https://bugs.openldap.org/show_bug.cgi?id=9027
--- Comment #3 from doug(a)hcsw.org ---
Hi! I would like to voice my support for this feature, and explain how this API
would help me.
First of all, a bit of background: I'm maintaining C++ bindings for LMDB
(https://github.com/hoytech/lmdbxx), and have been a contributor to the perl
bindings and others. I have published two interface layers that use LMDB,
https://github.com/hoytech/quadrable and https://github.com/hoytech/rasgueadb
and as my colleagues would attest, am a relentless LMDB advocate.
Application 1: Testing zero-copy
That previous link, RasgueaDB, is an indexing and query layer for LMDB. It uses
flatbuffers for its data format, which allows zero-copy access to fields. Since
there are several layers involved, I wanted to make sure that no copying was
happening, and also to add a test to the test-suite to make sure this remains
the case.
To do this, I have a library called assert_zerocopy:
https://github.com/hoytech/hoytech-cpp/blob/master/hoytech/assert_zerocopy.h
(and also a perl equivalent here: https://metacpan.org/pod/Test::ZeroCopy )
However, in order to verify the returned value is actually a zero-copy
reference, I need the pointer to the memory map (and the map's size). I have
added a terrible hack to the lmdbxx bindings to retrieve this:
https://github.com/hoytech/lmdbxx/blob/08eddafcc4613c7fc8ebd88f5db87c7d7bfb…
But this is obviously not a good approach (as mentioned by Nic in this thread)
and it would be much better if there was an API to retrieve this value (like
there is for me_mapsize).
Application 2: Virtual memory controls
In general I agree that mlock()ing large files like databases is
counter-productive. However, there are other controls that can be applied to
the virtual memory of an application.
For example, rsync attempts to preserve the filesystem cache state so that
rsync invocations have as small an impact as possible on the cache (since it's
a shared resource): https://insights.oetiker.ch/linux/fadvise/
Another example, before restarting a server, Instagram uses my utility vmtouch
to snapshot the virtual memory state (basically the set of "hot" files). After
rebooting, the state is restored before the server is added back to the active
pool of servers.
I have generalised this with my application/library vmprobe:
https://vmprobe.com/filesystem-cache
If I had access to me_map within my application, I would be able to integrate
libvmprobe more easily and portably. For instance, this would allow me to take
a snapshot of which pages are resident in memory, perform some large read query
that touches many pages, then restore the original VM page residency set after
the query completes.
Another variant of this: If you have multiple customers who use the same server
(at different times) then you can restore a customer's previous VM state when
they login. If you know approximately the pages that will be accessed in
advance, sequentially pre-paging them in can have significant performance
benefits. I did some experiments with Postgres pre-paging you can see here:
https://vmprobe.com/database-speedup
Conclusion
Although certainly a user could abuse me_map if it were exposed, one of the
reasons why I enjoy LMDB so much is that it generally assumes its users know
what they are doing and doesn't compromise on flexibility or performance for
the sake of users who don't. For example, although it is not recommended to use
MDB_WRITEMAP in most cases, it nevertheless exists.
As explained above, I have several use-cases for me_map that I feel are
legitimate. I am already accessing it in a hacky way but naturally would prefer
a more portable and future-proof API.
If this API is added, the documentation should of course make clear that
accessing or modifying (if MDB_WRITEMAP) data through me_map is not supported
in any way, and regular use-cases have no need for this value and should stick
to the supported APIs.
Thank you!
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https://bugs.openldap.org/show_bug.cgi?id=9570
Issue ID: 9570
Summary: Roadmap needs updating now that OpenLDAP 2.5 is
released
Product: website
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: ---
Component: website
Assignee: bugs(a)openldap.org
Reporter: quanah(a)openldap.org
Target Milestone: ---
Need to update the roadmap.
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https://bugs.openldap.org/show_bug.cgi?id=9557
Issue ID: 9557
Summary: syncrepl refreshonly sometimes finishes too early
Product: OpenLDAP
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Keywords: replication
Severity: normal
Priority: ---
Component: slapd
Assignee: bugs(a)openldap.org
Reporter: ondra(a)mistotebe.net
Target Milestone: ---
In a delta-MMR test environment where conflicts are intentionally introduced,
the fallback sessions sometimes cut off, not sending all entries they ought to.
Instead LDAP_SUCCESS is sent with the snapshot cookie at some point. That
cookie represents the correct contextCSN at the time of the search, so the
missing changes are skipped over forever.
As of now, the cause of the cutoff is under investigation. Currently, this was
only run with 2.5 + persistent sessionlog enabled but there are indications
this might not be limited to 2.5, tests with other versions/configs are
pending.
