feat: implement DynamoDBDataSource + tests by beekld · Pull Request #534 · launchdarkly/cpp-sdks

beekld · 2026-05-14T22:03:38Z

Summary

Implements DynamoDBDataSource, similar to RedisDataSource, using the Proxy Relay schema as per the schema.

DynamoDBClientOptions options;
options.region = "us-east-1";
options.endpoint = "http://localhost:8000";
auto src = DynamoDBDataSource::Create("my-table", "prefix", options);

Differences from the Redis source

All() paginates DynamoDB Query responses via LastEvaluatedKey; Redis hgetall is single-shot.
AWS SDK InitAPI/ShutdownAPI are owned by an singleton (AwsSdkGuard); Redis++ needs no equivalent.
Config takes a DynamoDBClientOptions struct (region/endpoint/credentials) instead of a single URI string.
All reads use ConsistentRead = true to avoid DynamoDB's default eventually-consistent staleness (same as Java)
When no prefix is configured, this source uses bare partition-key values (features, $inited), matching what Relay writes per the spec. The Redis source unconditionally does prefix + ":" + name, so an empty Redis prefix would produce leading-colon keys (:features) that no Relay deployment writes. That divergence is never exercised — Redis defaults to a non-empty prefix and the Redis tests always pass one, but wanted to note it.

Test plan

24/24 tests green against amazon/dynamodb-local
Unit-only error tests pass without a backend.
CI Ubuntu job runs against amazon/dynamodb-local; macOS / Windows build-only (matches Redis workflow).
No AWS header leakage in public surface.

Note

Medium Risk
Adds a new DynamoDB-backed data source implementation plus integration tests and CI wiring, and adjusts CMake/AWS SDK build behavior (static vs shared), which could impact build/link outcomes across platforms.

Overview
Implements a real DynamoDBDataSource (replacing the prior scaffold) that reads flags/segments from a Relay-compatible DynamoDB table, including Get, All (with pagination), and Initialized checks, with consistent-read requests and structured error handling for malformed rows.

Introduces DynamoDBClientOptions plus internal helpers (AwsSdkGuard, client factory, namespace/prefix utilities) to manage AWS SDK lifecycle and client configuration without leaking AWS headers in the public API.

Adds a new tests target with DynamoDB Local-backed coverage and updates CI/workflows and release scripts to enable DynamoDB builds/tests when requested; also forces the AWS SDK FetchContent build to static archives with cache save/restore to avoid macOS shared-link issues.

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…moDB source

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kinyoklion · 2026-05-15T22:10:34Z

+            Error{"DynamoDB row missing expected 'item' attribute"});
+    }
+
+    return SerializedItemDescriptor::Present(0, it->second.GetS());


I wonder if we should type check or empty check calls to GetS? I have claude working on a test so I can understand scope a little easier.

kinyoklion · 2026-05-15T22:12:25Z

+// first use and torn down during normal program termination via C++ static
+// destruction.
+//
+// Static-destruction ordering caveat: if a caller stashes a raw AWS SDK


Do we need to surface this someplace more customer visible? Readme? Or just when we make docs?

I guess I need to read further to understand if there is external impact. On some SDKs we allow passing clients, but they would then theoretically be non-owned. So more of an internal problem?

Oh, the AWS Api is a bit icky here.

I wonder if potentially we should have a way to disable the AWS SDK shutdown and let the customer be responsible for shutting it down?

kinyoklion · 2026-05-15T22:24:14Z

From Claude.

AttributeValue::GetS() on a non-String item attribute silently returns "". The source builds Present(0, ""), and downstream JsonDeserializer::DeserializeJsonDescriptor calls the throwing boost::json::parse("") overload — uncaught all the way to the SDK's evaluation entry point. DynamoDB enforces type only on key attributes, so a non-Relay writer can trigger this.

Verified with two tests against amazon/dynamodb-local: both fail on current code (result.has_value() == true), pass after the fix.

