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From paul-rogers <...@git.apache.org>
Subject [GitHub] drill pull request #923: DRILL-5723: Added System Internal Options That can ...
Date Fri, 01 Sep 2017 20:54:58 GMT
Github user paul-rogers commented on a diff in the pull request:

    --- Diff: exec/java-exec/src/test/java/org/apache/drill/exec/server/rest/StatusResourcesTest.java
    @@ -0,0 +1,80 @@
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
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    + */
    +package org.apache.drill.exec.server.rest;
    +import org.apache.drill.exec.ExecConstants;
    +import org.apache.drill.exec.server.options.OptionValidator;
    +import org.apache.drill.exec.server.options.TypeValidators;
    +import org.apache.drill.test.ClientFixture;
    +import org.apache.drill.test.ClusterFixture;
    +import org.apache.drill.test.FixtureBuilder;
    +import org.apache.drill.test.RestClientFixture;
    +import org.junit.Assert;
    +import org.junit.Test;
    +import static org.apache.drill.test.TestConfigLinkage.MOCK_PROPERTY;
    +import static org.apache.drill.test.TestConfigLinkage.createMockPropValidator;
    +public class StatusResourcesTest {
    +  @Test
    +  public void testRetrieveInternalOption() throws Exception {
    +    TypeValidators.StringValidator stringValidator = createMockPropValidator();
    +    FixtureBuilder builder = ClusterFixture.builder().
    +      configProperty(ExecConstants.HTTP_ENABLE, true).
    +      configProperty(OptionValidator.OPTION_DEFAULTS_ROOT + MOCK_PROPERTY, "a").
    +      putValidator(MOCK_PROPERTY, stringValidator);
    +    try (ClusterFixture cluster = builder.build();
    +         ClientFixture client = cluster.clientFixture()) {
    +      RestClientFixture restClientFixture = cluster.restClientFixture();
    +      Assert.assertNull(restClientFixture.getStatusOption(MOCK_PROPERTY));
    +      StatusResources.OptionWrapper option = restClientFixture.getStatusInternalOption(MOCK_PROPERTY);
    +      Assert.assertEquals("a", option.getValueAsString());
    +      client.alterSystem(MOCK_PROPERTY, "c");
    --- End diff --
    This test shows the value in allowing "extended" options defined outside of the usual
big table in `SystemOptionManager`.
    In fact, we can take a step back and say that having a global table is always a bad idea:
it introduces tight coupling. Tight coupling makes it much harder to do unit testing. For
an open source tool such as Drill, which should allow extensions, tight coupling is counter-productive
to the goal of extensibility.
    So, I wonder, can we add a mechanism that allows other modules (and tests) to add options?
Just brainstorming a bit...
    * For code modules, provide a config setting that names a class that builds options. The
Drillbit, during initialization, scans for these classes (the way it scans for, say, storage
plugins), instantiates the class, and calls a method to define the options.
    * The easiest way to define options is to add an `OptionBuilder` class, created by the
Drillbit in the constructor, that is available up to some point in time, such as once the
Drillbit starts running.
    The API might be:
    Drillbit bit = new Drillbit();
    bit.optionBuilder().add(new OptionDefinition("my.option", ...));
    The `add()` method can be called from tests (perhaps with added `ClusterFixture` support)
and from the module-specific option builder.
    Two issues in this model:
    * Is there any reason to add options after the Drillbit starts? Doing so adds complexity.
    * Do we have code in Drillbit startup that uses the option manager? If so, some careful
sequencing would be needed to call this code only *after* the options are built.

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