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
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sammy, 1234, 31/10/2015, 10000john, 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：
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@XmlRootElement(name = “transactionRecord”)@Datapublic 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
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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
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<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
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@Configuration@EnableBatchProcessingpublic 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
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@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服务器之家。
原文链接：https://blog.csdn.net/neweastsun/article/details/109264179
