Question

我正在使用用于php的Datastax Cassandra驱动程序，并且希望能够检查查询是否失败以及数据库中是否找不到结果。现在，如果查询失败，则日志会报告以下内容

PHP Fatal error:  Uncaught exception 'Cassandra\\Exception\\RuntimeException' with message 'No hosts available for the control connection' in /var/www/html/includes/conditions.php:153\nStack trace:\n#0 /var/www/html/includes/conditions.php(153): Cassandra\\DefaultCluster->connect('loop_non_hadoop')\n#1 /var/www/html/index.php(159): check_key('0x851702c16d824...')\n#2 {main}\n  thrown in /var/www/html/includes/conditions.php on line 153, referer: http://172.29.195.10:5050/html/index.php

如果查询成功，则按预期返回数据。这是函数

function check_key($key){
    $cluster = Cassandra::cluster()->build();
    //set this to the appropriate keyspace
    $keyspace = 'loop_non_hadoop'; 
    $session = $cluster->connect($keyspace);
    $query = "SELECT * FROM events WHERE key=$key";
    $statement = new Cassandra\SimpleStatement($query);

    $results = $session->execute($statement);

    if(empty($results)){
        return;
    }
    else {
        foreach ($results as $row) {
            echo "<tr id='cell'><td>Title</td><td>" . $row['title'] . "</td></tr>";
            echo "<tr><td>Location</td><td>" . $row['locationName'] . "</td></tr>";
            echo "<tr id='cell'><td>City</td><td>" . $row['city'] . "</td></tr>";
            echo "<tr><td>State</td><td>" . $row['state'] . "</td></tr>";
            echo "<tr id='cell'><td>Zip</td><td>" . $row['zipcode'] . "</td></tr>";
            echo "<tr><td>Address</td><td>" . $row['street'] . "</td></tr>";
            echo "<tr id='cell'><td>Description</td><td>" . $row['summary'] . "</td></tr>";
            echo "<tr><td>Url</td><td>" . $row['url'] . "</td></tr>";
            echo "<tr id='cell'><td>Start</td><td>" . $row['start'] . "</td></tr>";
            echo "<tr><td>End</td><td>" . $row['end'] . "</td></tr>";
        }
        return true;
    }
}

提前感谢您的帮助

更新

我发布的上一个错误可能与我的VM和cassandra崩溃有关，无论哪种方式，我仍然需要检查空结果。

由于

更新

根据发布的建议，我最终做了以下

function check_key($key){
    try{
        $cluster = Cassandra::cluster()->build();
        //set this to the appropriate keyspace
        $keyspace = 'loop_non_hadoop'; 
        $session = $cluster->connect($keyspace);
        $query = "SELECT * FROM events WHERE key=$key";
        $statement = new Cassandra\SimpleStatement($query);

        $results = $session->execute($statement);

        foreach ($results as $row) {
            echo "<tr id='cell'><td>Title</td><td>" . $row['title'] . "</td></tr>";
            echo "<tr><td>Location</td><td>" . $row['locationName'] . "</td></tr>";
            echo "<tr id='cell'><td>City</td><td>" . $row['city'] . "</td></tr>";
            echo "<tr><td>State</td><td>" . $row['state'] . "</td></tr>";
            echo "<tr id='cell'><td>Zip</td><td>" . $row['zipcode'] . "</td></tr>";
            echo "<tr><td>Address</td><td>" . $row['street'] . "</td></tr>";
            echo "<tr id='cell'><td>Description</td><td>" . $row['summary'] . "</td></tr>";
            echo "<tr><td>Url</td><td>" . $row['url'] . "</td></tr>";
            echo "<tr id='cell'><td>Start</td><td>" . $row['start'] . "</td></tr>";
            echo "<tr><td>End</td><td>" . $row['end'] . "</td></tr>";
        }
        return true;
    }
    catch(Exception $e){
        //Casandra error
        var_dump($e->getMessage());
    }
    finally {
        return;
    }
}

感谢您的建议

Answer 1

使用try catch：

function check_key($key){
    try{
        $cluster = Cassandra::cluster()->build();
        //set this to the appropriate keyspace
        $keyspace = 'loop_non_hadoop'; 
        $session = $cluster->connect($keyspace);
        $query = "SELECT * FROM events WHERE key=$key";
        $statement = new Cassandra\SimpleStatement($query);

        $results = $session->execute($statement);

        if(empty($results)){
            return;
        }
        else {
            foreach ($results as $row) {
                echo "<tr id='cell'><td>Title</td><td>" . $row['title'] . "</td></tr>";
                echo "<tr><td>Location</td><td>" . $row['locationName'] . "</td></tr>";
                echo "<tr id='cell'><td>City</td><td>" . $row['city'] . "</td></tr>";
                echo "<tr><td>State</td><td>" . $row['state'] . "</td></tr>";
                echo "<tr id='cell'><td>Zip</td><td>" . $row['zipcode'] . "</td></tr>";
                echo "<tr><td>Address</td><td>" . $row['street'] . "</td></tr>";
                echo "<tr id='cell'><td>Description</td><td>" . $row['summary'] . "</td></tr>";
                echo "<tr><td>Url</td><td>" . $row['url'] . "</td></tr>";
                echo "<tr id='cell'><td>Start</td><td>" . $row['start'] . "</td></tr>";
                echo "<tr><td>End</td><td>" . $row['end'] . "</td></tr>";
            }
            return true;
        }
    }catch(\Exception $e){
        //Casandra error
        var_dump($e->getMessage());
    }
}

Datastax Cassandra PHP驱动程序

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