Scanning keys in a cluster (RedisCommandExecutionException: MOVED)

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Daniel López

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Feb 15, 2016, 4:39:00 AM2/15/16

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Hey there,

I'm trying to scan the keys inside a hash in a redis cluster and I'm getting RedisCommandExecutionExceptions. A similar approach works without a cluster so I'm not sure if I'm not doing it correctly in a cluster.

Let's assume the cluster is defined as x.y.z.110:6379,x.y.z.111:6379,x.y.z.112:6379, with slaves running from 113 to 115.

My code looks like this:

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try (RedisAdvancedClusterCommands<String, Cacheable> redisConnection = redisClient.connect(codec).sync()) {

NodeSelection<String, Cacheable> masters = redisConnection.masters();

Set<Object> keys = Collections.synchronizedSet(new HashSet<>());

ScanArgs scanArgs = new ScanArgs();

scanArgs.match("*").limit(1000);

masters.asMap().values().forEach(commands -> {

MapScanCursor<String, Cacheable> cursor;

try {

cursor = commands.hscan(preffix, scanArgs);

keys.addAll(cursor.getMap().keySet());

while (!cursor.isFinished()) {

cursor = commands.hscan(preffix, ScanCursor.of(cursor.getCursor()), scanArgs);

keys.addAll(cursor.getMap().keySet());

}

} catch (Exception e) {

log.error("Error accessing redis cluster to scan keys", e);

}

});

return keys;

}

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And the exception I get is this one:

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Caused by: com.lambdaworks.redis.RedisCommandExecutionException: MOVED 9316 x.y.z.111:6379

at com.lambdaworks.redis.protocol.AsyncCommand.completeResult(AsyncCommand.java:86)

at com.lambdaworks.redis.protocol.AsyncCommand.complete(AsyncCommand.java:76)

at com.lambdaworks.redis.protocol.CommandHandler.decode(CommandHandler.java:170)

at com.lambdaworks.redis.protocol.CommandHandler.channelRead(CommandHandler.java:141)

at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:307)

at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:293)

at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86)