September 2010 - discuss - lists.mariadb.org

Re: [Maria-discuss] Per-db binlogging
by Weldon Whipple 14 Dec '10

14 Dec '10

Sergei, Thank you very much for your reply! A later post by Henrik Ingo seems to say that I should cc maria-discuss(a)lists.launchpad.net. I'll try it and see if it bounces--I THINK I'm registered with launchpad.net :-) Let me know if sending to both lists annoys anyone, and I will quit the cc :-) See my responses below On Wed, Sep 15, 2010 at 1:53 PM, Sergei Golubchik <serg(a)askmonty.org> wrote: > Hi, Weldon! > > On Sep 13, Weldon Whipple wrote: <snip/> >> Is it plausible to identify all places where a binlog addition might >> occur? In those places, if the singleton USER_BIN_LOG_MRG exists, ask >> it if the current DB is being binlogged. If so, send the request to >> the DB_BIN_LOG instance. > > By "addition" you mean when an event is written to binlog? Yes! (exactly)--any event relating to that database that is written to binlog. (Hmm ... I wonder if there might ever be more "global" events that should be written ... Maybe we don't care about them??). Also, since these databases are "tied" to a user on a box, we probably don't care about renaming a DB ... > See where mysql_bin_log.write is called. Excellent information! (I was hoping it might be that easy ???). If I succeed in making a DB_BINLOG class derive from MYSQL_BIN_LOG (with an instance of DB_BINLOG for each database that is currently binlogging), I could--in theory, at least--just call something like db_binlog->write () at those places. > >> Questions I Have. >> ---------------- >> >> 1. I notice that binlog is in the list of engines and plugins >> (displayed by SHOW ...). The bottom of log.cc has >> "mysql_declare_plugin(binlog)". Do I need one for db_plugin? >> (probably not?) > > depends. > binlog needs to be declated a plugin, to be able to pretent being a > storage engine, to be able to force two phase commit (2PC). > > 2PC is used to commit or rollback a transaction atomically in more than > one engine. And MySQL only uses 2PC when a transaction spans more than > one engine. But we want a transaction to be committed in the engine and > written to a binlog - and it should be done atomically too. So, binlog > pretends to be an engine, pretends to participate in a transaction, > which forces MySQL to use 2PC which can guarantee that a transaction > is either committed and written to a binlog - or not committed and not > written. Reliably, even if MySQL crashes in the middle. > > So, if you don't use innodb, or don't use > innodb_flush_log_at_trx_commit=1 or don't use sync_binlog=1 > you probably don't need to support 2PC as your setup is not crash proof > anyway. > > If you care about innodb<->binlog consistency in the presence of > crashes, you should support 2PC in your binlog, as explained above. We DO have a small percentage of innodb databases. If 2PC commits (rolls back, etc.) atomically to more than one engine, does that mean TWO (only)? ... or could it happen for three (specifically, innodb, MYSQL_BIN_LOG's binlog, and DB_BIN_LOG's binlog)? The two kinds of binlog files would have the same format (except that one is for only one database). Are they considered two storage engines/plugins? (I notice that the "mysql_declare_plugin(binlog)" declaration is at the bottom of log.cc. Most of the other storage engines' corresponding declarations are in files in the storage subdirectories. If I were to need a "mysql_declare_plugin(db_binlog)" declaration, could it also go at the bottom of log.cc? ... Or (since a DB_BINLOG is AKO [a kind of] MYSQL_BIN_LOG [in the OO sense]), are MYSQL_BIN_LOGs and DB_BINLOGs both kinds of binlog plugins ...? >> 2. I've diagrammed the binary log event taxonomy--the 24 classes that >> inherit from Log_event (in log_event.cc/h). That was my main >> motivation for wanting to inherit from MYSQL_BIN_LOG. > > Was that a question? :) No. Just justification for my desire to simplify by having DB_BINLOG extend the MYSQL_BIN_LOG class. (I realize that I MIGHT have to add "virtual" in front of a method or two--possibly. Hopefully I would need to make no--or minimal-- changes to MYSQL_BIN_LOG.) >> 3. On the other hand, I wonder if inheriting from MYSQL_BIN_LOG might >> be overkill for "master only" binlogging--without the >> slave/replication part of it. > > No, I think inheriting from MYSQL_BIN_LOG is correct. > At least it's much easier to build on existing binlogging than to > implement everything from scratch. Amen!! >> 4. What version should I be working on? (We're currently running >> 5.1.47.) What should I check out of bzr/launchpad? (Is that still >> what we're doing with the changes in ownership?) > > What version you plan to use? > If it'll be 5.1 - you have to work in 5.1, use lp:mysql-server/5.1 > branch: > > bzr branch lp:mysql-server/5.1 We TRY to keep