Struct MySqlElection

pub struct MySqlElection {
    leader_value: String,
    client: Mutex<ElectionMysqlClient>,
    is_leader: AtomicBool,
    leader_infancy: AtomicBool,
    leader_watcher: Sender<LeaderChangeMessage>,
    store_key_prefix: String,
    candidate_lease_ttl: Duration,
    meta_lease_ttl: Duration,
    sql_set: ElectionSqlSet,
}

MySQL implementation of Election.

Fields

leader_value: String

client: Mutex<ElectionMysqlClient>

is_leader: AtomicBool

leader_infancy: AtomicBool

leader_watcher: Sender<LeaderChangeMessage>

store_key_prefix: String

candidate_lease_ttl: Duration

meta_lease_ttl: Duration

sql_set: ElectionSqlSet

Implementations

impl MySqlElection

pub async fn with_mysql_client( leader_value: String, client: ElectionMysqlClient, store_key_prefix: String, candidate_lease_ttl: Duration, meta_lease_ttl: Duration, table_name: &str, ) -> Result<ElectionRef>

fn election_key(&self) -> String

fn candidate_root(&self) -> String

fn candidate_key(&self) -> String

async fn maybe_init_client(&self) -> Result<()>

impl MySqlElection

async fn get_value_with_lease( &self, key: &str, executor: &mut Executor<'_>, ) -> Result<Option<Lease>>

Returns value, expire time and current time.

async fn get_value_with_lease_by_prefix( &self, key_prefix: &str, executor: &mut Executor<'_>, ) -> Result<(Vec<(String, Timestamp)>, Timestamp)>

Returns all values and expire time with the given key prefix. Also returns the current time.

async fn update_value_with_lease( &self, key: &str, prev: &str, updated: &str, lease_ttl: u64, executor: &mut Executor<'_>, ) -> Result<()>

async fn put_value_with_lease( &self, key: &str, value: &str, lease_ttl_secs: u64, executor: &mut Executor<'_>, ) -> Result<bool>

Returns true if the insertion is successful

async fn delete_value( &self, key: &str, executor: &mut Executor<'_>, ) -> Result<bool>

Returns true if the deletion is successful. Caution: Should only delete the key if the lease is expired.

async fn do_campaign(&self) -> Result<()>

Attempts to acquire leadership by executing a campaign. This function continuously checks if the current lease is still valid.

async fn renew_lease(&self, executor: Executor<'_>, lease: Lease) -> Result<()>

Renew the lease

fn lease_check(&self, lease: &Option<Lease>) -> Result<Lease>

Performs a lease check during the election process.

This function performs the following checks and actions:

• Case 1: If the current instance is not the leader but the lease has expired, it raises an error to re-initiate the campaign. If the leader failed to renew the lease, its session will expire and the lock will be released.
• Case 2: If all checks pass, the function returns without performing any actions.

async fn step_down_without_lock(&self) -> Result<()>

Still consider itself as the leader locally but failed to acquire the lock. Step down without deleting the key.

async fn elected( &self, executor: Executor<'_>, expected_lease: Option<Lease>, ) -> Result<()>

Elected as leader. The leader should put the key and notify the leader watcher. Caution: Should only elected while holding the lock.

Trait Implementations

impl Election for MySqlElection

type Leader = LeaderValue

fn is_leader(&self) -> bool

Returns true if current node is the leader.

fn in_leader_infancy(&self) -> bool

When a new leader is born, it may need some initialization operations (asynchronous), this method tells us when these initialization operations can be performed.

fn register_candidate<'life0, 'life1, 'async_trait>( &'life0 self, node_info: &'life1 MetasrvNodeInfo, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait,

Registers a candidate for the election.

fn all_candidates<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Result<Vec<MetasrvNodeInfo>>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Gets all candidates in the election.

fn campaign<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Campaign waits to acquire leadership in an election.

fn reset_campaign<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = ()> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Resets the campaign.

fn leader<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Result<Self::Leader>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Returns the leader value for the current election.

fn resign<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Releases election leadership so other campaigners may acquire leadership on the election.

fn subscribe_leader_change(&self) -> Receiver<LeaderChangeMessage>