Merge pull request #7023 from segmentio/add-batch-event-limit

update http api guide with batch limit

Author: stayseesong

src/connections/sources/catalog/libraries/server/http-api/index.md

@@ -462,8 +462,9 @@ When sending a HTTP call from a user's device, you can collect the IP address by
 
 Segment returns a `200` response for all API requests except errors caused by large payloads and JSON errors (which return `400` responses.) To debug events that return `200` responses but aren't accepted by Segment, use the Segment Debugger.
 
-Common reasons events are not accepted by Segment include: 
-  - **Payload is too large:** The HTTP API can handle API requests that are 32KB or smaller. The batch API endpoint accepts a maximum of 500KB per request, with a limit of 32KB per event in the batch. If these limits are exceeded, Segment returns a 400 Bad Request error. 
+Common reasons that events are not accepted by Segment: 
+  - **Payload is too large:** Most HTTP API routes can handle API requests that are 32KB or smaller. If this limit is exceeded, Segment returns a 400 Bad Request error.
+  - **The `\batch` API endpoint:** This endpoint accepts a maximum of 500KB per batch API request. Each batch request can only have up to 2500 events, and each batched event needs to be less than 32KB. Segment returns a `200` response but rejects the event when the number of batched events exceeds the limit.
   - **Identifier is not present**: The HTTP API requires that each payload has a userId and/or anonymousId.  If you send events without either the userId or anonymousId, Segment’s tracking API responds with an no_user_anon_id error. Check the event payload and client instrumentation for more details.
   - **Track event is missing name**: All Track events sent to Segment must have an `event` field. 
   - **Deduplication**: Segment deduplicates events using the `messageId` field, which is automatically added to all payloads coming into Segment. If you're setting up the HTTP API yourself, ensure all events have unique messageId values with fewer than 100 characters.