This example shows how to set up Coherence CE 22.06.8 on a Raspberry Pi-4B using the Coherence CLI and setting it to auto-start on boot.
I was helping a colleague of mine setup Coherence on a Pi for storing state for Python programs and thought this may be a good alternative from a docker image.
Note 1. The Python client requires Coherence gRPC proxy dependencies to be able to start gGRPC proxy for the client to connect.
Note 2. This example just starts a single Coherence cache server to minimize memory overhead, but you could start multiple to allow for cluster HA. See the end of the readme for more details.
- A Raspberry Pi setup and connected to the Internet, that's all!
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Login as
piand run the following to install Java 17 and Maven.sudo apt install openjdk-17-jdk maven
mvn --version
Output:
Apache Maven 3.8.7 Maven home: /usr/share/maven Java version: 17.0.10, vendor: Debian, runtime: /usr/lib/jvm/java-17-openjdk-arm64 Default locale: en_GB, platform encoding: UTF-8 OS name: "linux", version: "6.6.20+rpt-rpi-v8", arch: "aarch64", family: "unix"
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Install the Coherence CLI
curl -sL https://raw.githubusercontent.com/oracle/coherence-cli/main/scripts/install.sh | bashOutput:
Installing Coherence CLI 1.6.1 for Linux/aarch64 into /usr/local/bin ... Using 'sudo' to mv cohctl binary to /usr/local/bin To uninstall the Coherence CLI execute the following: sudo rm /usr/local/bin/cohctl
cohctl version | bashpi@pi-4b:~ $ cohctl version Coherence Command Line Interface CLI Version: 1.6.1 Date: 2024-04-17T03:46:43Z Commit: 7e869a55e06476de92940b0f8b2887100d7921b0 OS: linux Architecture: arm64 Go Version: go1.20.14 -
Create a Profile to set the gRPC port
cohctl set profile grpc -v "-Dcoherence.grpc.server.port=1408" -y cohctl get profiles
Output:
PROFILE VALUE grpc -Dcoherence.grpc.server.port=1408
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Create a minimal cache config to reduce what is started
Create the file
/home/pi/pi-cache-config.xmlwith the following contents:<?xml version="1.0"?> <!-- Minimal cache config. --> <cache-config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.oracle.com/coherence/coherence-cache-config" xsi:schemaLocation="http://xmlns.oracle.com/coherence/coherence-cache-config coherence-cache-config.xsd"> <caching-scheme-mapping> <cache-mapping> <cache-name>*</cache-name> <scheme-name>server</scheme-name> </cache-mapping> </caching-scheme-mapping> <caching-schemes> <distributed-scheme> <scheme-name>server</scheme-name> <service-name>PartitionedCache</service-name> <backing-map-scheme> <local-scheme> <unit-calculator>BINARY</unit-calculator> </local-scheme> </backing-map-scheme> <autostart>true</autostart> </distributed-scheme> </caching-schemes> </cache-config>
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Create the Cluster
For this simple cluster we are creating and starting only 1 member. You can adjust the memory if you require more.
cohctl create cluster local -v 22.06.8 -P grpc -r 1 -M 256m -a coherence-grpc-proxy --cache-config /home/pi/pi-cache-config.xmlNote: The required Maven dependencies will be downloaded and the cluster started. This may take a short while.
Output:
Checking 4 Maven dependencies... - com.oracle.coherence.ce:coherence:22.06.8 - com.oracle.coherence.ce:coherence-grpc-proxy:22.06.8 - com.oracle.coherence.ce:coherence-json:22.06.8 - org.jline:jline:3.25.0 Starting 1 cluster members for cluster local Starting cluster member storage-0... Current context is now local Cluster added and started
After a 5-10 seconds, check the status of the cluster using:
cohctl get members
Output:
Using cluster connection 'local' from current context. Total cluster members: 1 Storage enabled count: 1 Departure count: 0 Cluster Heap - Total: 256 MB Used: 29 MB Available: 227 MB (88.7%) Storage Heap - Total: 256 MB Used: 29 MB Available: 227 MB (88.7%) NODE ID ADDRESS PORT PROCESS MEMBER ROLE STORAGE MAX HEAP USED HEAP AVAIL HEAP 1 /127.0.0.1 38975 2377 storage-0 CoherenceServer true 256 MB 29 MB 227 MB
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Setting the cluster to start on boot
As the
piuser, not sudo, issue the following:crontab -e
Add the following to the end of file and save:
@reboot /usr/local/bin/cohctl start cluster local -r 1 -M 256m -P grpcRestart you Pi by using the following:
sudo shutdown -r now
Once the Pi restarts, login again the use following command to verify the cluster is running:
cohctl get members
Output:
Using cluster connection 'local' from current context. Total cluster members: 1 Storage enabled count: 1 Departure count: 0 Cluster Heap - Total: 256 MB Used: 29 MB Available: 227 MB (88.7%) Storage Heap - Total: 256 MB Used: 29 MB Available: 227 MB (88.7%) NODE ID ADDRESS PORT PROCESS MEMBER ROLE STORAGE MAX HEAP USED HEAP AVAIL HEAP 1 /127.0.0.1 38975 2377 storage-0 CoherenceServer true 256 MB 29 MB 227 MB
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Log file locations
Issue the following if you wish to see the log files.
ls -l ~/.cohctl/logs/localOutput:
total 16 -rw-r--r-- 1 pi pi 13060 Apr 18 16:26 storage-0.log
You can issue the following to stop the cluster:
cohctl stop cluster local -yYou can issue the following to restart the cluster:
cohctl start cluster local -r 1 -M 256m -P grpcYou can issue the following to scale the cluster to 2 nodes. (We do not use the grpc profile as we only have one member exposing this port)
cohctl scale cluster local -r 2 -M 256mAfter a shot time you can issue the following command to view the members:
cohctl get membersOutput:
Using cluster connection 'local' from current context.
Total cluster members: 2
Storage enabled count: 2
Departure count: 0
Cluster Heap - Total: 512 MB Used: 88 MB Available: 424 MB (82.8%)
Storage Heap - Total: 512 MB Used: 88 MB Available: 424 MB (82.8%)
NODE ID ADDRESS PORT PROCESS MEMBER ROLE STORAGE MAX HEAP USED HEAP AVAIL HEAP
1 /127.0.0.1 39533 739 storage-0 CoherenceServer true 256 MB 72 MB 184 MB
2 /127.0.0.1 32835 1221 storage-1 CoherenceServer true 256 MB 16 MB 240 MB