as current as possible (at the company). At some point, we'll need to move to the next major release--whatever it ends up being. (Then there is also the unknown [to me] of MySQL vs. MariaDB ... :-) We'll use bzr branch lp:mysql-server/5.1 > >> 5. I see that THD is involved in binlogging. (Several THD methods are >> defined in log.cc.) Are there any caveats here? > > There is a binlog cache (or buffer) in THD that stores binlog events for > the current transaction. They all are written to disk together, when a > transaction is committed. You need to decide what you want to do when > the current database is changed in the middle of a transaction - what > binlog the transaction should be written to. By "the current database is changed", I imagine you refer to the "USE 'database';" command. That's a good question. I THINK we have decided to ignore (for the present, at least), queries (and also transactions?) that involve multiple databases. Because we are doing per-DB binlogging, if multiple databases are involved, we (almost) consider it an anomaly at our ISP ... (I'm thinking that we might need to consider THD's binlog cache only for transactions that involve innodb and no more than one database ...) >> 6. What files should I use? A new h/cc pair? ... or just add to the >> hierarchy in log.h/cc? > > As you like. > New pair of files is cleaner. But it may require you to move some > declarations from log.cc to a header file, or to make some static > functions extern. All my prototypes have just expanded what is in log.cc and log.h. (I came VERY close to creating db_binlog.cc/h, however, which I would have done in some of my past--non-MySQL--projects). However, noticing most of the logging hierarchy in the single log.cc/h pair, I decided the implementors must have done it for a reason, and have decided to follow suit--for now, at least. > >> What I've Implemented So Far (about 13 Prototypes). >> -------------------------------------------------- >> >> (PRELIMINARY NOTE:) >> >> Our initial plan was to call it "Per-User Binlogging". The user here >> is a cPanel [control panel] user. cPanel's database naming convention >> is to have all of a user's database names start with the username, >> followed by an underscore, followed by a distinctive database >> name. Thus all the commands above start with >> >> <verb> USER ... >> >> Originally most of them could end either "DATABASE <db>" or "USER >> <user>" (with user meaning cPanel user). Thus, in the original plan >> the first command above was: >> >> START USER BINLOG FOR (USER <user> | DATABASE <db>) >> >> We have realized that per-database binlogging is all we really need. >> We imagine that others in our situation might want something similar. >> Since not everyone uses cPanel, we should forget per[cPanel]-user >> binlogging, focusing on per-database binlogging. > > If every user is a different MySQL account - that it a different row in > the mysql.user table - than per-user binlogging is much cleaner and > better defined concept. > > A statement can affect more than one database (say, UPDATE db1.t1, > db2.t2 SET ...), the current database may be changed in the middle of > transaction, and so on. On the other hand, any statement or a > transaction is always executed in the context of as single user - you > cannot change user in the middle of transaction. (*) > > (*) changing security context only affect privileges, but not the > destination binlog. Actually (and this is because of the way cPanel does things--I have been "bitten" by this many times!!), each database has a (different) corresponding user in the mysql.user table (!!!). So (for example), if a user signs up with our ISP with a user name of elvispre every one of his (perhaps hundreds/thousands of) databases will have names something like: elvispre_friends elvispre_earlyyears elvispre_hitsongs . . . And (here's the surprising part)--each one of those databases will have a MATCHING ROW IN mysql.user!! So, for us to migrate our customer elvispre to another physical server, we DO (ultimately) need to binlog all of the databases/users that match/are like 'elvispre\_%'; . In some of my earlier prototypes, the START/FLUSH-LOCK/SHOW/UNLOCK/STOP commands have allowed for "like" clauses at the end. Maybe I need to go that route? ALL of my prototypes have had binlogging PER DATABASE. I wonder how difficult/feasible/desirable/useful it would be to create separate binlog files for databases (or users) whose name matches a "like" clause. ... Probably more important: Would this feature be of general interest to the MySQL user community at large? (... and, if so, should it be database- or user- or database_pattern- or user_pattern-based). (My initial idea is that per [single] database/user might be easiest to define/implement??) > > Regards, > Sergei Thanks again for your reply!! Weldon

