23 Feb
2023
23 Feb
'23
7:49 p.m.
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### Description
I have 2 jsonrpc servers configured with different prio's. For testing, I have the
servers configured to always delay the response to any request by more than the
module's timout setting.
The (initial) request is sent to the first server. As this one times out, I would expect a
retry to go to the second servers, but instead, all retries are sent to the same server.
The backup server is never contacted. This makes the whole "prio" system seem a
bit useless.
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Explain what you did, what you expected to happen, and what actually happened.
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### Troubleshooting
#### Reproduction
```
modparam("janssonrpcc", "server",
"conn=test;addr=pc1;port=8081;priority=5;weight=10")
modparam("janssonrpcc", "server",
"conn=test;addr=pc1;port=8082;priority=5;weight=10")
```
```
janssonrpc_request("test", "Test.Timeout", '[ {
"Timout": 1000} ]',
"route=JSONRPC_RESPONSE;retry=10;timeout=1000");
```
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#### Log Messages
No useful logs are produced. I verified the described behavior on the jsonrpc server.
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```
2023-02-23T16:59:34.585346+01:00 pc1 proxy1[340870]: INFO: janssonrpcc
[janssonrpc_connect.c:361]: bev_connect(): Connecting to server pc1:8081 for conn rating.
2023-02-23T16:59:34.585420+01:00 pc1 proxy1[340870]: INFO: janssonrpcc
[janssonrpc_connect.c:361]: bev_connect(): Connecting to server pc1:8082 for conn rating.
2023-02-23T16:59:34.585446+01:00 pc1 proxy1[340870]: INFO: janssonrpcc
[janssonrpc_connect.c:290]: bev_connect_cb(): Connected to host pc1:8081
2023-02-23T16:59:34.585462+01:00 pc1 proxy1[340870]: INFO: janssonrpcc
[janssonrpc_connect.c:290]: bev_connect_cb(): Connected to host pc1:8082
2023-02-23T17:05:10.903398+01:00 pc1 proxy1[340870]: WARNING: janssonrpcc
[janssonrpc_request.c:247]: schedule_retry(): Number of retries exceeded. Failing
request.
```
### Possible Solutions
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request with a fix.
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Retry in combination with a timeout and prio's is a bit tricky. When do what? Just
retrying on the first prio makes the lower prio servers completely useless, while going to
the next prio on every retry skips possibly useful high-prio servers and may exhaust the
number of candidate servers very fast.
Best solution IMHO would be to first try every server in the highest prio, before going to
the next prio. Do not do (exponential) backoff between these steps.
If there are still retries remaining after that, wrap around to the highest prio with the
exponentional backoff delay.
With the above, failover considers all servers and failover between servers is fast while
not overloading a single server.
BTW. If I configure multiple servers per prio, it seems to randomly select one of them for
every (re)try. It never selects one form the next prio.
### Additional Information
* **Kamailio Version** - output of `kamailio -v`
```
5.6.1
```
* **Operating System**:
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```
(paste your output here)
```
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