Sunday, April 18, 2021
Micro-FrontEnd
- Iframes
- Through NGINX
- Web Components/Angular Elements
- Angular Libraries
- Monorepos
- Customized Orchestrator
java.lang.OutOfMemoryError: Metaspace
So if you were familiar with PermGen then all you need to know as background is that – whatever was in PermGen before Java 8 (name and fields of the class, methods of a class with the bytecode of the methods, constant pool, JIT optimizations etc) – is now located in Metaspace.
As you can see, Metaspace size requirements depend both upon the number of classes loaded as well as the size of such class declarations. So it is easy to see the main cause for the java.lang.OutOfMemoryError: Metaspace is: either too many classes or too big classes being loaded to the Metaspace.
Classloader Leak
A classloader leak happens when an application is redeployed, but there are lingering instances of the previous deployment’s classes left. These lingering instances prevent their Classes from being garbage collected, which, in turn, prevent the classloaders and all the classes held therein from being collected, too. Here’s an example of that situation:
Apparently, the application starts a thread that cleans up connections. As noble of a goal as it is, the application does not stop the thread on un-deploy, so it keeps hold of the classloader. Cleanup threads and Timer threads are by far the most common reason for the leaks. A simple way of fixing this issue would be to add a shutdown hook by implementing a ServletContextListener:
public class CleanupCleanup implements ServletContextListener {
@Override
public void contextDestroyed(ServletContextEvent sce) {
// Stop the cleanup thread
}
//...
}Java + HTTPS: Unable to Find Valid Certification Path to Requested Target
https://www.baeldung.com/java-import-cer-certificate-into-keystore
From this documentation keytool - Key and Certificate Management Tool, the Changes section at the end of the page says :
Renamed commands:
-import, renamed to -importcert
The keytool has many options but the one we're interested in is importcert which is as straightforward as its name. Since there are usually different entries inside a KeyStore, we'll have to use the alias argument to assign it a unique name:
> keytool -importcert -alias baeldung_public_cert -file baeldung.cer -keystore sample_keystore
> Enter keystore password:
...
> Trust this certificate? [no]: y
> Certificate was added to keystoreFormat Disk in Linux
snap-9df717f4 US Census 1980
-------------------------------
lsblk
df -h
cat /etc/fstab
fdisk -l
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-using-volumes.html
--------------------------------
mount
available/in-use - Status of Volumes
If Snapshot is Encrypted, Volume is also Encrypted
If Snapshot is not-Encrypted, Volume is also unEncrypted
Shred Command
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-using-volumes.html
shred -u filename
shred overrides a File's Value and then removes it - so Restore from Recycle Bin does not happen
[ec2-user ~]$ sudo file -s /dev/xvdf
/dev/xvdf: data
Create a file system on the volume - [Conditional Step]
sudo mkfs -t xfs /dev/xvdf
Javabrains POC - Microservices - Part 2 [ Netflix OSS]
https://jsonplaceholder.typicode.com/posts/
Spring Cloud Azure
Spring Cloud for Amazon Web Services
Spring Cloud GCP
Spring Cloud Netflix [Ribbon, Feign, Eureka]
Spring Cloud Kubernetes
Spring Cloud Gateway
Spring Cloud Circuit Breaker
Spring Cloud Config
Spring Cloud OpenFeign
Spring Cloud Consul
Spring Cloud Vault
Spring Cloud Zookeeper
Feign - Declarative HTTP Client
Eureka - Service Register and Discovery
Ribbon - Client Side Load Balancing
Spring Cloud Netflix features:
Service Discovery: Eureka instances can be registered and clients can discover the instances using Spring-managed beans
Service Discovery: an embedded Eureka server can be created with declarative Java configuration
Circuit Breaker: Hystrix clients can be built with a simple annotation-driven method decorator
Circuit Breaker: embedded Hystrix dashboard with declarative Java configuration
Declarative REST Client: Feign creates a dynamic implementation of an interface decorated with JAX-RS or Spring MVC annotations
Client Side Load Balancer: Ribbon
External Configuration: a bridge from the Spring Environment to Archaius (enables native configuration of Netflix components using Spring Boot conventions)
Router and Filter: automatic registration of Zuul filters, and a simple convention over configuration approach to reverse proxy creation
| Release Train | Boot Version |
|---|---|
2020.0.x aka Ilford | 2.4.x |
2.2.x, 2.3.x (Starting with SR5) | |
2.1.x | |
2.0.x | |
1.5.x | |
1.5.x |
<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-ribbon</artifactId> </dependency>
http://microservice_provider_user/ is not a legal host name.