266 lines
9.5 KiB
PHP
266 lines
9.5 KiB
PHP
<?php
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namespace App\BusProNet\Transport;
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use App\BusProNet\Exception\ApiClientException;
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use App\BusProNet\Exception\ImmediateConnectionCloseException;
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use App\BusProNet\Exception\TimeoutException;
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use Psr\Log\LoggerInterface;
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/**
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* BusPro's socket framing: one connection per request, each message prefixed with its length
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* as a 10 byte header. Knows nothing about what the messages contain.
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*/
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class SocketTransport
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{
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private float $operationStartTime;
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private int $selectedPort;
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/** @param list<int|string> $ports */
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public function __construct(
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private readonly LoggerInterface $logger,
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private readonly string $host,
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private readonly array $ports,
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private readonly int $connectionTimeout = 5,
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private readonly int $streamTimeout = 30,
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private readonly int $totalTimeout = 45,
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private readonly int $maxRetries = 25,
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) {
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}
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/**
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* Sends $body over a fresh connection and returns the response payload. $logMessage is
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* logged with $context and the chosen port once the connection is open.
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*
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* @param array<string, mixed> $context
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*
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* @throws ApiClientException
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* @throws ImmediateConnectionCloseException
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*/
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public function exchange(string $body, string $logMessage, array $context = []): string
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{
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$socket = $this->connect();
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$this->logger->info($logMessage, [...$context, 'port' => $this->selectedPort]);
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$this->send($socket, $body);
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try {
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// the length header is consumed and verified by receive(), this is the payload
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return $this->receive($socket);
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} finally {
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$this->disconnect($socket);
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}
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}
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/**
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* @return resource
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*
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* @throws ApiClientException
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* @throws TimeoutException
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*/
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private function connect()
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{
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// Randomly select a port from the available ports for load balancing
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$this->selectedPort = $this->ports[array_rand($this->ports)];
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$this->operationStartTime = microtime(true);
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$tries = 1;
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$errNo = $errStr = '';
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$errorCodesForRetry = [
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SOCKET_ECONNREFUSED,
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SOCKET_EBADF,
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];
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$openSocket = function (&$errNo, &$errStr) {
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return @fsockopen(
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$this->host,
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$this->selectedPort,
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$errNo,
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$errStr,
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$this->connectionTimeout
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);
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};
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$socket = $openSocket($errNo, $errStr);
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while (false === $socket && true === in_array($errNo, $errorCodesForRetry) && $this->maxRetries > $tries) {
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// Check if we've exceeded total timeout during retries
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if (microtime(true) - $this->operationStartTime > $this->totalTimeout) {
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$this->logger->error('Connection retry timeout exceeded', [
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'elapsed_time' => microtime(true) - $this->operationStartTime,
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'total_timeout' => $this->totalTimeout,
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'port' => $this->selectedPort,
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]);
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throw new TimeoutException('Connection timeout exceeded during retries');
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}
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$this->logger->warning('Could not connect to socket, retrying', [
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'error_message' => $errStr,
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'error_number' => $errNo,
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'attempt' => $tries,
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'port' => $this->selectedPort,
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]);
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++$tries;
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sleep(1);
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$socket = $openSocket($errNo, $errStr);
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}
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if (false !== $socket) {
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stream_set_timeout($socket, $this->streamTimeout);
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} else {
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$this->logger->error('Unable to open socket', [
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'error_message' => $errStr,
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'error_number' => $errNo,
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'elapsed_time' => microtime(true) - $this->operationStartTime,
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'port' => $this->selectedPort,
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]);
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throw new ApiClientException('Unable to open socket');
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}
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return $socket;
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}
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/**
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* @param resource $socket
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*
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* @throws TimeoutException
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*/
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private function send($socket, string $data): void
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{
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// Check total timeout before sending
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if (microtime(true) - $this->operationStartTime > $this->totalTimeout) {
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$this->logger->error('Total timeout exceeded before send', [
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'elapsed_time' => microtime(true) - $this->operationStartTime,
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'port' => $this->selectedPort,
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]);
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throw new TimeoutException('Total operation timeout exceeded before send');
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}
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// message length is prepended to actual message
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$send = sprintf('%010s', strlen($data)).$data;
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fwrite($socket, $send);
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}
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/**
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* Reads a single response message and returns its payload. The protocol prepends the
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* payload length as a 10 byte header, so the announced length is compared against what
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* actually arrived: a peer closing mid-stream would otherwise yield a silently
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* truncated body that only surfaces later as an unexplained parse failure.
