feat(strategy): dynamic read write splitting

[wbtlb]

Development Task

Description

Now，Pisa-Proxy has supported static read write splitting strategy. Static strategy depends on config, once datasource status is changed, Pisa-Proxy can't route SQL correctly. In dynamic read write splitting strategy, Pisa-Proxy will probe datasource status and reconcile loadbalance strategy dynamicly.

Implement

In this version, Pisa-proxy will support MHA high availability strategy. Pisa-Proxy will spawn four kind of monitor to probe the status of datasource.The rules match module will fork a thread to recive loadbalance strategy from dynamic read write splitting module by channel.In this module, there are four kind of monitor to probe datasource status.

• Connect Monitor: probe the connectivity of datasource.
• Ping Monitor: probe health status of datasource.
• Lag Monitor: probe the late time between master node and slave node.
• ReadOnly Monitor: probe the role of datasource.

Future Design Chart

Glossary

• Monitor Reconcile: Monitor Reconcile. Get status from monitors and compute final read write splitting strategy.
• Discovery: The kind of discovery, like MHA,RDS,MGR etc.
• Monitor: The kind of Monitor, includes Connect Monitor, Ping Monitor, ReadOnly Monitor, Lag Monitor.

Probe Flow

1. Start Monitor to probe datasource.
2. Probe the connectivity of Master node and Slave node.
3. If connectivity is ok.
   3.1. probe the role of datasource.
   3.2. probe the late time between master node and slave node.
   3.2.1. If slave node is not late from master node, enter next time probe.
   3.2.2. If slave node is late from master node, update the list of loadbalance and enter next time probe.
4. If connectivity is not ok.
   4.1. If probe slave change to master,start Lag probe.
   4.1.1. If slave node is not late from master node, enter next time probe.
   4.1.2. If slave node is late from master node, update the list of loadbalance and enter next time probe.
   4.2.If slave node is not change to master, enter next time probe.

Configuration

param	type	required	default	description
user	string	yes	None	Monitor user name
password	string	yes	None	Monitor password
monitor_period	u64	yes	1000	The interval of Reconcile Monitor update strategy(millisecond)
connect_period	u64	yes	1000	The interval of Connect Monitor probe (millisecond)
connect_timeout	u64	yes	6000	The timeout of Connect Monitor(millisecond)
connect_failure_threshold	u64	yes	3	The max failures times of Connect Monitor probe
ping_period	u64	yes	1000	The interval of Ping Monitor probe(millisecond)
ping_timeout	u64	yes	6000	The timeout of Ping Monitor probe(millisecond)
ping_failure_threshold	u64	yes	3	The max failures times of Ping Monitor probe
replication_lag_period	u64	yes	1000	The interval of Lag Monitor probe(millisecond)
replication_lag_timeout	u64	yes	6000	The timeout of Lag Monitor probe(millisecond)
replication_lag_failure_threshold	u64	yes	3	The max failures of Lag Monitor probe
max_replication_lag	u64	yes	10000	The threshold of Lag Monitor probe(millisecond)
read_only_period	u64	yes	1000	The interval of ReadOnly Monitor probe(millisecond)
read_only_timeout	u64	yes	6000	The timeout of ReadOnly Monitor probe(millisecond)
read_only_failure_threshold	u64	yes	3	The max failures times of ReadOnly Monitor probe

Configuration

Configuration Structure

#[derive(Debug, Serialize, Deserialize, Clone, Default)]
pub struct ReadWriteSplitting {
    #[serde(rename = "static")]
    pub statics: Option<ReadWriteSplittingStatic>,
    pub dynamic: Option<ReadWriteSplitting>
}

#[derive(Debug, Serialize, Deserialize, Clone, Default)]
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct ReadWriteSplittingDynamic {
    pub default_target: TargetRole,
    #[serde(rename = "rule")]
    pub rules: Vec<ReadWriteSplittingRule>,
    pub discovery: Discovery,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
#[serde(rename_all = "lowercase", tag="type")]
pub enum Discovery {
    Mha(MasterHighAvailability),
}

#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Default)]
pub struct MasterHighAvailability {
    pub user: String,
    pub password: String,
    pub pool_size: Option<u8>,
    pub monitor_period: u64,
    pub connect_period: u64,
    pub connect_timeout: u64,
    pub connect_failure_threshold: u64,
    pub ping_period: u64,
    pub ping_timeout: u64,
    pub ping_failure_threshold: u64,
    pub replication_lag_period: u64,
    pub replication_lag_timeout: u64,
    pub replication_lag_failure_threshold: u64,
    pub max_replication_lag: u64,
    pub read_only_period: u64,
    pub read_only_timeout: u64,
    pub read_only_failure_threshold: u64,
}

Configuration Example

[proxy.config.read_write_splitting]

[proxy.config.read_write_splitting.dynamic]
default_target = "readwrite"

[proxy.config.read_write_splitting.dynamic.discovery]
type = "mha"
user = "monitor"
password = "monitor"
pool_size = 16
monitor_period = 1000
connect_period = 2000
connect_timeout = 200
connect_failure_threshold = 3
ping_period = 1000
ping_timeout = 100
ping_failure_threshold = 3
replication_lag_period = 1000
replication_lag_timeout = 3
replication_lag_failure_threshold = 3
max_replication_lag = 3
read_only_period = 1000
read_only_timeout = 3
read_only_failure_threshold = 3

[[proxy.config.read_write_splitting.dynamic.rule]]
name = "write-rule"
type = "regex"
regex = ["^insert"]
target = "readwrite"
algorithm_name = "roundrobin"

[[proxy.config.read_write_splitting.dynamic.rule]]
name = "read-rule"
type = "regex"
regex = ["^select"]
target = "read"
algorithm_name = "roundrobin"

Check List

• Monitor Reconcile.
• configuration.
• Pisa-Controller. @mlycore
• Rules Match dynamic update.
• Connect Monitor.
• Ping Monitor.
• Lag Monitor.
• ReadOnly Monitor.
• com query raw parse. @xuanyuan300

Association Issue #88

[mlycore]

For better understanding, we should use period instead of interval, using failureThreshold instead of MaxFailures`.