MONGOCRYPT-763 add in-place retry API

integrating.md

@@ -249,7 +249,7 @@ Ensure `mongocrypt_setopt_retry_kms` is called on the `mongocrypt_t` to enable r
         > until `mongocrypt_kms_ctx_bytes_needed` returns 0.
 
     If any step encounters a network error, call `mongocrypt_kms_ctx_fail`.
-    If `mongocrypt_kms_ctx_fail` returns true, continue to the next KMS context.
+    If `mongocrypt_kms_ctx_fail` returns true, retry the request by continuing to the next KMS context or by feeding the new response into the same context.
     If `mongocrypt_kms_ctx_fail` returns false, abort and report an error. Consider wrapping the error reported in `mongocrypt_kms_ctx_status` to include the last network error.
 
 2.  When done feeding all replies, call `mongocrypt_ctx_kms_done`.

src/mongocrypt-kms-ctx.c

@@ -1120,6 +1120,35 @@ static bool _ctx_done_kmip_decrypt(mongocrypt_kms_ctx_t *kms_ctx) {
     return ret;
 }
 
+static bool _is_retryable_req(_kms_request_type_t req_type) {
+    // Check if request type is retryable. Some requests are non-idempotent and cannot be safely retried.
+    _kms_request_type_t retryable_types[] = {MONGOCRYPT_KMS_AZURE_OAUTH,
+                                             MONGOCRYPT_KMS_GCP_OAUTH,
+                                             MONGOCRYPT_KMS_AWS_ENCRYPT,
+                                             MONGOCRYPT_KMS_AWS_DECRYPT,
+                                             MONGOCRYPT_KMS_AZURE_WRAPKEY,
+                                             MONGOCRYPT_KMS_AZURE_UNWRAPKEY,
+                                             MONGOCRYPT_KMS_GCP_ENCRYPT,
+                                             MONGOCRYPT_KMS_GCP_DECRYPT};
+    for (size_t i = 0; i < sizeof(retryable_types) / sizeof(retryable_types[0]); i++) {
+        if (retryable_types[i] == req_type) {
+            return true;
+        }
+    }
+    return false;
+}
+
+bool mongocrypt_kms_ctx_should_retry(mongocrypt_kms_ctx_t *kms) {
+    return kms && kms->should_retry;
+}
+
+void mongocrypt_kms_ctx_reset(mongocrypt_kms_ctx_t *kms) {
+    if (kms->parser) {
+        kms_response_parser_reset(kms->parser);
+    }
+    kms->should_retry = false;
+}
+
 bool mongocrypt_kms_ctx_fail(mongocrypt_kms_ctx_t *kms) {
     if (!kms) {
         return false;
@@ -1138,23 +1167,7 @@ bool mongocrypt_kms_ctx_fail(mongocrypt_kms_ctx_t *kms) {
         return false;
     }
 
-    // Check if request type is retryable. Some requests are non-idempotent and cannot be safely retried.
-    _kms_request_type_t retryable_types[] = {MONGOCRYPT_KMS_AZURE_OAUTH,
-                                             MONGOCRYPT_KMS_GCP_OAUTH,
-                                             MONGOCRYPT_KMS_AWS_ENCRYPT,
-                                             MONGOCRYPT_KMS_AWS_DECRYPT,
-                                             MONGOCRYPT_KMS_AZURE_WRAPKEY,
-                                             MONGOCRYPT_KMS_AZURE_UNWRAPKEY,
-                                             MONGOCRYPT_KMS_GCP_ENCRYPT,
-                                             MONGOCRYPT_KMS_GCP_DECRYPT};
-    bool is_retryable = false;
-    for (size_t i = 0; i < sizeof(retryable_types) / sizeof(retryable_types[0]); i++) {
-        if (retryable_types[i] == kms->req_type) {
-            is_retryable = true;
-            break;
-        }
-    }
-    if (!is_retryable) {
+    if (!_is_retryable_req(kms->req_type)) {
         CLIENT_ERR("KMS request failed due to network error");
         return false;
     }
@@ -1178,6 +1191,10 @@ bool mongocrypt_kms_ctx_feed(mongocrypt_kms_ctx_t *kms, mongocrypt_binary_t *byt
     if (!mongocrypt_status_ok(status)) {
         return false;
     }
+    if (kms->should_retry) {
+        // This happens when a KMS context is reused in-place
+        kms->should_retry = false;
+    }
 
     if (!bytes) {
         CLIENT_ERR("argument 'bytes' is required");

src/mongocrypt.h

@@ -1180,14 +1180,24 @@ MONGOCRYPT_EXPORT
 bool mongocrypt_kms_ctx_feed(mongocrypt_kms_ctx_t *kms, mongocrypt_binary_t *bytes);
 
 /**
- * Indicate a network-level failure.
+ * Indicate a failure. Discards all data fed to this KMS context with @ref mongocrypt_kms_ctx_feed.
+ * The @ref mongocrypt_kms_ctx_t may be reused.
  *
  * @param[in] kms The @ref mongocrypt_kms_ctx_t.
  * @return A boolean indicating whether the failed request may be retried.
  */
 MONGOCRYPT_EXPORT
 bool mongocrypt_kms_ctx_fail(mongocrypt_kms_ctx_t *kms);
 
