/**
* handle a GET. Since any node can handle a GET request, we need to gracefully handle misses.
* the algorithm follows
*
* ("target storage node" and "target node" refer to a node that is supposed to store the requested data)
*
* if we are NOT a target storage node for the file being requested
* send a redirect to a node that supposedly contains the data
*
* else if we are a target storage node
* if we contain the file
* send the file to the client
* else if we do not contain the file we might need to self heal
* if we are configured to self heal
* call the self healing function (described below)
* else
* send a 404 to the client
* endif
* endif
* endif
*
*/
public function handle()
{
$iAmATarget = $this->iAmATarget();
if ($iAmATarget) {
if (file_exists($this->finalPath)) {
$this->sendFile();
} else {
if ($this->canSelfHeal()) {
try {
if (!$this->selfHeal()) {
WebDFS_Helper::send404($this->params['name']);
}
} catch (Exception $e) {
$this->errorLog('selfHeal', $e->getMessage(), $e->getTraceAsString());
WebDFS_Helper::send500();
}
} else {
WebDFS_Helper::send404($this->params['name']);
}
}
} else {
// get the paths, choose one, and print a 301 redirect
$nodes = $this->getTargetNodes();
if ($nodes) {
WebDFS_Helper::send301(join('/', array($nodes[0]['staticUrl'], $this->params['pathHash'], $this->params['name'])));
}
}
}
/**
*
* self heal
*
* Self heal accomplishes one of two things depending on when and why it is called.
* It can be used to automatically move data from an old config when scaling.
* And it can be used to fetch and save to disk a copy of some data from a peer server when
* data has been lost; say, when a server failed.
*
* The self healing process is initiated when we have been asked for some data that is supposedly
* stored on our disk and we cannot find it.
*
* When we are asked to fetch data that is supposedly stored on our disk, one of the following things can be true:
*
* 1) The data never was put on disk and this is simply servicing a request for data that is non-existent
* ( we currently do not have a reliable way to tell what is supposedly on our disk
* this could change if we start keeping a partial index in memory of what is supposedly on the disk. )
*
* 2) For some reason, the data is missing or corrupted and we need to heal ourselves
*
* 3) New servers and disks have been added to the cluster configuration and we are performing
* an auto move operation
*
* Currently, we have to assume that we "might" or "probably" have been asked to store the data
* at some point in the past. Therefore we are forced to search for the data before we return a 404 to the client
*
* heal is the function that fecthes the file from a peer server
* and then saves it to the temp path.
*
* self heal will:
* iterate the all data configs starting with the oldest and look for the old data.
* if we locate the data
* we download it
* save it to disk
* fsync the data
*
* The above facilitates self heal and the first part of auto move
* To complete the auto move we need to check and see if the data needs to be deleted from the
* source. The source being the server from which we downloaded the file
* for the self healing process. we only delete the source if the server in question
* is NOT in the target nodes list we derive from the current data config
*
*
* If we cannot find that data at all;
* remove the tempfile
* we send a "404 not found" message back to the client
*
* endif
*
*/
public function selfHeal()
{
$filename = $this->params['name'];
$tmpPath = $this->tmpPath;
$fd = fopen($tmpPath, "wb+");
if (!$fd) {
$this->errorLog('selfHealNoFile', $tmpPath, $filename);
WebDFS_Helper::send500();
return;
}
$locator = null;
$configIdx = null;
$copiedFrom = null;
$fileSize = null;
$nodes = null;
$healed = false;
if ($this->params['getContext'] != self::GET_CONTEXT_AUTOMOVE) {
$headers = array();
$headers[0] = self::HEADER_GET_CONTEXT . ': ' . self::GET_CONTEXT_AUTOMOVE;
$curl = curl_init();
curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);
curl_setopt($curl, CURLOPT_FILE, $fd);
curl_setopt($curl, CURLOPT_TIMEOUT, 10);
curl_setopt($curl, CURLOPT_HEADER, false);
curl_setopt($curl, CURLOPT_FAILONERROR, true);
curl_setopt($curl, CURLOPT_BINARYTRANSFER, true);
curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);
$totalConfigs = count($this->config['data']);
for ($configIdx = $totalConfigs - 1; $configIdx >= 0; $configIdx--) {
if ($configIdx == 0) {
// 0 means we are looking at the most current config
$locator = $this->locator;
$nodes = $this->getTargetNodes();
} else {
$config = $this->config['data'][$configIdx];
$locClass = $config['locatorClassName'];
$locator = new $locClass($config);
$nodes = $locator->findNodes($filename);
}
foreach ($nodes as $node) {
// check to see if we are looking at node data for ourselves
// in which case we do not want to make a request as that
// would be wasted resources and pointless
if ($node['proxyUrl'] != $this->config['thisProxyUrl']) {
$url = join('/', array($node['staticUrl'], $this->params['pathHash'], $filename));
curl_setopt($curl, CURLOPT_URL, $url);
curl_exec($curl);
$info = curl_getinfo($curl);
if (!curl_errno($curl) && $info['http_code'] < 400) {
fclose($fd);
$copiedFrom = $node;
$this->debugLog('autoMove');
$healed = true;
break 2;
}
ftruncate($fd, 0);
}
}
}
}
// at this point we have achieved the same effect as a spoolData() call
// so now we:
// save the data
// return the file back to the caller
// if the source proxy url is NOT in the current target nodes list
// we issue a delete command to the source node
// and delete the data from the old location
// endif
if (!$healed) {
// we cannot find the data
// remove the temp file
// send a 404
fclose($fd);
unlink($tmpPath);
WebDFS_Helper::send404($this->params['name']);
} else {
if ($healed) {
// need to check to see if we wrote all of the data
// as dictated by the content length headeer
$fileSize = filesize($tmpPath);
if ($fileSize != $info['download_content_length']) {
unlink($tmpPath);
$msg = sprintf($this->config['exceptionMsgs']['incompleteWrite'], $info['download_content_length'], $fileSize);
throw new WebDFS_Exception($msg);
}
$this->saveData();
$this->sendFile();
// here we check if the source from where we copied
// is included in the the current target node list
$position = $this->getTargetNodePosition(null, $copiedFrom['proxyUrl']);
if ($position == WebDFS::POSITION_NONE) {
$this->sendDeleteForHeal($copiedFrom['proxyUrl'] . '/' . $filename);
}
}
}
}
