "storage/procarray.h" + +#include "utils/memutils.h" + +/* data for errcontext callback */ +typedef struct LogicalErrorCallbackState +{ + LogicalDecodingContext *ctx; + const char *callback_name; + XLogRecPtr report_location; +} LogicalErrorCallbackState; + +/* wrappers around output plugin callbacks */ +static void output_plugin_error_callback(void *arg); +static void startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, + bool is_init); +static void shutdown_cb_wrapper(LogicalDecodingContext *ctx); +static void begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn); +static void commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + XLogRecPtr commit_lsn); +static void change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + Relation relation, ReorderBufferChange *change); + +static void LoadOutputPlugin(OutputPluginCallbacks *callbacks, char *plugin); + +/* + * Make sure the current settings & environment are capable of doing logical + * decoding. + */ +void +CheckLogicalDecodingRequirements(void) +{ + CheckSlotRequirements(); + + if (wal_level < WAL_LEVEL_LOGICAL) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("logical decoding requires wal_level >= logical"))); + + if (MyDatabaseId == InvalidOid) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("logical decoding requires a database connection"))); + + /* ---- + * TODO: We got to change that someday soon... + * + * There's basically three things missing to allow this: + * 1) We need to be able to correctly and quickly identify the timeline a + * LSN belongs to + * 2) We need to force hot_standby_feedback to be enabled at all times so + * the primary cannot remove rows we need. + * 3) support dropping replication slots referring to a database, in + * dbase_redo. There can't be any active ones due to HS recovery + * conflicts, so that should be relatively easy. + * ---- + */ + if (RecoveryInProgress()) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("logical decoding cannot be used while in recovery"))); +} + +/* + * Helper function for CreateInitialDecodingContext() and + * CreateDecodingContext() performing common tasks. + */ +static LogicalDecodingContext * +StartupDecodingContext(List *output_plugin_options, + XLogRecPtr start_lsn, + TransactionId xmin_horizon, + XLogPageReadCB read_page, + LogicalOutputPluginWriterPrepareWrite prepare_write, + LogicalOutputPluginWriterWrite do_write) +{ + ReplicationSlot *slot; + MemoryContext context, old_context; + LogicalDecodingContext *ctx; + + /* shorter lines... */ + slot = MyReplicationSlot; + + context = AllocSetContextCreate(CurrentMemoryContext, + "Changeset Extraction Context", + ALLOCSET_DEFAULT_MINSIZE, + ALLOCSET_DEFAULT_INITSIZE, + ALLOCSET_DEFAULT_MAXSIZE); + old_context = MemoryContextSwitchTo(context); + ctx = palloc0(sizeof(LogicalDecodingContext)); + + ctx->context = context; + + /* (re-)load output plugins, so we detect a bad (removed) output plugin now. */ + LoadOutputPlugin(&ctx->callbacks, NameStr(slot->data.plugin)); + + /* + * Now that the slot's xmin has been set, we can announce ourselves as a + * logical decoding backend which doesn't need to be checked individually + * when computing the xmin horizon because the xmin is enforced via + * replication slots. + */ + LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); + MyPgXact->vacuumFlags |= PROC_IN_LOGICAL_DECODING; + LWLockRelease(ProcArrayLock); + + ctx->slot = slot; + + ctx->reader = XLogReaderAllocate(read_page, ctx); + ctx->reader->private_data = ctx; + + ctx->reorder = ReorderBufferAllocate(); + ctx->snapshot_builder = + AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn); + + ctx->reorder->private_data = ctx; + + /* wrap output plugin callbacks, so we can add error context information */ + ctx->reorder->begin = begin_cb_wrapper; + ctx->reorder->apply_change = change_cb_wrapper; + ctx->reorder->commit = commit_cb_wrapper; + + ctx->out = makeStringInfo(); + ctx->prepare_write = prepare_write; + ctx->write = do_write; + + ctx->output_plugin_options = output_plugin_options; + + MemoryContextSwitchTo(old_context); + + return ctx; +} + +/* + * Create a new decoding context, for a new logical slot. + * + * plugin contains the name of the output plugin + * output_plugin_options contains options passed to the output plugin + * read_page, prepare_write, do_write