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*
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* @param resource $socket
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*
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* @throws ApiClientException
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* @throws TimeoutException
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* @throws ImmediateConnectionCloseException
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*/
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private function receive($socket): string
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{
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$response = '';
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$readAttempts = 0;
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$totalTimeout = $this->totalTimeout;
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while (false === feof($socket)) {
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// Check total timeout before each read
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$elapsedTime = microtime(true) - $this->operationStartTime;
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if ($elapsedTime > $totalTimeout) {
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$this->logger->error('Total timeout exceeded during receive', [
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'elapsed_time' => $elapsedTime,
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'total_timeout' => $totalTimeout,
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'bytes_received' => strlen($response),
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'read_attempts' => $readAttempts,
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'port' => $this->selectedPort,
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]);
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throw new TimeoutException('Total operation timeout exceeded while receiving data');
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}
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$chunk = fread($socket, 4096);
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++$readAttempts;
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// Check if stream timed out on this specific read
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$metadata = stream_get_meta_data($socket);
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if (true === $metadata['timed_out']) {
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// Check if this is an immediate rejection (0 bytes, < 1 second)
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// This indicates the server is busy rather than a true timeout
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if (0 === strlen($response) && $elapsedTime < 1.0) {
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$this->logger->warning('Server closed connection immediately', [
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'elapsed_time' => $elapsedTime,
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'bytes_received' => 0,
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'read_attempts' => $readAttempts,
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'port' => $this->selectedPort,
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]);
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throw new ImmediateConnectionCloseException('Server closed connection immediately - server may be busy');
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}
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$this->logger->error('Stream read timeout detected', [
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'elapsed_time' => $elapsedTime,
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'bytes_received' => strlen($response),
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'read_attempts' => $readAttempts,
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'port' => $this->selectedPort,
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]);
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throw new TimeoutException('Stream timeout while reading from socket');
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}
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$response .= $chunk;
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}
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if (0 === strlen($response)) {
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$elapsedTime = microtime(true) - $this->operationStartTime;
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$this->logger->warning('Server closed connection without sending data', [
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'elapsed_time' => $elapsedTime,
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'read_attempts' => $readAttempts,
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'port' => $this->selectedPort,
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]);
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throw new ImmediateConnectionCloseException('Server closed connection without sending data');
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}
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return $this->extractPayload($response);
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}
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/**
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* @throws ApiClientException
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*/
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private function extractPayload(string $response): string
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{
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if (10 > strlen($response)) {
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$this->logger->error('Incomplete response header received from API', [
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'bytes_received' => strlen($response),
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'port' => $this->selectedPort,
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]);
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throw new ApiClientException(sprintf('Incomplete response header, got %d of 10 bytes', strlen($response)));
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}
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$header = substr($response, 0, 10);
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$announcedLength = (int) trim($header);
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$payload = substr($response, 10);
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if (1 > $announcedLength) {
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$this->logger->error('Empty response body announced by API', [
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'header' => trim($header),
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'port' => $this->selectedPort,
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]);
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throw new ApiClientException(sprintf('Response announced an empty body (header "%s")', trim($header)));
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}
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if (strlen($payload) !== $announcedLength) {
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$this->logger->error('Truncated response received from API', [
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'bytes_received' => strlen($payload),
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'announced_length' => $announcedLength,
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'port' => $this->selectedPort,
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]);
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throw new ApiClientException(sprintf('Truncated response, got %d of %d announced bytes', strlen($payload), $announcedLength));
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}
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return $payload;
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}
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/** @param resource $socket */
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private function disconnect($socket): void
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{
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@fclose($socket);
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}
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}
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