Container

A lot of boilerplate code is written when developers need to test their applications with different connected systems like databases, stream platforms and other collaborators. Docker allows to handle those dependencies but there is still some glue code required to bind the container’s lifecycle and the configuration to the concrete integration test. Testcontainers is a testing library that offers lightweight throwaway instances of anything able to run in a Docker container, with bindings to configure the specific containers and also provides wrappers to manage our own custom containers. ...

When implementing distributed systems, client-server architectures and simple applications with network related functionalities, everything is fine when we’re in the development or in the testing stage because the network is reliable and the communicating systems are not as stressed as they are in production. But to sleep well we want to validate how resilient we have implemented our systems, how they behave when the network fails, the latency rises, the bandwidth is limited, connections time out and so on. ...

Restrict Network Can be useful when using a third-party image that we do not trust Run with no network docker run --network none <image> Run with private isolated network At least containers attached to this network can talk with another docker network create --internal my_isolated_network docker run --network my_isolated_network <image> Block using firewall e.g. using iptables or ipfw # Get container's IP docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' <container_name> # Block all outbound connections from that IP sudo iptables -I DOCKER-USER -s <container_ip> -j DROP ...

Common operations Add Helm Repository helm repo add NAME URL e.g. for the Bitnami repository: helm repo add bitnami https://charts.bitnami.com/bitnami 1 ↵ "bitnami" has been added to your repositories List Repositories helm repo list 130 ↵ NAME URL bitnami https://charts.bitnami.com/bitnami Searching in a Helm Repository helm search repo wordpress NAME CHART VERSION APP VERSION DESCRIPTION bitnami/wordpress 15.2.30 6.1.1 WordPress is the world's most popular blogging ... bitnami/wordpress-intel 2.1.31 6.1.1 DEPRECATED WordPress for Intel is the most popu... ...

Start an Image with kcat / kafka-cat for Debugging kubectl -n NAMESPACE run "$(whoami)-debug" -it --rm \ --image=confluentinc/cp-kafkacat:6.1.9 \ --restart=Never \ -- bash Dockerfile for Kafka Analysis Container with different Tools With jq, kafka console tools, schema registry tools and kafkacat installed …​. Dockerfile FROM confluentinc/cp-kafka:6.2.1 as cp-kafka FROM confluentinc/cp-schema-registry:6.2.1 as cp-schema-registry FROM debian:10-slim ARG DEBIAN_FRONTEND=noninteractive # Install necessary tools RUN apt-get update && apt-get install -y \ curl \ jq \ yq \ && rm -rf /var/lib/apt/lists/* # Install kafkacat binary RUN apt-get update && apt-get install -y kafkacat && rm -rf /var/lib/apt/lists/* # Copy Kafka binaries COPY --from=cp-kafka /usr/bin/kafka-* /usr/bin/ COPY --from=cp-schema-registry /usr/bin/schema-registry* /usr/bin/ # Copy entrypoint script COPY entrypoint.sh /usr/bin/entrypoint.sh RUN chmod +x /usr/bin/entrypoint.sh ENTRYPOINT ["/usr/bin/entrypoint.sh"] ...

Administration & Configuration Connections Show Max Connections (value and source) SELECT setting, source, sourcefile, sourceline FROM pg_settings WHERE name = 'max_connections'; Set Max Connections ALTER system SET max_connections = 250; Kill Connections for a Database SELECT pg_terminate_backend(pid) FROM pg_catalog.pg_stat_activity -- we don't want to kill our own connection WHERE pid != pg_backend_pid() -- we don't want to kill connections to other databases AND datname = 'MYDATABASE' Show Statement Timeout Settings for All Users SELECT r.rolname, (SELECT unnest(s.setconfig) FROM pg_db_role_setting s WHERE s.setrole = r.oid AND s.setconfig::text LIKE '%statement_timeout%' LIMIT 1) AS statement_timeout FROM pg_roles r WHERE r.rolcanlogin ORDER BY r.rolname; ...