Subject: [PATCH] feat: external replication delay injection via external command

From: Nadav Shatz <[email-masked]>
Date: Tue, 23 Dec 2025 13:39:04 +0200

Add support for obtaining replication delay from an external command
    instead of querying pg_stat_replication directly. This allows for
    more flexible monitoring setups where replication delay information
    may come from external monitoring systems.

    New configuration parameters:
    - replication_delay_source_cmd: Path to external command that provides
      delay values. When set, pgpool calls this command instead of querying
      PostgreSQL directly.
    - replication_delay_source_timeout: Timeout in seconds for the external
      command (default: 10).

    The external command receives replica identifiers as arguments in
    "host:port" format and should output delay values in milliseconds,
    one per line, corresponding to each replica argument.

    Includes regression test (041.external_replication_delay) covering:
    - Argument format validation
    - Integer and floating-point delay parsing
    - Error handling for malformed output and timeouts

diff --git a/doc/src/sgml/stream-check.sgml b/doc/src/sgml/stream-check.sgml
index d2ca3ca49c62dd481fb8e18616b12ab521521b1f..fc479908072f6afc63923ac699be0f63e15bc90a 100644
--- a/doc/src/sgml/stream-check.sgml
+++ b/doc/src/sgml/stream-check.sgml
@@ -309,6 +309,74 @@ GRANT pg_monitor TO sr_check_user;
     </listitem>
   </varlistentry>
 
+  <varlistentry id="guc-replication-delay-source-cmd" xreflabel="replication_delay_source_cmd">
+   <term><varname>replication_delay_source_cmd</varname> (<type>string</type>)
+    <indexterm>
+     <primary><varname>replication_delay_source_cmd</varname> configuration parameter</primary>
+    </indexterm>
+   </term>
+   <listitem>
+    <para>
+     Specifies an external command to retrieve replication delay information for replica nodes.
+     When this parameter is set and not empty, <productname>Pgpool-II</productname> uses the
+     external command instead of built-in database queries to obtain replication delays.
+     The command is executed as the <productname>Pgpool-II</productname> process user.
+    </para>
+    <para>
+     The command receives replica node identifiers as positional arguments, with the primary
+     node omitted. Each identifier is in the format <literal>&lt;hostname&gt;:&lt;port&gt;</literal>,
+     for example <literal>server1:5432 server2:5432</literal>. The order matches
+     <productname>Pgpool-II</productname>'s backend order (excluding the primary), allowing the
+     script to correlate external metrics (such as from AWS CloudWatch for Aurora) to the correct nodes.
+    </para>
+    <para>
+     The command must write a single line to stdout containing one whitespace-separated delay value
+     per replica, in milliseconds, in the same order as the arguments. The primary node's delay is
+     implicitly zero and should not be included in the output. Delay values can be integers or
+     floating-point numbers.
+    </para>
+    <para>
+     Special value: <literal>-1</literal> indicates a replica that is down but not yet detected
+     by <productname>Pgpool-II</productname>'s health checks. <productname>Pgpool-II</productname>
+     will log this condition but rely on its own health-check logic to decide whether to trigger
+     failover; no failover is triggered solely by receiving <literal>-1</literal>.
+    </para>
+    <para>
+     Example for a 3-node cluster (1 primary + 2 replicas): if the command receives arguments
+     <literal>server1:5432 server2:5432</literal>, it should output <literal>"25.5 100"</literal>
+     to indicate the first replica has 25.5ms delay and the second has 100ms delay.
+    </para>
+    <para>
+     Default is empty (use built-in replication delay queries).
+    </para>
+    <para>
+     This parameter can be changed by reloading the <productname>Pgpool-II</> configurations.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry id="guc-replication-delay-source-timeout" xreflabel="replication_delay_source_timeout">
+   <term><varname>replication_delay_source_timeout</varname> (<type>integer</type>)
+    <indexterm>
+     <primary><varname>replication_delay_source_timeout</varname> configuration parameter</primary>
+    </indexterm>
+   </term>
+   <listitem>
+    <para>
+     Specifies the timeout in seconds for the external command specified by
+     <xref linkend="guc-replication-delay-source-cmd">.
+     If the command does not finish within the timeout, <productname>Pgpool-II</productname>
+     logs an error and continues using the built-in method.
+    </para>
+    <para>
+     Default is 10 seconds. Valid range is 1-3600 seconds.
+    </para>
+    <para>
+     This parameter can be changed by reloading the <productname>Pgpool-II</> configurations.
+    </para>
+   </listitem>
+  </varlistentry>
+
   <varlistentry id="guc-log-standby-delay" xreflabel="log_standby_delay">
    <term><varname>log_standby_delay</varname> (<type>enum</type>)
     <indexterm>
diff --git a/src/config/pool_config_variables.c b/src/config/pool_config_variables.c
index 0a0e483149190e14ca13406c08d0ee2ac0a9c53a..7c6d1803117541aaba50d9f9ff62e41e145c5d95 100644
--- a/src/config/pool_config_variables.c
+++ b/src/config/pool_config_variables.c
@@ -980,6 +980,16 @@ static struct config_string ConfigureNamesString[] =
 		NULL, NULL, NULL, NULL
 	},
 
+	{
+		{"replication_delay_source_cmd", CFGCXT_RELOAD, STREAMING_REPLICATION_CONFIG,
+			"External command to retrieve replication delay information.",
+			CONFIG_VAR_TYPE_STRING, false, 0
+		},
+		&g_pool_config.replication_delay_source_cmd,
+		"",
+		NULL, NULL, NULL, NULL
+	},
+
 	{
 		{"failback_command", CFGCXT_RELOAD, FAILOVER_CONFIG,
 			"Command to execute when backend node is attached.",
@@ -2334,6 +2344,17 @@ static struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"replication_delay_source_timeout", CFGCXT_RELOAD, STREAMING_REPLICATION_CONFIG,
+			"Timeout for external replication delay command execution in seconds.",
+			CONFIG_VAR_TYPE_INT, false, 0
+		},
+		&g_pool_config.replication_delay_source_timeout,
+		10,
+		1, 3600,
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	EMPTY_CONFIG_INT
 };
diff --git a/src/include/pool_config.h b/src/include/pool_config.h
index 758d515525c93c1c3f2686da049b294a286a574a..6f5f88fb200c2ea82cccddd8f02c35c8d0ade8f4 100644
--- a/src/include/pool_config.h
+++ b/src/include/pool_config.h
@@ -86,7 +86,6 @@ typedef enum LogStandbyDelayModes
 	LSD_NONE
 } LogStandbyDelayModes;
 