2 4

Re: [Maria-discuss] italian translation
by Bryan Alsdorf 25 Oct '10

25 Oct '10

Hi, On 09/14/2010 11:24 PM, Colin Charles wrote: > Hi! > > On 12 Sep 2010, at 07:51, Federico Razzoli wrote: > >> Hello. >> >> I appreciate so much your new Knowledge Base. The pages that are already on line >> are very clear and complete, as the MySQL docs. But, unlike the MySQL docs, the >> Knowledge Base has free licenses. For these reasons, I would like to translate >> into italian - which is my natural language. >> >> Am I allowed to do that? As far as I understand, both the licenses used (CC >> BY-SA and GNU FDL) allow translations, as long as they have the same licenses >> used by the original work. But I want to be sure before starting. >> >> I can't translate all the articles, so I'll only translate some of the most >> interesting documents. But, as the documentation grows, maybe I may try to set >> up a group of volounteers. We'll see. > > > You are absolutely allowed to do that. You can translate it to Italian with no issue at all > > Currently (and I think, by design) it seems that kb.askmonty.org will be in the English language. Bryan (CC'ed in this email) is the right person to help setup an instance for the Italian language (something like it.kb.askmonty.org) if you were planning on making a larger translation project. It would be great if you could harness a group of volunteers We actually want to setup a structure to support translations inside our KB, I just haven't had the time to design or implement it. My two concerns are how to properly display content in another language and how to keep translated articles up to date when the English version is updated (or vice versa). If you have any ideas, please let me know. > In the meantime however, as you'd like to just translate interesting documents, just go ahead, translate them, and it would rock if you'd point folk to the English version at the askmonty KB > > Good luck with your translation work and tell us if you need any help! Yes please let us know if there is anything we can do to help. I will try to work on supporting other languages soon since people are actually translating articles. Best Regards, -- Bryan Alsdorf, Lead Web Developer Monty Program AB. http://montyprogram.com

4 4

[Maria-discuss] MariaDB 5.2.2-gamma
by Daniel Bartholomew 29 Sep '10

29 Sep '10

All, MariaDB 5.2.2-gamma source and binary tarballs, and packages for various operating systems and Linux distributions are now available for download: http://askmonty.org/wiki/MariaDB:Download:MariaDB_5.2.2-gamma See also: Release Notes: http://kb.askmonty.org/v/mariadb-522-release-notes Changelog: http://kb.askmonty.org/v/mariadb-522-changelog Thanks. -- Daniel Bartholomew Monty Program - http://askmonty.org

3 3

[Maria-discuss] MariaDB Knowledgebase typo
by Yousif Masoud 16 Sep '10

16 Sep '10

Hi, I'd like to thank everyone working on this project. MariaDB is currently installed on one of my Dev environments, I am looking forward to switching to it. I noticed there was a minor typo on: http://kb.askmonty.org/v/compiling-with-the-innodb-plugin-from-oracle First sentence reads: Normally MariaDB comes with XtraDB <http://kb.askmonty.org/v/xtradb-storage-engine>, an enhanced version **if** the InnoDB plugin that comes from Oracle. I believe it should be: Normally MariaDB comes with XtraDB <http://kb.askmonty.org/v/xtradb-storage-engine>, an enhanced version **of** the InnoDB plugin that comes from Oracle. Many thanks, Yousif PS. I don't know if there is a formal method for reporting this. Please accept my apologies if this is not the best way to do it.

