forked from cerc-io/plugeth
f3314bb6df
This PR adds server-side limits for JSON-RPC batch requests. Before this change, batches were limited only by processing time. The server would pick calls from the batch and answer them until the response timeout occurred, then stop processing the remaining batch items. Here, we are adding two additional limits which can be configured: - the 'item limit': batches can have at most N items - the 'response size limit': batches can contain at most X response bytes These limits are optional in package rpc. In Geth, we set a default limit of 1000 items and 25MB response size. When a batch goes over the limit, an error response is returned to the client. However, doing this correctly isn't always possible. In JSON-RPC, only method calls with a valid `id` can be responded to. Since batches may also contain non-call messages or notifications, the best effort thing we can do to report an error with the batch itself is reporting the limit violation as an error for the first method call in the batch. If a batch is too large, but contains only notifications and responses, the error will be reported with a null `id`. The RPC client was also changed so it can deal with errors resulting from too large batches. An older client connected to the server code in this PR could get stuck until the request timeout occurred when the batch is too large. **Upgrading to a version of the RPC client containing this change is strongly recommended to avoid timeout issues.** For some weird reason, when writing the original client implementation, @fjl worked off of the assumption that responses could be distributed across batches arbitrarily. So for a batch request containing requests `[A B C]`, the server could respond with `[A B C]` but also with `[A B] [C]` or even `[A] [B] [C]` and it wouldn't make a difference to the client. So in the implementation of BatchCallContext, the client waited for all requests in the batch individually. If the server didn't respond to some of the requests in the batch, the client would eventually just time out (if a context was used). With the addition of batch limits into the server, we anticipate that people will hit this kind of error way more often. To handle this properly, the client now waits for a single response batch and expects it to contain all responses to the requests. --------- Co-authored-by: Felix Lange <fjl@twurst.com> Co-authored-by: Martin Holst Swende <martin@swende.se> |
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