Author: Lisa

JPA/Hibernate Naming Strategies

One of the challenges of inheriting support of systems and code is reverse engineering what exactly you’ve got. In this case, I have Java code that reads from a Postgresql table named calculation_config & populates the information into a Redis cache. Except I could not find any text containing the string calculation_config. Started to wonder if grep was getting thrown off by line splits (although splitting a line in the middle of a table name is asking for future confusion), so was searching for sub-strings.

Which got me to the code that performs the operation — but the table is absolutely named calculationConfig in the code. ?????

package com.example.applicationmodel;
import lombok.Data;

import jakarta.persistence.*;

@Entity // This tells Hibernate to make a table out of this class
@Data // Lombok: adds getters and setters
@Table(name = "calculationConfig", schema = "components")
public class CalculationInfo {
    @Id
    private int functionId;
    private String dataCollectionGroup;
    private String component;
    private String metricInputs;
    private String metricName;
    private String functionDef;
    private String resourceType;
    private String metricDatatype;
    private String deviceModel;
    private String collectionSystem;
    private int status;
}

And today, I’ve learned about “naming strategies”. A mechanism used by the Hibernate ORM (Object-Relational Mapping) framework to map entities within Java code to table and column names. Other than obfuscation, why are we applying middleware principals to code?? Ostensibly because database naming “best practices” and code naming “best practices” vary. As an aside, I was taught the best naming best practice was one someone was likely to figure out with minimal confusion or research. Explicitly indicating the naming strategy might fit that requirement — ohh, here’s some strange name mapping thing in my code. Let me see what that means.

By default, Hibernate uses ImplicitNamingStrategy and PhysicalNamingStrategy to map Java names to database names. The default PhysicalNamingStrategyStandardImpl converts camelCase to snake_case.

So, for future reference … when I find table_name or field_name in my database, I should be grepping for tableName and fieldName in the code. That is … not super obvious.

Black Raspberry Coulis

To go with our smoked lamb, I made a coulis with maple syrup and black raspberries Anya picked and froze last year. Easy recipe — a pint of black raspberries (thawed) and about 1/3 cup of maple syrup (this would be a “to taste” kind of thing!). Boil for about ten minutes to break down the berries a bit, run it all through a blender, then use fine mesh cloth to strain out the seeds. It will set up as a jam once it cools, but it’s a nice sauce to drizzle over food whilst it is still hot.

Brisket

We smoked a brisket and lamb shoulder this weekend — basic salt & pepper rub, smoked with fruit wood, then brought inside to finish cooking. We’re going to order some butcher paper to see what that’s like because wrapping it always gets the bark soggy!

Hazelnuts – 2024

The hazelnuts are just starting to form — it looks like we’ve got nuts developing on the newer plants on the north side too. As far as propagating plants, I’ve pretty well established that dropping a woody cutting in willow water doesn’t work. Dropping a green cutting in water doesn’t work. Next, I’m going to try a green cutting in soil and air layering. I’ve found a few places online that say air layering worked … even if it looks a little odd having bundles of soil wrapped around the branches of your shrubbery.

OpenZFS On RedHat 8 (From Package)

This process presumes you have generated a signing key (/root/signing/MOK.priv and /root/signing/MOK.der) that has been registered for signing modules.

################################################################################
## Install from Repo and Sign Modules
################################################################################
yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
yum install kernel-devel

# Install kmod version of ZS
yum install https://zfsonlinux.org/epel/zfs-release-2-3$(rpm --eval "%{dist}").noarch.rpm
dnf config-manager --disable zfs
dnf config-manager --enable zfs-kmod
yum install zfs

# And autoload
echo zfs >/etc/modules-load.d/zfs.conf

# Use rpm -ql to list out the kernel modules that this version of ZFS uses -- 2.1.x has quite a few of them, and they each need to be signed
# Sign zfs.ko and spl.ko in current kernel
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/$(uname -r)/weak-updates/zfs/zfs/zfs.ko
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/$(uname -r)/weak-updates/zfs/spl/spl.ko
# And sign the bunch of other ko files in the n-1 kernel rev (these are symlinked from the current kernel)
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/avl/zavl.ko
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/icp/icp.ko
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/lua/zlua.ko
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/nvpair/znvpair.ko
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/unicode/zunicode.ko
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/common/zcommon.ko
/usr/src/kernels/$(uname -r)/scripts/sign-file sha256 /root/signing/MOK.priv /root/signing/MOK.der /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/zstd/zzstd.ko

# Verify they are signed now
modinfo -F signer /usr/lib/modules/$(uname -r)/weak-updates/zfs/zfs/zfs.ko
modinfo -F signer /usr/lib/modules/$(uname -r)/weak-updates/zfs/spl/spl.ko

modinfo -F signer /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/avl/zavl.ko
modinfo -F signer /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/icp/icp.ko
modinfo -F signer /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/lua/zlua.ko
modinfo -F signer /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/nvpair/znvpair.ko
modinfo -F signer /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/unicode/zunicode.ko
modinfo -F signer /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/zcommon/zcommon.ko
modinfo -F signer /lib/modules/4.18.0-513.18.1.el8_9.x86_64/extra/zfs/zstd/zzstd.ko

# Reboot
init 6

# And we've got ZFS, so create the pool
zpool create pgpool sdc
zfs create zpool/zdata
zfs set compression=lz4 zpool/zdata

zfs get compressratio zpool/zdata
zfs set mountpoint=/zpool/zdata zpool/zdata

What happens if you only sign zfs.ko? All sorts of errors that look like there’s some sort of other problem — zfs will not load. It will tell you the required key is not available

May 22 23:42:44 sandboxserver systemd-modules-load[492]: Failed to insert 'zfs': Required key not available

Using insmod to try to manually load it will tell you there are dozens of unknown symbols:

May 22 23:23:23 sandboxserver kernel: zfs: Unknown symbol ddi_strtoll (err 0)
May 22 23:23:23 sandboxserver kernel: zfs: Unknown symbol spl_vmem_alloc (err 0)
May 22 23:23:23 sandboxserver kernel: zfs: Unknown symbol taskq_empty_ent (err 0)
May 22 23:23:23 sandboxserver kernel: zfs: Unknown symbol zone_get_hostid (err 0)
May 22 23:23:23 sandboxserver kernel: zfs: Unknown symbol tsd_set (err 0)

But the real problem is that there are unsigned modules so … there are unknown symbols. But not because something is incompatible. Just because the module providing that symbol will not load.