Pavel Fomin pavelfomin

Kubernetes Probes: Readiness, Liveness, Startup

Probe	Question it answers	Failure action	Endpoint here
startup	Has the app finished booting?	Kill & restart the container (only after the budget is exhausted)	`/actuator/health/liveness`
liveness	Is the app wedged and unrecoverable?	Kill & restart the container	`/actuator/health/liveness`
readiness	Can the app serve traffic right now?	Remove pod from Service endpoints (no restart)	`/actuator/health/readiness`

Key rule: **only liveness and startup restart the container. Readiness never

Spring Boot 3.5.8 added a docker-java.properties file into their jar causing the testcontainers to look for the Docker API version of 1.44 or higher. If your Docker environment does not support API 1.44, try upgrading it.

If for any reason you cannot upgrade your Docker environment, affected users can add this file to their local development environment as a temporary workaround, without committing it to the repository, until they are able to upgrade their Docker environment.

One way to do this is to maintain a single version of the file and create symlinks in the affected repos

create the file locally
- echo "api.version=1.41" > ~/docker-java.properties
in every affected repo

OAuth 2.0 Resource Server JWT :: Spring Security
Common Application Properties :: Spring Boot
OAuth2ResourceServerJwtConfiguration
Note. It does not use org.springframework.security.oauth2.jwt.JwtAudienceValidator class

A Mathematical Explanation for Why Knowledge Transfer Is Difficult

If we accept the classic equation knowledge = power, then by substitution, knowledge transfer becomes power transfer. In disciplines like physics, engineering, and especially politics, transferring power is rarely simple — it often involves resistance, inefficiency, and loss.

Ran into an issue with flyway script executing an alter table statement while Postgres auto-vacuum for the same table was in progress. As tables grow, Postgres runs the auto-vacuum for tables periodically. The flyway script was stuck waiting for the table lock to be released. To avoid this issue, one can disable the auto-vacuum before the flyway migration and re-enable it after migration is finished using beforeMigrate.sql and afterMigrate.sql.

Occasionally it can be helpful to parameterize a migration depending on an environment. Flyway supports the concept of placeholders to help with that.

Flyway provides default placeholders, whose values are automatically populated:

${flyway:defaultSchema} = The default schema for Flyway
${flyway:user} = The user Flyway will use to connect to the database
${flyway:database} = The name of the database from the connection url
${flyway:timestamp} = The time that Flyway parsed the script, formatted as 'yyyy-MM-dd HH:mm:ss'

	@Configuration
	public class KafkaConfig {

	@Bean
	public NewTopic fooTopic(@Value("${app.topics.fooTopic}") String topic) {
	return TopicBuilder.name(topic)
	.partitions(8)
	.build();
	}

	import com.fasterxml.jackson.annotation.JsonProperty;
	import com.fasterxml.jackson.annotation.JsonTypeInfo;
	import org.javers.core.ChangesByCommit;
	import org.javers.core.diff.Change;
	import org.javers.core.json.BasicStringTypeAdapter;
	import org.javers.core.json.typeadapter.util.UtilTypeCoreAdapters;
	import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
	import org.springframework.context.annotation.Bean;
	import org.springframework.context.annotation.Configuration;
	import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

	import org.springframework.boot.task.ThreadPoolTaskExecutorBuilder;
	import org.springframework.context.annotation.Bean;
	import org.springframework.context.annotation.Configuration;
	import org.springframework.core.task.AsyncTaskExecutor;
	import org.springframework.security.task.DelegatingSecurityContextAsyncTaskExecutor;

	@Configuration
	public class AsyncTaskExecutorConfiguration {

	/**

	import com.droidablebee.avro.BlueEvent;
	import com.droidablebee.avro.GreenEvent;
	import org.apache.avro.specific.SpecificRecord;
	import org.apache.kafka.clients.consumer.ConsumerRecord;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;
	import org.springframework.kafka.annotation.KafkaListener;
	import org.springframework.messaging.MessageHeaders;
	import org.springframework.stereotype.Service;