There is 3 Hashes in my redis database:
set:recentbooks
set:badbooks
set:funnybooks
All hashes contain book Ids as key.
I want to remove the book that has 234 Id from all hashes.
How can I do this:
Lua Scripting
Pipeline
Other?
Using the ServiceStack redis client API, you could pipeline your delete requests like thus:
var client = new RedisClient("localhost", 6379);
using (var pipeline = client.CreatePipeline())
{
pipeline.QueueCommand(r => r.RemoveEntryFromHash("set:recentbooks", "234"));
pipeline.QueueCommand(r => r.RemoveEntryFromHash("set:badbooks", "234"));
pipeline.QueueCommand(r => r.RemoveEntryFromHash("set:funnybooks", "234"));
// All deletes will be sent at once.
pipeline.Flush();
}
Using a LUA script, it's easy:
EVAL "redis.call('HDEL',KEYS[2],KEYS[1]);
redis.call('HDEL',KEYS[3],KEYS[1]);
redis.call('HDEL',KEYS[4],KEYS[1]);"
4 234 set:recentbooks set:badbooks set:funnybooks
I've never used ServiceStack, but with the info above you have what's required to invoke the redis client in ServiceStack to delete the keys.
You can also write the lua script in a file, then call it like this with parameters:
redis-cli> EVAL "$(cat myscript.lua)" 4 234 set:recentbooks set:badbooks set:funnybooks
Related
I follow some tutorial on web to setup Spring Cache with redis,
my function look like this:
#Cacheable(value = "post-single", key = "#id", unless = "#result.shares < 500")
#GetMapping("/{id}")
public Post getPostByID(#PathVariable String id) throws PostNotFoundException {
log.info("get post with id {}", id);
return postService.getPostByID(id);
}
As I understand, the value inside #Cacheable is the cache name and key is the cache key inside that cache name. I also know Redis is an in-memory key/value store. But now I'm confused about how Spring will store cache name to Redis because looks like Redis only manages key and value, not cache name.
Looking for anyone who can explain to me.
Thanks in advance
Spring uses cache name as the key prefix when storing your data. For example, when you call your endpoint with id=1 you will see in Redis this key
post-single::1
You can customize the prefix format through CacheKeyPrefix class.
I'm trying to push an entry in a list in Redis and also want to update the TTL of the list every time a new entry comes in. I can do that my simple calling the EXPIRE "my-list" ttl using Redis. Since my application is receiving heavy traffic, I want to reduce the number of calls to redis.
Can I set my TTL during the push operation in Redis, i.e RPUSH "mylist" I1 I2...IN ex "TTL", does redis support this time of command functionality. I can see that it does support this for the String data structures.
Redis does not have dedicated commands to push and expire the List, although as you've mentioned it does have something like that for the String data type.
The way you'd go about this challenge is to compose your own "command" from existing ones. Instead of having your application call these commands, however, you would use a Lua script as explained in the EVAL documentation page.
Lua scripts are cached and run atomically on the server. One such as the following would probably help in your case - it expects to get the key name, the pushed element and the expiry value:
local reply = redis.call('RPUSH', KEYS[1], ARGV[1])
redis.call('EXPIRE', KEYS[1], ARGV[2])
return reply
I am using redis in a node application for caching data and now i want to access and modify stored data using a django application on the same server but i can't access to the data.
Django connection:
CACHES = {
"default": {
"BACKEND": "django_redis.cache.RedisCache",
"LOCATION": "redis://127.0.0.1:6379/0",
"OPTIONS": {
"CLIENT_CLASS": "django_redis.client.DefaultClient",
}
}
}
using keys * command in terminal:
$ redis-cli
127.0.0.1:6379> keys *
1) "sess:Ok0eYOko5WaV7njfX04qgqG1oYe0xiL1" -> this key is set in node
2) ":1:from-django" -> this key is set in django
Accessing keys in django application:
keys = cache.keys('*')
print(keys) # prints only one key => ['from-django']
I can't access first key that is set in node application and also django stored keys are prifixed with :1: by default!
I want to share all keys between node and django but they only access their own keys.
Any idea?
You can access all of data from any where, But you are working with Redis in Cache model! and all of Cache systems has own unique data structure, You must work with Redis in Database model and scan it yourself.
Use Python Redis package to access all of Redis in your application.
I am using Jedis java client for redis. My requirement is that when someone add item to list, say mylist by doing jedisClient.lpush("mylist", "this is my msg"), I need to get notification.
Is this possible ?
Yes, it is possible to achieve that in one of two ways.
The first approach is to use Redis' keyspace notifications. Configure Redis to generate list events with the following configuration directive:
CONFIG SET notify-keyspace-events El
Then, subscribe to the relevant channel/channels. If you want to subscribe only to mylist's changes, do:
SUBSCRIBE __keyevent#0__:mylist
Or, use PSUBSCRIBE and listen to events to matching key names that match a pattern.
Note, however, that keysapce notifications will not provide the actual pushed value. You can use Lua scripts as an alternate approach and implement your own notifications mechanism. For example, use the following script to push and publish a custom message to a custom channel:
local l = redis.call("LPUSH", KEYS[1], ARGS[1])
redis.call("PUBLISH", "mylistnotif:" .. KEYS[1], "Pushed value " .. ARGS[1])
return l
Make sure that "someone" uses that script to do the actual list-pushing and subscribe to the relevant channel/channels.
User has DisplayName and it is unique for Users.
I want to Create User but firstly I have to check display name (DisplayName could not be duplicated for Users)
I've checked ServiceStack examples and I could not see Transactional Insert/Update with validation check.
How can I perform it. I dont want to write "Validation Tasks" for redis db.
I dont want inconsistency in db.
The ServiceStack.Redis client does have support for Redis's WATCH and transactions where these Redis commands:
WATCH mykey
test = EXIST mykey
MULTI
SET mykey $val
EXEC
Can be accomplished with:
var redis = new RedisClient();
redis.Watch("mykey");
if (!redis.ContainsKey("mykey")) return;
using (var trans = redis.CreateTransaction()) {
trans.QueueCommand(r => r.Set("mykey", "val"));
trans.Commit();
}
Is possible to perform redis transactions. More information here
WATCH mykey
test = EXIST mykey
MULTI
SET mykey $val
EXEC
Using PHP have um better example: here