+/**
+ * Indicate if a KMS context is completed but should be retried.
+ *
+ * @param[in] kms The @ref mongocrypt_kms_ctx_t.
+ * @return A boolean indicating whether the failed request should be retried.
+ */
+MONGOCRYPT_EXPORT
+bool mongocrypt_kms_ctx_should_retry(mongocrypt_kms_ctx_t *kms);
+
 /**
  * Get the status associated with a @ref mongocrypt_kms_ctx_t object.
  *

test/data/kms-aws/encrypt-response-partial.txt

@@ -0,0 +1,7 @@
+HTTP/1.1 200 OK
+x-amzn-RequestId: deeb35e5-4ecb-4bf1-9af5-84a54ff0af0e
+Content-Type: application/x-amz-json-1.1
+Content-Length: 446
+Connection: close
+
+{"KeyId": "arn:aws:k

test/test-mongocrypt-datakey.c

@@ -427,6 +427,33 @@ static void _test_create_datakey_with_retry(_mongocrypt_tester_t *tester) {
         mongocrypt_destroy(crypt);
     }
 
+    // Test that an HTTP error is retried in-place.
+    {
+        mongocrypt_t *crypt = _mongocrypt_tester_mongocrypt(TESTER_MONGOCRYPT_DEFAULT);
+        mongocrypt_ctx_t *ctx = mongocrypt_ctx_new(crypt);
+        ASSERT_OK(
+            mongocrypt_ctx_setopt_key_encryption_key(ctx,
+                                                     TEST_BSON("{'provider': 'aws', 'key': 'foo', 'region': 'bar'}")),
+            ctx);
+        ASSERT_OK(mongocrypt_ctx_datakey_init(ctx), ctx);
+        ASSERT_STATE_EQUAL(mongocrypt_ctx_state(ctx), MONGOCRYPT_CTX_NEED_KMS);
+        mongocrypt_kms_ctx_t *kms_ctx = mongocrypt_ctx_next_kms_ctx(ctx);
+        ASSERT_OK(kms_ctx, ctx);
+        // Expect no sleep is requested before any error.
+        ASSERT_CMPINT64(mongocrypt_kms_ctx_usleep(kms_ctx), ==, 0);
+        // Feed a retryable HTTP error.
+        ASSERT_OK(mongocrypt_kms_ctx_feed(kms_ctx, TEST_FILE("./test/data/rmd/kms-decrypt-reply-429.txt")), kms_ctx);
+        // In-place retry is indicated.
+        ASSERT(mongocrypt_kms_ctx_should_retry(kms_ctx));
+        ASSERT(mongocrypt_kms_ctx_fail(kms_ctx));
+        // Feed a successful response.
+        ASSERT_OK(mongocrypt_kms_ctx_feed(kms_ctx, TEST_FILE("./test/data/kms-aws/encrypt-response.txt")), kms_ctx);
+        ASSERT_OK(mongocrypt_ctx_kms_done(ctx), ctx);
+        _mongocrypt_tester_run_ctx_to(tester, ctx, MONGOCRYPT_CTX_DONE);
+        mongocrypt_ctx_destroy(ctx);
+        mongocrypt_destroy(crypt);
+    }
+
     // Test that a network error is retried.
     {
         mongocrypt_t *crypt = _mongocrypt_tester_mongocrypt(TESTER_MONGOCRYPT_DEFAULT);
@@ -454,6 +481,30 @@ static void _test_create_datakey_with_retry(_mongocrypt_tester_t *tester) {
         mongocrypt_destroy(crypt);
     }
 
+    // Test that a network error is retried in-place.
+    {
+        mongocrypt_t *crypt = _mongocrypt_tester_mongocrypt(TESTER_MONGOCRYPT_DEFAULT);
+        mongocrypt_ctx_t *ctx = mongocrypt_ctx_new(crypt);
+        ASSERT_OK(
+            mongocrypt_ctx_setopt_key_encryption_key(ctx,
+                                                     TEST_BSON("{'provider': 'aws', 'key': 'foo', 'region': 'bar'}")),
+            ctx);
+        ASSERT_OK(mongocrypt_ctx_datakey_init(ctx), ctx);
+        ASSERT_STATE_EQUAL(mongocrypt_ctx_state(ctx), MONGOCRYPT_CTX_NEED_KMS);
+        mongocrypt_kms_ctx_t *kms_ctx = mongocrypt_ctx_next_kms_ctx(ctx);
+        ASSERT_OK(kms_ctx, ctx);
+        // Expect no sleep is requested before any error.
+        ASSERT_CMPINT64(mongocrypt_kms_ctx_usleep(kms_ctx), ==, 0);
+        // Mark a network error.
+        ASSERT_OK(mongocrypt_kms_ctx_fail(kms_ctx), kms_ctx);
+        // Feed a successful response.
+        ASSERT_OK(mongocrypt_kms_ctx_feed(kms_ctx, TEST_FILE("./test/data/kms-aws/encrypt-response.txt")), kms_ctx);
+        ASSERT_OK(mongocrypt_ctx_kms_done(ctx), ctx);
+        _mongocrypt_tester_run_ctx_to(tester, ctx, MONGOCRYPT_CTX_DONE);
+        mongocrypt_ctx_destroy(ctx);
+        mongocrypt_destroy(crypt);
+    }
+
     // Test that an oauth request is retried for a network error.
     {
         mongocrypt_t *crypt = _mongocrypt_tester_mongocrypt(TESTER_MONGOCRYPT_DEFAULT);