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* Update copyrights for 2020Bruce Momjian2020-01-01
| | | | Backpatch-through: update all files in master, backpatch legal files through 9.4
* Fix inconsistencies and typos in the treeMichael Paquier2019-07-29
| | | | | | | | This is numbered take 8, and addresses again a set of issues with code comments, variable names and unreferenced variables. Author: Alexander Lakhin Discussion: https://postgr.es/m/b137b5eb-9c95-9c2f-586e-38aba7d59788@gmail.com
* Fix typos in various placesMichael Paquier2019-06-03
| | | | | | Author: Andrea Gelmini Reviewed-by: Michael Paquier, Justin Pryzby Discussion: https://postgr.es/m/20190528181718.GA39034@glet
* Phase 2 pgindent run for v12.Tom Lane2019-05-22
| | | | | | | | | Switch to 2.1 version of pg_bsd_indent. This formats multiline function declarations "correctly", that is with additional lines of parameter declarations indented to match where the first line's left parenthesis is. Discussion: https://postgr.es/m/CAEepm=0P3FeTXRcU5B2W3jv3PgRVZ-kGUXLGfd42FFhUROO3ug@mail.gmail.com
* Report progress of CREATE INDEX operationsAlvaro Herrera2019-04-02
| | | | | | | | | | | | | | | | | | | | This uses the progress reporting infrastructure added by c16dc1aca5e0, adding support for CREATE INDEX and CREATE INDEX CONCURRENTLY. There are two pieces to this: one is index-AM-agnostic, and the other is AM-specific. The latter is fairly elaborate for btrees, including reportage for parallel index builds and the separate phases that btree index creation uses; other index AMs, which are much simpler in their building procedures, have simplistic reporting only, but that seems sufficient, at least for non-concurrent builds. The index-AM-agnostic part is fairly complete, providing insight into the CONCURRENTLY wait phases as well as block-based progress during the index validation table scan. (The index validation index scan requires patching each AM, which has not been included here.) Reviewers: Rahila Syed, Pavan Deolasee, Tatsuro Yamada Discussion: https://postgr.es/m/20181220220022.mg63bhk26zdpvmcj@alvherre.pgsql
* Add basic infrastructure for 64 bit transaction IDs.Thomas Munro2019-03-28
| | | | | | | | | | | | | | | | | | | | | | | | Instead of inferring epoch progress from xids and checkpoints, introduce a 64 bit FullTransactionId type and use it to track xid generation. This fixes an unlikely bug where the epoch is reported incorrectly if the range of active xids wraps around more than once between checkpoints. The only user-visible effect of this commit is to correct the epoch used by txid_current() and txid_status(), also visible with pg_controldata, in those rare circumstances. It also creates some basic infrastructure so that later patches can use 64 bit transaction IDs in more places. The new type is a struct that we pass by value, as a form of strong typedef. This prevents the sort of accidental confusion between TransactionId and FullTransactionId that would be possible if we were to use a plain old uint64. Author: Thomas Munro Reported-by: Amit Kapila Reviewed-by: Andres Freund, Tom Lane, Heikki Linnakangas Discussion: https://postgr.es/m/CAA4eK1%2BMv%2Bmb0HFfWM9Srtc6MVe160WFurXV68iAFMcagRZ0dQ%40mail.gmail.com
* Update copyright for 2019Bruce Momjian2019-01-02
| | | | Backpatch-through: certain files through 9.4
* Don't ignore locktable-full failures in StandbyAcquireAccessExclusiveLock.Tom Lane2018-09-19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 37c54863c removed the code in StandbyAcquireAccessExclusiveLock that checked the return value of LockAcquireExtended. That created a bug, because it's still passing reportMemoryError = false to LockAcquireExtended, meaning that LOCKACQUIRE_NOT_AVAIL will be returned if we're out of shared memory for the lock table. In such a situation, the startup process would believe it had acquired an exclusive lock even though it hadn't, with potentially dire consequences. To fix, just drop the use of reportMemoryError = false, which allows us to simplify the call into a plain LockAcquire(). It's unclear that the locktable-full situation arises often enough that it's worth having a better recovery method than crash-and-restart. (I strongly suspect that the only reason the code path existed at all was that it was relatively simple to do in the pre-37c54863c implementation. But now it's not.) LockAcquireExtended's reportMemoryError parameter is now dead code and could be removed. I refrained from doing so, however, because there was some interest in resurrecting the behavior if we do get reports of locktable-full failures in the field. Also, it seems unwise to remove the parameter concurrently with shipping commit f868a8143, which added a parameter; if there are any third-party callers of LockAcquireExtended, we want them to get a wrong-number-of-parameters compile error rather than a possibly-silent misinterpretation of its last parameter. Back-patch to 9.6 where the bug was introduced. Discussion: https://postgr.es/m/6202.1536359835@sss.pgh.pa.us