-
 typedef enum MemCacheMethod
 {
 	SHMEM_CACHE = 1,
@@ -364,6 +363,8 @@ typedef struct
 	char	   *sr_check_password;	/* password for sr_check_user */
 	char	   *sr_check_database;	/* PostgreSQL database name for streaming
 									 * replication check */
+	char	   *replication_delay_source_cmd;	/* external command for replication delay */
+	int			replication_delay_source_timeout;	/* timeout for external command in seconds */
 	char	   *failover_command;	/* execute command when failover happens */
 	char	   *follow_primary_command; /* execute command when failover is
 										 * ended */
diff --git a/src/sample/pgpool.conf.sample-stream b/src/sample/pgpool.conf.sample-stream
index 797906491cb996d24c59b3710f462f1405737248..454fdb9e5d1fd65437b6a67f12ab62658ea08f49 100644
--- a/src/sample/pgpool.conf.sample-stream
+++ b/src/sample/pgpool.conf.sample-stream
@@ -519,6 +519,20 @@ backend_clustering_mode = streaming_replication
 
 #sr_check_database = 'postgres'
                                    # Database name for streaming replication check
+
+#replication_delay_source_cmd = ''
+                                   # External command to retrieve replication delay information
+                                   # If set, pgpool uses this command instead of built-in queries
+                                   # Command receives replica node identifiers (host:port) as arguments
+                                   # Primary node is omitted from arguments
+                                   # Command should output one delay value (in ms) per replica
+                                   # Use -1 to indicate a replica that is down but not yet detected
+                                   # Format: "25 100" for 2 replicas (e.g., 3-node cluster with 1 primary)
+                                   # Command runs as the pgpool process user
+#replication_delay_source_timeout = 10
+                                   # Timeout for external command execution in seconds
+                                   # Range: 1-3600 seconds (default: 10)
+
 #delay_threshold = 0
                                    # Threshold before not dispatching query to standby node
                                    # Unit is in bytes
diff --git a/src/streaming_replication/pool_worker_child.c b/src/streaming_replication/pool_worker_child.c
index 5bf19c37d0cf1033c624f34ab3737f18871bc2f5..457d0fab0912d44b19de70c05be8f2046dd987c5 100644
--- a/src/streaming_replication/pool_worker_child.c
+++ b/src/streaming_replication/pool_worker_child.c
@@ -43,6 +43,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <sys/time.h>
+#include <sys/wait.h>
 
 #ifdef HAVE_CRYPT_H
 #include <crypt.h>
@@ -76,6 +77,8 @@ static volatile sig_atomic_t restart_request = 0;
 static void establish_persistent_connection(void);
 static void discard_persistent_connection(void);
 static void check_replication_time_lag(void);
+static void check_replication_time_lag_with_cmd(void);
+static char *build_instance_identifier_for_node(int node_id);
 static void CheckReplicationTimeLagErrorCb(void *arg);
 static unsigned long long int text_to_lsn(char *text);
 static RETSIGTYPE my_signal_handler(int sig);
@@ -259,11 +262,16 @@ do_worker_child(void *params)
 					POOL_NODE_STATUS *node_status;
 					int			i;
 
-					/* Do replication time lag checking */
-					check_replication_time_lag();
+			/* Do replication time lag checking */
+			/* Use external command if replication_delay_source_cmd is configured */
+			if (pool_config->replication_delay_source_cmd &&
+				strlen(pool_config->replication_delay_source_cmd) > 0)
+				check_replication_time_lag_with_cmd();
+			else
+				check_replication_time_lag();
 
-					/* Check node status */
-					node_status = verify_backend_node_status(slots);
+			/* Check node status */
+			node_status = verify_backend_node_status(slots);

 					for (i = 0; i < NUM_BACKENDS; i++)
@@ -659,6 +667,420 @@ check_replication_time_lag(void)
 	error_context_stack = callback.previous;
 }
 
