Check if redis-server has started and is ready

[Thomas Fritz]

Hi,

How can i check if redis-server has started up and is ready for taking connections? Is it necessary?
I have to start redis daemonized first and then my application from a shell script. Do i have to check and wait until redis-server is "ready" for taking connections? If so, how can i do that? Maybe a 'redis-cli INFO' call until it is successful?

Kind regards

[Dvir Volk]

Hi Thomas.

In my company we are doing this before declaring a redis using service as operational.

basically we just iterate all important redis instances, check that the socket is open, try ping and make sure we're getting pong and not some error. we're not using the redis client library BTW, but direct TCP connection, to have a better lower level understanding of the errors, but it's not necessary.

it's a bit simplistic but it allows us to check all redis instances with one small function.

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[Thomas Fritz]

Thanks,
so a PING command is sufficient.
Thanks



---

Thomas FRITZ
web http://fritzthomas.com
twitter http://twitter.com/thomasf


2012/6/25 Dvir Volk <dv...@everything.me>:

[Dvir Volk]

it's sufficient to tell that:

1. the server is on

2. it's accepting new connections

3. it's not stuck (with a KEYS command, etc)

4. it's not loading data from disk

5. it's not in the middle of a master SYNC.

which is fine most of the time.

it does not guarantee that:

1. commands you need are not disabled.

2. replication works ok

3. this is the master or slave in case you're using master/slave.

4. it will accept newer connection than your connection.

5. the version is correct and supports all the commands you want to pass it.

6. this is the RIGHT INSTANCE - this is a major pitfall if you're using many instances. AUTH can be used to address this.

[Alexander Gladysh]

On Mon, Jun 25, 2012 at 1:43 PM, Dvir Volk <dv...@everything.me> wrote:
> it's sufficient to tell that:

> 4. it's not loading data from disk

I've got an impression that INFO *will* work in this case. Am I wrong?

Alexander.

[Dvir Volk]

it's easier to parse the PONG response (if you're using raw TCP like we do), plus info changes format from time to time.

I have the same PING/PONG check in place for 1.5 years and it didn't need to be changed.

for the simple check of "is this server online", it's good enough.

[Alexander Gladysh]

Ah, missed the part where discussion changed from INFO to PING. Sorry
for the noise :-)

Alexander.

[Thomas Fritz]

Thanks all for the great INFO. i will use PING, but INFO would work as
well in my case. But since i will check from a bash script i will use
PING. I just want to loop until i get a PONG back so i can stop the
loop and start the next service which will connect to the server.

Kind regards

---

Thomas FRITZ
web http://fritzthomas.com
twitter http://twitter.com/thomasf

2012/6/25 Alexander Gladysh <agla...@gmail.com>: