Github user geomacy commented on a diff in the pull request:
https://github.com/apache/brooklyn-server/pull/462#discussion_r94440253
--- Diff:
core/src/main/java/org/apache/brooklyn/core/config/BasicConfigInheritance.java
---
@@ -28,51 +32,188 @@
import org.apache.brooklyn.config.ConfigKey;
import org.apache.brooklyn.config.ConfigValueAtContainer;
import org.apache.brooklyn.util.collections.CollectionMerger;
+import org.apache.brooklyn.util.exceptions.Exceptions;
import org.apache.brooklyn.util.exceptions.ReferenceWithError;
import org.apache.brooklyn.util.guava.Maybe;
+import org.apache.brooklyn.util.text.Strings;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+@SuppressWarnings("serial")
public class BasicConfigInheritance implements ConfigInheritance {
+ private static final Logger log =
LoggerFactory.getLogger(BasicConfigInheritance.class);
+
private static final long serialVersionUID = -5916548049057961051L;
public static final String CONFLICT_RESOLUTION_STRATEGY_DEEP_MERGE =
"deep_merge";
public static final String CONFLICT_RESOLUTION_STRATEGY_OVERWRITE =
"overwrite";
+ public static abstract class DelegatingConfigInheritance implements
ConfigInheritance {
+ protected abstract ConfigInheritance getDelegate();
+
+ @Override @Deprecated public InheritanceMode
isInherited(ConfigKey<?> key, Object from, Object to) {
+ return getDelegate().isInherited(key, from, to);
+ }
+ @Override public <TContainer, TValue> boolean
isReinheritable(ConfigValueAtContainer<TContainer, TValue> parent,
ConfigInheritanceContext context) {
+ return getDelegate().isReinheritable(parent, context);
+ }
+ @Override public <TContainer, TValue> boolean
considerParent(ConfigValueAtContainer<TContainer, TValue> local,
ConfigValueAtContainer<TContainer, TValue> parent, ConfigInheritanceContext
context) {
+ return getDelegate().considerParent(local, parent, context);
+ }
+ @Override
+ public <TContainer, TValue>
ReferenceWithError<ConfigValueAtContainer<TContainer, TValue>>
resolveWithParent(ConfigValueAtContainer<TContainer, TValue> local,
ConfigValueAtContainer<TContainer, TValue> resolvedParent,
ConfigInheritanceContext context) {
+ return getDelegate().resolveWithParent(local, resolvedParent,
context);
+ }
+ @Override
+ public boolean equals(Object obj) {
+ return super.equals(obj) || getDelegate().equals(obj);
+ }
+
+ // standard deserialization method
+ protected ConfigInheritance readResolve() {
+ return returnEquivalentConstant(this);
+ }
+ }
+
+ private static ConfigInheritance
returnEquivalentConstant(ConfigInheritance candidate) {
+ for (ConfigInheritance knownMode: Arrays.asList(
+ NOT_REINHERITED, NOT_REINHERITED_ELSE_DEEP_MERGE,
NEVER_INHERITED, OVERWRITE, BasicConfigInheritance.DEEP_MERGE)) {
+ if (candidate.equals(knownMode)) return knownMode;
+ }
+ if (candidate.equals(new BasicConfigInheritance(false,
CONFLICT_RESOLUTION_STRATEGY_OVERWRITE, true, true))) {
+ // ignore the ancestor flag for this mode
+ return NEVER_INHERITED;
+ }
+ return candidate;
+ }
+
+ /*
+ * use of delegate is so that stateless classes can be defined to make
the serialization nice,
+ * both the name and hiding the implementation detail (also making it
easier for that detail to change);
+ * with aliased type names the field names here could even be aliases
for the type names.
+ * (we could alternatively have an "alias-for-final-instance" mode in
serialization,
+ * to optimize where we know that a java instance is final.)
+ */
+
+ private static class NotReinherited extends
DelegatingConfigInheritance {
+ final static BasicConfigInheritance DELEGATE = new
BasicConfigInheritance(false, CONFLICT_RESOLUTION_STRATEGY_OVERWRITE, false,
true);
+ @Override protected ConfigInheritance getDelegate() { return
DELEGATE; }
+ }
/** Indicates that a config key value should not be passed down from a
container where it is defined.
* Unlike {@link #NEVER_INHERITED} these values can be passed down if
set as anonymous keys at a container
* (ie the container does not expect it) to a container which does
expect it, but it will not be passed down further.
