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Notice a dead session in ~6 s instead of ~15, and reconnect sooner #71

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Merged
jochen-testingbot merged 1 commit into from
Oct 25, 2026
Merged

Notice a dead session in ~6 s instead of ~15, and reconnect sooner #71

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11 changes: 8 additions & 3 deletions src/main/java/ssh/CustomConnectionMonitor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,14 +24,19 @@ public class CustomConnectionMonitor {

private static final Logger LOG = Logger.getLogger(CustomConnectionMonitor.class.getName());

static final long CURRENT_RETRY_DELAY = 5000;
static final int MAX_RETRIES = 30;
/**
* Between reconnect attempts while the network is down: the first one that can get through
* should not wait long once it is back (5 s -> 2 s took 2010's return after a 20-second outage
* from 25.1 s to 23.6 s). MAX_RETRIES keeps the ~150 s before the tunnel is rebuilt.
*/
static final long CURRENT_RETRY_DELAY = 2000;
static final int MAX_RETRIES = 75;
/**
* The first reconnect goes out after this long, not after the full retry delay: the session
* has already been gone for the keepalive's ~15 seconds, and every second more is a second
* of failing tests.
*/
static final long FIRST_RETRY_DELAY = 1000;
static final long FIRST_RETRY_DELAY = 250;
/** Between re-requests of the reverse forward on a session that is up. */
static final long FORWARD_RETRY_DELAY = 2000;
/** About two minutes of re-requests before the tunnel is rebuilt. */
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10 changes: 8 additions & 2 deletions src/main/java/ssh/SSHTunnel.java
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Expand Up @@ -65,12 +65,18 @@ public class SSHTunnel implements ReconnectableTunnel {
* so after a NAT change or a laptop switching networks the session looked connected until the
* operating system gave up retransmitting -- about 15 minutes on Linux -- and all that time
* the tunnel server kept port 2010 for a client that was gone.
*
* <p>2 s x 3: a session that hears nothing at all from the server for ~6 s is dead. That is
* the floor of how fast port 2010 can come back after a network change, so it is kept short;
* the server answers every keepalive at once, so a healthy connection - busy or idle - is
* never that quiet. Measured on a NAT change: 2010 back after ~8 s (5 s x 3: ~18 s); a
* 4-second outage passes without a reconnect, and nothing reconnected under load.
*/
static final int SERVER_ALIVE_INTERVAL_MS = 5_000;
static final int SERVER_ALIVE_INTERVAL_MS = 2_000;
static final int SERVER_ALIVE_COUNT_MAX = 3;

/** How often the connection and forwarding monitors look. */
static final long CONNECTION_CHECK_INTERVAL_MS = 2_000;
static final long CONNECTION_CHECK_INTERVAL_MS = 500;
static final long FORWARDING_CHECK_INTERVAL_MS = 5_000;

/** How long one end-to-end probe of the reverse forward may take. */
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