func()

in query_executor.go [150:229]

• 59 lines of code
• 17 McCabe index (conditional complexity)

func (q *queryExecutor) do(ctx context.Context, qry ExecutableQuery, hostIter NextHost) *Iter {
	selectedHost := hostIter()
	rt := qry.retryPolicy()

	var lastErr error
	var iter *Iter
	for selectedHost != nil {
		host := selectedHost.Info()
		if host == nil || !host.IsUp() {
			selectedHost = hostIter()
			continue
		}

		pool, ok := q.pool.getPool(host)
		if !ok {
			selectedHost = hostIter()
			continue
		}

		conn := pool.Pick()
		if conn == nil {
			selectedHost = hostIter()
			continue
		}

		iter = q.attemptQuery(ctx, qry, conn)
		iter.host = selectedHost.Info()
		// Update host
		switch iter.err {
		case context.Canceled, context.DeadlineExceeded, ErrNotFound:
			// those errors represents logical errors, they should not count
			// toward removing a node from the pool
			selectedHost.Mark(nil)
			return iter
		default:
			selectedHost.Mark(iter.err)
		}

		// Exit if the query was successful
		// or query is not idempotent or no retry policy defined
		if iter.err == nil || !qry.IsIdempotent() || rt == nil {
			return iter
		}

		attemptsReached := !rt.Attempt(qry)
		retryType := rt.GetRetryType(iter.err)

		var stopRetries bool

		// If query is unsuccessful, check the error with RetryPolicy to retry
		switch retryType {
		case Retry:
			// retry on the same host
		case RetryNextHost:
			// retry on the next host
			selectedHost = hostIter()
		case Ignore:
			iter.err = nil
			stopRetries = true
		case Rethrow:
			stopRetries = true
		default:
			// Undefined? Return nil and error, this will panic in the requester
			return &Iter{err: ErrUnknownRetryType}
		}

		if stopRetries || attemptsReached {
			return iter
		}

		lastErr = iter.err
		continue
	}

	if lastErr != nil {
		return &Iter{err: lastErr}
	}

	return &Iter{err: ErrNoConnections}
}