* If the inheritor also defines a value the parent's value is ignored
irrespective
* (as in {@link #OVERWRITE}; see {@link
#NOT_REINHERITED_ELSE_DEEP_MERGE} if merging is desired). */
- public static BasicConfigInheritance NOT_REINHERITED = new
BasicConfigInheritance(false,CONFLICT_RESOLUTION_STRATEGY_OVERWRITE,false);
+ public static ConfigInheritance NOT_REINHERITED = new NotReinherited();
+
+ private static class NotReinheritedElseDeepMerge extends
DelegatingConfigInheritance {
+ final static BasicConfigInheritance DELEGATE = new
BasicConfigInheritance(false, CONFLICT_RESOLUTION_STRATEGY_DEEP_MERGE, false,
true);
+ @Override protected ConfigInheritance getDelegate() { return
DELEGATE; }
+ }
/** As {@link #NOT_REINHERITED} but in cases where a value is
inherited because a parent did not recognize it,
* if the inheritor also defines a value the two values should be
merged. */
- public static BasicConfigInheritance NOT_REINHERITED_ELSE_DEEP_MERGE =
new BasicConfigInheritance(false,CONFLICT_RESOLUTION_STRATEGY_DEEP_MERGE,false);
- /** Indicates that a key's value should never be inherited, even if
defined on a container that does not know the key.
- * Most usages will prefer {@link #NOT_REINHERITED}. */
- public static BasicConfigInheritance NEVER_INHERITED = new
BasicConfigInheritance(false,CONFLICT_RESOLUTION_STRATEGY_OVERWRITE,true);
+ public static ConfigInheritance NOT_REINHERITED_ELSE_DEEP_MERGE = new
NotReinheritedElseDeepMerge();
+
+ private static class NeverInherited extends
DelegatingConfigInheritance {
+ final static BasicConfigInheritance DELEGATE = new
BasicConfigInheritance(false, CONFLICT_RESOLUTION_STRATEGY_OVERWRITE, true,
false);
+ @Override protected ConfigInheritance getDelegate() { return
DELEGATE; }
+ }
+ /** Indicates that a key's value should never be inherited, even if
inherited from a value set on a container that does not know the key.
+ * (Most usages will prefer {@link #NOT_REINHERITED}.) */
+ public static ConfigInheritance NEVER_INHERITED = new NeverInherited();
+
+ private static class Overwrite extends DelegatingConfigInheritance {
+ final static BasicConfigInheritance DELEGATE = new
BasicConfigInheritance(true, CONFLICT_RESOLUTION_STRATEGY_OVERWRITE, false,
true);
+ @Override protected ConfigInheritance getDelegate() { return
DELEGATE; }
+ }
/** Indicates that if a key has a value at both an ancestor and a
descendant, the descendant and his descendants
* will prefer the value at the descendant. */
- public static BasicConfigInheritance OVERWRITE = new
BasicConfigInheritance(true,CONFLICT_RESOLUTION_STRATEGY_OVERWRITE,false);
+ public static ConfigInheritance OVERWRITE = new Overwrite();
+
+ private static class DeepMerge extends DelegatingConfigInheritance {
+ final static BasicConfigInheritance DELEGATE = new
BasicConfigInheritance(true, CONFLICT_RESOLUTION_STRATEGY_DEEP_MERGE, false,
true);
+ @Override protected ConfigInheritance getDelegate() { return
DELEGATE; }
+ }
/** Indicates that if a key has a value at both an ancestor and a
descendant, the descendant and his descendants
- * should attempt to merge the values. If the values are not mergable
behaviour is undefined
+ * should attempt to merge the values. If the values are not mergeable
behaviour is undefined
* (and often the descendant's value will simply overwrite). */
- public static BasicConfigInheritance DEEP_MERGE = new
BasicConfigInheritance(true,CONFLICT_RESOLUTION_STRATEGY_DEEP_MERGE,false);
+ public static ConfigInheritance DEEP_MERGE = new DeepMerge();
+
+ // support conversion from these legacy fields
+ @SuppressWarnings("deprecation")
+ private static void registerReplacements() {
+
ConfigInheritance.Legacy.registerReplacement(ConfigInheritance.DEEP_MERGE,
DEEP_MERGE);
+
ConfigInheritance.Legacy.registerReplacement(ConfigInheritance.ALWAYS,
OVERWRITE);
+
ConfigInheritance.Legacy.registerReplacement(ConfigInheritance.NONE,
NOT_REINHERITED);
+ }
+ static { registerReplacements(); }
- /** reinheritable? true/false; if false,
children/descendants/inheritors will never see it; default true */
+ /** whether a value on a key defined locally should be inheritable by
descendants.
+ * if false at a point where a key is defined,
+ * children/descendants/inheritors will not be able to see its value,
whether explicit or default.
+ * default true: things are normally reinherited.
