[jira] [Created] (KYLIN-5229) PropertiesDelegate introduce lock to KylinConfig

[Xiaoxiang Yu (Jira)]

Xiaoxiang Yu created KYLIN-5229:
-----------------------------------

             Summary: PropertiesDelegate introduce lock to KylinConfig
                 Key: KYLIN-5229
                 URL: https://issues.apache.org/jira/browse/KYLIN-5229
             Project: Kylin
          Issue Type: Sub-task
          Components: Metadata
            Reporter: Xiaoxiang Yu
             Fix For: 5.0-alpha
         Attachments: image-2022-08-17-13-17-40-751.png

h2. Background

Kylin 5.0 dev team plans to add new feature which supports reading config entry 
from external Config Server(such as Nacos) other than local kylin.properties. 
So we add {{PropertiesDelegate}} and {{IExternalConfigLoader}} to support this 
request.
h2. Issue

{{PropertiesDelegate }}introduces performance downgrade because it add lock to 
{{{}KylinConfigBase#getOptional{}}}, impact query concurrency badly, from 
Yanghong Team's load testing result, query concurrency change from 60 to 3.
h2. Root Cause

 
{code:java}
 protected String getOptional(String prop, String dft) {
    final String property = System.getProperty(prop);
    return property != null ? getSubstitutor().replace(property)
            : getSubstitutor().replace(properties.getProperty(prop, dft)); // 
Step 1
}
 
protected StrSubstitutor getSubstitutor() {
    // overrides > env > properties
    final Map<String, Object> all = Maps.newHashMap();
    all.putAll((Map) properties); // Step 2
    all.putAll(STATIC_SYSTEM_ENV);
    all.putAll(overrides);
    return new StrSubstitutor(all);
}


@Override
public Set<Map.Entry<Object, Object>> entrySet() {
    return getAllProperties().entrySet(); // Step 3
}



private synchronized Properties getAllProperties() { // Step4, synchronized     
    Properties propertiesView = new Properties();
    if (this.configLoader != null) {
        propertiesView.putAll(this.configLoader.getProperties());
    }
    propertiesView.putAll(this.properties);
    return propertiesView;
} {code}
 
h2. Screenshots

Java Stack of Query Thread:

!image-2022-08-17-13-16-25-721.png!



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