run.cmd - support explicit exec form

[mgurov]

At the moment it is not possible to run a more complicated command on a container start, e.g. docker run -it --rm busybox /bin/sh -c "while true; do echo Hello world; sleep 1; done" as the cmd is split by spaces at ContainerCreateConfig.command, and the following configuration:

              <image>
                  <name>busybox</name>
                  <run>
                      <cmd>/bin/sh -c "while true; do echo Hello world; sleep 1; done"</cmd>
                      <wait>
                          <log>Hello world</log>
                      </wait>
                  </run>
              </image>

produces container startup error true;: line 1: syntax error: unterminated quoted string.

It would be nice to have an ability to specify the exec form of the command explicitly, e.g.

              <image>
                  <name>busybox</name>
                  <run>
                      <cmd>
                          <params>
                              <param>/bin/sh</param>
                              <param>-c</param>
                              <param>while true; do echo Hello world; sleep 1; done</param>
                          </params>
                      </cmd>
                      <wait>
                          <log>Hello world</log>
                      </wait>
                  </run>
              </image>

in line with recent changes to ENTRYPOINT/CMD

[rhuss]

You are right, the command specified for <run> should support the same capabilities like in <build> i.e. specifying the shell and exec forms explicitely.

We will include this in one of the next section, if you like to speed this up you could help us with a PR: Starting point is the RunConfiguration where the command should be switched over to Arguments, similar as in BuildImageConfiguration for entryPoint and cmd. It is used here.

[mgurov]

I have created a branch with a draft implementation. Specifying arguments explicitly works like a charm:

                <env>
                  <BLAH>FOOE</BLAH>
                </env>
                <cmd>
                  <exec>
                    <arg>sh</arg>
                    <arg>-c</arg>
                    <arg>echo $BLAH</arg>
                  </exec>
                </cmd>

but switching the <shell> from array to simple string in API json didn't work as I expected. I kept getting System error: exec:...stat...no such file or directory. Fell back on splitting by spaces. The following configuration will produce cmd json ["the", "shell", "way"]

            <image>
              <name>debian:jessie</name>
              <run>
                <entrypoint>
                  <shell>/bin/echo</shell>
                </entrypoint>
                <cmd><shell>the shell way</shell></cmd>
                <log>
                  <prefix>keep splitting by the spaces</prefix>
                </log>
              </run>
            </image>

I suggest decreasing the configuration clutter by allowing the "Inlined collection" notation for the explicit arguments:

              <run>
                <entrypoint>
                  <arg>echo</arg>
                </entrypoint>
                <cmd>
                  <arg>inlined args</arg>
                  <arg>mean less clutter</arg>
                </cmd>
              </run>

and default property for the Arguments bean to be the shell form:

              <run>
                <entrypoint>echo</entrypoint>
                <cmd>default string for simple commands</cmd>
              </run>

I plan to ponder bit more on why doesn't plain string cmd/entrypoint work against the docker API, will then polish the branch (validation/tests) and create a pull request in a week time at worst.

[mgurov]

Pull request sent: #269