Proposed fix and tests:

// libs/server-sdk-dynamodb-source/src/dynamodb_source.cpp -- in Get(), after the
// "missing item attribute" check
auto const& serialized = it->second.GetS();
if (serialized.empty()) {
    return tl::make_unexpected(
        Error{"DynamoDB 'item' attribute is empty or not of type S"});
}
return SerializedItemDescriptor::Present(0, serialized);

// Same pattern inside All()'s per-row loop, applied to item_it->second.GetS().
// The third GetS() call (sort key, line 119) is left alone -- DynamoDB enforces
// the key schema at insert time, so it's guaranteed type S.

Test helper added to tests/prefixed_dynamodb_client.hpp:

void PutRowWithNumericItem(std::string const& ns_suffix,
                           std::string const& key) const {
    Aws::DynamoDB::Model::PutItemRequest request;
    request.SetTableName(table_name_);
    request.AddItem("namespace",
                    Aws::DynamoDB::Model::AttributeValue{Prefixed(ns_suffix)});
    request.AddItem("key", Aws::DynamoDB::Model::AttributeValue{key});
    Aws::DynamoDB::Model::AttributeValue numeric_item;
    numeric_item.SetN("12345");
    request.AddItem("item", numeric_item);
    auto outcome = client_.PutItem(request);
    if (!outcome.IsSuccess()) {
        FAIL() << "..." << outcome.GetError().GetMessage();
    }
}

Tests added to tests/dynamodb_source_test.cpp:

TEST_F(DynamoDBTests, GetReturnsErrorWhenItemAttributeIsNotString) {
    WithPrefixedClient(prefix_, [&](auto const& client) {
        client.PutRowWithNumericItem("features", "foo");
    });
    auto const result = source->Get(FlagKind{}, "foo");
    ASSERT_FALSE(result);
}

TEST_F(DynamoDBTests, AllReturnsErrorWhenItemAttributeIsNotString) {
    WithPrefixedClient(prefix_, [&](auto const& client) {
        client.PutFlag(Flag{"foo", 1, true});
        client.PutRowWithNumericItem("features", "bar");
    });
    auto const result = source->All(FlagKind{});
    ASSERT_FALSE(result);
}

Suite is 28/28 green with the fix applied. Reverting the source change makes only the two new tests red, with Actual: true / Expected: false — confirming each test is load-bearing for this specific defect.

Broader hardening worth a separate PR: wrap boost::json::parse in libs/server-sdk/src/data_components/serialization_adapters/json_deserializer.hpp:54 in try/catch (or use the error_code overload) so any serialized data source, including Redis, is one bad row away from a structured error rather than an uncaught exception.

DynamoDB does not enforce a type schema on non-key attributes, so a non-Relay writer (manual put-item, schema-migration tool, etc.) can produce a row whose 'item' attribute is stored as Number/Binary/Null/ Bool/List/Map instead of String. AttributeValue::GetS() on such a value silently returns an empty string. Without a check, the source returns Present(0, "") and the empty string flows into JsonDeserializer::DeserializeJsonDescriptor's throwing boost::json::parse, which propagates an uncaught exception out of the SDK's evaluation entry point. Treat an empty GetS() result as a structured error in both Get() and All(). The sort-key GetS() (All() line 119) is left untouched -- the DynamoDB service enforces the table's key schema at insert time, so the sort key is guaranteed type S by table-schema invariant. Adds PutRowWithNumericItem test helper that stores 'item' as a Number via AttributeValue::SetN, and two bug-proving tests (GetReturnsErrorWhenItemAttributeIsNotString, AllReturnsErrorWhenItemAttributeIsNotString) that fail without the fix and pass with it. Full dynamodb suite is 28/28 green. Per #534 (comment)