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https://bugs.openldap.org/show_bug.cgi?id=9551
Issue ID: 9551
Summary: dnSubtreeMatch and others do not handle empty DN as
asserted value
Product: OpenLDAP
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: ---
Component: slapd
Assignee: bugs(a)openldap.org
Reporter: ondra(a)mistotebe.net
Target Milestone: ---
AFAIK '(reqDN:dnSubtreeMatch:=)' should be equivalent to 'reqDN=*', however it
only seems to match the empty dn right now.
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https://bugs.openldap.org/show_bug.cgi?id=9537
Issue ID: 9537
Summary: slap_timestamp() can give a duplicated timestamp
across restarts
Product: OpenLDAP
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: ---
Component: slapd
Assignee: bugs(a)openldap.org
Reporter: ondra(a)mistotebe.net
Target Milestone: ---
On busy sites, when a slapd restart takes <1s, accesslog can fail to log
changes with LDAP_ALREADY_EXISTS. This is because slap_timestamp() only logs
timestamps with a 1s precision, disambiguating the rest with a counter that's
forgotten across restarts.
It is possible my analysis in ITS#9487 is partially invalidated because of
this.
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https://bugs.openldap.org/show_bug.cgi?id=9526
Issue ID: 9526
Summary: slapadd -w crashes
Product: OpenLDAP
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: ---
Component: slapd
Assignee: bugs(a)openldap.org
Reporter: grapvar(a)gmail.com
Target Milestone: ---
Let slapd.conf is:
> database mdb
> suffix "o=Foo"
> sync_use_subentry
database is blank and we are adding this foo.ldif:
> dn: o=FOO
> objectClass:organization
Let's load:
> slapd -T add -v -l foo.ldif -w
then on Solaris:
> added: "o=FOO" (00000001)
> Segmentation Fault (core dumped)
... on Linux:
> added: "o=FOO" (00000001)
> => mdb_next_id: get failed: Invalid argument (22)
> => mdb_tool_next_id: next_id failed: Invalid argument (22)
> => mdb_tool_entry_put: txn_aborted! Invalid argument (22)
> slapadd: couldn't create context entry
> Closing DB...
This is because:
* mdb_tool_next_id() takes dead global [tools.c`static MDB_cursor *mcp] for
further operations
* cursor is dead because mdb_tool_entry_put() didn't initialized it
* mdb_tool_entry_put() didn't initialized cursor because it thinks it is
initialized, because there is an active global [tools.c`MDB_txn *mdb_tool_txn]
* transaction was initialized by mdb_tool_dn2id_get(), which doesn't care about
cursors.
Long story short: the global state in tools.c is not managed consistently and
needs rethinking.
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https://bugs.openldap.org/show_bug.cgi?id=6467
Quanah Gibson-Mount <quanah(a)openldap.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |VERIFIED
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https://bugs.openldap.org/show_bug.cgi?id=9552
Issue ID: 9552
Summary: slapo-accesslog should record new DN after rename
Product: OpenLDAP
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: ---
Component: overlays
Assignee: bugs(a)openldap.org
Reporter: ondra(a)mistotebe.net
Target Milestone: ---
To use accesslog as a sessionlog source, one needs to be able to resolve
whether a modrdn moved an entry in/out of the search scope. Syncprov would
either have to examine every modrdn request or, if accesslog were to log the
final DN, it could check for entries which crossed the scope.
A new attribute 'reqNewDN' should be tracked for modrdn ops.
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https://bugs.openldap.org/show_bug.cgi?id=9529
Issue ID: 9529
Summary: pcache locking issue
Product: OpenLDAP
Version: 2.4.58
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: ---
Component: overlays
Assignee: bugs(a)openldap.org
Reporter: hyc(a)openldap.org
Target Milestone: ---
Since ITS#6954 commit ea228495148 the consistency_check function was changed
to hold the template t_rwlock for the entire duration of a query expiration.
There doesn't appear to be any valid reason for this change, and it causes
the cache to be unresponsive to new searches while expiration is removing
cached entries.
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https://bugs.openldap.org/show_bug.cgi?id=9295
Issue ID: 9295
Summary: ppolicy and replication: pwdLockedTime replication
fails to replicate
Product: OpenLDAP
Version: 2.4.50
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: ---
Component: overlays
Assignee: bugs(a)openldap.org
Reporter: quanah(a)openldap.org
Target Milestone: ---
If you have the following setup, a replica will hit an error during
replication.
a) ppolicy is configured on provider(s) and replicas. Replica has
schemachecking=on in its syncrepl configuration
b) account gets locked on the replica, so pwdAccountLockedTime is set on the
replica but not on the provider(s)
c) admin does a MOD/ADD op against a provider for the user entry to add a value
to pwdAccountLockedTime
dn: ...
changetype: modify
add: pwdAccountLockedTime
pwdAccountLockedTime: ...
d) provider accepts this modification.
e) replica rejects this modification because the resulting change means that
there would be two pwdAccountLockedTime values on the account in question
Generally I believe that in this scenario, the MOD/ADD on the provider should
be treated as a replace OP instead of an ADD op
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