StreamSets Groovy script retry on unknownHostException

groovy_retry_on_unknown_host_exception.groovy

In the Groovy Stage's init script, look for this line of code (around line 138):

            // Execute the request      
            HttpResponse response = httpClient.execute(request)

Comment out that line and replace that line with this section of code:

            // mbrooks 06/01/2024 -- comment out this line
            // HttpResponse response = httpClient.execute(request)

             
            // mbrooks 06/01/2024 -- begin section to add
            HttpResponse response
          
            // Retry counter for unknownHostException 
            int uheRetryCounter = 0

            // Number of retries if we get an unknownHostException
            int uheMaxRetries = 5

            // Sleep interval in ms between unknownHostException retries
            int uheSleepInterval = 1000 

            // Flag to keep retrying in case we get an unknownHostException
            boolean httpClientExecuteIsComplete = false 

            // Loop around the httpClient.execute call until we do not get an UnknownHostException
            // Typically, the loop will exit after the initial call
            while (!httpClientExecuteIsComplete && uheRetryCounter < uheMaxRetries){
          
                try {

                    // execute the HTTP request
                    response = httpClient.execute(request)
                  
                    // If we get to this line of code, we did not get an unknownHostException
                    // so set httpClientExecuteIsComplete to true to exit the retry loop
                    httpClientExecuteIsComplete = true
                  
                } catch (UnknownHostException uhe){
                  
                    sdc.log.error("Got an UnknownHostException in SaferPayments Groovy script ")
                    sdc.log.error(uhe.toString(), uhe)
                  
                    // Increment the retry counter
                    uheRetryCounter++

                    // If we have not reached max retries, sleep and stay in the loop
                    if (uheRetryCounter < uheMaxRetries){

                         // Calculate sleep interval to wait longer between each retry
                         int uheSleepMillis = uheSleepInterval * uheRetryCounter

                         // Sleep
                         sdc.log.info("Will sleep for " + uheSleepMillis + " millis after unknownHostException")
                         Thread.sleep(uheSleepMillis)

                         // Log the retry 
                         sdc.log.info("Will retry httpClient.execute command after unknownHostException")
                         sdc.log.info("unknownHostException retry # " + uheRetryCounter)
                      
                    // Rethrow the unknownHostException if we have exceeded max retries
                    } else {
                           sdc.log.info("Exceeded max retries of httpClient.execute command after unknownHostException")
                           throw(uhe)
                    }

                }
            }

            // mbrooks 06/01/2024 -- end section to add