When I run the info command in redis-cli against a redis 3.2.4 server, it shows me this for expires:
expires=223518
However, when I then run a keys * command and ask for the ttl for each key, and only print out keys with a ttl > 0, I only see a couple hundred.
I thought that the expires is a count of the number of expiring keys but I am not even within an order of magnitude of this number.
Can someone clarify exactly what expires is meant to convey? Does this include both to-be-expired and previously expired but not yet evicted keys?
Update:
Here is how I counted the number of keys expiring:
task count_tmp_keys: :environment do redis = Redis.new(timeout: 100) keys = redis.keys '*' ct_expiring = 0 keys.each do |k| ttl = redis.ttl(k) if ttl > 0 ct_expiring += 1 puts "Expiring: #{k}; ttl is #{ttl}; total: #{ct_expiring}" STDOUT.flush end end puts "Total expiring: #{ct_expiring}" puts "Done at #{Time.now}" end When I ran this script it shows I have a total expiring of 78
When I run info, it says db0:keys=10237963,expires=224098,avg_ttl=0
Because 224098 is so much larger than 78, I am very confused. Is there perhaps a better way for me to obtain a list of all 225k expiring keys?
Also, how is it that my average ttl is 0? Wouldn't you expect it to be nonzero?
UPDATE
I have new information and a simple, 100% repro of this situation locally!
To repro: setup two redis processes locally on your laptop. Make one a slave of the other. On the slave process, set the following:
config set slave-serve-stale-data yes config set slave-read-only no Now, connect to the slave (not the master) and run:
set foo 1 expire foo 10 After 10 seconds, you will no longer be able to access foo, but info command will still show that you have 1 key expiring with an average ttl of 0.
Can someone explain this behavior?
2 Answers
Answers 1
The expires just returns the size of keys that will expire not the time.
The source code of 3.2.4
long long keys, vkeys; keys = dictSize(server.db[j].dict); vkeys = dictSize(server.db[j].expires); if (keys || vkeys) { info = sdscatprintf(info, "db%d:keys=%lld,expires=%lld,avg_ttl=%lld\r\n", j, keys, vkeys, server.db[j].avg_ttl); } It just calculate the size of server.db[j].expires. (note j is the database index).
Answers 2
expires contains existing keys with TTL which will expire, not including already expired keys. Example ( with omission of extra information from info command for brevity ):
127.0.0.1:6379> flushall OK 127.0.0.1:6379> SETEX mykey1 1000 "1" OK 127.0.0.1:6379> SETEX mykey2 1000 "2" OK 127.0.0.1:6379> SETEX mykey3 1000 "3" OK 127.0.0.1:6379> info # Keyspace db0:keys=3,expires=3,avg_ttl=992766 127.0.0.1:6379> SETEX mykey4 1 "4" OK 127.0.0.1:6379> SETEX mykey5 1 "5" OK 127.0.0.1:6379> info # Keyspace db0:keys=3,expires=3,avg_ttl=969898 127.0.0.1:6379> keys * 1) "mykey2" 2) "mykey3" 3) "mykey1" 127.0.0.1:6379> Can you share your script which counts the keys ?
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