+#define MAX_CMD_OUTPUT 4096
+#define MAX_REASONABLE_DELAY_MS 3600000.0  /* 1 hour in milliseconds */
+
+/*
+ * Check replication time lag using external command
+ *
+ * The external command receives only replica (standby) node identifiers as arguments,
+ * omitting the primary node. It returns delay values in milliseconds for each replica.
+ * A value of -1 indicates a node that is down but not yet detected by pgpool's health checks.
+ */
+static void
+check_replication_time_lag_with_cmd(void)
+{
+	char		   *command = NULL;
+	char		   *line;
+	char		   *token;
+	char		   *saveptr;
+	double			delay_ms;
+	uint64			delay;
+	int				token_count = 0;
+	BackendInfo	   *bkinfo;
+	ErrorContextCallback callback;
+	int				pipefd[2] = {-1, -1};
+	pid_t			pid = -1;
+	int				ret;
+	struct timeval	timeout;
+	fd_set			readfds;
+	ssize_t			bytes_read;
+	int				status;
+	int				num_replicas;
+
+	if (NUM_BACKENDS <= 1)
+	{
+		/* If there's only one node, there's no point to do checking */
+		return;
+	}
+
+	if (REAL_PRIMARY_NODE_ID < 0)
+	{
+		/* No need to check if there's no primary */
+		return;
+	}
+
+	if (!VALID_BACKEND(REAL_PRIMARY_NODE_ID))
+	{
+		/* No need to check replication delay if primary is down */
+		return;
+	}
+
+	/* Capture primary node ID to avoid race conditions during execution */
+	int primary_node_id = REAL_PRIMARY_NODE_ID;
+
+	if (!pool_config->replication_delay_source_cmd ||
+		strlen(pool_config->replication_delay_source_cmd) == 0)
+	{
+		ereport(WARNING,
+				(errmsg("replication_delay_source_cmd is not configured"),
+				 errhint("Set replication_delay_source_cmd to use external command mode")));
+		/* Fall back to builtin method */
+		check_replication_time_lag();
+		return;
+	}
+
+	/* Allocate buffer for command output */
+	line = palloc(MAX_CMD_OUTPUT);
+	memset(line, 0, MAX_CMD_OUTPUT);
+
+	/*
+	 * Register a error context callback to throw proper context message
+	 */
+	callback.callback = CheckReplicationTimeLagErrorCb;
+	callback.arg = NULL;
+	callback.previous = error_context_stack;
+	error_context_stack = &callback;
+
+	/* Execute command as current process user */
+	PG_TRY();
+	{
+		const char *base_command = pool_config->replication_delay_source_cmd;
+		size_t total_len = strlen(base_command) + 1; /* +1 for NUL */
+
+		/* Build command with replica-only arguments (omit primary) */
+		/* Calculate total command length including space-separated replica identifiers */
+		for (int i = 0; i < NUM_BACKENDS; i++)
+		{
+			if (i == primary_node_id)
+				continue; /* Skip primary node */
+
+			char *ident = build_instance_identifier_for_node(i);
+			total_len += 1 /* space */ + strlen(ident);
+			pfree(ident);
+		}
+
+		command = palloc(total_len);
+		strlcpy(command, base_command, total_len);
+
+		/* Append replica identifiers */
+		size_t current_len = strlen(command);
+		for (int i = 0; i < NUM_BACKENDS; i++)
+		{
+			if (i == primary_node_id)
+				continue; /* Skip primary node */
+
+			char *ident = build_instance_identifier_for_node(i);
+
+			/* Append space and identifier */
+			snprintf(command + current_len, total_len - current_len, " %s", ident);
+			current_len += strlen(command + current_len);
+
+			pfree(ident);
+		}
+
+		ereport(DEBUG1,
+				(errmsg("executing replication delay command: %s", command)));
+
+		if (pipe(pipefd) == -1)
+		{
+			ereport(ERROR,
+					(errmsg("pipe failed: %m")));
+		}
+
+		pid = fork();
+		if (pid == -1)
+		{
+			close(pipefd[0]);
+			close(pipefd[1]);
+			ereport(ERROR,
+					(errmsg("fork failed: %m")));
+		}
+
+		if (pid == 0)
+		{
+			/* Child process */
+			close(pipefd[0]); /* Close read end */
+			if (dup2(pipefd[1], STDOUT_FILENO) == -1)
+			{
+				fprintf(stderr, "dup2 failed: %s\n", strerror(errno));
+				exit(1);
+			}
+			close(pipefd[1]); /* Close write end (duplicated to stdout) */
+
+			/* Execute command using shell */
+			execl("/bin/sh", "sh", "-c", command, (char *)NULL);
+
+			/* If execl fails */
+			fprintf(stderr, "execl failed: %s\n", strerror(errno));
+			_exit(127);
+		}
+
+		/* Parent process */
+		close(pipefd[1]); /* Close write end */
+		pipefd[1] = -1;
+
+		/* Set up timeout for select */
+		timeout.tv_sec = pool_config->replication_delay_source_timeout;
+		timeout.tv_usec = 0;
+
+		FD_ZERO(&readfds);
+		FD_SET(pipefd[0], &readfds);
+
+		/* Wait for output or timeout */
+		ret = select(pipefd[0] + 1, &readfds, NULL, NULL, &timeout);
+
+		if (ret == -1)
+		{
+			int save_errno = errno;
+			kill(pid, SIGKILL);
+			waitpid(pid, NULL, 0);
+			pid = -1;
+			close(pipefd[0]);
+			pipefd[0] = -1;
+			if (save_errno == EINTR)
+			{
+				/* Interrupted */
+				ereport(ERROR,
+						(errmsg("select interrupted during replication delay command execution")));
+			}
+			else
+			{
+				ereport(ERROR,
+						(errmsg("select failed: %m")));
+			}
+		}
+		else if (ret == 0)
+		{
+			/* Timeout */
+			kill(pid, SIGKILL);
+			waitpid(pid, NULL, 0);
+			pid = -1;
+			close(pipefd[0]);
+			pipefd[0] = -1;
+			ereport(ERROR,
+					(errmsg("replication delay command timed out after %d seconds: %s",
+							pool_config->replication_delay_source_timeout, command),
+					 errhint("Consider increasing replication_delay_source_timeout or optimizing the command")));
+		}
+
+		/* Data is available */
+		bytes_read = read(pipefd[0], line, MAX_CMD_OUTPUT - 1);
+		close(pipefd[0]);
+		pipefd[0] = -1;
+
+		/* Wait for child to finish */
+		waitpid(pid, &status, 0);
+		pid = -1;
+
+		if (bytes_read < 0)
+		{
+			ereport(ERROR,
+					(errmsg("failed to read output from replication delay command: %s", command),
+					 errdetail("read failed: %m")));
+		}
+
+		/* Check exit status */
+		if (WIFEXITED(status) && WEXITSTATUS(status) != 0)
+		{
+			ereport(ERROR,
+					(errmsg("replication delay command failed with exit code %d: %s",
+							WEXITSTATUS(status), command)));
+		}
+		else if (WIFSIGNALED(status))
+		{
+			ereport(ERROR,
+					(errmsg("replication delay command terminated by signal %d: %s",
+							WTERMSIG(status), command)));
+		}
+
+		/* Check if output was truncated */
+		if (bytes_read == MAX_CMD_OUTPUT - 1 && line[MAX_CMD_OUTPUT - 2] != '\n')
+		{
+			ereport(WARNING,
+					(errmsg("replication delay command output may have been truncated")));
+		}
+
+		/* Null-terminate the string */
+		line[bytes_read] = '\0';
+
+		pfree(command);
+		command = NULL;
+
+		/* Set primary node delay to 0 */
+		bkinfo = pool_get_node_info(primary_node_id);
+		bkinfo->standby_delay = 0;
+		bkinfo->standby_delay_by_time = true;