are callbacks that have to be filled to + * perform the use-case dependent, actual, work. + * + * Needs to be called while in a memory context that's at least as long lived + * as the the decoding context because further memory contexts will be created + * inside it. + * + * Returns an initialized decoding context after calling the output plugin's + * startup function. + */ +LogicalDecodingContext * +CreateInitDecodingContext(char *plugin, + List *output_plugin_options, + XLogPageReadCB read_page, + LogicalOutputPluginWriterPrepareWrite prepare_write, + LogicalOutputPluginWriterWrite do_write) +{ + TransactionId xmin_horizon = InvalidTransactionId; + ReplicationSlot *slot; + LogicalDecodingContext *ctx; + MemoryContext old_context; + + /* shorter lines... */ + slot = MyReplicationSlot; + + /* first some sanity checks that are unlikely to be violated */ + if (slot == NULL) + elog(ERROR, "cannot perform logical decoding without a acquired slot"); + + if (plugin == NULL) + elog(ERROR, "cannot initialize logical decoding without a specified plugin"); + + /* Make sure the passed slot is suitable. These are user facing errors. */ + if (slot->data.database == InvalidOid) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("cannot use physical replication slot created for logical decoding"))); + + if (slot->data.database != MyDatabaseId) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("replication slot \"%s\" was not created in this database", + NameStr(slot->data.name)))); + + if (IsTransactionState() && + GetTopTransactionIdIfAny() != InvalidTransactionId) + ereport(ERROR, + (errcode(ERRCODE_ACTIVE_SQL_TRANSACTION), + errmsg("cannot create logical replication slot in transaction that has performed writes"))); + + /* register output plugin name with slot */ + SpinLockAcquire(&slot->mutex); + strncpy(NameStr(slot->data.plugin), plugin, + NAMEDATALEN); + NameStr(slot->data.plugin)[NAMEDATALEN - 1] = '\0'; + SpinLockRelease(&slot->mutex); + + /* + * The replication slot mechanism is used to prevent removal of required + * WAL. As there is no interlock between this and checkpoints required WAL + * could be removed before ReplicationSlotsComputeRequiredLSN() has been + * called to prevent that. In the very unlikely case that this happens + * we'll just retry. + */ + while (true) + { + XLogSegNo segno; + + /* + * Let's start with enough information if we can, so log a standby + * snapshot and start decoding at exactly that position. + */ + if (!RecoveryInProgress()) + { + XLogRecPtr flushptr; + + /* start at current insert position*/ + slot->data.restart_lsn = GetXLogInsertRecPtr(); + + /* make sure we have enough information to start */ + flushptr = LogStandbySnapshot(); + + /* and make sure it's fsynced to disk */ + XLogFlush(flushptr); + } + else + slot->data.restart_lsn = GetRedoRecPtr(); + + /* prevent WAL removal as fast as possible */ + ReplicationSlotsComputeRequiredLSN(); + + /* + * If all required WAL is still there, great, otherwise retry. The + * slot should prevent further removal of WAL, unless there's a + * concurrent ReplicationSlotsComputeRequiredLSN() after we've written + * the new restart_lsn above, so normally we should never need to loop + * more than twice. + */ + XLByteToSeg(slot->data.restart_lsn, segno); + if (XLogGetLastRemovedSegno() < segno) + break; + } + + + /* ---- + * This is a bit tricky: We need to determine a safe xmin horizon to start + * decoding from, to avoid starting from a running xacts record referring + * to xids whose rows have been vacuumed or pruned + * already. GetOldestSafeDecodingTransactionId() returns such a value, but + * without further interlock it's return value might immediately be out of + * date. + * + * So we have to acquire the ProcArrayLock to prevent computation of new + * xmin horizons by other backends, get the safe decoding xid, and inform + * the slot machinery about the new limit. Once that's done the + * ProcArrayLock can be be released as the slot machinery now is + * protecting against vacuum. + * ---- + */ + LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); + + slot->effective_catalog_xmin = GetOldestSafeDecodingTransactionId(); + slot->data.catalog_xmin = slot->effective_catalog_xmin; + + ReplicationSlotsComputeRequiredXmin(true); + + LWLockRelease(ProcArrayLock); + + /* + * tell