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#![warn(missing_docs)]
//! The module contains Rust representation of Cassandra consistency levels.
use std::convert::From;
use std::default::Default;
use std::io;
use crate::error;
use crate::frame::{FromBytes, FromCursor, IntoBytes};
use crate::types::*;
/// `Consistency` is an enum which represents Cassandra's consistency levels.
/// To find more details about each consistency level please refer to Cassandra official docs.
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum Consistency {
/// A write must be written to the commit log and memtable on all replica nodes in the cluster
/// for that partition key. Provides the highest consistency
/// and the lowest availability of any other level.
Any,
///
/// A write must be written to the commit log and memtable of at least one replica node.
/// Satisfies the needs of most users because consistency requirements are not stringent.
One,
/// A write must be written to the commit log and memtable of at least two replica nodes.
/// Similar to ONE.
Two,
/// A write must be written to the commit log and memtable of at least three replica nodes.
/// Similar to TWO.
Three,
/// A write must be written to the commit log and memtable on a quorum of replica nodes.
/// Provides strong consistency if you can tolerate some level of failure.
Quorum,
/// A write must be written to the commit log and memtable on all replica nodes in the cluster
/// for that partition key.
/// Provides the highest consistency and the lowest availability of any other level.
All,
/// Strong consistency. A write must be written to the commit log and memtable on a quorum
/// of replica nodes in the same data center as thecoordinator node.
/// Avoids latency of inter-data center communication.
/// Used in multiple data center clusters with a rack-aware replica placement strategy,
/// such as NetworkTopologyStrategy, and a properly configured snitch.
/// Use to maintain consistency locally (within the single data center).
/// Can be used with SimpleStrategy.
LocalQuorum,
/// Strong consistency. A write must be written to the commit log and memtable on a quorum of
/// replica nodes in all data center.
/// Used in multiple data center clusters to strictly maintain consistency at the same level
/// in each data center. For example, choose this level
/// if you want a read to fail when a data center is down and the QUORUM
/// cannot be reached on that data center.
EachQuorum,
/// Achieves linearizable consistency for lightweight transactions by preventing unconditional
/// updates. You cannot configure this level as a normal consistency level,
/// configured at the driver level using the consistency level field.
/// You configure this level using the serial consistency field
/// as part of the native protocol operation. See failure scenarios.
Serial,
/// Same as SERIAL but confined to the data center. A write must be written conditionally
/// to the commit log and memtable on a quorum of replica nodes in the same data center.
/// Same as SERIAL. Used for disaster recovery. See failure scenarios.
LocalSerial,
/// A write must be sent to, and successfully acknowledged by,
/// at least one replica node in the local data center.
/// In a multiple data center clusters, a consistency level of ONE is often desirable,
/// but cross-DC traffic is not. LOCAL_ONE accomplishes this.
/// For security and quality reasons, you can use this consistency level
/// in an offline datacenter to prevent automatic connection
/// to online nodes in other data centers if an offline node goes down.
LocalOne,
/// This is an error scenario either the client code doesn't support it or server is sending
/// bad headers
Unknown,
}
impl Default for Consistency {
fn default() -> Consistency {
Consistency::One
}
}
impl IntoBytes for Consistency {
fn into_cbytes(&self) -> Vec<u8> {
match *self {
Consistency::Any => to_short(0x0000),
Consistency::One => to_short(0x0001),
Consistency::Two => to_short(0x0002),
Consistency::Three => to_short(0x0003),
Consistency::Quorum => to_short(0x0004),
Consistency::All => to_short(0x0005),
Consistency::LocalQuorum => to_short(0x0006),
Consistency::EachQuorum => to_short(0x0007),
Consistency::Serial => to_short(0x0008),
Consistency::LocalSerial => to_short(0x0009),
Consistency::LocalOne => to_short(0x000A),
Consistency::Unknown => to_short(0x0063),
// giving Unknown a value of 99
}
}
}
impl From<i32> for Consistency {
fn from(bytes: i32) -> Consistency {
match bytes {
0x0000 => Consistency::Any,
0x0001 => Consistency::One,
0x0002 => Consistency::Two,
