Method initialize

src/IO/ReadWriteBufferFromHTTP.cpp:406–462

std::unique_ptr<ReadBuffer> ReadWriteBufferFromHTTP::initialize()
{
    Poco::Net::HTTPResponse response;

    std::optional<HTTPRange> range;
    if (withPartialContent())
        range = HTTPRange{getOffset(), read_range.end};

    auto result = callWithRedirects(response, method, range);

    if (range.has_value() && response.getStatus() != Poco::Net::HTTPResponse::HTTPStatus::HTTP_PARTIAL_CONTENT)
    {
        /// Having `200 OK` instead of `206 Partial Content` is acceptable in case we retried with range.begin == 0.
        if (getOffset() != 0)
        {
            /// Retry 200 OK
            if (response.getStatus() == Poco::Net::HTTPResponse::HTTPStatus::HTTP_OK)
            {
                String explanation = fmt::format(
                    "Cannot read with range: [{}, {}] (response status: {}, reason: {}), will retry",
                    getOffset(), read_range.end ? toString(*read_range.end) : "-",
                    toString(response.getStatus()), response.getReason());

                /// it is retriable error
                throw HTTPException(
                    ErrorCodes::HTTP_RANGE_NOT_SATISFIABLE,
                    current_uri.toString(),
                    Poco::Net::HTTPResponse::HTTP_REQUESTED_RANGE_NOT_SATISFIABLE,
                    response.getReason(),
                    explanation);
            }
            throw Exception(
                ErrorCodes::HTTP_RANGE_NOT_SATISFIABLE,
                "Cannot read with range: [{}, {}] (response status: {}, reason: {})",
                getOffset(),
                read_range.end ? toString(*read_range.end) : "-",
                toString(response.getStatus()),
                response.getReason());
        }
        if (read_range.end)
        {
            /// We could have range.begin == 0 and range.end != 0 in case of DiskWeb and failing to read with partial content
            /// will affect only performance, so a warning is enough.
            LOG_WARNING(log, "Unable to read with range header: [{}, {}]", read_range.begin.value_or(0), *read_range.end);
        }
    }

    response.getCookies(cookies);
    response.getHeaders(response_headers);
    content_encoding = response.get("Content-Encoding", "");

    // Remember file size. It'll be used to report eof in next nextImpl() call.
    if (!read_range.end && response.hasContentLength())
        file_info = parseFileInfo(response, range.has_value() ? getOffset() : 0);

    return std::move(result).transformToReadBuffer(use_external_buffer ? 0 : buffer_size);
}