chore: Add FDv2 data source interfaces. #100

kinyoklion · 2026-01-13T18:55:58Z

BEGIN_COMMIT_OVERRIDE
chore: Add FDv2 data source interfaces.
chore: Add FDv2 polling data source.
chore: Scaffold FDv2 Data Source.
END_COMMIT_OVERRIDE

kinyoklion · 2026-01-13T18:59:16Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/datasources/FDv2SourceResult.java

+     */
+    public static class Status {
+        private final State state;
+        private final DataSourceStatusProvider.ErrorInfo errorInfo;


I don't particularly care for this type, but also we may not want what is effectively a duplicate.

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/datasources/FDv2SourceResult.java

tanderson-ld · 2026-01-13T19:10:37Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/datasources/FDv2SourceResult.java

+ * an FDv2 synchronizer produces a stream of results.
+ */
+public class FDv2SourceResult {
+    public enum State {


Do you want running in this enum?

Maybe I shouldn't call it State. Its more like a notification of change, and it doesn't represents valid/running because that is handled by a changeset.

tanderson-ld · 2026-01-13T19:18:00Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/datasources/FDv2SourceResult.java

+        /**
+         * The data source has been instructed to disconnect and will not produce any further results.
+         */
+        GOODBYE,


The current description of GOODBYE and SHUTDOWN leaves room for me to think GOODBYE -> SHUTDOWN could be a thing.

I see the diagrams in the specific ones down below that shows that is not possible, but the enum details make it look like it could be?

GOODBYE is effectively a more specific shutdown. We didn't handle it in .Net because SDKs generally don't seem to have handled it yet, but it also is really hard to handle with data source updates.

Basically in .Net we had an overload broad OFF and it is hard to get the correct behavior because there were are really 2-3 different meanings. Overall we don't need to emit any data source status in most situations for something being shutdown or something being told to exit by flag delivery (but we may handle them different, I am still unsure how to handle goodbye).

SHUTDOWN means I asked the thing to shutdown.
GOODBYE means that FD or some external source asked it to disconnect. Having it different means we can decide to do something different. (I think just by entering this situation we handle most of the problems, because we can be like, cool we aren't running anymore, I don't care about this disconnect I just got from the event source.)
TERMINAL_ERROR means something has gone wrong.

…-interfaces

lib/sdk/server/build.gradle

…dd-fdv2-data-source-interfaces

kinyoklion · 2026-01-14T19:12:10Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/FDv2DataSource.java

This is very early scaffold that gives an idea how this stuff would connect together.

kinyoklion · 2026-01-14T19:12:45Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/IterableAsyncQueue.java

Convenience class that allows for easy mapping of producer/consumer to an iterator.

kinyoklion · 2026-01-14T19:13:23Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/PollingBase.java

Encapsulates all the poll-specific logic which is then used by the polling synchronizer/initializer.

…unchdarkly/java-core into rlamb/add-fdv2-data-source-interfaces

tanderson-ld

Posting partial review, will resume tomorrow.

tanderson-ld · 2026-01-14T20:55:46Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/DefaultFDv2Requestor.java

Some usage of "poll / polling" in this file, not sure if you want to eliminate that so if this requestor is used elsewhere, the concept of polling doesn't come with.

I will change the types in the interface level, but this implementation is specific to our polling implementation and the format of data it provides as well as the cycle it operates on.

tanderson-ld · 2026-01-14T20:57:46Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/DefaultFDv2Requestor.java

+
+            if (selector.getVersion() > 0) {
+                requestUri = HttpHelpers.addQueryParam(requestUri, VERSION_QUERY_PARAM, String.valueOf(selector.getVersion()));
+            }


I see this version constraint on the Dotnet impl. I'm wondering why this ever was imposed? What if 0 is valid?

I think a couple reasons. 0 and not present would be the same, and 0 is the "zero" value for the go implementation.

That said this should use !selector.isEmpty() and I will change it.

tanderson-ld · 2026-01-14T21:04:31Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/DefaultFDv2Requestor.java

+
+                        // Parse the response body
+                        if (response.body() == null) {
+                            future.completeExceptionally(new IOException("Response body is null"));


Is a null body necessarily an IO Exception? Seems like an application layer exception.

It represents an implementation error at this level. Though it isn't strictly an IOError, but it is better than a segfault/NPE. (Which seems to be what the existing implementation would do if this was somehow possible.)

There are a series of conditions which can make this null, which the layer above this shouldn't know about.