+
+		/* Count expected replicas */
+		num_replicas = NUM_BACKENDS - 1; /* Total nodes minus primary */
+
+		/* Count tokens in output for validation */
+		char *line_copy = pstrdup(line);
+		char *temp_token = strtok(line_copy, " \t\n");
+		while (temp_token != NULL)
+		{
+			token_count++;
+			temp_token = strtok(NULL, " \t\n");
+		}
+		pfree(line_copy);
+
+		/* Validate output format */
+		if (token_count == 0)
+		{
+			ereport(WARNING,
+					(errmsg("replication delay command produced no output"),
+					 errhint("Command should output delay values separated by spaces, one per replica node")));
+		}
+		else if (token_count < num_replicas)
+		{
+			ereport(WARNING,
+					(errmsg("replication delay command returned %d values, expected %d (one per replica, excluding primary)",
+							token_count, num_replicas),
+					 errhint("Command should output one delay value per replica node. Missing values will be treated as 0.")));
+		}
+		else if (token_count > num_replicas)
+		{
+			ereport(WARNING,
+					(errmsg("replication delay command returned %d values, expected %d (one per replica, excluding primary)",
+							token_count, num_replicas),
+					 errhint("Command should output exactly one delay value per replica node. Extra values will be ignored.")));
+		}
+
+		/* Parse the output - one delay value per replica in order */
+		token = strtok_r(line, " \t\n", &saveptr);
+
+		for (int i = 0; i < NUM_BACKENDS && token != NULL; i++)
+		{
+			if (i == primary_node_id)
+				continue; /* Skip primary - it's not in the output */
+
+			if (!VALID_BACKEND(i))
+			{
+				/* Skip invalid backend but consume token */
+				token = strtok_r(NULL, " \t\n", &saveptr);
+				continue;
+			}
+
+			char *endptr;
+			delay_ms = strtod(token, &endptr);
+
+			/* Validate the conversion */
+			if (*endptr != '\0')
+			{
+				ereport(WARNING,
+						(errmsg("invalid delay value '%s' for node %d, treating as 0",
+								token, i)));
+				delay_ms = 0;
+			}
+
+			bkinfo = pool_get_node_info(i);
+
+			/* Handle -1 for down nodes */
+			if (delay_ms == -1.0)
+			{
+				ereport(LOG,
+						(errmsg("node %d reported as down by external command (delay -1), relying on health check for failover decision",
+								i)));
+				/* Keep previous delay value, don't trigger failover */
+				token = strtok_r(NULL, " \t\n", &saveptr);
+				continue;
+			}
+
+			/* Validate delay value range */
+			if (delay_ms < 0)
+			{
+				ereport(WARNING,
+						(errmsg("negative delay value %.3f for node %d (other than -1), treating as 0",
+								delay_ms, i)));
+				delay_ms = 0;
+			}
+			else if (delay_ms > MAX_REASONABLE_DELAY_MS)
+			{
+				ereport(WARNING,
+						(errmsg("extremely large delay value %.3f for node %d",
+								delay_ms, i)));
+			}
+
+			/* Convert delay from milliseconds to microseconds for internal storage */
+			delay = (uint64)(delay_ms * 1000);
+			bkinfo->standby_delay = delay;
+			bkinfo->standby_delay_by_time = true;
+
+			/* Log delay if necessary */
+			uint64 delay_threshold_by_time = pool_config->delay_threshold_by_time * 1000; /* threshold is in milliseconds, convert to microseconds */
+
+			if ((pool_config->log_standby_delay == LSD_ALWAYS && delay_ms > 0) ||
+				(pool_config->log_standby_delay == LSD_OVER_THRESHOLD &&
+				 bkinfo->standby_delay > delay_threshold_by_time))
+			{
+				ereport(LOG,
+						(errmsg("Replication of node: %d is behind %.3f second(s) from the primary server (node: %d) [external command]",
+								i, delay_ms / 1000, primary_node_id)));
+			}
+
+			token = strtok_r(NULL, " \t\n", &saveptr);
+		}
+
+	}
+	PG_CATCH();
+	{
+		/* Cleanup in case of error */
+		if (pid > 0) {
+			kill(pid, SIGKILL);
+			waitpid(pid, NULL, 0);
+		}
+		if (pipefd[0] != -1) close(pipefd[0]);
+		if (pipefd[1] != -1) close(pipefd[1]);
+
+		if (line)
+			pfree(line);
+		if (command)
+			pfree(command);
+		error_context_stack = callback.previous;
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	/* Normal cleanup */
+	if (line)
+		pfree(line);
+
+	error_context_stack = callback.previous;
+}
+
+/*
+ * build_instance_identifier_for_node
+ *  Build an identifier string for a backend node for passing to external commands.
+ *  Format: "<hostname>:<port>"
+ */
+static char *
+build_instance_identifier_for_node(int node_id)
+{
+	BackendInfo *bi = pool_get_node_info(node_id);
+	const char *hostname;
+
+	if (!bi || bi->backend_hostname[0] == '\0' || bi->backend_port <= 0)
+	{
+		/* Fallback if hostname or port is not set */
+		return psprintf("unknown_node_%d", node_id);
+	}
+
+	hostname = bi->backend_hostname;
+
+	/* Validate hostname for security - check for shell metacharacters */
+	if (strpbrk(hostname, "$`\\|;&<>()[]{}\"\'\n\r\t") != NULL)
+	{
+		ereport(LOG,
+				(errmsg("hostname for node %d contains potentially dangerous characters: %s",
+						node_id, hostname),
+				 errhint("Hostnames with shell metacharacters may pose security risks when used with external commands. Consider using IP addresses or sanitized hostnames.")));
+	}
+
+	/* Use hostname:port format */
+	return psprintf("%s:%d", hostname, bi->backend_port);
+}
+
 static void
 CheckReplicationTimeLagErrorCb(void *arg)
 {
diff --git a/src/test/regression/tests/041.external_replication_delay/README b/src/test/regression/tests/041.external_replication_delay/README
new file mode 100644
index 0000000000000000000000000000000000000000..b4df5da402b557190c8f6a2bc7822944cc5b04cc
--- /dev/null
+++ b/src/test/regression/tests/041.external_replication_delay/README
@@ -0,0 +1,59 @@
+External Replication Delay Command Test
+========================================
+
+This test verifies the external command replication delay source feature.
+
+Test Coverage:
+- External command receives replica node identifiers only (primary omitted)
+- Instance identifiers in host:port format
+- Basic external command execution with integer and float millisecond values
+- Delay threshold functionality with external commands
+- Command execution as pgpool process user (no su wrapper)
+- Error handling for missing/invalid commands
+- Command execution failure scenarios
+- Command timeout handling with configurable timeout values
+- Input validation for invalid, negative (other than -1), and extremely large delay values
+- Handling of -1 for down nodes (logged but no immediate failover)
+- Wrong number of output values validation
+- Multiple -1 values (multiple down replicas)
+- Mixed scenarios (some replicas up, some down)
+- Output truncation detection
+
