## Problem
We have several serious data corruption incidents caused by mismatch of
get-age requests:
https://neondb.slack.com/archives/C07FJS4QF7V/p1723032720164359
We hope that the problem is fixed now. But it is better to prevent such
kind of problems in future.
Part of https://github.com/neondatabase/cloud/issues/16472
## Summary of changes
This PR introduce new V3 version of compute<->pageserver protocol,
adding tag to getpage response.
So now compute is able to check if it really gets response to the
requested page.
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
Apparently, we failed to do this bookkeeping in quite a few places...
## Problem
Fixes https://github.com/neondatabase/cloud/issues/22364
## Summary of changes
Add accounting of dropped requests. Note that this includes prefetches
dropped due to things like "PS connection dropped unexpectedly" or
"prefetch queue is already full", but *not* (yet?) "dropped due to
backend shutdown".
Using `min(0, ...)` causes us to fail to wait in most situations, so a
lack of data would be a hot wait loop, which is bad.
## Problem
We noticed high CPU usage in some situations
## Problem
When entry was dropped and password wasn't set, new entry
had uninitialized memory in controlplane adapter
Resolves: https://github.com/neondatabase/cloud/issues/14914
## Summary of changes
Initialize password in all cases, add tests.
Minor formatting for less indentation
Improved comments will help others when they read the code, and the log
messages will help others understand why the logical replication monitor
works the way it does.
Signed-off-by: Tristan Partin <tristan@neon.tech>
## Problem
LFC used_pages statistic is not updated in case of LFC resize (shrinking
`neon.file_cache_size_limit`)
## Summary of changes
Update `lfc_ctl->used_pages` in `lfc_change_limit_hook`
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
We have metrics for GetPage request latencies, but this is an extra
measure to capture requests that take way too long in the logs. The log
message is printed every 10 s, until the response is received:
```
PG:2024-12-09 16:02:07.715 GMT [1782845] LOG: [NEON_SMGR] [shard 0] no response received from pageserver for 10.000 s, still waiting (sent 10613 requests, received 10612 responses)
PG:2024-12-09 16:02:17.723 GMT [1782845] LOG: [NEON_SMGR] [shard 0] no response received from pageserver for 20.008 s, still waiting (sent 10613 requests, received 10612 responses)
PG:2024-12-09 16:02:19.719 GMT [1782845] LOG: [NEON_SMGR] [shard 0] received response from pageserver after 22.006 s
```
## Problem
See https://github.com/neondatabase/neon/issues/9961
Current implementation of prefetch buffer resize doesn't correctly
handle in-flight requests
## Summary of changes
1. Fix index of entry we should wait for if new prefetch buffer size is
smaller than number of in-flight requests.
2. Correctly set flush position
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
If the pageserver connection is lost while receiving the prefetch
request, the prefetch queue is cleared. The error message prints the
values from the prefetch slot, but because the slot was already cleared,
they're all zeros:
LOG: [NEON_SMGR] [shard 0] No response from reading prefetch entry 0:
0/0/0.0 block 0. This can be caused by a concurrent disconnect
To fix, make local copies of the values.
In the passing, also add a sanity check that if the receive() call
succeeds, the prefetch slot is still intact.
## Problem
See https://neondb.slack.com/archives/C04DGM6SMTM/p1732110190129479
We observe the following error in the logs
```
[XX000] ERROR: [NEON_SMGR] [shard 3] Incorrect prefetch read: status=1 response=0x7fafef335138 my=128 receive=128
```
most likely caused by changing `neon.readahead_buffer_size`
## Summary of changes
1. Copy shard state
2. Do not use prefetch_set_unused in readahead_buffer_resize
3. Change prefetch buffer overflow criteria
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
In ea32f1d0a3, Matthias added a feature to
our extension to expose more granular wait events. However, due to the
typo, those wait events were never registered, so we used the more
generic wait events instead.
Signed-off-by: Tristan Partin <tristan@neon.tech>
This GUC will drop replication slots if the size of the
pg_logical/snapshots directory (not including temp snapshot files)
becomes larger than the specified size. Keeping the size of this
directory smaller will help with basebackup size from the pageserver.
Part-of: https://github.com/neondatabase/neon/issues/8619
Signed-off-by: Tristan Partin <tristan@neon.tech>
Fix direct reading from WAL buffers.
Pointer wasn't advanced which resulted in sending corrupted WAL if part
of read used WAL buffers and part read from the file. Also move it to
neon_walreader so that e.g. replication could also make use of it.
ref https://github.com/neondatabase/cloud/issues/19567
We will only have a C string if the specified role is a string.
Otherwise, we need to resolve references to public, current_role,
current_user, and session_user.