2 1

Re: [Maria-discuss] Seeking command syntax feedback (Still Re: Per-db binlogging)
by Weldon Whipple 15 Sep '10

15 Sep '10

On Wed, Sep 15, 2010 at 2:00 PM, Sergei Golubchik <serg(a)askmonty.org> wrote: > Hi, Weldon! Hi, Sergei! > > On Sep 15, Weldon Whipple wrote: <snip/> >> 2. FLUSH TABLES WITH READ LOCK FOR DATABASE dbname; >> >> (I just added an optional 'FOR DATABASE dbname' to the already >> existing command--which still works, BTW. Is this a misuse of the word >> "FOR"?) >> This is the command that locks the tables before someone (some >> program) dumps/copies the tables that will be moved to another server. >> It flushes and locks only one database. > > This would be difficult to implement. > > FLUSH TABLES WITH READ LOCK is not implemented in a way that can be > generalized to support per-database locks :( I had guessed as much. (The method in my DB_BINLOG_MGR method that implements that functionality consists of a mutex lock, a comment about some sort of miracle happening, then a mutex unlock.) I wonder if there might be a way of inhibiting some user database (temporarily) from changing ... Alternately, I suppose we could do a global FLUSH TABLE WITH READ LOCK/ UNLOCK TABLES. Or ... (???) > Besides, I personally wouldn't worry much about the syntax. It's > something you can easily change anytime - e.g. replace BINLOG with > BINLOGGING or FOR with something else. Yeah, every time I write a new prototype I tweak the syntax a bit. At the moment I'm just trying to settle on an implementation that would work for our company (and still be of some sort of general use). > > Regards, > Sergei > Thanks, Weldon

