bool DBInterface::_unavailable_data_handler()

in common/dbinterface.cpp [244:290]

• 37 lines of code
• 8 McCabe index (conditional complexity)

bool DBInterface::_unavailable_data_handler(const std::string& dbName, const char *data)
{
    auto start = system_clock::now();
    SWSS_LOG_DEBUG("Listening on pubsub channel '%s'", dbName.c_str());
    auto wait = duration<float>(PUB_SUB_MAXIMUM_DATA_WAIT);
    while (system_clock::now() - start < wait)
    {
        auto& channel = keyspace_notification_channels.at(dbName);
        auto ctx = channel->getContext();
        redisReply *reply;
        ctx->err = REDIS_OK; // Stop later redisGetReply early return on no data after first redisReply timeout
        int rc = redisGetReply(ctx, reinterpret_cast<void**>(&reply));
        if (rc == REDIS_ERR && ctx->err == REDIS_ERR_IO && errno == EAGAIN)
        {
            // Timeout
            continue;
        }
        if (rc != REDIS_OK)
        {
            throw RedisError("Failed to redisGetReply with on pubsub channel on dbName=" + dbName, ctx);
        }

        RedisReply r(reply);
        // r is an array of:
        //   0. 'type': 'pmessage',
        //   1. 'pattern': '__key*__:*'
        //   2. 'channel':
        //   3. 'data':
        redisReply& r3 = *r.getChild(3);
        if (r3.type != REDIS_REPLY_STRING)
        {
            throw system_error(make_error_code(errc::io_error),
                               "Wrong expected type of result");
        }

        if (strcmp(r3.str, data) == 0)
        {
            SWSS_LOG_INFO("'%s' acquired via pub-sub dbName=%s. Unblocking...", data, dbName.c_str());
            // Wait for a "settling" period before releasing the wait.
            sleep(DATA_RETRIEVAL_WAIT_TIME);
            return true;
        }
    }

    SWSS_LOG_WARN("No notification for '%s' from '%s' received before timeout.", data, dbName.c_str());
    return false;
}