Fixes: https://github.com/neondatabase/cloud/issues/19323
Signed-off-by: Tristan Partin <tristan@neon.tech>
As a DBaaS provider, Neon needs to provide a stable platform for
customers to build applications upon. At the same time however, we also
need to enable customers to use the latest and greatest technology, so
they can prototype their work, and we can solicit feedback. If all
extensions are treated the same in terms of stability, it is hard to
meet that goal.
There are now two new GUCs created by the Neon extension:
neon.allow_unstable_extensions: This is a session GUC which allows
a session to install and load unstable extensions.
neon.unstable_extensions: This is a comma-separated list of extension
names. We can check if a CREATE EXTENSION statement is attempting to
install an unstable extension, and if so, deny the request if
neon.allow_unstable_extensions is not set to true.
Signed-off-by: Tristan Partin <tristan@neon.tech>
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
neon.c is getting crowded and the logical replication slot monitor is
a good candidate for reorganization. It is very self-contained, and
being in a separate file will make it that much easier to find.
Signed-off-by: Tristan Partin <tristan@neon.tech>
A sizeof on a pointer on a 64 bit machine is 8 bytes whereas
Entry::old_name is a 64 byte array of characters. There was most likely
no fallout since the string would start with NUL bytes, but best to fix
nonetheless.
Signed-off-by: Tristan Partin <tristan@neon.tech>
At least as far as removing individual files goes, this is the best
pattern for removing. I can't say the same for removing directories, but
I went ahead and changed those to `$(RM) -r` anyway.
Signed-off-by: Tristan Partin <tristan@neon.tech>
## Problem
See
https://neondb.slack.com/archives/C033A2WE6BZ/p1729007738526309?thread_ts=1722942856.987979&cid=C033A2WE6BZ
When replica receives WAL record which target page is not present in
shared buffer, we evict this page from LFC.
If all pages from the LFC chunk are evicted, then chunk is moved to the
beginning of LRU least to force it reuse.
Unfortunately access_count is not checked and if the entry is access at
this moment then this operation can cause LRU list corruption.
## Summary of changes
Check `access_count` in `lfc_evict`
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
## Problem
There is double update of resize cache in `put_rel_truncation`
Also `page_server_request` contains check that fork is MAIN_FORKNUM
which
1. is incorrect (because Vm/FSM pages are shreded in the same way as
MAIN fork pages and
2. is redundant because `page_server_request` is never called for `get
page` request so first part to OR condition is always true.
## Summary of changes
Remove redundant code
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
We now also track:
- Number of PS IOs in-flight
- Number of pages cached by smgr prefetch implementation
- IO timing histograms for LFC reads and writes, per IO issued
## Problem
There's little insight into the timing metrics of LFC, and what the
prefetch state of each backend is.
This changes that, by measuring (and subsequently exposing) these data
points.
## Summary of changes
- Extract IOHistogram as separate type, rather than a collection of
fields on NeonMetrics
- others, see items above.
Part of https://github.com/neondatabase/neon/issues/8926
## Problem
On macOS:
```
/Users/runner/work/neon/neon//pgxn/neon/file_cache.c:623:19: error: variable 'has_remaining_pages' is used uninitialized whenever 'for' loop exits because its condition is false [-Werror,-Wsometimes-uninitialized]
```
## Summary of changes
- Initialise `has_remaining_pages` with `false`
It's not a bug, the variable is initialized when it's used, but the
compiler isn't smart enough to see that through all the conditions.
Part of the cleanup issue #9217.
/pgxn/neon/walproposer_compat.c:192:9: warning: function ‘WalProposerLibLog’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format]
192 | vsnprintf(buf, sizeof(buf), fmt, args);
| ^~~~~~~~~
The warning:
warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
It's PostgreSQL project style to stick to the old C90 style.
(Alternatively, we could disable it for our extension.)
Part of the cleanup issue #9217.
Prototypes for neon_writev(), neon_readv(), and neon_regisersync()
were missing. But instead of adding the missing prototypes, mark all
the smgr functions 'static'.
Part of the cleanup issue #9217.
Silences these compiler warnings:
/pgxn/neon_walredo/walredoproc.c:452:1: warning: ‘CreateFakeSharedMemoryAndSemaphores’ was used with no prototype before its definition [-Wmissing-prototypes]
452 | CreateFakeSharedMemoryAndSemaphores()
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/pgxn/neon/walproposer_pg.c:541:1: warning: no previous prototype for ‘GetWalpropShmemState’ [-Wmissing-prototypes]
541 | GetWalpropShmemState()
| ^~~~~~~~~~~~~~~~~~~~
Part of the cleanup issue #9217.
In v16 merge, we copied much of heap RMGR, to distinguish vanilla
Postgres heap records from records generated with neon patches, with
the additional CID fields. This function is only used by the
HEAP_TRUNCATE records, however, which we didn't need to copy.
Part of the cleanup issue #9217.
In PostgreSQL v16, BUFFERTAGS_EQUAL was replaced with a static inline
macro, BufferTagsEqual. Let's use the new name going forward, and have
backwards-compatibility glue to allow using the new name on v14 and v15,
rather than the other way round. This also makes BufferTagsEquals
consistent with InitBufferTag, for which we were already using the new
name.
The prefetch-queue hash table uses a BufferTag struct as the hash key,
and it's hashed using hash_bytes(). It's important that all the padding
bytes in the key are cleared, because hash_bytes() will include them.
I was getting compiler warnings like this on v14 and v15, when compiling
with -Warray-bounds:
In function ‘prfh_lookup_hash_internal’,
inlined from ‘prfh_lookup’ at
pg_install/v14/include/postgresql/server/lib/simplehash.h:821:9,
inlined from ‘neon_read_at_lsnv’ at pgxn/neon/pagestore_smgr.c:2789:11,
inlined from ‘neon_read_at_lsn’ at pgxn/neon/pagestore_smgr.c:2904:2:
pg_install/v14/include/postgresql/server/storage/relfilenode.h:90:43:
warning: array subscript ‘PrefetchRequest[0]’ is partly outside array
bounds of ‘BufferTag[1]’ {aka ‘struct buftag[1]’} [-Warray-bounds]
89 | ((node1).relNode == (node2).relNode && \
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
90 | (node1).dbNode == (node2).dbNode && \
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
91 | (node1).spcNode == (node2).spcNode)
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pg_install/v14/include/postgresql/server/storage/buf_internals.h:116:9:
note: in expansion of macro ‘RelFileNodeEquals’
116 | RelFileNodeEquals((a).rnode, (b).rnode) && \
| ^~~~~~~~~~~~~~~~~
pgxn/neon/neon_pgversioncompat.h:25:31: note: in expansion of macro
‘BUFFERTAGS_EQUAL’
25 | #define BufferTagsEqual(a, b) BUFFERTAGS_EQUAL(*(a), *(b))
| ^~~~~~~~~~~~~~~~
pgxn/neon/pagestore_smgr.c:220:34: note: in expansion of macro
‘BufferTagsEqual’
220 | #define SH_EQUAL(tb, a, b) (BufferTagsEqual(&(a)->buftag,
&(b)->buftag))
| ^~~~~~~~~~~~~~~
pg_install/v14/include/postgresql/server/lib/simplehash.h:280:77: note:
in expansion of macro ‘SH_EQUAL’
280 | #define SH_COMPARE_KEYS(tb, ahash, akey, b) (ahash ==
SH_GET_HASH(tb, b) && SH_EQUAL(tb, b->SH_KEY, akey))
| ^~~~~~~~
pg_install/v14/include/postgresql/server/lib/simplehash.h:799:21: note:
in expansion of macro ‘SH_COMPARE_KEYS’
799 | if (SH_COMPARE_KEYS(tb, hash, key, entry))
| ^~~~~~~~~~~~~~~
pgxn/neon/pagestore_smgr.c: In function ‘neon_read_at_lsn’:
pgxn/neon/pagestore_smgr.c:2742:25: note: object ‘buftag’ of size 20
2742 | BufferTag buftag = {0};
| ^~~~~~
This commit silences those warnings, although it's not clear to me why
the compiler complained like that in the first place. I found the issue
with padding bytes while looking into those warnings, but that was
coincidental, I don't think the padding bytes explain the warnings as
such.
In v16, the BUFFERTAGS_EQUAL macro was replaced with a static inline
function, and that also silences the compiler warning. Not clear to me
why.
## Problem
See #9199
## Summary of changes
Fix update of hits/misses for LFC and prefetch introduced in
78938d1b59
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
NeonWALReader needs to know LSN before which WAL is not available
locally, that is, basebackup LSN. Previously it was taken from
WalpropShmemState, but that's racy, as walproposer sets its there only
after successfull election. Get it directly with GetRedoStartLsn.
Should fix flakiness of
test_ondemand_wal_download_in_replication_slot_funcs etc.
ref #9201
Some parentheses in conditional expressions are redundant or necessary
for clarity conditional expressions in walproposer.
## Summary of changes
Change some parentheses to clarify conditions in walproposer.
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
In PG17, there is this newfangled custom wait events system. This commit
adds that feature to Neon, so that users can see what their backends may
be waiting for when a PostgreSQL backend is playing the waiting game in
Neon code.
MaxBackends doesn't include auxiliary processes. Whenever an aux process
made IO operations that updated the counters, they would scribble over
shared memory beoynd the end of the array. The relsize cache hash table
comes after the array, so the symptom was an error about hash table
corruption in the relsize cache hash.
Found while searching for other issues in shared memory.
The bug should be benign, in that it over-allocates memory for this
struct, but doesn't allow for out-of-bounds writes.