+Files:
+- test.sh: Main test script
+- test_parsing.sh: Unit test for parsing logic
+- test_validation.sh: Validation and edge case testing
+- README: This documentation
+
+Key Changes from Original Version:
+- Primary node is omitted from command arguments
+- Command receives only replica identifiers
+- Instance identifiers are in host:port format (not application_name)
+- Output format: one delay per replica (not per all nodes)
+- -1 value indicates down replica without triggering failover
+- Format example: "25 100" for 2 replicas (3-node cluster = 1 primary + 2 replicas)
+
+The test creates temporary command scripts that output delay values in the format:
+"replica1_delay replica2_delay ..."
+
+Where delays are in milliseconds and can be integer or floating-point values.
+Special value -1 indicates a replica that is down but not yet detected by pgpool.
+
+Test Environment:
+- Uses streaming replication mode with 3 nodes
+- Node 0 is primary (omitted from command arguments)
+- Nodes 1 and 2 are replicas (included in command arguments)
+- Configures sr_check_period = 1 second for faster testing
+- Tests various delay scenarios and threshold behaviors
+
+Expected Behavior:
+- External commands receive replica identifiers in host:port format
+- Primary node identifier is never passed to command
+- Command outputs one delay value per replica
+- -1 values are logged but don't trigger immediate failover
+- Delay values are parsed correctly (both int and float)
+- Threshold comparisons work properly
+- Error conditions are handled gracefully
+- Commands timeout appropriately based on configuration
+- Timeout errors provide helpful messages and hints
+- Tests are reliable with proper wait mechanisms instead of fixed sleeps
diff --git a/src/test/regression/tests/041.external_replication_delay/test.sh b/src/test/regression/tests/041.external_replication_delay/test.sh
new file mode 100755
index 0000000000000000000000000000000000000000..de704e55331247893f4b2e26fb67977875f1ba42
--- /dev/null
+++ b/src/test/regression/tests/041.external_replication_delay/test.sh
@@ -0,0 +1,409 @@
+#!/usr/bin/env bash
+#-------------------------------------------------------------------
+# test script for external command replication delay source
+#
+source $TESTLIBS
+TESTDIR=testdir
+PG_CTL=$PGBIN/pg_ctl
+PSQL="$PGBIN/psql -X "
+
+rm -fr $TESTDIR
+mkdir $TESTDIR
+cd $TESTDIR
+
+# create test environment
+echo -n "creating test environment..."
+$PGPOOL_SETUP -m s -n 3 || exit 1
+echo "done."
+source ./bashrc.ports
+export PGPORT=$PGPOOL_PORT
+
+# Create external command scripts for testing
+# NOTE: Commands now only output delay values for REPLICAS (not primary)
+cat > delay_cmd_static.sh << 'EOF'
+#!/bin/bash
+# Static delay values for replicas: node1=25ms, node2=50ms (node0 is primary, not included)
+echo "25 50"
+EOF
+chmod +x delay_cmd_static.sh
+
+cat > delay_cmd_float.sh << 'EOF'
+#!/bin/bash
+# Float delay values for replicas: node1=25.5ms, node2=100.75ms
+echo "25.5 100.75"
+EOF
+chmod +x delay_cmd_float.sh
+
+cat > delay_cmd_high.sh << 'EOF'
+#!/bin/bash
+# High delay values to test threshold: node1=2000ms, node2=3000ms
+echo "2000 3000"
+EOF
+chmod +x delay_cmd_high.sh
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test0: External command receives replica identifiers only (primary omitted) ==="
+# ----------------------------------------------------------------------------------------
+# Command that captures its arguments and outputs valid delays for 2 replicas
+cat > delay_cmd_args.sh << 'EOF'
+#!/bin/bash
+printf "%s " "$@" > args.txt
+echo "25 50"
+EOF
+chmod +x delay_cmd_args.sh
+
+echo "replication_delay_source_cmd = './delay_cmd_args.sh'" >> etc/pgpool.conf
+echo "sr_check_period = 1" >> etc/pgpool.conf
+echo "log_min_messages = 'DEBUG1'" >> etc/pgpool.conf
+# Reduce memory requirements for macOS shared memory limits
+echo "num_init_children = 4" >> etc/pgpool.conf
+echo "max_pool = 2" >> etc/pgpool.conf
+# Disable query caching to avoid shared memory issues on macOS
+echo "memory_cache_enabled = off" >> etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+echo "Waiting for sr_check to pass args..."
+for i in {1..10}; do
+    if [ -f args.txt ]; then
+        break
+    fi
+    sleep 1
+done
+
+if [ ! -f args.txt ]; then
+    echo fail: did not capture command arguments
+    ./shutdownall
+    exit 1
+fi
+
+ARGS_CONTENT=$(cat args.txt | sed 's/[[:space:]]*$//')
+# Should receive 2 replica identifiers in host:port format (localhost:11003 localhost:11004 or server1:11003 server2:11004)
+# Primary (localhost:11002 or server0:11002) should be omitted
+if ! echo "$ARGS_CONTENT" | grep -qE "(server1|localhost):11003"; then
+    echo "fail: expected replica1:11003 in arguments, got: '$ARGS_CONTENT'"
+    ./shutdownall
+    exit 1
+fi
+if ! echo "$ARGS_CONTENT" | grep -qE "(server2|localhost):11004"; then
+    echo "fail: expected replica2:11004 in arguments, got: '$ARGS_CONTENT'"
+    ./shutdownall
+    exit 1
+fi
+if echo "$ARGS_CONTENT" | grep -qE "(server0|localhost):11002"; then
+    echo "fail: primary should not be in arguments, got: '$ARGS_CONTENT'"
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: argument order correct - replicas only, primary omitted, host:port format
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test1: Basic external command with integer millisecond values ==="
+# ----------------------------------------------------------------------------------------
+echo "replication_delay_source_cmd = './delay_cmd_static.sh'" >> etc/pgpool.conf
+echo "sr_check_period = 1" >> etc/pgpool.conf
+echo "log_standby_delay = 'always'" >> etc/pgpool.conf
+echo "log_min_messages = 'DEBUG1'" >> etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+$PSQL test <<EOF
+CREATE TABLE t1(i INTEGER);
+EOF
+
+# Wait for sr_check to run and populate delay values
+# sr_check_period is 1 second, so wait a bit longer to ensure it runs
+echo "Waiting for sr_check to run..."
+for i in {1..10}; do
+    if grep -q "executing replication delay command" log/pgpool.log 2>/dev/null; then
+        echo "Command executed after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+$PSQL test <<EOF
+SHOW POOL_NODES;
+EOF
+
+# Check that delay values are populated in the log
+grep "executing replication delay command" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: external command was not executed
+    echo "Log contents:"
+    tail -20 log/pgpool.log
+    ./shutdownall
+    exit 1
+fi
+
