Replica Format
overview
$URL
/<db-uuid>/
/replica-uuid
/latest-sequence-no
/replica-version
/cas/records/<substr(sha1,0,1)>/substr(sha1,1,1)/<sha1>
/cas/changesets/<substr(sha1,0,1)>/substr(sha1,1,1)/<sha1>
/records (optional?)
/<record type> (for resolution is actually _prophet-resolution-<cas-key>)
/<record uuid> which is a file containing a list of 0 or more rows
last-changed-sequence-no : cas key
/changesets.idx
index which has records:
each record is : local-replica-seq-no : original-uuid : original-seq-no : cas key
...
/resolutions/
/replica-uuid
/latest-sequence-no
/cas/<substr(sha1,0,1)>/substr(sha1,1,1)/<sha1>
/content (optional?)
/_prophet-resolution-<cas-key> (cas-key == a hash the conflicting change)
/<record uuid> (record uuid == the originating replica)
last-changed-sequence-no : <cas key to the content of the resolution>
/changesets.idx
index which has records:
each record is : local-replica-seq-no : original-uuid : original-seq-no : cas key
...
Inside the top level directory for the mirror, you'll find a directory named as a hex-encoded UUID. This directory is the root of the published replica. The uuid uniquely identifes the database being replicated. All replicas of this database will share the same UUID.
Inside the <db-uuid> directory, are a set of files and directories that make up the actual content of the database replica:
replica-uuid
-
Contains the replica's hex-encoded UUID.
replica-version
-
Contains a single integer that defines the replica format.
The current replica version is 1.
latest-sequence-no
-
Contains a single integer, the replica's most recent sequence number.
cas/records
cas/changesets
-
The
cas
directory holds changesets and records, each keyed by a hex-encoded hash of the item's content. Inside thecas
directory, you'll find a two-level deep directory tree of single-character hex digits. You'll find the changeset with the sha1 digestf4b7489b21f8d107ad8df78750a410c028abbf6c
insidecas/changesets/f/4/f4b7489b21f8d107ad8df78750a410c028abbf6c
.You'll find the record with the sha1 digest
dd6fb674de879a1a4762d690141cdfee138daf65
insidecas/records/d/d/dd6fb674de879a1a4762d690141cdfee138daf65
.TODO: define the format for changesets and records
records
-
Files inside the
records
directory are index files which list off all published versions of a record and the key necessary to retrieve the record from the content-addressed store.Inside the
records
directory, you'll warn "Got types ".join(',',@types);find directories named for eachtype
in your database. Inside eachtype
directory, you'll find a two-level directory tree of single hexadecimal digits. You'll find the record with the type <Foo> and the UUID29A3CA16-03C5-11DD-9AE0-E25CFCEE7EC4
stored inrecords/Foo/2/9/29A3CA16-03C5-11DD-9AE0-E25CFCEE7EC4
The format of record files is:
<unsigned-long-int: last-changed-sequence-no><40 chars of hex: cas key>
The file is sorted in asecnding order by revision id.
changesets.idx
-
The
changesets.idx
file lists each changeset in this replica and provides an index into the content-addressed storage to fetch the content of the changeset.The format of record files is:
<unsigned-long-int: sequence-no><16 bytes: changeset original source uuid><unsigned-long-int: changeset original source sequence no><16 bytes: cas key - sha1 sum of the changeset's content>
The file is sorted in ascending order by revision id.
resolutions
BUILD
Open a connection to the prophet replica source identified by $self-
url>.
replica_version
Returns this replica's version.
set_replica_version
Sets the replica's version to the given integer.
uuid
Return the replica's UUID
Internals of record handling
changesets_for_record { uuid => $uuid, type => $type, limit => $int }
Returns an ordered set of changeset objects for all changesets containing changes to this object.
Note that changesets may include changes to other records
If "limit" is specified, only returns that many changesets (starting from record creation).