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1416 discussions

questions about LMDB
by Shu, Xinxin 19 Mar '15

19 Mar '15

Hi list , Recently I read docs about lmdb , there are two sentences 1) readers do not block writers 2) writers do not block readers I can understand 'readers do not block writers' , but cannot understand the second one , can someone help explain , how lmdb achieve 'writers do not block readers', below is my understandings , please correct me if anything wrong. if the access pattern is write - read, since lmdb only support two version of data , when the write has been started but not committed , the concurrent read may read stale data since write has not been committed. Cheers, xinxin

2 4

version numbers for release candidates
by Michael Ströder 08 Mar '15

08 Mar '15

HI! Sometimes many interesting changes are solely in RE24 and releasing the next true release takes some time. During this period I'd love to see pre-release version numbers assigned to RE24. Especially in case Quanah sends out an inquiry for another RE24 test round something like currently 2.4.41a1 or 2.4.41b5 or 2.4.41rc42 could be assigned (see http://semver.org/). This would make it possible to package RPMs etc. of pre-releases with non-conflicting version numbers which get replace by the real release package later. And for test rounds everybody would test the same snapshot. What do you think? Ciao, Michael.

2 2

Enhancing back-sock to use JSON
by Dagobert Michelsen 08 Mar '15

08 Mar '15

Hi, I have made some enhancements to back-sock to use JSON for the passed data and JSON-RPC to map LDAP calls to method invocations. The function signatures of the JSON-RPC calls are modeled to be similar to the ones used in json2ldap (which does just the opposite direction to talk LDAP via JSON-RPC) [1]. The previous hand-crafted format passed on the socket was harder to parse and needed a manually built parser whereas now a standard library can be used. However, handling the JSON data structures now imposes an additional dependency to Jansson (a JSON access library in C) [2]. Jansson itself is leightweight and has no dependencies itself. Due to the limited use of back-sock and the enhanced ease of use I think it would be acceptable to add this dependency. I would be glad if the modification would be possible to be applied to OpenLDAP and I happily submit a patch. Best regards -- Dago [1] JSON2LDAP interface from JSON-RPC to LDAP http://connect2id.com/products/json2ldap/web-api#ldap-compare [2] Jansson, a C library for reading and writing JSON data structures http://www.digip.org/jansson/ -- "You don't become great by trying to be great, you become great by wanting to do something, and then doing it so hard that you become great in the process." - xkcd #896

4 8

RE24 testing call #3 (2.4.41), LMDB RE0.9 testing call #3 (0.9.15)
by Quanah Gibson-Mount 03 Mar '15