+# Verify actual delay values were parsed
+if ! $PSQL -t -c "SHOW POOL_NODES" test | grep -E "[0-9]+\.[0-9]+" >/dev/null; then
+    echo "Warning: No delay values found in POOL_NODES output"
+fi
+
+# Check for delay log messages
+grep "Replication of node.*external command" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: external command delay logging not found
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: basic external command test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test2: External command with floating-point millisecond values ==="
+# ----------------------------------------------------------------------------------------
+# Update configuration to use float command
+sed -i.bak "s|delay_cmd_static.sh|delay_cmd_float.sh|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run with float values
+echo "Waiting for sr_check with float values..."
+for i in {1..10}; do
+    if grep -q "executing replication delay command.*delay_cmd_float.sh" log/pgpool.log 2>/dev/null; then
+        echo "Float command executed after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+$PSQL test <<EOF
+SHOW POOL_NODES;
+EOF
+
+# Check that float values are handled correctly
+grep "executing replication delay command.*delay_cmd_float.sh" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: float command was not executed
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: floating-point values test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test3: External command with delay threshold ==="
+# ----------------------------------------------------------------------------------------
+# Update configuration to use high delay command and set threshold
+sed -i.bak "s|delay_cmd_float.sh|delay_cmd_high.sh|" etc/pgpool.conf
+echo "delay_threshold_by_time = 1000" >> etc/pgpool.conf
+echo "backend_weight0 = 0" >> etc/pgpool.conf  # Force queries to standby normally
+echo "backend_weight2 = 0" >> etc/pgpool.conf  # Only use node 1 as standby
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run and detect high delays
+echo "Waiting for sr_check with high delay values..."
+for i in {1..10}; do
+    if grep -q "executing replication delay command.*delay_cmd_high.sh" log/pgpool.log 2>/dev/null; then
+        echo "High delay command executed after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+$PSQL test <<EOF
+SELECT * FROM t1 LIMIT 1;
+EOF
+
+# With high delays (2000ms > 1000ms threshold), query should go to primary (node 0)
+# Log format can vary: either "statement: SELECT..." or "SELECT... DB node id:"
+if ! grep -E "DB node id: 0.*statement: SELECT \* FROM t1 LIMIT 1" log/pgpool.log >/dev/null 2>&1 && \
+   ! grep -E "SELECT \* FROM t1 LIMIT 1.*DB node id: 0" log/pgpool.log >/dev/null 2>&1; then
+    echo fail: query was not sent to primary node despite high delay
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: delay threshold test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test4: External command execution as process user ==="
+# ----------------------------------------------------------------------------------------
+# Test that command runs as the current pgpool process user
+sed -i.bak "s|delay_cmd_high.sh|delay_cmd_static.sh|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run
+echo "Waiting for sr_check to run as process user..."
+for i in {1..10}; do
+    if grep -q "executing replication delay command.*delay_cmd_static.sh" log/pgpool.log 2>/dev/null; then
+        echo "Command executed as process user after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check that command was executed (without su wrapper)
+grep "executing replication delay command.*delay_cmd_static.sh" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: command was not executed as process user
+    ./shutdownall
+    exit 1
+fi
+
+# Verify no su command was used
+if grep -q "executing replication delay command.*su.*" log/pgpool.log 2>/dev/null; then
+    echo fail: command should not use su wrapper
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: process user execution test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test5: Error handling - missing command ==="
+# ----------------------------------------------------------------------------------------
+# Test error handling when command is not configured
+sed -i.bak "s|replication_delay_source_cmd = './delay_cmd_static.sh'|replication_delay_source_cmd = ''|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# With empty command, should fall back to builtin method
+# No specific error message expected - just verify it doesn't crash
+sleep 3
+
+echo "ok: empty command test succeeded (fallback to builtin)"
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test6: Error handling - command execution failure ==="
+# ----------------------------------------------------------------------------------------
+# Test error handling when command fails
+echo "replication_delay_source_cmd = './nonexistent_command.sh'" >> etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run with failing command
+echo "Waiting for sr_check with failing command..."
+for i in {1..5}; do
+    # Check for various error conditions: exit code failure, no output, or explicit failure message
+    if grep -qE "(replication delay command failed with exit code|replication delay command produced no output|failed to (execute|read output from) replication delay command)" log/pgpool.log 2>/dev/null; then
+        echo "Command failure detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for error message about command execution failure
+# Accept multiple possible error messages depending on shell behavior:
+# - "failed with exit code" when command returns non-zero
+# - "produced no output" when command produces empty output
+# - "failed to execute/read" for other failures
+if ! grep -qE "(replication delay command failed with exit code|replication delay command produced no output|failed to (execute|read output from) replication delay command)" log/pgpool.log 2>/dev/null; then
+    echo fail: command execution failure not detected
+    echo "Log contents:"
+    tail -50 log/pgpool.log
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: command failure test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test7: Command timeout handling ==="
+# ----------------------------------------------------------------------------------------
+# Create a command that takes longer than the timeout
+cat > delay_cmd_slow.sh << 'EOF'