+ * <p>
+ * note that this only takes effect where a key is defined locally.
+ * if a key is not defined at an ancestor, a descendant setting this
value false will not prevent it
+ * from inheriting values from ancestors.
+ * <p>
+ * typical use case for setting this is false is where a key is
consumed and descendants should not
+ * "reconsume" it. for example setting files to install on a VM need
only be applied once,
+ * and if it has <b>runtime management</b> hierarchy descendants which
also understand that field they
+ * should not install the same files.
+ * (there is normally no reason to set this false in the context of
<b>type hierarchy</b> inheritance because
+ * an ancestor type cannot "consume" a value.) */
protected final boolean isReinherited;
- /** conflict-resolution-strategy? in {@link BasicConfigInheritance}
supported values are
+
+ /** a symbol indicating a conflict-resolution-strategy understood by
the implementation.
+ * in {@link BasicConfigInheritance} supported values are
* {@link #CONFLICT_RESOLUTION_STRATEGY_DEEP_MERGE} and {@link
#CONFLICT_RESOLUTION_STRATEGY_OVERWRITE}.
- * subclasses may pass null if they provide a custom implementaton of
{@link #resolveWithParentCustomStrategy(ConfigValueAtContainer,
ConfigValueAtContainer,
org.apache.brooklyn.config.ConfigInheritance.ConfigInheritanceContext)} */
+ * subclasses may pass null or a different string if they provide a
custom implementaton
+ * of {@link #resolveWithParentCustomStrategy(ConfigValueAtContainer,
ConfigValueAtContainer,
org.apache.brooklyn.config.ConfigInheritance.ConfigInheritanceContext)} */
@Nullable protected final String conflictResolutionStrategy;
- /** use-local-default-value? true/false; if true, overwrite above
means "always ignore (even if null)"; default false
- * whereas merge means "use local default (if non-null)" */
- protected final boolean useLocalDefaultValue;
+
+ /** @deprecated since 0.10.0 when this was introduced, now renamed
{@link #localDefaultResolvesWithAncestorValue} */
+ @Deprecated protected final Boolean useLocalDefaultValue;
+ /** whether a local default value should be considered for resolution
in the presence of an ancestor value.
+ * can use true with overwrite to mean don't inherit, or true with
merge to mean local default merged on top of inherited
+ * (but be careful here, if local default is null in a merge it will
delete ancestor values).
+ * <p>
+ * in most cases this is false, meaning a default value is ignored if
the parent has a value.
+ * <p>
+ * null should not be used. a boxed object is taken (as opposed to a
primitive boolean) only in order to support migration.
+ */
+ @Nonnull
+ protected final Boolean localDefaultResolvesWithAncestorValue;
- protected BasicConfigInheritance(boolean isReinherited, @Nullable
String conflictResolutionStrategy, boolean useLocalDefaultValue) {
+ /** whether a default set in an ancestor container's key definition
will be considered as the
+ * local default value at descendants who don't define any other value
(nothing set locally and local default is null);
+ * <p>
+ * if true (now the usual behaviour), if an ancestor defines a default
and a descendant doesn't, the ancestor's value will be taken as a default.
+ * if it is also the case that localDefaultResolvesWithAncestorValue
is true at the <i>ancestor</i> then a descendant who
+ * defines a local default value (with this field true) will have its
conflict resolution strategy
+ * applied with the ancestor's default value.
+ * <p>
+ * if this is false, ancestor defaults are completely ignored; prior
to 0.10.0 this was the normal behaviour,
+ * but it caused surprises where default values in parameters did not
take effect.
+ * <p>
+ * null should not be used. a boxed object is taken (as opposed to a
primitive boolean) only in order to support migration.
+ */
+ @Nonnull
+ protected final Boolean ancestorDefaultInheritable;
--- End diff --
Is this really needed? Is this condition actually an independent
dimension of the behaviour of the class (i.e. it makes sense to specify it as
an independently settable parameter), or is it really an "emergent" behaviour
that can be inferred from other requirements?
Looking at how it's actually used in the strategies above, it turns out
that it is always the logical inverse of
`localDefaultResolvesWithAncestorValue`. How about we use Occam's Razor and
do without this parameter, but instead replace its use with
`!getLocalDefaultResolvesWithAncestorValue()`, and then tidy up the logic?
It's a small change to the code, but it does avoid introducing the overhead
of another concept for developers to have to consider (config inheritance is
complicated enough already!). The only changes that would be needed, aside
from trivial simplifications to `readResolve` and `equals`, would be a couple
of lines in `resolveWithParent`, where line 268 becomes slightly simpler with
the loss of one test, and at line 283 you just replace the condition.
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