03 Mar '15

OpenLDAP 2.4.41 Engineering Fixed libldap double free of request during abandon (ITS#7967) Fixed libldap segfault in ldap_sync_initialize (ITS#8001) Fixed libldap ldif-wrap off by one error (ITS#8003) Fixed libldap handling of TLS in async mode (ITS#8022) Fixed libldap null pointer dereference (ITS#8028) Fixed libldap mutex handling with LDAP_OPT_SESSION_REFCNT (ITS#8050) Fixed slapd slapadd onetime leak with -w (ITS#8014) Fixed slapd syncrepl delta-mmr issue with overlays and slapd.conf (ITS#7976) Fixed slapd syncrepl mutex for cookie state (ITS#7968) Fixed slapd syncrepl memory leaks (ITS#8035) Fixed slapd syncrepl to free presentlist at end of refresh mode (ITS#8038) Fixed slapd syncrepl to streamline presentlist (ITS#8042) Fixed slapd segfault when using matched values control (ITS#8046) Fixed slapd-mdb minor case typo (ITS#8049) Fixed slapd-mdb one-level search (ITS#7975) Fixed slapd-mdb heap corruption (ITS#7965) Fixed slapd-mdb crash after deleting in-use schema (ITS#7995) Fixed slapd-mdb minor code cleanup (ITS#8011) Fixed slapd-mdb to return errors when using incorrect env flags (ITS#8016) Fixed slapd-mdb to correctly update search candidates (ITS#8036, ITS#7904) Fixed slapd-meta TLS initialization with ldaps URIs (ITS#8022) Fixed slapo-collect segfault (ITS#7797) Fixed slapo-constraint with 0 count constraint (ITS#7780,ITS#7781) Fixed slapo-deref with empty attribute list (ITS#8027) Fixed slapo-sock result parser for CONTINUE (ITS#8048) Fixed slapo-syncprov synprov_matchops usage of test_filter (ITS#8013) Fixed slapo-syncprov segfault on disconnect/abandon (ITS#5452,ITS#8012) Fixed slapo-syncprov memory leak (ITS#8039) Fixed slapo-syncprov segfault on disconnect/abandon (ITS#8043) Fixed slapo-unique enforcement of uniqueness with manageDSAit control (ITS#8057) Build Environment Fixed libdb detection with gcc 5.x (ITS#8056) Enhanced contrib modules build paths (ITS#7782) Fixed contrib/autogroup internal operation identity (ITS#8006) Fixed contrib/passwd/sha2 compiler warning (ITS#8000) Fixed contrib/noopsrch compiler warning (ITS#7998) Fixed contrib/dupent compiler warnings (ITS#7997) Test suite: Added vrFilter test (ITS#8046) Contrib Added pbkdf2 sha256 and sha512 schemes (ITS#7977) Fixed autogroup modification callback responses (ITS#6970) Documentation Added ldap_get_option(3) LDAP_FEATURE_INFO_VERSION information (ITS#8032) Added ldap_get_option(3) LDAP_OPT_API_INFO_VERSION information (ITS#8032) LMDB 0.9.15 Release Engineering Fix txn init (ITS#7961,#7987) Fix MDB_PREV_DUP (ITS#7955,#7671) Fix compact of empty env (ITS#7956) Added workaround for fdatasync bug in ext3fs Build Don't use -fPIC for static lib Update .gitignore (ITS#7952,#7953) Cleanup for "make test" (ITS#7841) Misc. Android/Windows cleanup Documentation Fix MDB_APPEND doc Clarify mdb_dbi_open doc Thanks! --Quanah -- Quanah Gibson-Mount Platform Architect Zimbra, Inc. -------------------- Zimbra :: the leader in open source messaging and collaboration

3 5

Fwd: multiple sequential lmdb readers + spinning media = slow / thrashes?
by Matthew Moskewicz 26 Feb '15

26 Feb '15

warnings: new to list, first post, lmdb noob. i'm a caffe user: https://github.com/BVLC/caffe in one use case, caffe sequentially streams though >100GB lmdbs at a rate of ~30MB/s in blocks of about 40MB. however, if multiple caffe processes are reading the same lmdb (opened with MDB_RDONLY), read performance becomes limiting (i.e. the processes become IO bound), even though the disk has sufficient read bandwidth (say ~180MB/s). some of the relevant caffe lmdb code is here: https://github.com/BVLC/caffe/blob/master/src/caffe/util/db.cpp however, if i *both* 1) run blockdev --setra 65536 --setfra 65536 /dev/sdwhatever 2) modify lmdb to call posix_madvise(env->me_map, env->me_mapsize, POSIX_MADV_SEQUENTIAL); then i can get >1 reader to run without being IO limited. for (2), see https://github.com/moskewcz/scratch/tree/lmdb_seq_read_opt similarly, using a sequential read microbenchmark designed to model the caffe reads from here: https://github.com/moskewcz/boda/blob/master/src/lmdbif.cc if i run one reader, i get 180MB/s bandwidth. with two readers, but neither (1) nor (2) above, each gets ~30MB/s bandwidth. with (1) and (2) enabled, and two readers, each gets ~90MB/s bandwidth. any advice? mwm PS: backstory (skippable): caffe originally used LevelDB to get better read performance for sequentially loading sets of ~1M 227x227x3 raw images (~200GB data). typically processing time is ~2 hours for this data set size, yielding a read BW need of 30MB/s or so. it's not really clear if/why LevelDB was uses aside from the fact that the caffe author was a google intern at the time he wrote it, but anecdotally i think the claim is that reading the raw .jpgs had perf. issues, although it's unclear exactly what or why. i guess it was the usual story about not getting sequential reads without using LevelDB. they switched to lmdb a while back. <openldap-devel(a)openldap.org>

3 3

Security alerts on OpenLDAP (CVE-2015-1545 / CVE-2015-1546)
by Clément OUDOT 23 Feb '15

23 Feb '15

Hi, I saw today two CVE on OpenLDAP: * http://vigilance.fr/vulnerability/OpenLDAP-NULL-pointer-dereference-via-der… * http://vigilance.fr/vulnerability/OpenLDAP-use-after-free-via-Matched-Value… Don't know if they are reported in some ITS. Clément OUDOT.