+#!/bin/bash
+# Slow command that takes 15 seconds (longer than default 10s timeout)
+sleep 15
+echo "25 50"
+EOF
+chmod +x delay_cmd_slow.sh
+
+# Set a short timeout and use the slow command
+sed -i.bak "s|replication_delay_source_cmd = './nonexistent_command.sh'|replication_delay_source_cmd = './delay_cmd_slow.sh'|" etc/pgpool.conf
+echo "replication_delay_source_timeout = 3" >> etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run and timeout
+echo "Waiting for command timeout..."
+for i in {1..15}; do
+    if grep -q "replication delay command timed out" log/pgpool.log 2>/dev/null; then
+        echo "Command timeout detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for timeout error message
+grep "replication delay command timed out after 3 seconds" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: command timeout not detected
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: command timeout test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test8: Handling of -1 for down nodes ==="
+# ----------------------------------------------------------------------------------------
+# Create a command that returns -1 for one replica
+cat > delay_cmd_with_down_node.sh << 'EOF'
+#!/bin/bash
+# Return -1 for first replica (indicating it's down), normal value for second
+echo "-1 50"
+EOF
+chmod +x delay_cmd_with_down_node.sh
+
+# Reset config
+rm -f etc/pgpool.conf.bak
+sed -i.bak "s|delay_cmd_slow.sh|delay_cmd_with_down_node.sh|" etc/pgpool.conf
+sed -i.bak "s|replication_delay_source_timeout = 3|replication_delay_source_timeout = 10|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to process -1 value
+echo "Waiting for sr_check to process -1 value..."
+for i in {1..10}; do
+    if grep -q "node.*reported as down by external command.*delay -1" log/pgpool.log 2>/dev/null; then
+        echo "-1 handling detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for -1 logging message
+grep "node.*reported as down by external command.*delay -1.*relying on health check" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: -1 handling message not found
+    ./shutdownall
+    exit 1
+fi
+
+# Verify that pgpool didn't trigger failover just from -1
+# Check for actual failover execution, not just config mentions of failover_command
+if grep -qE "(starting.*(failover|degeneration)|failover done|execute.*(failover|failback)_command)" log/pgpool.log 2>/dev/null; then
+    echo "fail: -1 should not trigger immediate failover"
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: -1 handling test succeeded
+./shutdownall
+
+echo "All external replication delay tests passed!"
+exit 0
diff --git a/src/test/regression/tests/041.external_replication_delay/test_parsing.sh b/src/test/regression/tests/041.external_replication_delay/test_parsing.sh
new file mode 100755
index 0000000000000000000000000000000000000000..82fdad144cf5a94efbf79020a50ebc2ef00d6fb8
--- /dev/null
+++ b/src/test/regression/tests/041.external_replication_delay/test_parsing.sh
@@ -0,0 +1,54 @@
+#!/bin/bash
+#-------------------------------------------------------------------
+# Unit test for external command parsing logic
+# This tests the parsing without needing a full pgpool setup
+#
+
+echo "=== Testing external command output parsing ==="
+
+# Test 1: Integer values
+echo "Test 1: Integer millisecond values"
+echo "0 25 50" > test_output.txt
+echo "Expected: 0ms, 25ms, 50ms"
+echo "Output: $(cat test_output.txt)"
+echo ""
+
+# Test 2: Float values
+echo "Test 2: Floating-point millisecond values"
+echo "0 25.5 100.75" > test_output_float.txt
+echo "Expected: 0ms, 25.5ms, 100.75ms"
+echo "Output: $(cat test_output_float.txt)"
+echo ""
+
+# Test 3: High precision float values
+echo "Test 3: High precision values"
+echo "0 0.001 999.999" > test_output_precision.txt
+echo "Expected: 0ms, 0.001ms, 999.999ms"
+echo "Output: $(cat test_output_precision.txt)"
+echo ""
+
+# Test 4: Edge case - zero values
+echo "Test 4: All zero values"
+echo "0 0 0" > test_output_zeros.txt
+echo "Expected: 0ms, 0ms, 0ms"
+echo "Output: $(cat test_output_zeros.txt)"
+echo ""
+
+# Test 5: Edge case - large values
+echo "Test 5: Large delay values"
+echo "0 5000 10000" > test_output_large.txt
+echo "Expected: 0ms, 5000ms, 10000ms"
+echo "Output: $(cat test_output_large.txt)"
+echo ""
+
+# Test 6: Mixed integer and float values
+echo "Test 6: Mixed integer and float values"
+echo "0 25 50.5" > test_output_mixed.txt
+echo "Expected: 0ms, 25ms, 50.5ms"
+echo "Output: $(cat test_output_mixed.txt)"
+echo ""
+
+# Cleanup
+rm -f test_output_*.txt
+
+echo "All parsing tests completed. These outputs should be parseable by the external command feature."
diff --git a/src/test/regression/tests/041.external_replication_delay/test_validation.sh b/src/test/regression/tests/041.external_replication_delay/test_validation.sh
new file mode 100755
index 0000000000000000000000000000000000000000..2cd4a7f0b35e152b6d4b770931ed4821cdd9d201
--- /dev/null
+++ b/src/test/regression/tests/041.external_replication_delay/test_validation.sh
@@ -0,0 +1,323 @@
+#!/usr/bin/env bash
+#-------------------------------------------------------------------
+# test script for external command validation and edge cases
+#
+source $TESTLIBS
+TESTDIR=testdir_validation
+PG_CTL=$PGBIN/pg_ctl
+PSQL="$PGBIN/psql -X "
+
+rm -fr $TESTDIR
+mkdir $TESTDIR
+cd $TESTDIR
+
+# create test environment
+echo -n "creating test environment..."
+$PGPOOL_SETUP -m s -n 3 || exit 1
+echo "done."
+source ./bashrc.ports
+export PGPORT=$PGPOOL_PORT
+
+# Create test command scripts
+# NOTE: All commands output values for REPLICAS only (primary omitted)
+cat > delay_cmd_validation.sh << 'EOF'
+#!/bin/bash
+# Test validation: output with invalid values for 2 replicas
+echo "invalid_value 50.5"
+EOF
+chmod +x delay_cmd_validation.sh
+
+cat > delay_cmd_negative.sh << 'EOF'
+#!/bin/bash
+# Test negative values (other than -1)
+echo "-25 50"
+EOF
+chmod +x delay_cmd_negative.sh
+
+cat > delay_cmd_large.sh << 'EOF'
+#!/bin/bash
+# Test extremely large values
+echo "9999999 50"
+EOF
+chmod +x delay_cmd_large.sh
+
+cat > delay_cmd_wrong_count.sh << 'EOF'
+#!/bin/bash
+# Test wrong number of values (only 1 instead of 2 for 2 replicas)
+echo "25"
+EOF
+chmod +x delay_cmd_wrong_count.sh
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test1: Validation of invalid delay values ==="
+# ----------------------------------------------------------------------------------------
