cachedb_redis: add ASK redirect handling for cluster resharding#3852
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dondetir wants to merge 1 commit intoOpenSIPS:masterfrom
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cachedb_redis: add ASK redirect handling for cluster resharding#3852dondetir wants to merge 1 commit intoOpenSIPS:masterfrom
dondetir wants to merge 1 commit intoOpenSIPS:masterfrom
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This appears to be a partial duplicate of #3815 |
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Thanks for pointing that out @NormB. You're right — the hash slot fix ( The unique part of this PR is the ASK redirect handling (detection + Happy to rebase and drop the hash slot change once #3815 merges, keeping only the ASK redirect logic. Or if you'd prefer, I can split this into a separate ASK-only PR right now. Let me know what works best. |
This was referenced Mar 30, 2026
Add support for Redis ASK redirects during cluster resharding. When a slot is being migrated between nodes, Redis returns an ASK response instead of MOVED. Unlike MOVED (permanent redirect), ASK is a one-time redirect that requires sending the ASKING command to the target node before retrying the original query. The implementation: - Detects ASK responses alongside existing MOVED handling - Sends ASKING command to the target node before retrying - Reuses the MOVED redirect infrastructure (endpoint lookup, reconnection, retry logic) Also refactor parse_moved_reply() into parse_redirect_reply() that accepts the prefix as a parameter, with inline wrappers parse_moved_reply() and parse_ask_reply() for backward compatibility. Partially addresses OpenSIPS#2811
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With use_tls=1 on cachedb_redis, every SIP worker that touches a
Redis/Valkey connection SIGSEGVs on the first SSL_new. Two
independent problems stacked on the same line:
1. The old code indexed d->ctx as a per-process array:
SSL_new(((void**)d->ctx)[process_no])
This predates the tls_mgm refactor (upstream 11aa15d,
'refactor TCP/TLS code to have everything in a single process'),
after which ctx became a single SSL_CTX *. Every worker with
process_no > 0 read garbage past the SSL_CTX struct.
2. Even after fixing the dereference, d->ctx is not safely usable
from sibling workers. tls_mgm builds its SSL_CTX in
child_init(PROC_TCP_MAIN), which runs *after* SIP workers and
the MI process have already forked. So those workers see
d->ctx == NULL when their cachedb_redis:child_init ->
cachedb_do_init -> redis_init_ssl path fires. Even waiting for
TCP_MAIN doesn't help: the SSL_CTX was built post-fork in
TCP_MAIN's address space, and OpenSSL embeds pointers into
per-process storage inside the CTX (method tables, providers,
OSSL_LIB_CTX).
Fix: each worker builds its own SSL_CTX from the static
configuration on the tls_domain (cert, pkey, ca, verify_cert).
CTXs are cached per-worker, keyed by tls_domain pointer, so
multiple connections sharing a domain share one CTX inside that
worker. Floors min proto at TLS 1.2 to match Valkey/Redis 7+
defaults and the tls_method=TLSv1_2 that most tls_mgm configs
already set.
Also tightens the adjacent error paths: SSL_free the SSL on
redisInitiateSSL failure, and promote the printf in that path to
LM_ERR for consistency.
Note: a companion parser fix for 'tls-port' in parse_cluster_shards
is still needed for TLS cluster topology updates to use the right
port on MOVED/ASK redirects, but depends on PR OpenSIPS#3852
(parse_cluster_shards introduction); it can land as a small
follow-up once that PR is merged.
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Summary
Add support for Redis ASK redirects during cluster resharding, completing the cluster redirect handling started in PR #3639.
Background
When a Redis cluster is resharding (migrating slots between nodes), the source node returns an
ASKresponse instead ofMOVED. The key difference:ASKINGto the target node before retryingWithout ASK handling, queries during resharding operations fail with unhandled error responses.
Implementation
ASKINGcommand to the target node before retrying the original queryparse_moved_reply()intoparse_redirect_reply()that accepts the prefix as a parameter, with inline wrappersparse_moved_reply()andparse_ask_reply()for backward compatibilityNote on hash slot fix
The original version of this PR also included a hash slot calculation fix. That has been removed per @NormB's feedback, as his PR #3815 addresses this more comprehensively (including hash tag support). This PR now contains only the ASK redirect handling.
Testing
parse_redirect_reply()refactor passes integration tests with live slot migrations across a 3-node clusterPartially addresses #2811