> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
The bulk API allows multiple updates or queries to be executed in a single request. Both non-paramterized and parameterized requests are supported by the Bulk API. The API does not support mixing the parameterized and non-parameterized form in a single request.
A bulk update is contained within a single Raft log entry, so round-trips between nodes are at a minimum. This should result in much better throughput, if it is possible to use this kind of update. You can also ask rqlite to do the batching for you automatically, through the use of [_Queued Writes_](https://github.com/rqlite/rqlite/blob/master/DOC/QUEUED_WRITES.md). This relieves the client of doing any batching before transmitting a request to rqlite.
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
rqlite comes with a CLI, which makes it easier to interact with a rqlite system. It is installed in the same directory as the node binary `rqlited`. Since rqlite is built on SQLite, you should consult the [SQLite query language documentation](https://www.sqlite.org/lang.html) for full details on what is supported.
> **⚠ WARNING: Only enter one command at a time at CLI. Don't enter multiple commands at once, separated by ;**
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
_rqlite has been run through Jepsen-style testing. You can read about it [here](https://github.com/wildarch/jepsen.rqlite/blob/main/doc/blog.md)._
Even though serving queries does not require Raft consensus (because the database is not changed), [queries should generally be served by the Leader](https://github.com/rqlite/rqlite/issues/5). Why is this? Because, without this check, queries on a node could return results that are out-of-date i.e. _stale_. This could happen for one, or both, of the following two reasons:
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
Each rqlite node exposes an HTTP API allowing data to be inserted into, and read back from, the database. Any changes to the database (`INSERT`, `UPDATE`, `DELETE`) **must** be sent to the `/db/execute` endpoint, and reads (`SELECT`) should be sent to the `/db/query` endpoint. _It is important to use the correct endpoint for the operation you wish to perform._
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
You can find details on the design and implementation of rqlite from [these blog posts](https://www.philipotoole.com/tag/rqlite/) (in particular [this post](https://www.philipotoole.com/replicating-sqlite-using-raft-consensus/) and [this post](https://www.philipotoole.com/rqlite-replicated-sqlite-with-new-raft-consensus-and-api/)).
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
Since SQLite does not enforce foreign key constraints by default, neither does rqlite. However you can enable foreign key constraints in rqlite via the command line option `-fk=true`. Setting this command line will enable Foreign Key constraints on all connections that rqlite makes to the underlying SQLite database.
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
rqlite replicates SQLite for fault-tolerance. It does not replicate it for performance. In fact performance is reduced relative to a standalone SQLite database due to the nature of distributed systems. _There is no such thing as a free lunch_.
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
You can issue [`PRAGMA`](https://www.sqlite.org/pragma.html) directives to rqlite, and they will be passed to the underlying SQLite database. Certain `PRAGMA` directives, which alter the operation of the SQLite database, may not make sense in the context of rqlite (since rqlite does not given direct control over its connections to the SQLite database). Furthermore some `PRAGMA` directives may even break rqlite. If you have questions about a specific `PRAGMA` directive, the [rqlite Google Group](https://groups.google.com/group/rqlite) is a good place to start the discussion.
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
rqlite supports adding _read-only_ nodes. You can use this feature to add read scalability to the cluster if you need a high volume of reads, or want to distribute copies of the data nearer to clients -- but don't want those nodes counted towards the quorum. These types of nodes are also known as _non-voting_ nodes.
What this means is that a read-only node doesn't participate in the Raft consensus system i.e. it doesn't contribute towards quorum, nor does it cast a vote during the leader election process. Just like voting nodes, however, read-only nodes still subscribe to the stream of committed log entries broadcast by the Leader, and update the SQLite database using the log entries they receive from the Leader.
> :warning: **This page is no longer updated. Visit [rqlite.io](https://www.rqlite.io) for the latest docs.**
rqlite supports loading a node directly from two sources, either of which can be used to initialize your system from preexisting SQLite data, or to restore from an existing [node backup](https://github.com/rqlite/rqlite/blob/master/DOC/BACKUPS.md):
- An actual SQLite database file. This is the fastest way to initialize a rqlite node from an existing SQLite database. Even large SQLite databases can be loaded into rqlite in a matter of seconds. This the recommended way to initialize your rqlite node from existing SQLite data. In addition any preexisting SQLite database is completely overwritten by this type of load operation, so it's safe to perform regardless of any data already loaded into your rqlite cluster. Finally, this type of load request can be sent to any node. The receiving node will transparently forward the request to the Leader as needed, and return the response of the Leader to the client. If you would prefer to be explicitly redirected to the Leader, add `redirect` as a URL query parameter.
Philip O'Toole
2 years ago