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CiviCRM Replay-on-Write: Installation

The "General" section gives a general overview of the install process. Many specifics can depend on your organization/deployment, iso t is a bit light on MySQL details - and only gives details that are specific to rpow.

The subsequent sections provide more specific, concrete install options. These are geared toward local development and experimentation:

  • "Using civibuild and harvey-dent" provides the lightest simulation. It uses the existing DB and sets up a split personality, with two users (RO user and RW user).
  • "Using civibuild and rundb" provides the most realistic simulation. It launches two new instances of mysqld and automatically syncs between their databases.
  • "Using rebuild-ro" provides a more manual simulation. It uses your existing mysqld and makes a read-only copy of the Civi DB. It does not sync automatically - you must run rebuild-ro whenever you want to sync. (This is useful for carefully inspecting/playing each step or edge-case manually.)

General

cd /var/www/sites/default/civicrm/ext
git clone https://github.com/totten/rpow

  • Setup the MySQL read-write and read-only databases -- and determine their DSNs. That process is outside the scope of this README. See also: MySQL 5.7 Reference Manual: Replication Howto

  • Edit civicrm.settings.php. In lieu of setting define('CIVICRM_DSN', '...'), call this:

require_once '<RPOW-SRC>/autoload.php';
rpow_init([
  'masters' => ['mysql://rw_user:rw_pass@rw_host/rw_db?new_link=true'],
  'slaves' => ['mysql://ro_user:ro_pass@ro_host/ro_db?new_link=true'],
]);

Using civibuild and harvey-dent

If you're doing local development on a civibuild site, then you can simulate a master/slave topology using the script harvey-dent. This will create a split between two user accounts which have access to the same DB. The original MySQL account has read-write access -- and the new secondary account has read-only access.

This is handy for quick-and-dirty experiments without having a proper MySQL replication environment.

cd ~/buildkit/build/dmaster/web/sites/default/civicrm/ext
git clone https://github.com/totten/rpow
  • Create the read-only user and register DSNs.
./bin/harvey-dent -r ~/buildkit/build/dmaster/web/

The harvey-dent script will:

  • Add a user with read-only permission for the existing Civi database.
  • Create a file civicrm.settings.d/pre.d/100-civirpow.php to call rpow_init() with the appropriate credentials for the masters and slaves.

Using civibuild and rundb

If you usually develop locally with a civibuild site, then you might temporarily spin-up a master-slave DB (via rundb) and temporarily migrate to it. These instances run on alternate, local-only ports with insecure passwords.

curl https://nixos.org/nix/install | sh

  • Setup CiviCRM to store caches in Redis

    • Tip: This command will download and start redis-server. Any persistence/dumps will go in /tmp. 
      cd /tmp; nix run nixpkgs.redis -c redis-server

  • Download the rpow extension, e.g.

cd /var/www/sites/default/civicrm/ext
git clone https://github.com/totten/rpow
cd rpow
  • Setup rundb
## Start the temporary database process in the foreground
./bin/use-rundb fg

## Open a console; then...
## Migate to the new database
./bin/use-rundb copy on

Using rebuild-ro

If you're doing local development on a civibuild site, then you can simulate a master/slave topology using the script the script rebuild-ro to make a read-only copy of your database.

cd /var/www/sites/default/civicrm/ext
git clone https://github.com/totten/rpow
  • Setup a config file (rebuild-ro.conf), esp CIVIRO_PASS (for security) andSITE_ROOT` (for convenience)

``` cp etc/rebuild-ro.conf.example etc/rebuild-ro.conf vi etc/rebuild-ro.conf

  • Create the read-only DB. Copy data from the main DB. Register the DSNs via civicrm.settings.d.
./bin/rebuild-ro

The rebuild-ro script will:

  • Make a new database
  • Copy the CiviCRM tables to the new database
  • Add a user with read-only permission for the new database
  • Create a file civicrm.settings.d/pre.d/100-civirpow.php to call rpow_init() with the appropriate credentials for the masters and slaves.

This is handy for simulating master=>slave replication manually. It does not require any special mysqld options, but it does assume that you have a civibuild-based environment.