the snapshot builder to only assemble snapshot once reaching + * the a running_xact's record with the respective xmin. + */ + xmin_horizon = slot->data.catalog_xmin; + + ReplicationSlotMarkDirty(); + ReplicationSlotSave(); + + ctx = StartupDecodingContext(NIL, InvalidXLogRecPtr, xmin_horizon, + read_page, prepare_write, do_write); + + /* call output plugin initialization callback */ + old_context = MemoryContextSwitchTo(ctx->context); + if (ctx->callbacks.startup_cb != NULL) + startup_cb_wrapper(ctx, &ctx->options, true); + MemoryContextSwitchTo(old_context); + + return ctx; +} + +/* + * Create a new decoding context, for a logical slot that has previously been + * used already. + * + * start_lsn contains the LSN of the last received data or InvalidXLogRecPtr + * output_plugin_options contains options passed to the output plugin + * read_page, prepare_write, do_write are callbacks that have to be filled to + * perform the use-case dependent, actual, work. + * + * Needs to be called while in a memory context that's at least as long lived + * as the the decoding context because further memory contexts will be created + * inside it. + * + * Returns an initialized decoding context after calling the output plugin's + * startup function. + */ +LogicalDecodingContext * +CreateDecodingContext(XLogRecPtr start_lsn, + List *output_plugin_options, + XLogPageReadCB read_page, + LogicalOutputPluginWriterPrepareWrite prepare_write, + LogicalOutputPluginWriterWrite do_write) +{ + LogicalDecodingContext *ctx; + ReplicationSlot *slot; + MemoryContext old_context; + + /* shorter lines... */ + slot = MyReplicationSlot; + + /* first some sanity checks that are unlikely to be violated */ + if (slot == NULL) + elog(ERROR, "cannot perform logical decoding without a acquired slot"); + + /* make sure the passed slot is suitable, these are user facing errors */ + if (slot->data.database == InvalidOid) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + (errmsg("cannot use physical replication slot for logical decoding")))); + + if (slot->data.database != MyDatabaseId) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + (errmsg("replication slot \"%s\" was not created in this database", + NameStr(slot->data.name))))); + + if (start_lsn == InvalidXLogRecPtr) + { + /* continue from last position */ + start_lsn = slot->data.confirmed_flush; + } + else if (start_lsn < slot->data.confirmed_flush) + { + /* + * It might seem like we should error out in this case, but it's + * pretty common for a client to acknowledge a LSN it doesn't have to + * do anything for, and thus didn't store persistently, because the + * xlog records didn't result in anything relevant for logical + * decoding. Clients have to be able to do that to support + * synchronous replication. + */ + start_lsn = slot->data.confirmed_flush; + elog(DEBUG1, "cannot stream from %X/%X, minimum is %X/%X, forwarding", + (uint32)(start_lsn >> 32), (uint32)start_lsn, + (uint32)(slot->data.confirmed_flush >> 32), + (uint32)slot->data.confirmed_flush); + } + + ctx = StartupDecodingContext(output_plugin_options, + start_lsn, InvalidTransactionId, + read_page, prepare_write, do_write); + + /* call output plugin initialization callback */ + old_context = MemoryContextSwitchTo(ctx->context); + if (ctx->callbacks.startup_cb != NULL) + startup_cb_wrapper(ctx, &ctx->options, true); + MemoryContextSwitchTo(old_context); + + ereport(LOG, + (errmsg("starting logical decoding for slot %s", + NameStr(slot->data.name)), + errdetail("streaming transactions committing after %X/%X, reading WAL from %X/%X", + (uint32)(slot->data.confirmed_flush >> 32), + (uint32)slot->data.confirmed_flush, + (uint32)(slot->data.restart_lsn >> 32), + (uint32)slot->data.restart_lsn))); + + return ctx; +} + +/* + * Returns true if an consistent initial decoding snapshot has been built. + */ +bool +DecodingContextReady(LogicalDecodingContext *ctx) +{ + return SnapBuildCurrentState(ctx->snapshot_builder) == SNAPBUILD_CONSISTENT; +} + +/* + * Read from the decoding slot, until it is ready to start extracting changes. + */ +void +DecodingContextFindStartpoint(LogicalDecodingContext *ctx) +{ + XLogRecPtr startptr; + + /* Initialize from where to start reading WAL. */ + startptr = ctx->slot->data.restart_lsn; + + elog(DEBUG1, "searching for logical decoding starting