Optional blockingOptional dataUsed for "database" commands to enforce type checking.
Protected loggerMaximum number of parameters allowed. -1 for no maximum.
Minimum number of parameters require.
Optional pubUsed when PUB/SUB is in effect.
Optional signSign is used in commands with a compliment command. The only current example is INCR/DECR. Sign is 1 for INCR and -1 for DECR
Optional txUsed in transactions to enqueue a command.
Every command must implement the execute method.
Protected processPrivate remove
Available since 2.0.0.
BLPOP key [key ...] timeout
BLPOP is a blocking list pop primitive. It is the blocking version of LPOP because it blocks the connection when there are no elements to pop from any of the given lists. An element is popped from the head of the first list that is non-empty, with the given keys being checked in the order that they are given.
Non-blocking behavior
When BLPOP is called, if at least one of the specified keys contains a non-empty list, an element is popped from the head of the list and returned to the caller together with the key it was popped from.
Keys are checked in the order that they are given. Let's say that the key list1 doesn't exist and list2 and list3 hold non-empty lists. Consider the following command:
BLPOP guarantees to return an element from the list stored at list2 (since it is the first non empty list when checking list1, list2 and list3 in that order).
Blocking behavior
If none of the specified keys exist, BLPOP blocks the connection until another client performs an LPUSH or RPUSH operation against one of the keys.
Once new data is present on one of the lists, the client returns with the name of the key unblocking it and the popped value.
When BLPOP causes a client to block and a non-zero timeout is specified, the client will unblock returning a nil multi-bulk value when the specified timeout has expired without a push operation against at least one of the specified keys.
The timeout argument is interpreted as an integer value specifying the maximum number of seconds to block. A timeout of zero can be used to block indefinitely.