* Fix longstanding recursion hazard in sinval message processing.Tom Lane2018-09-07
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | LockRelationOid and sibling routines supposed that, if our session already holds the lock they were asked to acquire, they could skip calling AcceptInvalidationMessages on the grounds that we must have already read any remote sinval messages issued against the relation being locked. This is normally true, but there's a critical special case where it's not: processing inside AcceptInvalidationMessages might attempt to access system relations, resulting in a recursive call to acquire a relation lock. Hence, if the outer call had acquired that same system catalog lock, we'd fall through, despite the possibility that there's an as-yet-unread sinval message for that system catalog. This could, for example, result in failure to access a system catalog or index that had just been processed by VACUUM FULL. This is the explanation for buildfarm failures we've been seeing intermittently for the past three months. The bug is far older than that, but commits a54e1f158 et al added a new recursion case within AcceptInvalidationMessages that is apparently easier to hit than any previous case. To fix this, we must not skip calling AcceptInvalidationMessages until we have *finished* a call to it since acquiring a relation lock, not merely acquired the lock. (There's already adequate logic inside AcceptInvalidationMessages to deal with being called recursively.) Fortunately, we can implement that at trivial cost, by adding a flag to LOCALLOCK hashtable entries that tracks whether we know we have completed such a call. There is an API hazard added by this patch for external callers of LockAcquire: if anything is testing for LOCKACQUIRE_ALREADY_HELD, it might be fooled by the new return code LOCKACQUIRE_ALREADY_CLEAR into thinking the lock wasn't already held. This should be a fail-soft condition, though, unless something very bizarre is being done in response to the test. Also, I added an additional output argument to LockAcquireExtended, assuming that that probably isn't called by any outside code given the very limited usefulness of its additional functionality. Back-patch to all supported branches. Discussion: https://postgr.es/m/12259.1532117714@sss.pgh.pa.us
* pgindent run prior to branchingAndrew Dunstan2018-06-30
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* Move RecoveryLockList into a hash table.Thomas Munro2018-06-26
| | | | | | | | | | | | | | | | | | Standbys frequently need to release all locks held by a given xid. Instead of searching one big list linearly, let's create one list per xid and put them in a hash table, so we can find what we need in O(1) time. Earlier analysis and a prototype were done by David Rowley, though this isn't his patch. Back-patch all the way. Author: Thomas Munro Diagnosed-by: David Rowley, Andres Freund Reviewed-by: Andres Freund, Tom Lane, Robert Haas Discussion: https://postgr.es/m/CAEepm%3D1mL0KiQ2KJ4yuPpLGX94a4Ns_W6TL4EGRouxWibu56pA%40mail.gmail.com Discussion: https://postgr.es/m/CAKJS1f9vJ841HY%3DwonnLVbfkTWGYWdPN72VMxnArcGCjF3SywA%40mail.gmail.com
* Remove AELs from subxids correctly on standbySimon Riggs2018-06-16
| | | | | | | | | | | | | | | | | | | | Issues relate only to subtransactions that hold AccessExclusiveLocks when replayed on standby. Prior to PG10, aborting subtransactions that held an AccessExclusiveLock failed to release the lock until top level commit or abort. 49bff5300d527 fixed that. However, 49bff5300d527 also introduced a similar bug where subtransaction commit would fail to release an AccessExclusiveLock, leaving the lock to be removed sometimes early and sometimes late. This commit fixes that bug also. Backpatch to PG10 needed. Tested by observation. Note need for multi-node isolationtester to improve test coverage for this and other HS cases. Reported-by: Simon Riggs Author: Simon Riggs
* Remove spurious code comments in standby related codeSimon Riggs2018-06-14
| | | | | | | | | GetRunningTransactionData() suggested that subxids were not worth optimizing away if overflowed, yet they have already been removed for that case. Changes to LogAccessExclusiveLock() API forgot to remove the prior comment when it was copied to LockAcquire().
