Hare User Guide

What Hare does?

1. Configures Motr object store.
2. Starts/stops Motr services.
3. Notifies Motr of service and device faults.

Hare implementation uses Consul key-value store and health-checking mechanisms.

Installation

Building from source

• Download hare.

  git clone https://github.com/Seagate/cortx-hare.git hare
  cd hare

• Install Python (≥ 3.6), libraries and header files needed to compile Python extensions.

  sudo yum -y install python3 python3-devel

• Install Consul.

  sudo yum -y install yum-utils
  sudo yum-config-manager --add-repo https://rpm.releases.hashicorp.com/RHEL/hashicorp.repo
  sudo yum -y install consul-1.9.1

• Build and Install Motr.

  • Follow Motr quick start guide to build Motr from source. After compiling Motr sources, please continue with the below steps to build Hare using Motr sources.

    sudo scripts/install-motr-service --link
    
    export M0_SRC_DIR=$PWD
    cd -

• Build and install hare.

  make
  sudo make install

• Add current user to hare group.

  sudo usermod --append --groups hare $USER

  Log out and log back in.

Build and install rpms from source

NOTE: If you have built Motr and HARE from sources you need not generate RPM packages as below, however, it might be more convenient to build and install rpms on a multinode setup sometimes

• Build Motr RPMs

  • From sources

    git clone --recursive https://github.com/Seagate/cortx-motr.git
    cd cortx-motr
    
    scripts/m0 make rpms
    sudo rpm -ivh ~/rpmbuild/RPMS/x86_64/cortx-motr-*.rpm

• Build hare RPMs

  • Download hare source as mentioned above

    cd hare
    make rpm
    sudo rpm -ivh ~/rpmbuild/RPMS/x86_64/cortx-hare-*.rpm

Quick start

☑️ Checklist

Before starting the cluster as <user> at <origin> machine, ensure that

#	Check	Where
1	passwordless sudo works for <user>	all machines
2	<user> can ssh from <origin> to other machines	<origin>
3	cortx-hare and cortx-s3server RPMs are installed	all machines
4	/opt/seagate/cortx/hare/bin is in <user>'s PATH	all machines
5	<user> is a member of hare group	all machines
6	CDF exists and corresponds to the actual cluster configuration	<origin>

Prepare the CDF

If you are starting the cluster for the first time, you will need a cluster description file (CDF).

See cfgen --help-schema for the description of CDF format.

You can make a copy of /opt/seagate/cortx/hare/share/cfgen/examples/singlenode.yaml (single-node setup) or /opt/seagate/cortx/hare/share/cfgen/examples/ldr1-cluster.yaml (dual-node setup) and edit it as necessary.

cp /opt/seagate/cortx/hare/share/cfgen/examples/singlenode.yaml ~/CDF.yaml
vi ~/CDF.yaml

You will probably need to modify host, data_iface, and io_disks values.

data_iface

• Make sure that data_iface value refers to existing network interface (it should be present in the output of ip a command).

• This network interface must be configured for LNet. If you can see its IP address in the output of sudo lctl list_nids command, you are all set. Otherwise, configure LNet by executing this code snippet on each node:

  IFACE=eth1  # XXX `data_iface` value from the CDF
  sudo tee /etc/modprobe.d/lnet.conf <<< \
      "options lnet networks=tcp($IFACE) config_on_load=1"

io_disks

• Devices specified in io_disks section must exist.

• Sometimes it is convenient to use loop devices instead of actual disks:

  sudo mkdir -p /var/motr
  for i in {0..9}; do
      sudo dd if=/dev/zero of=/var/motr/disk$i.img bs=1M seek=9999 count=1
      sudo losetup /dev/loop$i /var/motr/disk$i.img
  done

Hare we go

• Start the cluster.

  hctl bootstrap --mkfs ~/CDF.yaml

• Run I/O test.

  /opt/seagate/cortx/hare/libexec/m0crate-io-conf >/tmp/m0crate-io.yaml
  dd if=/dev/urandom of=/tmp/128M bs=1M count=128
  sudo m0crate -S /tmp/m0crate-io.yaml

  Please note that m0crate will run as shown above when it will be available in default system PATH which will be the case when setup is created using RPMs. If its created by building Motr source code, then m0crate utility can be run using full path from the motr source directory (say MOTR_SRC). ./MOTR_SRC/motr/m0crate/m0crate

• Stop the cluster.

  hctl shutdown

Reporting problems

To request changes or report a bug, please log an issue and describe the problem you are facing.

When reporting a bug, consider running

hctl reportbug

to collect forensic data. Run this command on every node of the cluster and attach generated files to the GitHub issue.

Troubleshooting

LNet is not configured

• To check, run

  sudo lctl list_nids

  This command should show network identifiers.

• If it doesn't, try to start LNet manually:

  sudo modprobe lnet
  sudo lctl network up

  Run sudo lctl list_nids again.

• Still no luck? Perhaps /etc/modprobe.d/lnet.conf file is missing or corrupted. Create it with these commands:

  IFACE=eth1  # XXX `data_iface` value from the CDF
  sudo tee /etc/modprobe.d/lnet.conf <<< \
      "options lnet networks=tcp($IFACE) config_on_load=1"

  Try to start LNet one more time.

RC Leader cannot be elected

If hctl bootstrap cannot complete and keeps printing dots..........

2020-01-14 10:57:25: Generating cluster configuration... Ok.
2020-01-14 10:57:26: Starting Consul server agent on this node.......... Ok.
2020-01-14 10:57:34: Importing configuration into the KV Store... Ok.
2020-01-14 10:57:35: Starting Consul agents on remaining cluster nodes... Ok.
2020-01-14 10:57:35: Update Consul agents configs from the KV Store... Ok.
2020-01-14 10:57:36: Install Motr configuration files... Ok.
2020-01-14 10:57:36: Waiting for the RC Leader to get elected..................[goes on forever]

try these commands

hctl shutdown
sudo systemctl reset-failed hare-hax

and bootstrap again.

See also

• Hare RFCs
• Hare wiki