Improve/mdc

[testower]

Related to entur/lamassu#250

This adds possibility to provide interceptor for subscription updates. Example implementation from application code:

public class LoggingSubscriptionUpdateInterceptor implements SubscriptionUpdateInterceptor {
    private final FeedProvider feedProvider;

    public LoggingSubscriptionUpdateInterceptor(
            FeedProvider feedProvider
    ) {
        this.feedProvider = feedProvider;
    }
    @Override
    public void beforeUpdate() {
        MDC.put("systemId", feedProvider.getSystemId());
    }

    @Override
    public void afterUpdate() {
        MDC.remove("systemId");
    }
}

Which in turn enables systemId to be logged from log statements within this library by configuring logback as this example shows:

            <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
                <encoder class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">
                    <providers>
                        <pattern>
                            <pattern>
                                {
                                    "serviceContext": {
                                        "service": "lamassu"
                                    },
                                    "mdc": {
                                        "systemId": "%X{systemId}"
                                    },
                                    "message": "%message\n%ex{full}",
                                    "severity": "%level",
                                    "reportLocation": {
                                        "filePath": "%logger",
                                        "lineNumber": "%line",
                                        "functionName": "%method"
                                    }
                                }
                            </pattern>
                        </pattern>
                    </providers>
                </encoder>
            </appender>

[testower]

I wonder if there's some sort of best practice for adding stuff to MDC from libraries. Maybe namespacing?

[testower]

These may also be relevant:

https://stackoverflow.com/questions/6073019/how-to-use-mdc-with-thread-pools
https://talktotheduck.dev/logging-best-practices-mdc-ingestion-and-scale#heading-plan-for-failure-eg-custom-thread-pool

[testower]

One way to improve this is to add some lifecycle hooks or interceptors to the subscription, so that the application can make the MDC calls in stead of the library code.

[hbruch]

Calling the updateInterceptor in the update method does not support the intended use case to have a the system_id logged in case of exceptions, as exception logging occurs after update() was called and hence the externally set MDC is cleared already.

Possible solution could be to add beforeUpdate/afterUpdate as lifecycle methods to the GBFSSubscription classes and let them be called by the GBFSSubscriptionManager before/after calling update, e.g. like this

public void update() {
    subscriptions
      .values()
      .parallelStream()
      .forEach(subscription ->
        Optional
          .ofNullable(customThreadPool)
          .orElse(ForkJoinPool.commonPool())
          .execute(() -> this.update(subscription))
      );
  }

  public void update(GbfsSubscription subscription) {
    try {
      subscription.beforeUpdate();
      subscription.update();
    } catch (RuntimeException e) {
      LOG.error("Error updating subscription", e);
    } finally {
      subscription.afterUpdate();
    }
  }

[sonarcloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
86.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud