My application that is running on a client uses a MySQL database running on a server. So multiple clients are connected to the same server. That works well when the server is online. But now I would like to enhance my application to be able to run in an offline mode.
+--------------+
| |
+-----------+ SERVER +----------+
| | | |
| +-------+------+ |
| | |
+------+-------+ +-------+------+ +-------+------+
| | | | | |
| Client 1 | | Client 2 | | Client X |
| | | | | |
+--------------+ +--------------+ +--------------+
Now comes the problem: what happens when the client is offline? I need a copy of my MySQL database on each client too. By default the application interacts with the MySQL on the server. If this server is not accessible (for what reason ever: server is offline or client has no internet connection) it should use the MySQL running on the client. If the client/server connection is available again the databases need to be synched automatically.
My question is now: how to achieve this? First of all I checked the MySQL-replication, but in my scenario I have multiple "masters" and an unknown number of clients. So I afraid that replication is not my solution. Is it possible to solve my problem with MaxScale? I never worked with that so I really appreciate any help.
Related
Following steps are followed to enable MySQL encryption.
Mysql version 5.7 is installed on apache server. So by default keyring_file.so is available at following path: /usr/lib64/mysql/plugin/keyring_file.
In /etc/my.cnf below 2 code is added and MySQL is restarted.
early-plugin-load=keyring_file.so
keyring_file_data=/var/lib/mysql-keyring/keyring
When below query is executed to check if keyring plugin is active. It outputs as active
SELECT PLUGIN_NAME, PLUGIN_STATUS FROM INFORMATION_SCHEMA.PLUGINS WHERE PLUGIN_NAME LIKE 'keyring%';
+--------------+---------------+
| PLUGIN_NAME | PLUGIN_STATUS |
+--------------+---------------+
| keyring_file | ACTIVE |
+--------------+---------------+
Encryption is enabled on table level (on table author of DB testDB), It can be checked using below query
SELECT TABLE_SCHEMA, TABLE_NAME, CREATE_OPTIONS FROM INFORMATION_SCHEMA.TABLES WHERE CREATE_OPTIONS LIKE '%ENCRYPTION%';
+--------------+------------+----------------+
| TABLE_SCHEMA | TABLE_NAME | CREATE_OPTIONS |
+--------------+------------+----------------+
| testDB | author | ENCRYPTION="Y" |
+--------------+------------+----------------+
Data is inserted in author table as "plain text". However, though the table is encrypted.
select * from author;
+------+----------+-------------+
| id | name | email |
+------+----------+-------------+
| 1 | PQR | xuz#abc.com |
| 1 | XYZ | abc#abc.com |
| 1 | SSSS | xyz#abc.com |
| 1 | dfdfdf | prq#abc.com |
+------+----------+-------------+
What needs to be done to enable encryption on MySQL table?
What you enabled was innodb data at rest encryption, which is a transparent encryption technique, meaning authenticated and authorised users will not even notice it. As the mysql FAQ says on decryption:
InnoDB data-at-rest encryption is designed to transparently apply encryption within the database without impacting existing applications. Returning data in encrypted format would break most existing applications. InnoDB data-at-rest encryption provides the benefit of encryption without the overhead associated with traditional database encryption solutions, which would typically require expensive and substantial changes to applications, database triggers, and views.
I have a mysql database set up on a mac mini server on a local network. When I query the database from the server as the root user, everything behaves well. However, I am having serious problems when I log into mysql from another machine on the local network I perform those same queries.
For example, the table items has 1,831,218 rows and two columns, item and total (not indexed). When I perform the following query is is very quick as expected:
mysql> select * from items limit 10;
+------+-----------+
| item | total |
+------+-----------+
| a | 577846916 |
| b | 489378579 |
| c | 485798873 |
| d | 476865689 |
| e | 425954264 |
| f | 399431640 |
| g | 375218023 |
| h | 325892006 |
| i | 169948795 |
| j | 116927132 |
+------+-----------+
10 rows in set (0.00 sec)
Now by logging in remotely from another machine on the network:>mysql --host=192.168.2.2 -u newuser -p, where newuser has select privileges on the database, I perform the same query and get wildly different execution times.
mysql> select * from items limit 10;
+------+-----------+
| item | total |
+------+-----------+
| a | 577846916 |
| b | 489378579 |
| c | 485798873 |
| d | 476865689 |
| e | 425954264 |
| f | 399431640 |
| g | 375218023 |
| h | 325892006 |
| i | 169948795 |
| j | 116927132 |
+------+-----------+
10 rows in set (7 min 3.10 sec)
This is an exceptionally bad example that doesn't happen all the time, but in general queries are much slower (usually 10-100 times slower (or more) than on the server itself). For this much of a slow down it doesn't seem likely that the bottleneck has to do with latency in the network, but rather some configuration issue that is causing mysql to not communicate well with between the server and the various nodes.
Aside from verifying that both machines are running he same version of mysql: mysql Ver 14.14 Distrib 5.6.19, for osx10.7 (x86_64) using EditLine wrapper, I am not sure what other settings to verify and what else to do to try to fix this problem.
