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https://issues.apache.org/jira/browse/COUCHDB-1153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13089512#comment-13089512
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Damien Katz commented on COUCHDB-1153:
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Robert, Benoit, your issues can still be addressed. You can submit patches that
improve upon Filipes work. But telling Filipe to code the patch your way,
without code is not how this community works. Filipe's work is a feature people
care about, and any objections of correctness have been addressed. Switching
the code to an evented model, or any other improvements is welcome from you or
any other community member, but users want this feature, and Filipe should not
be expected to code it up to everyone else expectations before any check-in can
occur. Improvement can, and should, happen continuously.
> Database and view index compaction daemon
> -----------------------------------------
>
> Key: COUCHDB-1153
> URL: https://issues.apache.org/jira/browse/COUCHDB-1153
> Project: CouchDB
> Issue Type: New Feature
> Environment: trunk
> Reporter: Filipe Manana
> Assignee: Filipe Manana
> Priority: Minor
> Labels: compaction
>
> I've recently written an Erlang process to automatically compact databases
> and they're views based on some configurable parameters. These parameters can
> be global or per database and are: minimum database fragmentation, minimum
> view fragmentation, allowed period and "strict_window" (whether an ongoing
> compaction should be canceled if it doesn't finish within the allowed
> period). These fragmentation values are based on the recently added
> "data_size" parameter to the database and view group information URIs
> (COUCHDB-1132).
> I've documented the .ini configuration, as a comment in default.ini, which I
> paste here:
> [compaction_daemon]
> ; The delay, in seconds, between each check for which database and view
> indexes
> ; need to be compacted.
> check_interval = 60
> ; If a database or view index file is smaller then this value (in bytes),
> ; compaction will not happen. Very small files always have a very high
> ; fragmentation therefore it's not worth to compact them.
> min_file_size = 131072
> [compactions]
> ; List of compaction rules for the compaction daemon.
> ; The daemon compacts databases and they're respective view groups when all
> the
> ; condition parameters are satisfied. Configuration can be per database or
> ; global, and it has the following format:
> ;
> ; database_name = parameter=value [, parameter=value]*
> ; _default = parameter=value [, parameter=value]*
> ;
> ; Possible parameters:
> ;
> ; * db_fragmentation - If the ratio (as an integer percentage), of the amount
> ; of old data (and its supporting metadata) over the
> database
> ; file size is equal to or greater then this value, this
> ; database compaction condition is satisfied.
> ; This value is computed as:
> ;
> ; (file_size - data_size) / file_size * 100
> ;
> ; The data_size and file_size values can be obtained when
> ; querying a database's information URI (GET /dbname/).
> ;
> ; * view_fragmentation - If the ratio (as an integer percentage), of the
> amount
> ; of old data (and its supporting metadata) over the
> view
> ; index (view group) file size is equal to or greater
> then
> ; this value, then this view index compaction
> condition is
> ; satisfied. This value is computed as:
> ;
> ; (file_size - data_size) / file_size * 100
> ;
> ; The data_size and file_size values can be obtained
> when
> ; querying a view group's information URI
> ; (GET /dbname/_design/groupname/_info).
> ;
> ; * period - The period for which a database (and its view groups) compaction
> ; is allowed. This value must obey the following format:
> ;
> ; HH:MM - HH:MM (HH in [0..23], MM in [0..59])
> ;
> ; * strict_window - If a compaction is still running after the end of the
> allowed
> ; period, it will be canceled if this parameter is set to
> "yes".
> ; It defaults to "no" and it's meaningful only if the
> *period*
> ; parameter is also specified.
> ;
> ; * parallel_view_compaction - If set to "yes", the database and its views are
> ; compacted in parallel. This is only useful on
> ; certain setups, like for example when the
> database
> ; and view index directories point to different
> ; disks. It defaults to "no".
> ;
> ; Before a compaction is triggered, an estimation of how much free disk space
> is
> ; needed is computed. This estimation corresponds to 2 times the data size of
> ; the database or view index. When there's not enough free disk space to
> compact
> ; a particular database or view index, a warning message is logged.
> ;
> ; Examples:
> ;
> ; 1) foo = db_fragmentation = 70%, view_fragmentation = 60%
> ; The `foo` database is compacted if its fragmentation is 70% or more.
> ; Any view index of this database is compacted only if its fragmentation
> ; is 60% or more.
> ;
> ; 2) foo = db_fragmentation = 70%, view_fragmentation = 60%, period =
> 00:00-04:00
> ; Similar to the preceding example but a compaction (database or view
> index)
> ; is only triggered if the current time is between midnight and 4 AM.
> ;
> ; 3) foo = db_fragmentation = 70%, view_fragmentation = 60%, period =
> 00:00-04:00, strict_window = yes
> ; Similar to the preceding example - a compaction (database or view index)
> ; is only triggered if the current time is between midnight and 4 AM. If at
> ; 4 AM the database or one of its views is still compacting, the compaction
> ; process will be canceled.
> ;
> ;_default = db_fragmentation = 70%, view_fragmentation = 60%, period = 23:00
> - 04:00
> (from https://github.com/fdmanana/couchdb/compare/compaction_daemon#L0R195)
> The full patch is mostly a new module but also does some minimal changes and
> a small refactoring to the view compaction code, not changing the current
> behaviour.
> Patch is at:
> https://github.com/fdmanana/couchdb/compare/compaction_daemon.patch
> By default the daemon is idle, without any configuration enabled. I'm open to
> suggestions on additional parameters and a better configuration system.
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