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Add missing documentation for special keys

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Chaoguang Lin 2021-05-05 10:10:18 -07:00
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documentation/sphinx/source/developer-guide.rst
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@ -955,12 +955,26 @@ that process, and wait for necessary data to be moved away.
Maintenance mode will be unable to use until the key is cleared, which is the same as the fdbcli command ``datadistribution enable ssfailure``.
While the key is set, any commit that tries to set a key in the range will fail with the ``special_keys_api_failure`` error.
#. ``\xff\xff/management/data_distribution/<mode|rebalance_ignored>`` Read/write. Changing these two keys will change the two corresponding system keys ``\xff/dataDistributionMode`` and ``\xff\x02/rebalanceDDIgnored``. The value of ``\xff\xff/management/data_distribution/mode`` is a literal text of ``0`` (disable) or ``1`` (enable). Transactions committed with invalid values will throw ``special_keys_api_failure`` . The value of ``\xff\xff/management/data_distribution/rebalance_ignored`` is empty. If present, it means data distribution is disabled for rebalance. Any transaction committed with non-empty value for this key will throw ``special_keys_api_failure``. For more details, see help text of ``fdbcli`` command ``datadistribution``.
#. ``\xff\xff/management/consistency_check_suspended`` Read/write. Set or read this key will set or read the underlying system key ``\xff\x02/ConsistencyCheck/Suspend``. The value of this special key is unused thus if present, will be empty. In particular, if the key exists, then consistency is suspended. For more details, see help text of ``fdbcli`` command ``consistencycheck``.
#. ``\xff\xff/management/consistency_check_suspended`` Read/write. Set or read this key will set or read the underlying system key ``\xff\x02/ConsistencyCheck/Suspend``. The value of this special key is unused thus if present, will be empty. In particular, if the key exists, then consistency is suspended. For more details, see help text of ``fdbcli`` command ``consistencycheck``. For more details, see help text of ``fdbcli`` command ``lock`` and ``unlock``.
#. ``\xff\xff/management/db_locked`` Read/write. A single key that can be read and modified. Set the key will lock the database and clear the key will unlock. If the database is already locked, then the commit will fail with ``special_keys_api_failure`` error.
#. ``\xff\xff/management/auto_coordinators`` Read-only. A single key, if read, will return a group of coordinators that satisfies the current redundency level. The value is a comma delimited string of network addresses of coordinators, i.e. ``<ip:port>,<ip:port>,...,<ip:port>``.
An exclusion is syntactically either an ip address (e.g. ``127.0.0.1``), or
an ip address and port (e.g. ``127.0.0.1:4500``). If no port is specified,
then all processes on that host match the exclusion.
Configuration module
~~~~~~~~~~~~~~~~~~~~
The configuration module is for changing the cluster configuration.
For example, you can change a process type or update coordinators through transactions manipulating related special keys.
#. ``\xff\xff/configuration/process/class_type/<address> := <class_type>`` Read/write. Reading keys in the range will give processes' class types. Setting keys in this range can update processes' class types. The process matching ``<address>`` will be assigned to the given type if the commit is successful. The valid class types are ``storage``, ``transaction``, ``resolution`` and etc. A full list can be found via ``fdbcli`` command ``help setclass``. Clear keys are forbidden in the range. Instead, you can set the type as ``default``, which will clear the assigned class type if existing. For more details, see help text of ``fdbcli`` command ``setclass``.
#. ``\xff\xff/configuration/process/class_source/<address> := <class_source>`` Read-only. Reading keys in the range will give processes' class source. The class source can be one of ``command_line``, ``configure_auto``, ``set_class`` and ``invalid``, and each represents where the process's class type came from.
#. ``\xff\xff/configuration/coordinators`` Read/write. Modifying keys in the range can change cooridinators or cluster description. Read ``\xff\xff/configuration/coordinators/cluster_description := <new_description>`` will return the cluster description and thus modify the key will update the decription. The new description needs to match ``[A-Za-z0-9_]+``, otherwise, the ``special_keys_api_failure`` error will be thrown. Read ``\xff\xff/configuration/coordinators/processes`` will return a comma delimited string of coordinators's network addresses, i.e. ``<ip:port>,<ip:port>,...,<ip:port>``. Thus to provide a new set of cooridinators, set the key with a correct formatted string of new coordinators' network addresses. For more details, see help text of ``fdbcli`` command ``coordinators``.
The ``<address>`` here is the network address of the corresponding process. Thus the general form is ``ip:port``.
Error message module
~~~~~~~~~~~~~~~~~~~~