point, starting at %X/%X", + (uint32)(ctx->slot->data.restart_lsn >> 32), + (uint32)ctx->slot->data.restart_lsn); + + /* Wait for a consistent starting point */ + for (;;) + { + XLogRecord *record; + char *err = NULL; + + /* + * If the caller requires that interrupts be checked, the read_page + * callback should do so, as those will often wait. + */ + + /* the read_page callback waits for new WAL */ + record = XLogReadRecord(ctx->reader, startptr, &err); + if (err) + elog(ERROR, "%s", err); + + Assert(record); + + startptr = InvalidXLogRecPtr; + + LogicalDecodingProcessRecord(ctx, record); + + /* only continue till we found a consistent spot */ + if (DecodingContextReady(ctx)) + break; + } + + ctx->slot->data.confirmed_flush = ctx->reader->EndRecPtr; +} + +/* + * Free a previously allocated decoding context, invoking the shutdown + * callback if necessary. + */ +void +FreeDecodingContext(LogicalDecodingContext *ctx) +{ + if (ctx->callbacks.shutdown_cb != NULL) + shutdown_cb_wrapper(ctx); + + ReorderBufferFree(ctx->reorder); + FreeSnapshotBuilder(ctx->snapshot_builder); + XLogReaderFree(ctx->reader); + MemoryContextDelete(ctx->context); +} + +/* + * Prepare a write using the context's output routine. + */ +void +OutputPluginPrepareWrite(struct LogicalDecodingContext *ctx, bool last_write) +{ + if (!ctx->accept_writes) + elog(ERROR, "writes are only accepted in commit, begin and change callbacks"); + + ctx->prepare_write(ctx, ctx->write_location, ctx->write_xid, last_write); + ctx->prepared_write = true; +} + +/* + * Perform a write using the context's output routine. + */ +void +OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write) +{ + if (!ctx->prepared_write) + elog(ERROR, "OutputPluginPrepareWrite needs to be called before OutputPluginWrite"); + + ctx->write(ctx, ctx->write_location, ctx->write_xid, last_write); + ctx->prepared_write = false; +} + +/* + * Load the output plugin, lookup its output plugin init function, and check + * that it provides the required callbacks. + */ +static void +LoadOutputPlugin(OutputPluginCallbacks *callbacks, char *plugin) +{ + LogicalOutputPluginInit plugin_init; + + plugin_init = (LogicalOutputPluginInit) + load_external_function(plugin, "_PG_output_plugin_init", false, NULL); + + if (plugin_init == NULL) + elog(ERROR, "output plugins have to declare the _PG_output_plugin_init symbol"); + + /* ask the output plugin to fill the callback struct */ + plugin_init(callbacks); + + if (callbacks->begin_cb == NULL) + elog(ERROR, "output plugins have to register a begin callback"); + if (callbacks->change_cb == NULL) + elog(ERROR, "output plugins have to register a change callback"); + if (callbacks->commit_cb == NULL) + elog(ERROR, "output plugins have to register a commit callback"); +} + +static void +output_plugin_error_callback(void *arg) +{ + LogicalErrorCallbackState *state = (LogicalErrorCallbackState *) arg; + /* not all callbacks have an associated LSN */ + if (state->report_location != InvalidXLogRecPtr) + errcontext("slot \"%s\", output plugin \"%s\", in the %s callback, associated LSN %X/%X", + NameStr(state->ctx->slot->data.name), + NameStr(state->ctx->slot->data.plugin), + state->callback_name, + (uint32)(state->report_location >> 32), + (uint32)state->report_location); + else + errcontext("slot \"%s\", output plugin \"%s\", in the %s callback", + NameStr(state->ctx->slot->data.name), + NameStr(state->ctx->slot->data.plugin), + state->callback_name); +} + +static void +startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool is_init) +{ + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "startup"; + state.report_location = InvalidXLogRecPtr; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = false; + + /* do the actual work: call callback */ + ctx->callbacks.startup_cb(ctx, opt, is_init); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +static void +shutdown_cb_wrapper(LogicalDecodingContext *ctx) +{ + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "shutdown"; + state.report_location = InvalidXLogRecPtr; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = false; + + /* do the actual work: call callback */ + ctx->callbacks.shutdown_cb(ctx); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + + +/* + * Callbacks for ReorderBuffer which add in some more information and then call + * output_plugin.h