{"record":{"id":"7e4d2d7fc5b31f90","repo":"alibaba/canal","slug":"failed-to-ack-after","errorCode":null,"errorMessage":"failed to ack after ","messagePattern":"failed to ack after ","errorType":"exception","errorClass":"CanalClientException","httpStatus":null,"severity":"error","filePath":"client/src/main/java/com/alibaba/otter/canal/client/impl/ClusterCanalConnector.java","lineNumber":275,"sourceCode":"    }\n\n    @Override\n    public void ack(long batchId) throws CanalClientException {\n        int times = 0;\n        while (times < retryTimes) {\n            try {\n                currentConnector.ack(batchId);\n                return;\n            } catch (Throwable t) {\n                logger.warn(String.format(\"something goes wrong when acking data from server:%s\",\n                    currentConnector != null ? currentConnector.getAddress() : \"null\"), t);\n                times++;\n                restart();\n                logger.info(\"restart the connector for next round retry.\");\n            }\n        }\n\n        throw new CanalClientException(\"failed to ack after \" + times + \" times retry\");\n    }\n\n    private void restart() throws CanalClientException {\n        disconnect();\n        try {\n            Thread.sleep(retryInterval);\n        } catch (InterruptedException e) {\n            throw new CanalClientException(e);\n        }\n        connect();\n    }\n\n    // ============================= setter / getter\n    // ============================\n\n    public String getUsername() {\n        return username;\n    }","sourceCodeStart":257,"sourceCodeEnd":293,"githubUrl":"https://github.com/alibaba/canal/blob/87be50e87686a3e8af08c368d0e1ffd1f59eb04a/client/src/main/java/com/alibaba/otter/canal/client/impl/ClusterCanalConnector.java#L257-L293","documentation":"Error \"failed to ack after \" thrown in alibaba/canal.","triggerScenarios":"Thrown at client/src/main/java/com/alibaba/otter/canal/client/impl/ClusterCanalConnector.java:275 when the library encounters an invalid state.","commonSituations":"Ack failure after get. Retry the ack on the next available node with the same batchId, and treat repeated failure as data-loss risk requiring reconciliation from the last confirmed position.","solutions":["Ensure the batchId passed to ack() matches one returned by getWithoutAck and has not been acked already.","If the connector failed over to a standby canal server, re-subscribe and re-fetch instead of acking the old batchId.","Catch CanalClientException around ack() and retry with backoff, or restart the consumer to resume from the last confirmed position."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"87be50e87686a3e8af08c368d0e1ffd1f59eb04a","analyzedAt":"2026-08-14T04:30:11.918Z","schemaVersion":2},"datasetVersion":"2026-08-14T05:17:29.042Z"}