* Update copyright for 2018Bruce Momjian2018-01-02
| | | | Backpatch-through: certain files through 9.3
* Fix variable and type name in comment.Heikki Linnakangas2017-07-12
| | | | | | Kyotaro Horiguchi Discussion: https://www.postgresql.org/message-id/20170711.163441.241981736.horiguchi.kyotaro@lab.ntt.co.jp
* Phase 3 of pgindent updates.Tom Lane2017-06-21
| | | | | | | | | | | | | | | | | | | | | | | | | Don't move parenthesized lines to the left, even if that means they flow past the right margin. By default, BSD indent lines up statement continuation lines that are within parentheses so that they start just to the right of the preceding left parenthesis. However, traditionally, if that resulted in the continuation line extending to the right of the desired right margin, then indent would push it left just far enough to not overrun the margin, if it could do so without making the continuation line start to the left of the current statement indent. That makes for a weird mix of indentations unless one has been completely rigid about never violating the 80-column limit. This behavior has been pretty universally panned by Postgres developers. Hence, disable it with indent's new -lpl switch, so that parenthesized lines are always lined up with the preceding left paren. This patch is much less interesting than the first round of indent changes, but also bulkier, so I thought it best to separate the effects. Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
* Assign AccessExclusiveLocks against subxacts in Hot StandbySimon Riggs2017-03-22
| | | | | | | | | | | | Previously AELs were registered against the top-level xid, which could cause locks to be held much longer than necessary in some cases during Hot Standby replay. We now record locks directly against their appropriate xids. Requires few code changes because original code allowed for this situation but didn’t fully implement it. Discussion: CAKJS1f9vJ841HY=wonnLVbfkTWGYWdPN72VMxnArcGCjF3SywA@mail.gmail.com Author: Simon Riggs and David Rowley
* Improve performance of replay of AccessExclusiveLocksSimon Riggs2017-03-22
| | | | | | | | | | | | | | | | | | | | A hot standby replica keeps a list of Access Exclusive locks for a top level transaction. These locks are released when the top level transaction ends. Searching of this list is O(N^2), and each transaction had to pay the price of searching this list for locks, even if it didn't take any AE locks itself. This patch optimizes this case by having the master server track which transactions took AE locks, and passes that along to the standby server in the commit/abort record. This allows the standby to only try to release locks for transactions which actually took any, avoiding the majority of the performance issue. Refactor MyXactAccessedTempRel into MyXactFlags to allow minimal additional cruft with this. Analysis and initial patch by David Rowley Author: David Rowley and Simon Riggs
* Fix typos in comments.Heikki Linnakangas2017-02-06
| | | | | | | | | Backpatch to all supported versions, where applicable, to make backpatching of future fixes go more smoothly. Josh Soref Discussion: https://www.postgresql.org/message-id/CACZqfqCf+5qRztLPgmmosr-B0Ye4srWzzw_mo4c_8_B_mtjmJQ@mail.gmail.com
* Check interrupts during hot standby waitsSimon Riggs2017-01-26
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* Update copyright via script for 2017Bruce Momjian2017-01-03
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* Skip checkpoints, archiving on idle systems.Andres Freund2016-12-22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Some background activity (like checkpoints, archive timeout, standby snapshots) is not supposed to happen on an idle system. Unfortunately so far it was not easy to determine when a system is idle, which defeated some of the attempts to avoid redundant activity on an idle system. To make that easier, allow to make individual WAL insertions as not being "important". By checking whether any important activity happened since the last time an activity was performed, it now is easy to check whether some action needs to be repeated. Use the new facility for checkpoints, archive timeout and standby snapshots. The lack of a facility causes some issues in older releases, but in my opinion the consequences (superflous checkpoints / archived segments) aren't grave enough to warrant backpatching. Author: Michael Paquier, editorialized by Andres Freund Reviewed-By: Andres Freund, David Steele, Amit Kapila, Kyotaro HORIGUCHI Bug: #13685 Discussion: https://www.postgresql.org/message-id/20151016203031.3019.72930@wrigleys.postgresql.org https://www.postgresql.org/message-id/CAB7nPqQcPqxEM3S735Bd2RzApNqSNJVietAC=6kfkYv_45dKwA@mail.gmail.com Backpatch: -
* Rename WAIT_* constants to PG_WAIT_*.Robert Haas2016-10-05
| | | | | | | | Windows apparently has a constant named WAIT_TIMEOUT, and some of these other names are pretty generic, too. Insert "PG_" at the front of each name in order to disambiguate. Michael Paquier
* Extend framework from commit 53be0b1ad to report latch waits.Robert Haas2016-10-04
| | | | | | | | | | | | | | | | | | | | | | WaitLatch, WaitLatchOrSocket, and WaitEventSetWait now taken an additional wait_event_info parameter; legal values are defined in pgstat.h. This makes it possible to uniquely identify every point in the core code where we are waiting for a latch; extensions can pass WAIT_EXTENSION. Because latches were the major wait primitive not previously covered by this patch, it is now possible to see information in pg_stat_activity on a large number of important wait events not previously addressed, such as ClientRead, ClientWrite, and SyncRep. Unfortunately, many of the wait events added by this patch will fail to appear in pg_stat_activity because they're only used in background processes which don't currently appear in pg_stat_activity. We should fix this either by creating a separate view for such information, or else by deciding to include them in pg_stat_activity after all. Michael Paquier and Robert Haas, reviewed by Alexander Korotkov and Thomas Munro.
