In the previous, when you query the tail pages, all the front of rows
will be queried out and formatted. It greatly hurts the speed of query.
Currently, we only format the final result rows. i.e, the query for the
last page of data will be 10x faster.
This commit adds a rule engine configuration option for changing the
implementation module used for the rule engine function jq. The two
options are `jq_port` (uses Erlang port programs to interact with jq)
and `jq_nif` (uses an Erlang NIF library to interact with jq).
Thanks to @terry-xiaoyu (Xinyu Liu <506895667@qq.com>) for Chinese
translations
Due to:
* Cluster RPC MFA is not idempotent!
* There is a lack of rollback for callback's side-effects
For instance, when two nodes try to add a cluster-singleton
concurrently, one of them will have to wait for the table lock
then try to catch-up, then try to apply MFA.
The catch-up will have the singleton created, but the initiated
initiated multicall apply will fail causing the commit to rollback,
but not to 'undo' the singleton creation.
Later, the retries will fail indefinitely.
This commit adds a default timeout of 10 seconds to the rule engine's
`jq/2` function, and adds a new function `jq/3` (where the last parameter is
a timeout value). The default timeout can be configured with the setting
"rule_engine.jq_function_default_timeout".
Having a timeout when executing jq code in the rule engine is important
as jq code can potentially run forever. Also, the Erlang jq library
limits the number of jq programs that can execute concurrently so a jq
program that loops forever could potentially also prevent a "non-buggy"
jq program from ever starting.
This commit adds a function to the rule engine that alows users
to transform text or JSON objects using [jq filter programs][1].
[jq][1] is a command line tool that can be used to transform
and filter JSON text using jq's built-in language. The rule engine
function that is added with this commit uses the
[Erlang jq NIF library][2] that wraps the jq C library in an
Erlang NIF function.
[1]: https://stedolan.github.io/jq/
[2]: https://github.com/emqx/jq
