rjansen

JNI Example (Mac OS)

JNI (Java Native Interface) allows implementing methods in C/C++, and use them in Java.

1. Create JNIExample.java file

class JNIExample {

  // Native method, no body.

rjansen

Kafka Topics

List existing topics

bin/kafka-topics.sh --zookeeper localhost:2181 --list

Describe a topic

bin/kafka-topics.sh --zookeeper localhost:2181 --describe --topic mytopic

Purge a topic

bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic mytopic --config retention.ms=1000

... wait a minute ...

rjansen

With the following code, you can (1) become your own CA, (2) then sign your SSL certificate as a CA. (3) Then import the CA certificate (not the SSL certificate, which goes onto your server) into Chrome/Chromium. (Yes, this works even on Linux.) NB: For Windows, some reports say that openssl must be run with winpty to avoid a crash.

Become a Certificate Authority

Generate private key

openssl genrsa -des3 -out myCA.key 2048

Generate root certificate

openssl req -x509 -new -nodes -key myCA.key -sha256 -days 825 -out myCA.pem

rjansen

Docker - How to cleanup (unused) resources

Once in a while, you may need to cleanup resources (containers, volumes, images, networks) ...

delete volumes

// see: https://github.com/chadoe/docker-cleanup-volumes

$ docker volume rm $(docker volume ls -qf dangling=true)

$ docker volume ls -qf dangling=true | xargs -r docker volume rm

rjansen

How to Change Open Files Limit on OS X and macOS

This text is the section about OS X Yosemite (which also works for macOS Sierra) from https://docs.basho.com/riak/kv/2.1.4/using/performance/open-files-limit/#mac-os-x

The last time i visited this link it was dead (403), so I cloned it here from the latest snapshot in Archive.org's Wayback Machine https://web.archive.org/web/20170523131633/https://docs.basho.com/riak/kv/2.1.4/using/performance/open-files-limit/

Mac OS X

To check the current limits on your Mac OS X system, run:

rjansen

SELECT o.tenant_id,
       o.object_uuid,
       ARRAY(SELECT AS STRUCT os.string_value, os.field_name
             FROM object_string_values AS os
             WHERE os.tenant_id = o.tenant_id AND os.object_type = o.object_type AND os.object_uuid = o.object_uuid) AS string_values,
       ARRAY(SELECT AS STRUCT oi.int_value, oi.field_name
             FROM object_int_values AS oi
             WHERE oi.tenant_id = o.tenant_id AND oi.object_type = o.object_type AND oi.object_uuid = o.object_uuid) AS int_values,
       ARRAY(SELECT AS STRUCT ob.bool_value, ob.field_name
             FROM object_bool_values AS ob