[HBASE-11686] Shell code should create a binding / irb workspace instead of polluting the root namespace

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1, 2.4.0
• Component/s: shell
• Hadoop Flags: Incompatible change, Reviewed

Release Note

In shell, all HBase constants and commands have been moved out of the top-level and into an IRB Workspace. Piped stdin and scripts passed by name to the shell will be evaluated within this workspace. If you absolutely need the top-level definitions, use the new compatibility flag, ie. hbase shell --top-level-defs or hbase shell --top-level-defs script2run.rb.

• Assignee: Elliot Miller
• Reporter: Sean Busbey
• Created: 06/Aug/14 18:59
• Updated: 17/Jun/22 06:12
• Resolved: 31/Jul/20 13:40

Description

Right now, the shell builds a list of commands and then injects them into the root exectution's context

bin/hirb.rb

# Add commands to this namespace
@shell.export_commands(self)

hbase-shell/src/main/ruby/shell.rb

    def export_commands(where)
      ::Shell.commands.keys.each do |cmd|
        # here where is the IRB namespace
        # this method just adds the call to the specified command
        # which just references back to 'this' shell object
        # a decently extensible way to add commands
        where.send :instance_eval, <<-EOF
          def #{cmd}(*args)
            ret = @shell.command('#{cmd}', *args)
            puts
            return ret
          end
        EOF
      end
    end

This is an unclean abstraction. For one, it requires that there be an instance variable in the main namespace called '@shell' without making that clear in the docs. Additionally, it complicates maintenance by breaking isolation.

We should update things so that shell can provide a binding for eval or a workspace for IRB execution and then use it directly when we construct our IRB session.

Issue Links

• causes: HBASE-26269 Shell 'load' command behavior has changed
• causes: HBASE-26469 correct HBase shell exit behavior to match code passed to exit
• links to: GitHub Pull Request #2141

Sub-Tasks

• Small Updates to Functionality of Shell IRB Workspace: Closed