java.lang.ClassCastException: [B cannot be cast to java.util.List

Spring JIRA | Mark Paluch | 8 months ago
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    The concurrent use of {{SCAN}} and iteration over the resulting {{Cursor}} causes various Exceptions using the Jedis Driver. Test case: https://gist.github.com/mp911de/327cb876117bc1d74049aff25e5509cb {code} redis.clients.jedis.exceptions.JedisConnectionException: Unknown reply: 5 at redis.clients.jedis.Protocol.process(Protocol.java:154) at redis.clients.jedis.Protocol.processMultiBulkReply(Protocol.java:196) at redis.clients.jedis.Protocol.process(Protocol.java:147) at redis.clients.jedis.Protocol.processMultiBulkReply(Protocol.java:196) at redis.clients.jedis.Protocol.process(Protocol.java:147) at redis.clients.jedis.Protocol.read(Protocol.java:205) at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:297) at redis.clients.jedis.Connection.getRawObjectMultiBulkReply(Connection.java:242) at redis.clients.jedis.Connection.getObjectMultiBulkReply(Connection.java:248) at redis.clients.jedis.BinaryJedis.hscan(BinaryJedis.java:3300) at org.springframework.data.redis.connection.jedis.JedisConnection$5.doScan(JedisConnection.java:3437) {code} {code} java.lang.ClassCastException: [B cannot be cast to java.util.List at redis.clients.jedis.Connection.getRawObjectMultiBulkReply(Connection.java:242) at redis.clients.jedis.Connection.getObjectMultiBulkReply(Connection.java:248) at redis.clients.jedis.BinaryJedis.hscan(BinaryJedis.java:3300) at org.springframework.data.redis.connection.jedis.JedisConnection$5.doScan(JedisConnection.java:3437) {code} This issue gets only visible if: 1. Multiple threads try to use the {{SCAN}} command and iterate over the resulting {{Cursor}} 2. There is enough data to keep the iteration busy The reason is that the resulting {{Cursor}} s hold a reference to the connection that was allocated during the {{.scan()}} invocation. {{.scan()}} allocates a connection but then it releases the connection back and so can multiple {{Cursors}} in different {{Thread}} s share the same Jedis connection.

    Spring JIRA | 8 months ago | Mark Paluch
    java.lang.ClassCastException: [B cannot be cast to java.util.List

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    Root Cause Analysis

    1. java.lang.ClassCastException

      [B cannot be cast to java.util.List

      at redis.clients.jedis.Connection.getRawObjectMultiBulkReply()
    2. Jedis
      BinaryJedis.hscan
      1. redis.clients.jedis.Connection.getRawObjectMultiBulkReply(Connection.java:242)
      2. redis.clients.jedis.Connection.getObjectMultiBulkReply(Connection.java:248)
      3. redis.clients.jedis.BinaryJedis.hscan(BinaryJedis.java:3300)
      3 frames
    3. Spring Data Redis
      JedisConnection$5.doScan
      1. org.springframework.data.redis.connection.jedis.JedisConnection$5.doScan(JedisConnection.java:3437)
      1 frame