3 3

git.openldap.org (port 9418) (Name or service not known)
by Michael Ströder 22 Feb '15

22 Feb '15

HI! What's wrong with the git server's DNS RR? $ git pull fatal: Unable to look up git.openldap.org (port 9418) (Name or service not known) Ciao, Michael.

2 1

syncrepl multicast MMR
by Howard Chu 09 Feb '15

09 Feb '15

Been thinking this would be worth trying for a while now. Set a config option for syncprov to send Persist messages to a multicast group instead of the original TCP session. All the consumers would also join the group and listen for updates. This would also exercise the cldap:// support in libldap. Implementation details: since datagrams are unreliable, we need to include sequence numbers on each message, which the consumer can check to make sure it hasn't missed an update. Moreover, it should be able to send a request to the provider to resend (over the TCP session) the message corresponding to a given sequence number. (Currently I envision using a small circular array in the provider to remember the last N messages for potential retransmit.) Config: both consumer and provider will need to be configured with a particular multicast group ID. It should be possible to participate in more than 1 group at a time (in which case, an update must be explicitly sent to each active group) but in general, I expect a cluster of cooperating MMR servers to all use a single multicast group, and so any update will only need to be forwarded to the network once. Thoughts? -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/

2 2

Re: syncrepl multicast MMR
by Emmanuel Lécharny 08 Feb '15

08 Feb '15

Le 09/02/15 05:15, Howard Chu a écrit : > Emmanuel Lécharny wrote: >> Le 08/02/15 13:52, Howard Chu a écrit : >>> Been thinking this would be worth trying for a while now. Set a config >>> option for syncprov to send Persist messages to a multicast group >>> instead of the original TCP session. All the consumers would also join >>> the group and listen for updates. This would also exercise the >>> cldap:// support in libldap. >>> >>> Implementation details: since datagrams are unreliable, we need to >>> include sequence numbers on each message, which the consumer can check >>> to make sure it hasn't missed an update. Moreover, it should be able >>> to send a request to the provider to resend (over the TCP session) the >>> message corresponding to a given sequence number. >> >> Ok but how do you detect that a consumer has missed an update, if no >> other update occurs ? You may have some desunchronized server for quite >> a long period of time if you don't have a mechinism for the consumer to >> regularly check if it is up to date. > > Good point, but easily solved with a periodic keepalive msg. One more thing : you will have to deal with TLS at some point. There is a RFC draft (https://tools.ietf.org/html/draft-keoh-tls-multicast-security-00) that proposes something, it seems to be 3 years old, and not active anymore.

1 0

Re: syncrepl multicast MMR
by Emmanuel Lécharny 08 Feb '15

08 Feb '15

Le 09/02/15 05:15, Howard Chu a écrit : > Emmanuel Lécharny wrote: >> Le 08/02/15 13:52, Howard Chu a écrit : >>> Been thinking this would be worth trying for a while now. Set a config >>> option for syncprov to send Persist messages to a multicast group >>> instead of the original TCP session. All the consumers would also join >>> the group and listen for updates. This would also exercise the >>> cldap:// support in libldap. >>> >>> Implementation details: since datagrams are unreliable, we need to >>> include sequence numbers on each message, which the consumer can check >>> to make sure it hasn't missed an update. Moreover, it should be able >>> to send a request to the provider to resend (over the TCP session) the >>> message corresponding to a given sequence number. >> >> Ok but how do you detect that a consumer has missed an update, if no >> other update occurs ? You may have some desunchronized server for quite >> a long period of time if you don't have a mechinism for the consumer to >> regularly check if it is up to date. > > Good point, but easily solved with a periodic keepalive msg. A heart-beat would be good to have : the producer would periodically multi-cast the latest CSN, allowing desynchronized servers to catch up. Another pb iw that Datagram are limited in size, which means big entries will have to be split in many parts.

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