Hello. CentOS 7.6.1810 (and other 7) 1. New master and new slave. Empty base. tls-replication starts successfully and works. Ok. 2. Old master and old slave. Base about 1-2 MB. Replication without TLS. Works normally. I changed replication to tls-replication. All works great. Ok. 3. Old master with base about 1-2 MB and new empty slave. Tried tls-replication between them - NOT OK. Unable to SYNC (sorry, already delete log-file) 4. Same servers. Replication started without TLS normally. Stop slave & change replication to tls-replication. All works great.

Comment From: boreevyuri

29093:S 12 May 2020 11:28:15.167 * Loading RDB produced by version 6.0.1
29093:S 12 May 2020 11:28:15.167 * RDB age 9 seconds
29093:S 12 May 2020 11:28:15.167 * RDB memory usage when created 0.77 Mb
29093:S 12 May 2020 11:28:15.167 * DB loaded from disk: 0.000 seconds
29093:S 12 May 2020 11:28:15.167 * Ready to accept connections
29093:S 12 May 2020 11:28:15.168 . 0 clients connected (0 replicas), 803296 bytes in use
29093:S 12 May 2020 11:28:15.168 * Connecting to MASTER 10.10.10.11:6380
29093:S 12 May 2020 11:28:15.168 * MASTER <-> REPLICA sync started
29093:S 12 May 2020 11:28:15.184 * Non blocking connect for SYNC fired the event.
29093:S 12 May 2020 11:28:15.187 * Master replied to PING, replication can continue...
29093:S 12 May 2020 11:28:15.196 * Partial resynchronization not possible (no cached master)
29093:S 12 May 2020 11:28:15.199 * Full resync from master: e9bd4b2784145701033f119c76f615fb949697f4:10894852
29093:S 12 May 2020 11:28:15.374 * MASTER <-> REPLICA sync: receiving 10680189 bytes from master to disk
29093:S 12 May 2020 11:28:15.374 # I/O error trying to sync with MASTER: Resource temporarily unavailable
29093:S 12 May 2020 11:28:16.170 * Connecting to MASTER 10.10.10.11:6380
29093:S 12 May 2020 11:28:16.170 * MASTER <-> REPLICA sync started
29093:S 12 May 2020 11:28:16.185 * Non blocking connect for SYNC fired the event.
29093:S 12 May 2020 11:28:16.188 * Master replied to PING, replication can continue...
29093:S 12 May 2020 11:28:16.198 * Partial resynchronization not possible (no cached master)
29093:S 12 May 2020 11:28:16.201 * Full resync from master: e9bd4b2784145701033f119c76f615fb949697f4:10894852
29093:S 12 May 2020 11:28:16.376 * MASTER <-> REPLICA sync: receiving 10680189 bytes from master to disk
29093:S 12 May 2020 11:28:16.376 # I/O error trying to sync with MASTER: Resource temporarily unavailable

Comment From: boreevyuri

After replicaof changed to non-TLS port and tls-options deactivated replica started:

30048:S 12 May 2020 11:31:47.030 * Connecting to MASTER 10.10.10.11:6379
30048:S 12 May 2020 11:31:47.030 * MASTER <-> REPLICA sync started
30048:S 12 May 2020 11:31:47.033 * Non blocking connect for SYNC fired the event.
30048:S 12 May 2020 11:31:47.036 * Master replied to PING, replication can continue...
30048:S 12 May 2020 11:31:47.045 * Partial resynchronization not possible (no cached master)
30048:S 12 May 2020 11:31:47.049 * Full resync from master: e9bd4b2784145701033f119c76f615fb949697f4:10898417
30048:S 12 May 2020 11:31:47.264 * MASTER <-> REPLICA sync: receiving 10682838 bytes from master to disk
30048:S 12 May 2020 11:31:48.174 * MASTER <-> REPLICA sync: Flushing old data
30048:S 12 May 2020 11:31:48.175 * MASTER <-> REPLICA sync: Loading DB in memory
30048:S 12 May 2020 11:31:48.175 * Loading RDB produced by version 6.0.1
30048:S 12 May 2020 11:31:48.175 * RDB age 1 seconds
30048:S 12 May 2020 11:31:48.175 * RDB memory usage when created 16.71 Mb

After that I enable TLS-options and tls-replication. All worked as normal:

30273:S 12 May 2020 11:32:44.955 * Before turning into a replica, using my own master parameters to synthesize a cached master: I may be able to synchronize with the new master with just a partial transfer.
30273:S 12 May 2020 11:32:44.955 * Ready to accept connections
30273:S 12 May 2020 11:32:44.955 * Connecting to MASTER 10.10.10.11:6380
30273:S 12 May 2020 11:32:44.956 * MASTER <-> REPLICA sync started
30273:S 12 May 2020 11:32:44.972 * Non blocking connect for SYNC fired the event.
30273:S 12 May 2020 11:32:44.975 * Master replied to PING, replication can continue...
30273:S 12 May 2020 11:32:44.985 * Trying a partial resynchronization (request e9bd4b2784145701033f119c76f615fb949697f4:10898460).
30273:S 12 May 2020 11:32:44.988 * Successful partial resynchronization with master.
30273:S 12 May 2020 11:32:44.988 * MASTER <-> REPLICA sync: Master accepted a Partial Resynchronization.

Comment From: yossigo

@boreevyuri IIRC there were some fixes around that since 6.0.1, can you please let me know if that still reproduces with latest unstable? Thanks!

Comment From: yossigo

No new information received, closing this ticket. If the problem reproduces with the latest/unstable please re-open with more information. Thanks!