duke8253 opened a new issue, #8734:
URL: https://github.com/apache/trafficserver/issues/8734

   When developing a new plugin for sharing STEK (Session Ticket Encryption 
Key) on a colo, I discovered that some of the boxes on the colo I was testing 
cannot be synced up. Upon further investigation, the problem exists even with 
manually setting a key file 
(https://docs.trafficserver.apache.org/admin-guide/files/records.config.en.html#proxy-config-ssl-server-ticket-key-filename),
 and uploading it to all the servers. This issue is also present with Apple, 
and @masaori335 was doing testing on their side. However, this issue 
disappeared over the past weekend for no apparent reason. 
   
   Below is the description of the problem, please add comments if I missed 
anything @bneradt @bryancall @masaori335:
   - When STEK is shared among servers, the normal behavior is these servers 
can reuse TLS sessions from each other, e.g. server X can resume sessions 
created on server Y, X and Y being any of the servers in that colo.
   - The problem we're seeing now is, even though STEK is being shared 
correctly among all servers in the same colo, sometimes there will be a small 
group of servers that cannot resume session created on others.
   - The group of servers that cannot resume session from other servers, can 
share session within the group (always the case), essentially splitting the 
colo into two groups of servers that can resume session within their own group, 
but not across.
   - Of the two groups formed, the larger group usually contains 75% or more 
servers of that colo.
   - It's always two groups of servers if this problem is present.
   - It's always the same servers in the same group on the same colo, but it 
can be different servers on different colos, and the servers persists after ATS 
restart. E.g. on colo 1, it's always the servers A, C, F, M that forms a group; 
while on colo 2,  it's always the servers B, F, S that forms a group.
   - All related OpenSSL API calls for session encrypt/decrypt return success 
with the same values across all servers,  `HMAC_Init_ex`, `EVP_EncryptInit_ex`, 
`EVP_DecryptInit_ex`, `RAND_bytes`.
   


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