RTFM · Medical healthchecks
lb.saphira.hl7.mllp: ask the hospital bus a question (HL7 over MLLP)
HL7 v2 moves every admission, discharge and order in a hospital, framed over TCP by MLLP. The check sends a real query for a patient who cannot exist and requires a real, valid acknowledgement back; the message bus, proven, without touching a single record.
What it proves
A complete MLLP transaction: the check frames an HL7 v2 QRY^A19 patient query (MLLP framing: 0x0B … 0x1C 0x0D) and requires a properly framed ACK whose MSA-1 field is AA or CA; a genuine application-level acceptance, not merely a socket that echoed bytes. The queried patient (SAPHIRA-SYNTHETIC-PATIENT) does not exist, so no patient data is created or modified; the ACK itself is the proof.
This is the named capability "the HIS/integration engine answers HL7 queries"; deeper than any HTTP check can honestly claim about an MLLP-only system.
How it works
A small packaged python3 program does the transaction (the engine pattern in miniature): connect, send the framed query, accumulate until the end-block arrives, verify the framing, extract MSA-1, and vote. The whole payload can be overridden with LB_SAPHIRA_HL7_MESSAGE for sites whose integration engine demands a specific query shape; env only, never echoed, so operators who embed site-specific credentials in the override can do so safely.
Configuration
| Variable | Default | Meaning |
|---|---|---|
| LB_SAPHIRA_HL7_MESSAGE | built-in QRY^A19 | Full payload override (env only, never echoed) |
| LB_SAPHIRA_TIMEOUT | 3 | Transaction deadline |
| (target port) | $4, else 2575 | The MLLP listener: 2575 is the conventional port |
Wiring it up
# ldirectord.cf - integration engine pool
virtual = 203.0.113.10:2575
protocol = tcp
scheduler = lc
real = 192.168.20.31:2575 gate 1
real = 192.168.20.32:2575 gate 1
checktype = external
checkcommand = "/var/lib/lb/saphira/lb.saphira.hl7.mllp"# haproxy.cfg - MLLP is plain TCP, pass-through mode
global
external-check
backend his_mllp
mode tcp
option external-check
external-check command "/var/lib/lb/saphira/lb.saphira.hl7.mllp"
server his1 192.168.20.31:2575 check inter 5s fall 3 rise 2Run it by hand
/var/lib/lb/saphira/lb.saphira.hl7.mllp his-pool 2575 192.168.20.31 2575
echo $?
# 0 = framed ACK with MSA-1 AA/CA
# 1 = no answer, broken framing, or a negative ACKFailure modes
- Connected but unframed garbage; the endpoint is not speaking MLLP (a raw TCP echo, a different framing): a mis-wired integration
- ACK with MSA-1 AE-missing: some engines answer a nonexistent patient with an application error code; if your site does, override the payload to a query your engine ACKs positively
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