plugins. + */ +static void +begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn) +{ + LogicalDecodingContext *ctx = cache->private_data; + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "begin"; + state.report_location = txn->first_lsn; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = true; + ctx->write_xid = txn->xid; + ctx->write_location = txn->first_lsn; + + /* do the actual work: call callback */ + ctx->callbacks.begin_cb(ctx, txn); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +static void +commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + XLogRecPtr commit_lsn) +{ + LogicalDecodingContext *ctx = cache->private_data; + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "commit"; + state.report_location = txn->final_lsn; /* beginning of commit record */ + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = true; + ctx->write_xid = txn->xid; + ctx->write_location = txn->end_lsn; /* points to the end of the record */ + + /* do the actual work: call callback */ + ctx->callbacks.commit_cb(ctx, txn, commit_lsn); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +static void +change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + Relation relation, ReorderBufferChange *change) +{ + LogicalDecodingContext *ctx = cache->private_data; + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "change"; + state.report_location = change->lsn; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = true; + ctx->write_xid = txn->xid; + /* + * report this change's lsn so replies from clients can give an up2date + * answer. This won't ever be enough (and shouldn't be!) to confirm + * receipt of this transaction, but it might allow another transaction's + * commit to be confirmed with one message. + */ + ctx->write_location = change->lsn; + + ctx->callbacks.change_cb(ctx, txn, relation, change); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +/* + * Set the required catalog xmin horizon for historic snapshots in the current + * replication slot. + * + * Note that in the most cases, we won't be able to immediately use the xmin + * to increase the xmin horizon, we need to wait till the client has confirmed + * receiving current_lsn with LogicalConfirmReceivedLocation(). + */ +void +LogicalIncreaseXminForSlot(XLogRecPtr current_lsn, TransactionId xmin) +{ + bool updated_xmin = false; + ReplicationSlot *slot; + + slot = MyReplicationSlot; + + Assert(slot != NULL); + + SpinLockAcquire(&slot->mutex); + + /* + * don't overwrite if we already have a newer xmin. This can + * happen if we restart decoding in a slot. + */ + if (TransactionIdPrecedesOrEquals(xmin, slot->data.catalog_xmin)) + { + } + /* + * If the client has already confirmed up to this lsn, we directly + * can mark this as accepted. This can happen if we restart + * decoding in a slot. + */ + else if (current_lsn <= slot->data.confirmed_flush) + { + slot->candidate_catalog_xmin = xmin; + slot->candidate_xmin_lsn = current_lsn; + + /* our candidate can directly be used */ + updated_xmin = true; + } + /* + * Only increase if the previous values have been applied, otherwise we + * might never end up updating if the receiver acks too slowly. + */ + else if (slot->candidate_xmin_lsn == InvalidXLogRecPtr) + { + slot->candidate_catalog_xmin = xmin; + slot->candidate_xmin_lsn = current_lsn; + } + SpinLockRelease(&slot->mutex); + + /* candidate already valid with the current flush position, apply */ + if (updated_xmin) + LogicalConfirmReceivedLocation(slot->data.confirmed_flush); +} + +/* + * Mark the minimal LSN (restart_lsn) we need to read to replay all + * transactions that have not yet committed at current_lsn. + * + * Just like IncreaseRestartDecodingForSlot this nly takes effect when the + * client has confirmed to have received current_lsn. + */ +void +LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn, XLogRecPtr restart_lsn) +{ + bool updated_lsn = false; + ReplicationSlot *slot; + + slot = MyReplicationSlot; + + Assert(slot != NULL); + Assert(restart_lsn != InvalidXLogRecPtr); + Assert(current_lsn != InvalidXLogRecPtr); + + SpinLockAcquire(&slot->mutex); + + /* don't overwrite if have a newer restart lsn*/ + if (restart_lsn <= slot->data.restart_lsn) + { + } + /* + * We might have already flushed far enough to directly accept this lsn, in + * this case there is no