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Card class: Sensitivity • Category: Capacity

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At a glance

The number of client connections that MariaDB started to accept but then aborted during the last 24 hours. This is the server’s Aborted_connects status counter, sampled and differenced over the window. A connection is “aborted” before the client ever runs a query: the handshake failed, the credentials were wrong, the client gave up mid-authentication, or max_connect_errors tripped. For a DBA, a steady trickle is normal background noise (port scanners, health-check probes, the odd typo). A spike is a signal: a misconfigured application node, a credential rotation that did not propagate, or an early sign that something is hammering the auth path.
What it tracksAborted Connects (24h): the delta in the global Aborted_connects status variable over a rolling 24-hour window. Counts connection attempts that failed before a successful authenticated session was established.
Data sourceMariaDB SHOW GLOBAL STATUS LIKE 'Aborted_connects' (or information_schema.GLOBAL_STATUS), polled on the Nerve Centre sampling interval and differenced to produce a per-window count.
Distinct fromAborted_clients, which counts sessions that connected successfully but were then dropped (client died, wait_timeout fired, packet too large). Aborted connects are pre-auth failures; aborted clients are post-auth disconnects. Do not conflate them.
Time window24h rolling. The headline is the count of aborted connects across the trailing 24 hours.
Alert trigger> 100 aborted connects in the 24-hour window. Above this the card turns amber and surfaces in the Sensitivity feed.
RolesDBA, platform, SRE

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Calculation

MariaDB maintains a monotonic global counter, Aborted_connects, that increments every time a connection attempt fails before authentication completes. It is reset only on server restart (or an explicit FLUSH STATUS). Because the raw counter only ever grows, the card does not display its absolute value; it displays the difference between the counter now and the counter 24 hours ago. 
aborted_connects_24h = Aborted_connects(now) - Aborted_connects(now - 24h)
If the server restarted inside the window, the counter resets to zero, so the engine clamps any negative delta to the value of the current counter (treating a restart boundary as “everything since restart”). The detail line for this card is simply: Aborted Connects (24h) for the selected period. The underlying counter increments for, among others: bad username or password, a client that disconnects during the handshake, SSL/TLS negotiation failure, a host blocked by max_connect_errors, and init_connect statement failures.

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Worked example

A platform team runs a 3-node MariaDB 10.6 cluster behind an application tier of 12 web nodes. Snapshot taken on 14 Apr 26 at 09:00 BST.
ReadingValue
Aborted_connects now4,820
Aborted_connects 24h ago4,690
Aborted Connects (24h)130
Card stateAmber (threshold > 100)
130 over 24 hours is roughly one every 11 minutes, which has tripped the amber threshold. The DBA’s first move is to find where the failures come from, because the counter itself does not record the offending host. Two native paths: 
-- Per-host connect errors (resets with FLUSH HOSTS)
SELECT * FROM performance_schema.host_cache
WHERE COUNT_AUTHENTICATION_ERRORS > 0
   OR COUNT_HANDSHAKE_ERRORS > 0
ORDER BY SUM_CONNECT_ERRORS DESC;
The host cache shows 118 of the 130 failures came from a single application node (10.2.4.17) with COUNT_AUTHENTICATION_ERRORS = 118. The team checks that node: it was redeployed at 02:00 with a stale Kubernetes secret after a password rotation. The application retried its connection pool every 10 seconds, each retry adding one aborted connect. Three takeaways:
  1. The count is a symptom; the host cache is the diagnosis. Always pair the headline with performance_schema.host_cache (or the older SHOW STATUS LIKE 'Connection_errors%') to attribute the failures.
  2. A retrying connection pool is a multiplier. A single bad credential on one node can generate hundreds of aborted connects per day because pools reconnect aggressively. Fix the source, do not just raise the threshold.
  3. Watch for max_connect_errors lockout. Once a host accumulates max_connect_errors failures (default 100), MariaDB blocks it entirely with Host '...' is blocked. At that point the application sees hard connection failures, not slow ones. Run FLUSH HOSTS (or FLUSH PRIVILEGES) after fixing the credential to clear the block.

