概述
Spring Batch在处理过程中遇到错误job默认会执行失败。为了提高应用程序的健壮性，我们需要处理临时异常造成失败。本文我们探讨如何配置Spring Batch的重试逻辑。
1. 应用示例
批处理应用读取csv文件
sammy, 1234, 31/10/2015, 10000 john, 9999, 3/12/2015, 12321
然后，通过调用rest接口处理每条记录，获取用户的年龄和邮编属性，为了正确输出日期，可以在属性上增加@XmlJavaTypeAdapter(LocalDateTimeAdapter.class)注解：
@XmlRootElement(name = “transactionRecord”)
@Data
public class Transaction {
private String username;
private int userId;
private int age;
private String postCode;
private LocalDateTime transactionDate;
private double amount;
}
处理类如下
public class RetryItemProcessor implements ItemProcessor<Transaction, Transaction> {
private static final Logger LOGGER = LoggerFactory.getLogger(RetryItemProcessor.class);
@Autowired
private CloseableHttpClient closeableHttpClient;
@Override
public Transaction process(Transaction transaction) throws IOException, JSONException {
LOGGER.info("Attempting to process user with id={}", transaction.getUserId());
HttpResponse response = fetchMoreUserDetails(transaction.getUserId());
//parse user's age and postCode from response and update transaction
String result = EntityUtils.toString(response.getEntity());
JSONObject userObject = new JSONObject(result);
transaction.setAge(Integer.parseInt(userObject.getString("age")));
transaction.setPostCode(userObject.getString("postCode"));
return transaction;
}
private HttpResponse fetchMoreUserDetails(int id) throws IOException {
final HttpGet request = new HttpGet("http://www.testapi.com:81/user/" + id);
return closeableHttpClient.execute(request);
}
}
这里当然也可以使用RestTemplate进行调用，调用服务仅为了测试，读者可以搭建测试接口。
最终输出结果为
<transactionRecord>
<transactionRecord>
<amount>10000.0</amount>
<transactionDate>2015-10-31 00:00:00</transactionDate>
<userId>1234</userId>
<username>sammy</username>
<age>10</age>
<postCode>430222</postCode>
</transactionRecord>
...
</transactionRecord>
2. 给处理增加重试功能
如果连接rest接口因为网络不稳定导致连接超时，那么批处理将失败。但这种错误并不是不能恢复，可以通过重试几次进行尝试。
因此我们配置批处理job在失败的情况下重试三次
@Configuration
@EnableBatchProcessing
public class SpringBatchRetryConfig {
private static final String[] tokens = { "username", "userid", "transactiondate", "amount" };
private static final int TWO_SECONDS = 2000;
@Autowired
private JobBuilderFactory jobBuilderFactory;
@Autowired
private StepBuilderFactory stepBuilderFactory;
@Value("input/recordRetry.csv")
private Resource inputCsv;
@Value("file:xml/retryOutput.xml")
private Resource outputXml;
public ItemReader<Transaction> itemReader(Resource inputData) throws ParseException {
DelimitedLineTokenizer tokenizer = new DelimitedLineTokenizer();
tokenizer.setNames(tokens);
DefaultLineMapper<Transaction> lineMapper = new DefaultLineMapper<>();
lineMapper.setLineTokenizer(tokenizer);
lineMapper.setFieldSetMapper(new RecordFieldSetMapper());
FlatFileItemReader<Transaction> reader = new FlatFileItemReader<>();
reader.setResource(inputData);
reader.setLinesToSkip(1);
reader.setLineMapper(lineMapper);
return reader;
}
@Bean
public CloseableHttpClient closeableHttpClient() {
final RequestConfig config = RequestConfig.custom()
.setConnectTimeout(TWO_SECONDS)
.build();
return HttpClientBuilder.create().setDefaultRequestConfig(config).build();
}
@Bean
public ItemProcessor<Transaction, Transaction> retryItemProcessor() {
return new RetryItemProcessor();
}
@Bean
public ItemWriter<Transaction> itemWriter(Marshaller marshaller) {
StaxEventItemWriter<Transaction> itemWriter = new StaxEventItemWriter<>();
itemWriter.setMarshaller(marshaller);
itemWriter.setRootTagName("transactionRecord");
itemWriter.setResource(outputXml);
return itemWriter;
}
@Bean
public Marshaller marshaller() {
Jaxb2Marshaller marshaller = new Jaxb2Marshaller();
marshaller.setClassesToBeBound(Transaction.class);
return marshaller;
}
@Bean
