Is there a delay between a SET and a GET with the same key in Redis? - c

Question

I have three processes on one computer:
A test (T)
A nginx server with my own module (M) --- the test starts and stops this process between each test case section
A Redis server (R), which is always running --- the test does not handle the start/stop sequence of this service (I'm testing my nginx module, not Redis.)
Here is a diagram of the various events:
T M R
| | |
O-------->+ FLUSHDB
| | |
+<--------O (FLUSHDB acknowledge as successful)
| | |
O-------->+ SET key value
| | |
+<--------O (SET acknowledge as successful)
| | |
O--->+ | Start nginx including my module
| | |
| O--->+ GET key
| | |
| +<---O (SUCCESS 80% and FAILURE 20%)
| | |
The test clears the Redis database with FLUSHDB then adds a key with SET key value. The test then starts nginx including my module. There, once in a while, the nginx module GET key action fails.
Note 1: I am not using the ASync implementation of Redis.
Note 2: I am using the C library hiredis.
Is it possible that there would be a delay between a SET and a following GET with the same key which would explain that this process would fail once in a while? Is there a way for me to ensure that the SET is really done once the redisCommand() function returns?
IMPORTANT NOTE: if I run one such test and the GET fails in my nginx module, the key appears in my Redis:
redis-cli
127.0.0.1:6379> KEYS *
1) "8b95d48d13e379f1ccbcdfc39fee4acc5523a"
127.0.0.1:6379> GET "8b95d48d13e379f1ccbcdfc39fee4acc5523a"
"the expected value"
So the
SET "8b95d48d13e379f1ccbcdfc39fee4acc5523a" "the expected value"
worked as expected. Only the GET failed and I would assume that it is because it somehow occurred too quickly. Any idea how to tackle this problem?

Answer 1

No, there is no delay between set and get. What you are doing should work.
Try running the monitor command in a separate window. When it fails - does the set command come before/after the get command?