* Adjust spellings of forms of "cancel"Peter Eisentraut2016-07-14
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* pgindent run for 9.6Robert Haas2016-06-09
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* Emit invalidations to standby for transactions without xid.Andres Freund2016-04-26
| | | | | | | | | | | | | | | | | | | | | | | | | | | So far, when a transaction with pending invalidations, but without an assigned xid, committed, we simply ignored those invalidation messages. That's problematic, because those are actually sent for a reason. Known symptoms of this include that existing sessions on a hot-standby replica sometimes fail to notice new concurrently built indexes and visibility map updates. The solution is to WAL log such invalidations in transactions without an xid. We considered to alternatively force-assign an xid, but that'd be problematic for vacuum, which might be run in systems with few xids. Important: This adds a new WAL record, but as the patch has to be back-patched, we can't bump the WAL page magic. This means that standbys have to be updated before primaries; otherwise "PANIC: standby_redo: unknown op code 32" errors can be encountered. XXX: Reported-By: Васильев Дмитрий, Masahiko Sawada Discussion: CAB-SwXY6oH=9twBkXJtgR4UC1NqT-vpYAtxCseME62ADwyK5OA@mail.gmail.com CAD21AoDpZ6Xjg=gFrGPnSn4oTRRcwK1EBrWCq9OqOHuAcMMC=w@mail.gmail.com
* Revert bf08f2292ffca14fd133aa0901d1563b6ecd6894Simon Riggs2016-04-06
| | | | Remove recent changes to logging XLOG_RUNNING_XACTS by request.
* Avoid archiving XLOG_RUNNING_XACTS on idle serverSimon Riggs2016-04-04
| | | | | | | | | | If archive_timeout > 0 we should avoid logging XLOG_RUNNING_XACTS if idle. Bug 13685 reported by Laurence Rowe, investigated in detail by Michael Paquier, though this is not his proposed fix. 20151016203031.3019.72930@wrigleys.postgresql.org Simple non-invasive patch to allow later backpatch to 9.4 and 9.5
* Rework wait for AccessExclusiveLocks on Hot StandbySimon Riggs2016-03-10
| | | | | | | | Earlier version committed in 9.0 caused spurious waits in some cases. New infrastructure for lock waits in 9.3 used to correct and improve this. Jeff Janes based upon a proposal by Simon Riggs, who also reviewed Additional review comments from Amit Kapila
* Change the format of the VM fork to add a second bit per page.Robert Haas2016-03-01
| | | | | | | | | | | | | | | | | | | | | | | The new bit indicates whether every tuple on the page is already frozen. It is cleared only when the all-visible bit is cleared, and it can be set only when we vacuum a page and find that every tuple on that page is both visible to every transaction and in no need of any future vacuuming. A future commit will use this new bit to optimize away full-table scans that would otherwise be triggered by XID wraparound considerations. A page which is merely all-visible must still be scanned in that case, but a page which is all-frozen need not be. This commit does not attempt that optimization, although that optimization is the goal here. It seems better to get the basic infrastructure in place first. Per discussion, it's very desirable for pg_upgrade to automatically migrate existing VM forks from the old format to the new format. That, too, will be handled in a follow-on patch. Masahiko Sawada, reviewed by Kyotaro Horiguchi, Fujii Masao, Amit Kapila, Simon Riggs, Andres Freund, and others, and substantially revised by me.