0x0003 => Consistency::Three,
0x0004 => Consistency::Quorum,
0x0005 => Consistency::All,
0x0006 => Consistency::LocalQuorum,
0x0007 => Consistency::EachQuorum,
0x0008 => Consistency::Serial,
0x0009 => Consistency::LocalSerial,
0x000A => Consistency::LocalOne,
_ => Consistency::Unknown,
}
}
}
impl FromBytes for Consistency {
fn from_bytes(bytes: &[u8]) -> error::Result<Consistency> {
try_from_bytes(bytes).map_err(Into::into).map(|b| match b {
0x0000 => Consistency::Any,
0x0001 => Consistency::One,
0x0002 => Consistency::Two,
0x0003 => Consistency::Three,
0x0004 => Consistency::Quorum,
0x0005 => Consistency::All,
0x0006 => Consistency::LocalQuorum,
0x0007 => Consistency::EachQuorum,
0x0008 => Consistency::Serial,
0x0009 => Consistency::LocalSerial,
0x000A => Consistency::LocalOne,
_ => Consistency::Unknown,
})
}
}
impl FromCursor for Consistency {
fn from_cursor(mut cursor: &mut io::Cursor<&[u8]>) -> error::Result<Consistency> {
let consistency_num = CIntShort::from_cursor(&mut cursor)? as i32;
Ok(Consistency::from(consistency_num))
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::frame::traits::{FromBytes, FromCursor, IntoBytes};
use std::io::Cursor;
#[test]
fn test_consistency_into_cbytes() {
assert_eq!(Consistency::Any.into_cbytes(), &[0, 0]);
assert_eq!(Consistency::One.into_cbytes(), &[0, 1]);
assert_eq!(Consistency::Two.into_cbytes(), &[0, 2]);
assert_eq!(Consistency::Three.into_cbytes(), &[0, 3]);
assert_eq!(Consistency::Quorum.into_cbytes(), &[0, 4]);
assert_eq!(Consistency::All.into_cbytes(), &[0, 5]);
assert_eq!(Consistency::LocalQuorum.into_cbytes(), &[0, 6]);
assert_eq!(Consistency::EachQuorum.into_cbytes(), &[0, 7]);
assert_eq!(Consistency::Serial.into_cbytes(), &[0, 8]);
assert_eq!(Consistency::LocalSerial.into_cbytes(), &[0, 9]);
assert_eq!(Consistency::LocalOne.into_cbytes(), &[0, 10]);
assert_eq!(Consistency::Unknown.into_cbytes(), &[0, 99]);
}
#[test]
fn test_consistency_from() {
assert_eq!(Consistency::from(0), Consistency::Any);
assert_eq!(Consistency::from(1), Consistency::One);
assert_eq!(Consistency::from(2), Consistency::Two);
assert_eq!(Consistency::from(3), Consistency::Three);
assert_eq!(Consistency::from(4), Consistency::Quorum);
assert_eq!(Consistency::from(5), Consistency::All);
assert_eq!(Consistency::from(6), Consistency::LocalQuorum);
assert_eq!(Consistency::from(7), Consistency::EachQuorum);
assert_eq!(Consistency::from(8), Consistency::Serial);
assert_eq!(Consistency::from(9), Consistency::LocalSerial);
assert_eq!(Consistency::from(10), Consistency::LocalOne);
assert_eq!(Consistency::from(11), Consistency::Unknown);
}
#[test]
fn test_consistency_from_bytes() {
assert_eq!(Consistency::from_bytes(&[0, 0]).unwrap(), Consistency::Any);
assert_eq!(Consistency::from_bytes(&[0, 1]).unwrap(), Consistency::One);
assert_eq!(Consistency::from_bytes(&[0, 2]).unwrap(), Consistency::Two);
assert_eq!(
Consistency::from_bytes(&[0, 3]).unwrap(),
Consistency::Three
);
assert_eq!(
Consistency::from_bytes(&[0, 4]).unwrap(),
Consistency::Quorum
);
assert_eq!(Consistency::from_bytes(&[0, 5]).unwrap(), Consistency::All);
assert_eq!(
Consistency::from_bytes(&[0, 6]).unwrap(),
Consistency::LocalQuorum
);
assert_eq!(
Consistency::from_bytes(&[0, 7]).unwrap(),
Consistency::EachQuorum
);
assert_eq!(
Consistency::from_bytes(&[0, 8]).unwrap(),
Consistency::Serial
);
assert_eq!(
Consistency::from_bytes(&[0, 9]).unwrap(),
Consistency::LocalSerial
);
assert_eq!(
Consistency::from_bytes(&[0, 10]).unwrap(),
Consistency::LocalOne
);
assert_eq!(
Consistency::from_bytes(&[0, 11]).unwrap(),
Consistency::Unknown
);
}
#[test]
fn test_consistency_from_cursor() {
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 0])).unwrap(),
Consistency::Any
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 1])).unwrap(),
Consistency::One
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 2])).unwrap(),
Consistency::Two
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 3])).unwrap(),
Consistency::Three
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 4])).unwrap(),
Consistency::Quorum
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 5])).unwrap(),
Consistency::All
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 6])).unwrap(),
Consistency::LocalQuorum
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 7])).unwrap(),
Consistency::EachQuorum
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 8])).unwrap(),
Consistency::Serial
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 9])).unwrap(),
Consistency::LocalSerial
);
assert_eq!(
Consistency::from_cursor(&mut Cursor::new(&[0, 10])).unwrap(),
Consistency::LocalOne
);
}
}