public Step retryStep(@Qualifier("retryItemProcessor") ItemProcessor<Transaction, Transaction> processor,
ItemWriter<Transaction> writer) throws ParseException {
return stepBuilderFactory.get("retryStep")
.<Transaction, Transaction>chunk(10)
.reader(itemReader(inputCsv))
.processor(processor)
.writer(writer)
.faultTolerant()
.retryLimit(3)
.retry(ConnectTimeoutException.class)
.retry(DeadlockLoserDataAccessException.class)
.build();
}
@Bean(name = "retryBatchJob")
public Job retryJob(@Qualifier("retryStep") Step retryStep) {
return jobBuilderFactory
.get("retryBatchJob")
.start(retryStep)
.build();
}
这里调用faultTolerant()方法启用重试功能，并设置重试次数和对应异常。
3. 测试重试功能
我们测试场景，期望接口在一定时间内返回年龄和邮编。前两次调用API抛出异常ConnectTimeoutException
第三次成功调用
@RunWith(SpringRunner.class)
@SpringBatchTest
@EnableAutoConfiguration
@ContextConfiguration(classes = { SpringBatchRetryConfig.class })
public class SpringBatchRetryIntegrationTest {
private static final String TEST_OUTPUT = "xml/retryOutput.xml";
private static final String EXPECTED_OUTPUT = "src/test/resources/output/batchRetry/retryOutput.xml";
@Autowired
private JobLauncherTestUtils jobLauncherTestUtils;
@MockBean
private CloseableHttpClient closeableHttpClient;
@Mock
private CloseableHttpResponse httpResponse;
@Test
public void whenEndpointAlwaysFail_thenJobFails() throws Exception {
when(closeableHttpClient.execute(any()))
.thenThrow(new ConnectTimeoutException("Endpoint is down"));
JobExecution jobExecution = jobLauncherTestUtils.launchJob(defaultJobParameters());
JobInstance actualJobInstance = jobExecution.getJobInstance();
ExitStatus actualJobExitStatus = jobExecution.getExitStatus();
assertThat(actualJobInstance.getJobName(), is("retryBatchJob"));
assertThat(actualJobExitStatus.getExitCode(), is("FAILED"));
assertThat(actualJobExitStatus.getExitDescription(), containsString("org.apache.http.conn.ConnectTimeoutException"));
}
@Test
public void whenEndpointFailsTwicePasses3rdTime_thenSuccess() throws Exception {
FileSystemResource expectedResult = new FileSystemResource(EXPECTED_OUTPUT);
FileSystemResource actualResult = new FileSystemResource(TEST_OUTPUT);
//前两次调用失败，第三次继续执行
when(httpResponse.getEntity())
.thenReturn(new StringEntity("{ "age":10, "postCode":"430222" }"));
when(closeableHttpClient.execute(any()))
.thenThrow(new ConnectTimeoutException("Timeout count 1"))
.thenThrow(new ConnectTimeoutException("Timeout count 2"))
.thenReturn(httpResponse);
JobExecution jobExecution = jobLauncherTestUtils.launchJob(defaultJobParameters());
JobInstance actualJobInstance = jobExecution.getJobInstance();
ExitStatus actualJobExitStatus = jobExecution.getExitStatus();
assertThat(actualJobInstance.getJobName(), is("retryBatchJob"));
assertThat(actualJobExitStatus.getExitCode(), is("COMPLETED"));
AssertFile.assertFileEquals(expectedResult, actualResult);
}
private JobParameters defaultJobParameters() {
JobParametersBuilder paramsBuilder = new JobParametersBuilder();
paramsBuilder.addString("jobID", String.valueOf(System.currentTimeMillis()));
return paramsBuilder.toJobParameters();
}
}
job成功执行
从日志可以看到两次失败，最终调用成功。
19:06:57.758 [main] INFO o.b.batch.service.RetryItemProcessor - Attempting to process user with id=1234
19:06:57.758 [main] INFO o.b.batch.service.RetryItemProcessor - Attempting to process user with id=1234
19:06:57.758 [main] INFO o.b.batch.service.RetryItemProcessor - Attempting to process user with id=1234
19:06:57.758 [main] INFO o.b.batch.service.RetryItemProcessor - Attempting to process user with id=9999
19:06:57.773 [main] INFO o.s.batch.core.step.AbstractStep - Step: [retryStep] executed in 31ms
同时也定义了另一个测试，重试多次并失败，抛出异常 ConnectTimeoutException。
4. 总结
本文我们学习如何配置Spring Batch的重试逻辑。通过示例学习配置并机型测试，仅为个人经验，希望能给大家一个参考，也希望大家多多支持靠谱客。
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