* Update copyright for 2016Bruce Momjian2016-01-02
| | | | Backpatch certain files through 9.1
* Update copyright for 2015Bruce Momjian2015-01-06
| | | | Backpatch certain files through 9.0
* Revamp the WAL record format.Heikki Linnakangas2014-11-20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Each WAL record now carries information about the modified relation and block(s) in a standardized format. That makes it easier to write tools that need that information, like pg_rewind, prefetching the blocks to speed up recovery, etc. There's a whole new API for building WAL records, replacing the XLogRecData chains used previously. The new API consists of XLogRegister* functions, which are called for each buffer and chunk of data that is added to the record. The new API also gives more control over when a full-page image is written, by passing flags to the XLogRegisterBuffer function. This also simplifies the XLogReadBufferForRedo() calls. The function can dig the relation and block number from the WAL record, so they no longer need to be passed as arguments. For the convenience of redo routines, XLogReader now disects each WAL record after reading it, copying the main data part and the per-block data into MAXALIGNed buffers. The data chunks are not aligned within the WAL record, but the redo routines can assume that the pointers returned by XLogRecGet* functions are. Redo routines are now passed the XLogReaderState, which contains the record in the already-disected format, instead of the plain XLogRecord. The new record format also makes the fixed size XLogRecord header smaller, by removing the xl_len field. The length of the "main data" portion is now stored at the end of the WAL record, and there's a separate header after XLogRecord for it. The alignment padding at the end of XLogRecord is also removed. This compansates for the fact that the new format would otherwise be more bulky than the old format. Reviewed by Andres Freund, Amit Kapila, Michael Paquier, Alvaro Herrera, Fujii Masao.
* Move the backup-block logic from XLogInsert to a new file, xloginsert.c.Heikki Linnakangas2014-11-06
| | | | | | | | | | | | xlog.c is huge, this makes it a little bit smaller, which is nice. Functions related to putting together the WAL record are in xloginsert.c, and the lower level stuff for managing WAL buffers and such are in xlog.c. Also move the definition of XLogRecord to a separate header file. This causes churn in the #includes of all the files that write WAL records, and redo routines, but it avoids pulling in xlog.h into most places. Reviewed by Michael Paquier, Alvaro Herrera, Andres Freund and Amit Kapila.
* Fix typos in comments.Heikki Linnakangas2014-05-21
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* pgindent run for 9.4Bruce Momjian2014-05-06
| | | | | This includes removing tabs after periods in C comments, which was applied to back branches, so this change should not effect backpatching.
* Introduce logical decoding.Robert Haas2014-03-03
| | | | | | | | | | | | | | | | | | | | | | This feature, building on previous commits, allows the write-ahead log stream to be decoded into a series of logical changes; that is, inserts, updates, and deletes and the transactions which contain them. It is capable of handling decoding even across changes to the schema of the effected tables. The output format is controlled by a so-called "output plugin"; an example is included. To make use of this in a real replication system, the output plugin will need to be modified to produce output in the format appropriate to that system, and to perform filtering. Currently, information can be extracted from the logical decoding system only via SQL; future commits will add the ability to stream changes via walsender. Andres Freund, with review and other contributions from many other people, including Álvaro Herrera, Abhijit Menon-Sen, Peter Gheogegan, Kevin Grittner, Robert Haas, Heikki Linnakangas, Fujii Masao, Abhijit Menon-Sen, Michael Paquier, Simon Riggs, Craig Ringer, and Steve Singer.
* Logging running transactions every 15 seconds.Robert Haas2014-01-15
| | | | | | | | | Previously, we did this just once per checkpoint, but that could make Hot Standby take a long time to initialize. To avoid busying an otherwise-idle system, we don't do this if no WAL has been written since we did it last. Andres Freund
* Update copyright for 2014Bruce Momjian2014-01-07
| | | | | Update all files in head, and files COPYRIGHT and legal.sgml in all back branches.
