zc.zrs 3.1.0

Configuration with ZConfig

If using an application, like a ZEO server or Zope, that uses ZConfig to configure ZODB storages, the configuration of a ZRS primary or secondary storage may be included in the configuration file as with any other storage e.g, to configure a primary storage, use something like:

%import zc.zrs

<zrs>
 replicate-to 5000

 <filestorage>
     path /path/to/data/file
 </filestorage>
</zrs>

Here is a line-by-line walk through:

%import zc.zrs

The import statement is necessary to load the ZConfig schema definitions for ZRS.

<zrs>

The zrs section defines a ZRS storage. A ZRS storage may be a primary storage or a secondary storage. A ZRS storage without a replicate-from option (as in the example above) is a primary storage.

replicate-to 5000

The replicate-to option specifies the replication address. Secondary storages will connect to this address to download replication data. This address can be a port number or a host name (interface name) and port number separated by a colon.

<filestorage>
  path /path/to/data/file
</filestorage>

A ZRS storage section must include a filestorage section specifying a file storage to contain the data.

Configuring a secondary storage is similar to configuring a primary storage:

%import zc.zrs

<zrs>
 replicate-from primary-host:5000
 replicate-to 5000
 keep-alive-delay 60

 <filestorage>
     path /path/to/secondary/data/file
 </filestorage>
</zrs>

For a secondary storage, a replicate-from option is used to specify the address to replicate data from.

Because primary and secondary storages are generally on separate machines, the host is usually specified in a replicate-from option.

A secondary storage can also specify a replicate-to option. If this option is used, other secondary storages can then replicate from the secondary, rather than replicating from the primary.

Secondary storages also support the following optional option:

keep-alive-delay SECONDS

In some network configurations, TCP connections are broken after extended periods of inactivity. This may even be done in a way that a client doesn’t detect the disconnection. To prevent this, you can use the keep-alive-delay option to cause the secondary storage to send periodic no-operation messages to the server.

3.1.0 (2017-04-07)

• Python 3 (3.4 amd 3.5) support.

  3.6 support will be added when Twisted supports Python 3.6. (There are worrying test failures under Python 3.6.)

• Minor convenience change to API: When instantiating primary or secondary servers, you can pass a file-name instead of a storage instance and a file storage will be created automatically.

3.0.0 (2017-04-04)

• Add support for ZODB 5

• Drop ZooKeeper support.