1 0

Re: [Maria-discuss] Per-db binlogging
by MARK CALLAGHAN 15 Sep '10

15 Sep '10

+maria-discuss as they are working in replication too +robert.hodges as tungsten replicator has features that could be used here I am very interested in a subset of this. I want one SQL thread per database on a slave (stream per database on the slave). However I don't need to split the binlog on the master to get that and writing a binlog file per database on the master might complicate the sync_binlog option that keeps the binlog and InnoDB in sync during crash recovery. How will this work in that case? Note that a stream (SQL slave thread) per database on the slave will break rpl_transaction_enabled. Some of us rely on that to keep slaves consistent during crash recovery. I assume you don't use that feature. MySQL has worklogs to use db tables in place of relay-log.info and when that code is production ready, then this is not a problem. On Mon, Sep 13, 2010 at 1:52 PM, Weldon Whipple <weldon(a)whipple.org> wrote: > Greetings! > > My employer has asked me to implement per-DB binlogging for > MySQL. I've been working on prototypes for 3-4 weeks now, and decided > it's time to post to this list to ask for comments, suggestions, > condolences, etc. (I've been a "lurker" for quite awhile. I hope this > post isn't too far off the mark) The assignment is *only* for master-side > binlogging. (It doesn't require a slave/replication-side implementation.) > > > Why I Want to Do It. > ------------------- > > I work for an ISP that hosts (last I heard--I HOPE I'm not lying) over > 2 million domains. Customers are allowed to have (almost) unlimited > MySQL databases. Migrating an account from one physical server to > another is a daunting task. (A typical server has easily 2000+ > [sometimes far more] databases.) Global mysqld binlogging isn't > feasible when we want to migrate (for example) a single account to > another server. > > Our proposed scenario goes something like this: > > 1. START USER BINLOG FOR DATABASE <db> > 2. FLUSH USER TABLES WITH READ LOCK FOR DATABASE <db> > 3. SHOW USER BINLOG STATUS [WHERE DATABASE LIKE <pattern>] > > SHOW output might look something like: > ================================= > mysql> show user binlog status; > +----------------------+----------+---------------------------------+------------+ > | Database | User | Binlog_file | > Binlog_pos | > +----------------------+----------+---------------------------------+------------+ > | booklibs | wwhipple | booklibs-bin.000003 | > 248 | > | charmins_gravestones | charmins | charmins_gravestones-bin.000001 | > 4 | > +----------------------+----------+---------------------------------+------------+ > 2 rows in set (0.01 sec) > > The "where" clause also works: > > mysql> show user binlog status where user like 'charmins'; > +----------------------+----------+---------------------------------+------------+ > | Database | User | Binlog_file | > Binlog_pos | > +----------------------+----------+---------------------------------+------------+ > | charmins_gravestones | charmins | charmins_gravestones-bin.000001 | > 4 | > +----------------------+----------+---------------------------------+------------+ > 1 row in set (0.01 sec) > ================================= > > At this point the migration tools note the binlog coordinates and > start copying the databases to the new server. (For myisam tables, the > tools writers want to just copy [scp?] the files. For innodb, they > will use something like mysqldump.) > > (Note: We might want to "lose" the "User" column in the above table] > in our recent designs.) > > Then the sequence of MySQL commands resumes: > > 4. UNLOCK USER BINLOG FOR DATABASE <db> > > Finally, when migration is complete: > > 5. STOP USER BINLOG FOR DATABASE <db> > > A high percentage of users (infrequent bloggers, etc.) go several days > (sometimes even weeks or months) without updating their databases. For > them--after migrating the files to the new server, a final check of > the binlog coordinates on the old box can verify that nothing has > changed. > > If it HAS changed, migration can copy the binlog file(s) to the new > box and use the mysqlbinlog command (specifying the starting > coordinates) to bring the new database in sync with the old one. > > (This scenario is probably oversimplified, ignoring things like DNS > caching, TTL, etc., etc. Hopefully it doesn't include too many lies.) > > > How I Plan to Do It. > ------------------- > > I've noticed that: > > 1. The class MYSQL_BIN_LOG seems to be involved in most binlogging > 2. MYSQL_BIN_LOG inherits from TC_LOG and MYSQL_LOG. It is created in > mysqld.cc at startup. > > My current partial implementation has: > > 1. Class DB_BIN_LOG inheriting from MYSQL_BIN_LOG, adding members like > db_name > db_binlog_name > db_index_name > and methods to access them, etc. > > 2. Singleton class USER_BIN_LOG_MGR. (Should probably be DB_BIN_LOG_MGR), > which maintains a db_binlog_hash of information about each DB being > binlogged. A DB_BIN_LOG_ENTRY (in the hash) contains: > dbname > locked (bool)--has it been locked by FLUSH ... TABLES WITH READ LOCK? > binlog file > binlog_pos > is_active > a pointer to a DB_BIN_LOG instance > > USER_BINLOG_MGR has a rw lock to protect access to its hash of > currently binlogging db's. (Most accesses will probably be > read-only?) > > Is it plausible to identify all places where a binlog addition might > occur? In those places, if the singleton USER_BIN_LOG_MRG exists, ask > it if the current DB is being binlogged. If so, send the request to > the DB_BIN_LOG instance. > > > Questions I Have. > ---------------- > > 1. I notice that binlog is in the list of engines and plugins > (displayed by SHOW ...). The bottom of log.cc has > "mysql_declare_plugin(binlog)". Do I need one for db_plugin? > (probably not?) > 2. I've diagrammed the binary log event taxonomy--the 24 classes that > inherit from Log_event (in log_event.cc/h). That was my main > motivation for wanting to inherit from MYSQL_BIN_LOG. > 3. On the other hand, I wonder if inheriting from MYSQL_BIN_LOG might > be overkill for "master only" binlogging--without the > slave/replication part of it. > 4. What version should I be working on? (We're currently running > 5.1.47.) What should I check out of bzr/launchpad? (Is that still > what we're doing with the changes in ownership?) > 5. I see that THD is involved in binlogging. (Several THD methods are > defined in log.cc.) Are there any caveats here? > 6. What files should I use? A new h/cc pair? ... or just add to the > hierarchy in log.h/cc? > > In an ideal world, it would be nice to inherit polymorphically from > MYSQL_BIN_LOG, overriding methods that set the names of the binlog > file and index file (etc.) then just call the methods and have it do > the "right thing." On the other hand, I get the impression that I > might be oversimplifying. > > I welcome your advice!! > > What I've Implemented So Far (about 13 Prototypes). > -------------------------------------------------- > > (PRELIMINARY NOTE:) > > Our initial plan was to call it "Per-User Binlogging". The user here > is a cPanel [control panel] user. cPanel's database naming convention > is to have all of a user's database names start with the username, > followed by an underscore, followed by a distinctive database > name. Thus all the commands above start with > > <verb> USER ... > > Originally most of them could end either "DATABASE <db>" or "USER > <user>" (with user meaning cPanel user). Thus, in the original plan > the first command above was: > > START USER BINLOG FOR (USER <user> | DATABASE <db>) > > We have realized that per-database binlogging is all we really need. > We imagine that others in our situation might want something similar. > Since not everyone uses cPanel, we should forget per[cPanel]-user > binlogging, focusing on per-database binlogging. > > I have several versions of lex and bison/yacc files (sql_yacc.yy, > lex.h) to implement the above (and earlier variants). The recent > versions avoid increasing the %expect'ed 169 shift/reduce conflicts > specified in sql_yacc.yy. > > (END OF PRELIMINARY NOTE) > > I currently have 13 different Subversion branches with different > (partial) implementations. > > 1. All have some lex/bison grammer defined. (I'm not completely > satisfied with any of them.) > > 2. Per-db binlogging is enabled by two my.cnf (or command-line) > options: > > user_binlog_dir=/full/directory/path > user_binlog_persist_file=user_binlog.info > > Our servers have fast solid-state drives that we will use for per-db > binlogging. We want to specify a separate directory to store all the > per-db binlogs > > The persist_file stores information about the current state of > db-binlogging--to survive a restart. > > Just about every instance of "user_binlog" in this note should > probably be changed to "db_binlog" ... (???) > > 3. I have added cases in sql_parse.cc for > > SQLCOM_START_USER_BINLOG_DB: > SQLCOM_FLUSH_AND_LOCK_DB: > SQLCOM_SHOW_USER_BINLOG_STATUS: > SQLCOM_UNLOCK_DB: > SQLCOM_STOP_USER_BINLOG_DB: > > (as well as some "USER" variants like SQLCOM_START_USER_BINLOG_USER:, > which should probably abandoned.) > > They should probably be changed to something like: > > SQLCOM_START_DB_BINLOG: > SQLCOM_FLUSH_AND_LOCK_DB: > SQLCOM_SHOW_DB_BINLOG_STATUS: > SQLCOM_UNLOCK_DB: > SQLCOM_STOP_DB_BINLOG: > > ----------------- > > Now that you've read it, please feel free to throw darts, etc. At this > point I'm willing to discard everytning and start over. (In the worst > case--if everyone on this list thinks per-db binlogging is a terrible > idea--I guess I'll be forced to create our own patch [sigh].) > > On the other hand, I would love to help contribute to this effort. (If > per-db binlogging is already underway, let me know, and I'll likely help.) > Thanks in advance for feedback/suggestions/help. Feel free to contact > me privately if you want to. > > Weldon Whipple > weldon(a)whipple.org > > -- > MySQL Internals Mailing List > For list archives: http://lists.mysql.com/internals > To unsubscribe: http://lists.mysql.com/internals?unsub=mdcallag@gmail.com > > -- Mark Callaghan mdcallag(a)gmail.com

3 2

[Maria-discuss] italian translation
by Federico Razzoli 12 Sep '10

12 Sep '10

Hello. I appreciate so much your new Knowledge Base. The pages that are already on line are very clear and complete, as the MySQL docs. But, unlike the MySQL docs, the Knowledge Base has free licenses. For these reasons, I would like to translate into italian - which is my natural language. Am I allowed to do that? As far as I understand, both the licenses used (CC BY-SA and GNU FDL) allow translations, as long as they have the same licenses used by the original work. But I want to be sure before starting. I can't translate all the articles, so I'll only translate some of the most interesting documents. But, as the documentation grows, maybe I may try to set up a group of volounteers. We'll see. Regards, Federico

2 1