* Fix memory leak in LogStandbySnapshot().Tom Lane2013-06-04
| | | | | | | | | | | | | | The array allocated by GetRunningTransactionLocks() needs to be pfree'd when we're done with it. Otherwise we leak some memory during each checkpoint, if wal_level = hot_standby. This manifests as memory bloat in the checkpointer process, or in bgwriter in versions before we made the checkpointer separate. Reported and fixed by Naoya Anzai. Back-patch to 9.0 where the issue was introduced. In passing, improve comments for GetRunningTransactionLocks(), and add an Assert that we didn't overrun the palloc'd array.
* pgindent run for release 9.3Bruce Momjian2013-05-29
| | | | | This is the first run of the Perl-based pgindent script. Also update pgindent instructions.
* Add lock_timeout configuration parameter.Tom Lane2013-03-16
| | | | | | | | | | | | | This GUC allows limiting the time spent waiting to acquire any one heavyweight lock. In support of this, improve the recently-added timeout infrastructure to permit efficiently enabling or disabling multiple timeouts at once. That reduces the performance hit from turning on lock_timeout, though it's still not zero. Zoltán Böszörményi, reviewed by Tom Lane, Stephen Frost, and Hari Babu
* Update copyrights for 2013Bruce Momjian2013-01-01
| | | | | Fully update git head, and update back branches in ./COPYRIGHT and legal.sgml files.
* Don't advance checkPoint.nextXid near the end of a checkpoint sequence.Tom Lane2012-12-02
| | | | | | | | | | | | | | | | | | | | | | This reverts commit c11130690d6dca64267201a169cfb38c1adec5ef in favor of actually fixing the problem: namely, that we should never have been modifying the checkpoint record's nextXid at this point to begin with. The nextXid should match the state as of the checkpoint's logical WAL position (ie the redo point), not the state as of its physical position. It's especially bogus to advance it in some wal_levels and not others. In any case there is no need for the checkpoint record to carry the same nextXid shown in the XLOG_RUNNING_XACTS record just emitted by LogStandbySnapshot, as any replay operation will already have adopted that value as current. This fixes bug #7710 from Tarvi Pillessaar, and probably also explains bug #6291 from Daniel Farina, in that if a checkpoint were in progress at the instant of XID wraparound, the epoch bump would be lost as reported. (And, of course, these days there's at least a 50-50 chance of a checkpoint being in progress at any given instant.) Diagnosed by me and independently by Andres Freund. Back-patch to all branches supporting hot standby.
* Rearrange storage of data in xl_running_xacts.Simon Riggs2012-12-02
| | | | | | | | | | | | | Previously we stored all xids mixed together. Now we store top-level xids first, followed by all subxids. Also skip logging any subxids if the snapshot is suboverflowed, since there are potentially large numbers of them and they are not useful in that case anyway. Has value in the envisaged design for decoding of WAL. No planned effect on Hot Standby. Andres Freund, reviewed by me
* Cleanup VirtualXact at end of Hot Standby.Simon Riggs2012-11-29
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* Split out rmgr rm_desc functions into their own filesAlvaro Herrera2012-11-28
| | | | | This is necessary (but not sufficient) to have them compilable outside of a backend environment.
* Clarify docs on hot standby lock releaseSimon Riggs2012-11-13
| | | | Andres Freund and Simon Riggs
* Introduce timeout handling frameworkAlvaro Herrera2012-07-16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Management of timeouts was getting a little cumbersome; what we originally had was more than enough back when we were only concerned about deadlocks and query cancel; however, when we added timeouts for standby processes, the code got considerably messier. Since there are plans to add more complex timeouts, this seems a good time to introduce a central timeout handling module. External modules register their timeout handlers during process initialization, and later enable and disable them as they see fit using a simple API; timeout.c is in charge of keeping track of which timeouts are in effect at any time, installing a common SIGALRM signal handler, and calling setitimer() as appropriate to ensure timely firing of external handlers. timeout.c additionally supports pluggable modules to add their own timeouts, though this capability isn't exercised anywhere yet. Additionally, as of this commit, walsender processes are aware of timeouts; we had a preexisting bug there that made those ignore SIGALRM, thus being subject to unhandled deadlocks, particularly during the authentication phase. This has already been fixed in back branches in commit 0bf8eb2a, which see for more details. Main author: Zoltán Böszörményi Some review and cleanup by Álvaro Herrera Extensive reworking by Tom Lane
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