Ticket: SDK-2363 · Follows #534 ## Summary Adds the public `IBigSegmentStore` interface, the `Membership` / `StoreMetadata` value types, and concrete DynamoDB + Redis implementations. Schema strings match what the Relay Proxy writes. ```cpp auto redis_store = RedisBigSegmentStore::Create("redis://localhost:6379", "prefix"); auto dynamo_store = DynamoDBBigSegmentStore::Create("my-table", "prefix", options); ``` ## Design notes - **`synchronizedOn` parsing.** Stored as DynamoDB N / Redis string. Both stores reject malformed values (non-numeric strings, wrong DynamoDB attribute type) rather than silently returning 0, matching the existing `dynamodb_source.cpp` row validation. - **No hashing here.** The interface contract says callers pass the already-hashed base64 SHA-256 context key; the SDK will hash in the wrapper, not the store implementations. ## Not in scope - `BigSegmentsBuilder` config plumbing. - `BigSegmentStoreWrapper` (LRU cache + staleness polling) and the hashing path. - Evaluator wiring / replacing the `rules.cpp` big-segments TODO. ## Test plan - [x] 7 `Membership` unit tests pass. - [x] 9 `RedisBigSegmentStore` integration tests pass against Redis 7 (docker). - [x] 8 `DynamoDBBigSegmentStore` integration tests pass against DynamoDB Local. - [x] Full server-sdk test suite (468 tests) still green. - [x] Schema constants match what Relay writes (verified against the LocalStack/Redis fixture data).  --- > [!NOTE] > **Medium Risk** > New external-store read path for segment targeting with strict schema validation; not yet wired into evaluation, so production flag behavior is unchanged until follow-up PRs land. > > **Overview** > Introduces a **Big Segments persistent store** surface for the server SDK: public `IBigSegmentStore`, inline `Membership` / `StoreMetadata`, and read-only **Redis** and **DynamoDB** backends that follow Relay’s key/schema layout (prefix scoping, include/exclude refs, sync metadata). > > Stores perform point lookups by opaque context hash, build membership via `Membership::FromSegmentRefs` (inclusion wins on overlap), and return errors on malformed DynamoDB attribute types or non-numeric sync timestamps instead of silent empty/zero results. **Config, caching wrapper, hashing, and flag evaluation wiring are not included** in this change. > > Integration tests cover membership/metadata behavior, prefix isolation, and error paths against Redis and DynamoDB Local. > > <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit d2622d9. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup>

beekld added 3 commits May 14, 2026 15:00

feat: implement DynamoDBDataSource + tests

4701ab1

fix: return errors for malformed rows and partial credentials in Dyna…

f070f2a

…moDB source

refactor: use unique_ptr for DynamoDB client ownership

e7ffabb

beekld marked this pull request as ready for review May 14, 2026 23:25

beekld requested a review from a team as a code owner May 14, 2026 23:25

beekld added 4 commits May 14, 2026 16:46

fix: pass LD_BUILD_DYNAMODB_SUPPORT through release scripts

a3078b5

fix: pass LD_BUILD_DYNAMODB_SUPPORT through Windows release script

69b9a87

fix: build AWS SDK statically to avoid macOS shared-link failure

54f65e2

fix: save and restore BUILD_SHARED_LIBS around AWS SDK FetchContent

d936b5d

cursor Bot reviewed May 15, 2026

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Comment thread libs/server-sdk-dynamodb-source/src/dynamodb_attributes.hpp Outdated

chore: drop unused kVersionAttribute constant

e1dafd8

kinyoklion reviewed May 15, 2026

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kinyoklion approved these changes May 15, 2026

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beekld merged commit a0c2790 into main May 18, 2026
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beekld deleted the beeklimt/SDK-2362 branch May 18, 2026 05:55

github-actions Bot mentioned this pull request May 15, 2026

chore: release main #530

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beekld mentioned this pull request May 19, 2026

feat: add IBigSegmentStore interface + Redis and DynamoDB stores #536

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feat: implement DynamoDBDataSource + tests#534

feat: implement DynamoDBDataSource + tests#534
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beekld commented May 14, 2026 •

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beekld commented May 14, 2026 • edited by cursor Bot Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Differences from the Redis source

Test plan

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beekld commented May 14, 2026 •

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