Dgraph errors about context deadline and hash mismatch

We’re using a shared Slash instance running v21.03.0-46-g7346eac24, and we suddenly started getting several strange errors from it. Here’s a sampling from our API server’s logs:

2 UNKNOWN: hash mismatch the claimed startTs|namespace
2 UNKNOWN: : context deadline exceeded
2 UNKNOWN: Please retry again, server is not ready to accept requests

I can access this Dgraph instance via Ratel, where queries seem to work fine.

Any ideas what might be wrong?

I’ve narrowed the problem down to the transaction type. Read-only queries are working from both our API server and Ratel with no problems. Mutations via Ratel are working, but all mutation attempts from our API server are failing with:

2 UNKNOWN: hash mismatch the claimed startTs|namespace

We’re using the JavaScript gRPC client, and my working theory is that the error occurs when we try to start a new write transaction on our DgraphClient instance:

client.newTxn({ readOnly: false })

Is it expected that a client can get into this state? Should we be attempting to catch these errors and instantiate a new DgraphClient instance?

@tron Are you using the latest Dgraph client? Based on your example code, it looks like you’re using on of the dgraph-js or the dgraph-js-http client. Both of these clients are currently at v21.03.1.

We’re using the dgraph-js client, but it’s only at v20.3.1. Is this a known issue that will be solved by updating the client to v21.03.1?

@dmai Thanks for your suggestion. Upgrading the dgraph-js client to v21.03.1 resolved the issue for us.

Now a different question: Can we control precisely when our Slash instance is upgraded? Naturally we’d like to avoid surprises like this in the future.

1 Like

Glad that the client version upgrade fixed your issue.

In Dgraph Cloud, you can choose when the upgrade times for dedicated backends. For free and shared backends, upgrades happen automatically.