Experimental `getDiagnostics` request (#24480).

pkg/analysis_server/tool/spec/spec_input.html

Index: pkg/analysis_server/tool/spec/spec_input.html
diff --git a/pkg/analysis_server/tool/spec/spec_input.html b/pkg/analysis_server/tool/spec/spec_input.html
index 7c8f75333ad26d9c2642ad2f2c8a60e257816db1..aae4f5ba121d325d5aa5cb8bd1bdd9f1959daaf8 100644
--- a/pkg/analysis_server/tool/spec/spec_input.html
+++ b/pkg/analysis_server/tool/spec/spec_input.html
@@ -1959,6 +1959,25 @@
         </params>
       </notification>
     </domain>
+    <domain name="experimental" experimental="true">
+      <p>
+        The experimental domain contains experimental server APIs.  Experimental
+        APIs are not considered to be part of the analysis server's API, docs are
+        not generated for them and they are subject to change without notice.
+        Because the experimental domain is not part of the analysis server's API,
+        the version number of the API will not be updated when changes are made.
+        Caveat emptor!
+      </p>
+      <request method="getDiagnostics">
+        <p>Return server diagnostics.</p>
+        <result>
+          <field name="contexts">
+            <list><ref>ContextInfo</ref></list>
+            <p>The list of analysis contexts.</p>
+          </field>
+        </result>
+      </request>
+    </domain>
     <types>
       <h2 class="domain"><a name="types">Types</a></h2>
       <p>
@@ -2441,6 +2460,43 @@
           <value><code>PARAMETER</code></value>
         </enum>
       </type>
+      <type name="ContextInfo" experimental="true">
+        <p>
+          Information about an analysis context.
+        </p>
+        <object>
+          <field name="name">
+            <ref>String</ref>
+            <p>
+              The name of the context.
+            </p>
+          </field>
+          <field name="explicitlyAnalyzedFiles">
+            <ref>int</ref>
+            <p>
+              Explicitly analyzed files.
+            </p>
+          </field>
+          <field name="implicitlyAnalyzedFiles">
+            <ref>int</ref>
+            <p>
+              Implicitly analyzed files.
+            </p>
+          </field>
+          <field name="workItemQueueLength">
+            <ref>int</ref>
+            <p>
+              The number of work items in the queue.

[scheglov, 2015/11/05 21:22:22]

It seems to me that it's not very useful metrics.
It's just a number of steps for the current work order.
And it will be changing quickly, but reaching zero does not mean much.
There might be unknown number of work orders to be scheduled later.

[pquitslund, 2015/11/05 22:28:54]

Yeah.  I'm not sure.  The idea was that maybe if over time we see that there are
always items queued maybe that would indicate something?

Definitely something to experiment with.

Very open to other ideas!

+            </p>
+          </field>
+          <field name="cacheEntryExceptions">
+            <list><ref>String</ref></list>
+            <p>
+              Exceptions associated with cache entries.

[scheglov, 2015/11/05 21:22:22]

If any of these exceptions are going to be used to open issues against analyzer,
I'd like to know the entry target.

[pquitslund, 2015/11/05 22:28:54]

At this point that's not the intention though it may down the road.  In short
order this is just to give us an indication of health.

If it turns out that Devon wants to do something interesting with these
exceptions, you're right that we should add at least the target for sure.

+            </p>
+          </field>
+        </object>
+      </type>
       <type name="Element">
         <p>
           Information about an element (something that can be declared