It could be an empty string, at which point the attempt at parsing would resolve the error, but that would be different.

I will add a comment.

tanderson-ld · 2026-01-14T21:19:20Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/FDv2DataSource.java

+             * This synchronizer is recovering from a previous failure and will be available to use
+             * after a delay.
+             */
+            Recovering


Maybe TempBlocked or OnCooldown? Recovering seems to imply we know it is doing something to recover, but we don't know anything about its internals to glean that. If you like TempBlocked, consider Blocked -> PermBlocked.

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/FDv2DataSource.java

tanderson-ld · 2026-01-14T21:45:24Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/FDv2DataSource.java

+                // TODO: Log.
+                // Move to next synchronizer.
+            }
+            availableSynchronizer = getFirstAvailableSynchronizer();


I think this deviates from the spec slightly, but it is probably ok, and possibly an improvement?

tanderson-ld · 2026-01-14T21:48:02Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/FDv2DataSource.java

+    @Override
+    public boolean isInitialized() {
+        try {
+            return startFuture.isDone() && startFuture.get();


Is it ok that startFuture.get() could block? I think existing data sources interacted with atomic booleans for the return.

tanderson-ld · 2026-01-14T21:49:28Z

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/FDv2DataSource.java

+    @Override
+    public void close() throws IOException {
+        // If this is already set, then this has no impact.
+        startFuture.complete(false);


Does this need to interrupt initializers?

tanderson-ld and others added 6 commits January 12, 2026 11:47

chore: adds fdv2 payload parsing and protocol handling

19d9c02

adding package info files and fixing package name issue

fbea872

more checkstyle fixes

adcaa0e

chore: Add interfaces for synchronizer/initializer.

f2b209d

Merge branch 'main' into rlamb/add-fdv2-data-source-interfaces

8c115cc

Revert version change

de2fded

kinyoklion commented Jan 13, 2026

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tanderson-ld reviewed Jan 13, 2026

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lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/datasources/FDv2SourceResult.java Outdated Show resolved Hide resolved

tanderson-ld reviewed Jan 13, 2026

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kinyoklion added 4 commits January 13, 2026 14:19

feat: Add FDv2 polling support.

98d3b39

Merge remote-tracking branch 'origin' into rlamb/add-fdv2-data-source…

da3c639

…-interfaces

WIP: Polling initializer/synchronizer.

8fb88ed

Use updated internal lib.

da27015

kinyoklion changed the title ~~Rlamb/add fdv2 data source interfaces~~ chore: Add FDv2 data source interfaces. Jan 14, 2026

kinyoklion added 3 commits January 13, 2026 16:25

Update comment

aba46ef

Add termination.

7401331

Remove test file that isn't ready.

bba0cdc

kinyoklion commented Jan 14, 2026

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lib/sdk/server/build.gradle Outdated Show resolved Hide resolved

kinyoklion commented Jan 14, 2026

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lib/sdk/server/build.gradle Outdated Show resolved Hide resolved

kinyoklion added 5 commits January 13, 2026 17:39

Polling tests and some fixes.

89bd017

Try pre block.

228f3e6

Add streaming path.

9469b23

Merge branch 'main' of github.com:launchdarkly/java-core into rlamb/a…

9a450e6

…dd-fdv2-data-source-interfaces

Use the DataStoreTypes.ChangeSet type for data source results.

4b8313b

kinyoklion force-pushed the rlamb/add-fdv2-data-source-interfaces branch from dcbd9fd to 4b8313b Compare January 14, 2026 19:00

Make iterable async queue package private.

31eb13e

kinyoklion commented Jan 14, 2026

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kinyoklion added 6 commits January 14, 2026 11:14

Revert Version.java

4a2fe3b

Add comments to SelectorSource.

3428591

Revert build.gradle.

ff60216

Update launchdarklyJavaSdkInternal version to 1.6.1

e985f80

Move mermaid out of doc comment.

a956484

Merge branch 'rlamb/add-fdv2-data-source-interfaces' of github.com:la…

ff2376e

…unchdarkly/java-core into rlamb/add-fdv2-data-source-interfaces

kinyoklion marked this pull request as ready for review January 14, 2026 19:33

kinyoklion requested a review from a team as a code owner January 14, 2026 19:33

tanderson-ld reviewed Jan 14, 2026

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PR feedback.

194c30c

chore: Add FDv2 data source interfaces. #100

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chore: Add FDv2 data source interfaces. #100

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kinyoklion commented Jan 13, 2026 •

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