Libs-compat: yum upgrade mysql-wsrep-shared-5.5 on Centos 7 + mysql-wsrep-5.5

[philip-galera]

On centos 7 + mysql-wsrep-5.5 , attempting to use the following command to preserve postfix, etc, fails:

+ sudo yum upgrade -y mysql-wsrep-shared-5.5
Loaded plugins: fastestmirror
base                                                                                                                                                                           | 3.6 kB  00:00:00
extras                                                                                                                                                                         | 3.4 kB  00:00:00
galera                                                                                                                                                                         | 2.9 kB  00:00:00
updates                                                                                                                                                                        | 3.4 kB  00:00:00
(1/5): galera/primary_db                                                                                                                                                       |  14 kB  00:00:00
(2/5): extras/7/x86_64/primary_db                                                                                                                                              |  99 kB  00:00:00
(3/5): base/7/x86_64/group_gz                                                                                                                                                  | 154 kB  00:00:00
(4/5): base/7/x86_64/primary_db                                                                                                                                                | 5.1 MB  00:00:01
(5/5): updates/7/x86_64/primary_db                                                                                                                                             | 4.0 MB  00:00:01
Determining fastest mirrors
 * base: mirror.nsc.liu.se
 * extras: mirror.nsc.liu.se
 * updates: mirror.nsc.liu.se
Resolving Dependencies
--> Running transaction check
---> Package mariadb-libs.x86_64 1:5.5.35-3.el7 will be obsoleted
--> Processing Dependency: libmysqlclient.so.18(libmysqlclient_18)(64bit) for package: 2:postfix-2.10.1-6.el7.x86_64
---> Package mysql-wsrep-shared-5.5.x86_64 0:5.5.45-25.12.20151029.0d322e7.el7 will be obsoleting
--> Running transaction check
---> Package mysql-wsrep-shared-5.6.x86_64 0:5.6.26-25.11.20151029.565d385.el7 will be obsoleting
--> Finished Dependency Resolution

Dependencies Resolved

======================================================================================================================================================================================================
 Package                                              Arch                                 Version                                                         Repository                            Size
======================================================================================================================================================================================================
Installing:
 mysql-wsrep-shared-5.5                               x86_64                               5.5.45-25.12.20151029.0d322e7.el7                               galera                               1.8 M
     replacing  mariadb-libs.x86_64 1:5.5.35-3.el7
 mysql-wsrep-shared-5.6                               x86_64                               5.6.26-25.11.20151029.565d385.el7                               galera                               1.2 M
     replacing  mariadb-libs.x86_64 1:5.5.35-3.el7

Transaction Summary
======================================================================================================================================================================================================
Install  2 Packages

Total download size: 3.0 M
Downloading packages:
warning: /var/cache/yum/x86_64/7/galera/packages/mysql-wsrep-shared-5.6-5.6.26-25.11.20151029.565d385.el7.x86_64.rpm: Header V4 RSA/SHA1 Signature, key ID bc19ddba: NOKEY
Public key for mysql-wsrep-shared-5.6-5.6.26-25.11.20151029.565d385.el7.x86_64.rpm is not installed
(1/2): mysql-wsrep-shared-5.6-5.6.26-25.11.20151029.565d385.el7.x86_64.rpm                                                                                                     | 1.2 MB  00:00:00
(2/2): mysql-wsrep-shared-5.5-5.5.45-25.12.20151029.0d322e7.el7.x86_64.rpm                                                                                                     | 1.8 MB  00:00:00
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Total                                                                                                                                                                  11 MB/s | 3.0 MB  00:00:00
Retrieving key from http://repos.codership.com/libs-compat/GPG-KEY-galeracluster.com
Importing GPG key 0xBC19DDBA:
 Userid     : "Codership Oy <info@galeracluster.com>"
 Fingerprint: 44b7 3457 38eb de52 594d ad80 d669 017e bc19 ddba
 From       : http://repos.codership.com/libs-compat/GPG-KEY-galeracluster.com
Running transaction check
Running transaction test


Transaction check error:
  file /usr/lib64/libmysqlclient.so.18 conflicts between attempted installs of mysql-wsrep-shared-5.6-5.6.26-25.11.20151029.565d385.el7.x86_64 and mysql-wsrep-shared-5.5-5.5.45-25.12.20151029.0d322e7.el7.x86_64

It seems that the 5.6 package somehow gets involved.

[fromdualjb]

Sorry, this seems to be a design problem of yum:

1. Installed "postfix" has a "requires" for "libmysqlclient.so.18(libmysqlclient_18)(64bit)" (see the log message "Processing Dependency:".
2. Both "mysql-wsrep-shared-5.5" and "mysql-wsrep-shared-5.6" include a "provides" for that.
3. Yum checks dependencies and tries to fulfill them, and if there is more than one provider package then yum will prefer the one with the highest version. 5.6.26 is a higher version than 5.5.45, so yum will prefer the 5.6 one.

AIUI and TTBOMK, this can only be prevented by having separate repositories for the 5.5 and 5.6 package series, and configuring the target machine to use only one seems to be the only clean solution.

Until then, the "-x" option of yum may be the only way to make yum do what the user wants.
The other alternative is an explicit download and then a local installation using rpm, but this is even more complicated and probably not what should be recommended to users.