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Sibling cards

CardWhy pair it with Aborted ConnectsWhat the combination tells you
Connection Errors (24h)The broader connection-error counter family (Connection_errors_*).Aborted connects rising with Connection_errors_max_connections rising equals capacity exhaustion, not bad credentials.
Connections In UseThe live count of established threads.Aborted connects high while connections-in-use is near max_connections points at saturation refusing new clients.
Connection Pool Saturation %How close threads are to max_connections.Aborts at high saturation are capacity-driven; aborts at low saturation are auth or network-driven.
Connection Pool at >90% SaturationThe real-time exhaustion alert.If both fire together, the pool is full and turning clients away.
Query Error Rate %Post-auth query failures.Aborts are pre-auth; query errors are post-auth. Together they bracket the request lifecycle.
Instance UptimeDetects restarts that reset the counter.A recent restart explains a sudden drop (or a clamped delta) in this card.
MariaDB Health ScoreThe composite that weights connection health.A sustained abort spike pulls the composite down even when queries look healthy.

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Reconciling against the source

Where to look in MariaDB’s own tooling:
SHOW GLOBAL STATUS LIKE 'Aborted_connects'; for the raw monotonic counter. SELECT * FROM performance_schema.host_cache; to attribute failures to specific client hosts. SHOW GLOBAL STATUS LIKE 'Connection_errors_%'; for the breakdown by failure reason (max connections, accept, internal, peer address, select, tcpwrap).
Why our number may legitimately differ from a raw SHOW STATUS:
ReasonDirectionWhy
WindowingOurs is smallerSHOW GLOBAL STATUS shows the cumulative count since startup; our card shows only the trailing 24 hours.
Restart inside the windowOurs may read lowWhen the counter resets to zero at restart, we clamp the negative delta and report from the restart point, not the lost history.
Sampling intervalMarginal lagThe card differences two samples; failures in the seconds between the last poll and your manual SHOW STATUS are not yet reflected.
FLUSH STATUS run manuallyOurs may read lowIf an operator ran FLUSH STATUS, the underlying counter resets and our delta restarts from zero.
On managed services: Amazon RDS / Aurora for MariaDB exposes Aborted_connects via the same SHOW GLOBAL STATUS and via Enhanced Monitoring; SkySQL and Azure Database for MariaDB surface it through their own metrics consoles. The number should agree once you align the window. For per-host attribution you still need performance_schema.host_cache, which the managed consoles do not summarise.

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Known limitations / FAQs

Q: What is the difference between Aborted_connects and Aborted_clients? Aborted_connects counts attempts that failed before authentication completed (bad password, handshake timeout, TLS failure, blocked host). Aborted_clients counts sessions that authenticated successfully but were later dropped without a clean mysql_close() (the client process died, wait_timeout/interactive_timeout fired, or max_allowed_packet was exceeded). This card tracks the former. Post-auth disconnects belong to the client counter. Q: A spike appeared but the host cache is empty. Why? performance_schema.host_cache is itself capped at host_cache_size rows and is cleared by FLUSH HOSTS, FLUSH PRIVILEGES, or FLUSH STATUS. If someone ran one of those after the failures, the attribution is gone even though the cumulative Aborted_connects counter persists. Enable the general_log or audit plugin temporarily to capture future offenders, or check application logs on the suspected nodes. Q: We see a steady ~5 aborts per hour with no application errors. Is that a problem? Usually not. A low constant rate is typical of load-balancer TCP health checks that open and close the port without authenticating, port scanners, and monitoring probes. Establish your own baseline; the > 100 per 24h default is a generic starting point. If your background noise sits at 120/day and nothing is broken, raise the threshold in the Sensitivity tab rather than chasing the noise. Q: Why does the count suddenly drop to near zero? The most common cause is a server restart (or FLUSH STATUS), which resets the underlying counter. Cross-check Instance Uptime: a low uptime explains the reset. The card clamps the negative delta so you will not see a misleading negative number. Q: Could a single failing application cause this? Yes, and it is the most common real cause. Connection pools reconnect on a fixed interval (commonly every 5 to 30 seconds). One node with a stale credential after a password rotation can generate hundreds of aborted connects per day on its own. Fix the secret on that node and run FLUSH HOSTS to clear any max_connect_errors block. Q: Does this counter include connections refused because max_connections was reached? Those are counted in Connection_errors_max_connections, surfaced by the Connection Errors (24h) card, and depending on the failure stage may or may not increment Aborted_connects. When the abort spike coincides with high Connection Pool Saturation %, treat it as a capacity problem rather than an auth problem.

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Tracked live in Vortex IQ Nerve Centre

Aborted Connects (24h) is one of hundreds of KPI pulses Vortex IQ tracks across MariaDB and 70+ other ecommerce connectors. Nerve Centre runs the detection layer; Vortex Mind investigates the cause when something moves; Ask Viq lets you interrogate any number in plain English. Start for free or book a demo to see this metric running on your own data.