need to check for existing candidate LSNs + */ + else if (current_lsn <= slot->data.confirmed_flush) + { + slot->candidate_restart_valid = current_lsn; + slot->candidate_restart_lsn = restart_lsn; + + /* our candidate can directly be used */ + updated_lsn = true; + } + /* + * Only increase if the previous values have been applied, otherwise we + * might never end up updating if the receiver acks too slowly. A missed + * value here will just cause some extra effort after reconnecting. + */ + if (slot->candidate_restart_valid == InvalidXLogRecPtr) + { + slot->candidate_restart_valid = current_lsn; + slot->candidate_restart_lsn = restart_lsn; + + elog(DEBUG1, "got new restart lsn %X/%X at %X/%X", + (uint32) (restart_lsn >> 32), (uint32) restart_lsn, + (uint32) (current_lsn >> 32), (uint32) current_lsn); + } + else + { + elog(DEBUG1, "failed to increase restart lsn: proposed %X/%X, after %X/%X, current candidate %X/%X, current after %X/%X, flushed up to %X/%X", + (uint32) (restart_lsn >> 32), (uint32) restart_lsn, + (uint32) (current_lsn >> 32), (uint32) current_lsn, + (uint32) (slot->candidate_restart_lsn >> 32), + (uint32) slot->candidate_restart_lsn, + (uint32) (slot->candidate_restart_valid >> 32), + (uint32) slot->candidate_restart_valid, + (uint32) (slot->data.confirmed_flush >> 32), + (uint32) slot->data.confirmed_flush + ); + } + SpinLockRelease(&slot->mutex); + + /* candidates are already valid with the current flush position, apply */ + if (updated_lsn) + LogicalConfirmReceivedLocation(slot->data.confirmed_flush); +} + +/* + * Handle a consumer's conformation having received all changes up to lsn. + */ +void +LogicalConfirmReceivedLocation(XLogRecPtr lsn) +{ + Assert(lsn != InvalidXLogRecPtr); + + /* Do an unlocked check for candidate_lsn first. */ + if (MyReplicationSlot->candidate_xmin_lsn != InvalidXLogRecPtr || + MyReplicationSlot->candidate_restart_valid != InvalidXLogRecPtr) + { + bool updated_xmin = false; + bool updated_restart = false; + + /* use volatile pointer to prevent code rearrangement */ + volatile ReplicationSlot *slot = MyReplicationSlot; + + SpinLockAcquire(&slot->mutex); + + slot->data.confirmed_flush = lsn; + + /* if were past the location required for bumping xmin, do so */ + if (slot->candidate_xmin_lsn != InvalidXLogRecPtr && + slot->candidate_xmin_lsn <= lsn) + { + /* + * We have to write the changed xmin to disk *before* we change + * the in-memory value, otherwise after a crash we wouldn't know + * that some catalog tuples might have been removed already. + * + * Ensure that by first writing to ->xmin and only update + * ->effective_xmin once the new state is synced to disk. After a + * crash ->effective_xmin is set to ->xmin. + */ + if (TransactionIdIsValid(slot->candidate_catalog_xmin) && + slot->data.catalog_xmin != slot->candidate_catalog_xmin) + { + slot->data.catalog_xmin = slot->candidate_catalog_xmin; + slot->candidate_catalog_xmin = InvalidTransactionId; + slot->candidate_xmin_lsn = InvalidXLogRecPtr; + updated_xmin = true; + } + } + + if (slot->candidate_restart_valid != InvalidXLogRecPtr && + slot->candidate_restart_valid <= lsn) + { + Assert(slot->candidate_restart_lsn != InvalidXLogRecPtr); + + slot->data.restart_lsn = slot->candidate_restart_lsn; + slot->candidate_restart_lsn = InvalidXLogRecPtr; + slot->candidate_restart_valid = InvalidXLogRecPtr; + updated_restart = true; + } + + SpinLockRelease(&slot->mutex); + + /* first write new xmin to disk, so we know whats up after a crash */ + if (updated_xmin || updated_restart) + { + ReplicationSlotMarkDirty(); + ReplicationSlotSave(); + elog(DEBUG1, "updated xmin: %u restart: %u", updated_xmin, updated_restart); + } + /* + * Now the new xmin is safely on disk, we can let the global value + * advance. We do not take ProcArrayLock or similar since we only + * advance xmin here and there's not much harm done by a concurrent + * computation missing that. + */ + if (updated_xmin) + { + SpinLockAcquire(&slot->mutex); + slot->effective_catalog_xmin = slot->data.catalog_xmin; + SpinLockRelease(&slot->mutex); + + ReplicationSlotsComputeRequiredXmin(false); + ReplicationSlotsComputeRequiredLSN(); + } + } + else + { + volatile ReplicationSlot *slot = MyReplicationSlot; + + SpinLockAcquire(&slot->mutex); + slot->data.confirmed_flush = lsn; + SpinLockRelease(&slot->mutex); + } +} |