Please let me know if anyone has any ideas, thank you.
I have a database table, with 300,000 rows and 113.7 MB in size. I have my database running on Ubuntu 13.10 with 8 Cores and 8GB of RAM. As things are now, the MySQL server uses up an average of 750% CPU. and 6.5 %MEM (results obtained by running top in the CLI). Also to note, it runs on the same server as Apache2 Web Server.
Here's what I get on the Mem line:
Mem: 8141292k total, 6938244k used, 1203048k free, 211396k buffers
When I run: show processlist; I get something like this in return:
2098812 | admin | localhost | phpb | Query | 12 | Sending data | SELECT * FROM items WHERE thumb = 'Halloween 2013 Horns/thumbs/Halloween 2013 Horns (Original).png'
2098813 | admin | localhost | phpb | Query | 12 | Sending data | SELECT * FROM items WHERE thumb = 'Halloween 2013 Witch Hat/thumbs/Halloween 2013 Witch Hat (Origina
2098814 | admin | localhost | phpb | Query | 12 | Sending data | SELECT * FROM items WHERE thumb = 'Halloween 2013 Blouse/thumbs/Halloween 2013 Blouse (Original).png
2098818 | admin | localhost | phpb | Query | 11 | Sending data | SELECT * FROM items WHERE parent = 210162 OR auto = 210162
Some queries are taking an excess of 10 seconds to execute, this is not the top of the list, but somewhere in the middle just to give kind of a perspective of how many queries are stacking up in this list. I feel that it may have something to do with my Query Cash configurations. Here are the configurations show from running the SHOW STATUS LIKE 'Qc%';
+-------------------------+----------+
| Variable_name | Value |
+-------------------------+----------+
| Qcache_free_blocks | 434 |
| Qcache_free_memory | 2037880 |
| Qcache_hits | 62580686 |
| Qcache_inserts | 10865474 |
| Qcache_lowmem_prunes | 4157011 |
| Qcache_not_cached | 3140518 |
| Qcache_queries_in_cache | 1260 |
| Qcache_total_blocks | 4440 |
+-------------------------+----------+
I noticed that the Qcache_lowmem_prunes seem a bit high, is this normal?
I've been searching around StackOverflow, but I couldn't find anything that would solve my problem. Any help with this would be greatly appreciated, thank you!
This is probably one for http://dba.stackexchange.com. That said...
Why are your queries running slow? Do they return a large result set, or are they just really complex?
Have you tried running one of these queries using EXPLAIN SELECT column FROM ...?
Are you using indexes correctly?
How have you configured MySQL in your my.cnf file?
What table types are you using?
Are you getting any errors?
Edit: Okay, looking at your query examples. What data type is items.thumb? Varchar, Text? Is it not at all possible to query this table using another method than literal text matching? (e.g. ID number). Does this column have an index?
I see frequently when I run mysqladmin proc or when I review the MySQL Server process list a user marked with: unauthenticated user trying to connect.
+-----+----------------------+--------------+-----------------+---------+------+------------------+------------------+-----------+---------------+-----------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read |
+-----+----------------------+--------------+-----------------+---------+------+------------------+------------------+-----------+---------------+-----------+
| 40 | unauthenticated user | x.x.x.x:xxxx | | Connect | | Reading from net | | 0 | 0 | 0 |
What may causes such thing?
Is that normal, or should I investigate my system for any vulnerability or security breach?
Thanks
unauthenticated user is the user connected and not yet sent authentication credentials. Doesn't look like a hack attempt to me.
My debian-based is booting so slow after I installed MySQL and imported some databases on it. Looking for some statement, I found this one during boot:
mysql> show full processlist;
+----+------------------+-----------+------+---------+------+----------------+----------------------------------------------------------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+------------------+-----------+------+---------+------+----------------+----------------------------------------------------------------------+
| 9 | debian-sys-maint | localhost | NULL | Query | 12 | Opening tables | select count(*) into #discard from `information_schema`.`PARTITIONS` |
| 10 | root | localhost | NULL | Query | 0 | NULL | show full processlist |
+----+------------------+-----------+------+---------+------+----------------+----------------------------------------------------------------------+
2 rows in set (0.00 sec)
Here the statement that causing trouble:
select count(*) into #discard from `information_schema`.`PARTITIONS`
I have +-10 databases totaling over 8gb of data.
Is there any configuration to disable this query on system booting ? If yes, why run it during boot ?
Information
I have a standard MySQL installation without custom configs.
Best regards.
It seems Debian, whose Linux Mint is based upon, have scripts that get executed when the mysql server is started or restarted, to check for corrupted tables and make an alert for that.
In my Debian server, the culprit seems to be /etc/mysql/debian-start bash script, which in turn calls /usr/share/mysql/debian-start.inc.sh , so check both scripts and comment out the function that is iterating all your tables, from a quick look it seems the following:
check_for_crashed_tables;
which is called from the debian-start script I mentioned above.