+echo "replication_delay_source_cmd = './delay_cmd_validation.sh'" >> etc/pgpool.conf
+echo "sr_check_period = 1" >> etc/pgpool.conf
+echo "log_standby_delay = 'always'" >> etc/pgpool.conf
+echo "log_min_messages = 'DEBUG1'" >> etc/pgpool.conf
+# Reduce memory requirements for macOS shared memory limits
+echo "num_init_children = 4" >> etc/pgpool.conf
+echo "max_pool = 2" >> etc/pgpool.conf
+# Disable query caching to avoid shared memory issues on macOS
+echo "memory_cache_enabled = off" >> etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+$PSQL test <<EOF
+CREATE TABLE t1(i INTEGER);
+EOF
+
+# Wait for sr_check to run
+echo "Waiting for validation test..."
+for i in {1..10}; do
+    if grep -q "invalid delay value" log/pgpool.log 2>/dev/null; then
+        echo "Validation error detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for validation warning
+grep "invalid delay value 'invalid_value' for node" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: validation warning not found
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: invalid value validation test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test2: Negative delay values (other than -1) ==="
+# ----------------------------------------------------------------------------------------
+sed -i.bak "s|delay_cmd_validation.sh|delay_cmd_negative.sh|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run
+echo "Waiting for negative value test..."
+for i in {1..10}; do
+    if grep -q "negative delay value.*other than -1" log/pgpool.log 2>/dev/null; then
+        echo "Negative value warning detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for negative value warning
+grep "negative delay value.*other than -1.*treating as 0" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: negative value warning not found
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: negative value validation test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test3: Extremely large delay values ==="
+# ----------------------------------------------------------------------------------------
+sed -i.bak "s|delay_cmd_negative.sh|delay_cmd_large.sh|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run
+echo "Waiting for large value test..."
+for i in {1..10}; do
+    if grep -q "extremely large delay value" log/pgpool.log 2>/dev/null; then
+        echo "Large value warning detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for large value warning
+grep "extremely large delay value.*for node" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: large value warning not found
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: large value validation test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test4: Wrong number of output values ==="
+# ----------------------------------------------------------------------------------------
+sed -i.bak "s|delay_cmd_large.sh|delay_cmd_wrong_count.sh|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run
+echo "Waiting for wrong count test..."
+for i in {1..10}; do
+    if grep -q "returned.*values, expected.*replica" log/pgpool.log 2>/dev/null; then
+        echo "Wrong count warning detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for wrong count warning
+grep "returned.*values, expected.*replica.*Command should output one delay value per replica" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: wrong count validation test not found
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: wrong count validation test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test5: Multiple -1 values ==="
+# ----------------------------------------------------------------------------------------
+cat > delay_cmd_multi_down.sh << 'EOF'
+#!/bin/bash
+# Test multiple replicas down
+echo "-1 -1"
+EOF
+chmod +x delay_cmd_multi_down.sh
+
+sed -i.bak "s|delay_cmd_wrong_count.sh|delay_cmd_multi_down.sh|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check to run
+echo "Waiting for multi-down test..."
+for i in {1..10}; do
+    if grep -q "node.*reported as down by external command" log/pgpool.log 2>/dev/null; then
+        echo "Multiple down nodes detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for multiple -1 handling
+DOWN_COUNT=$(grep -c "node.*reported as down by external command.*delay -1" log/pgpool.log)
+if [ "$DOWN_COUNT" -lt 2 ]; then
+    echo fail: expected 2 down node messages, found $DOWN_COUNT
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: multiple -1 handling test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test6: Command timeout with different timeout values ==="
+# ----------------------------------------------------------------------------------------
+cat > delay_cmd_timeout.sh << 'EOF'
+#!/bin/bash
+# Command that takes 5 seconds
+sleep 5
+echo "25 50"
+EOF
+chmod +x delay_cmd_timeout.sh
+
+# Test with timeout shorter than command duration
+sed -i.bak "s|delay_cmd_multi_down.sh|delay_cmd_timeout.sh|" etc/pgpool.conf
+echo "replication_delay_source_timeout = 2" >> etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for timeout
+echo "Waiting for timeout test (2s timeout, 5s command)..."
+for i in {1..10}; do
+    if grep -q "replication delay command timed out after 2 seconds" log/pgpool.log 2>/dev/null; then
+        echo "Timeout detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Check for timeout message
+grep "replication delay command timed out after 2 seconds" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: timeout not detected
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: timeout test succeeded
+./shutdownall
+
+# Test with timeout longer than command duration
+sed -i.bak "s|replication_delay_source_timeout = 2|replication_delay_source_timeout = 10|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for successful execution
+echo "Waiting for successful execution (10s timeout, 5s command)..."
+for i in {1..15}; do
+    if grep -q "executing replication delay command.*delay_cmd_timeout.sh" log/pgpool.log 2>/dev/null; then
+        echo "Command executed successfully after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Should not timeout this time
+if grep -q "replication delay command timed out" log/pgpool.log 2>/dev/null; then
+    echo fail: command should not have timed out with 10s timeout
+    ./shutdownall
+    exit 1
+fi
+
+echo ok: extended timeout test succeeded
+./shutdownall
+
+# ----------------------------------------------------------------------------------------
+echo "=== Test7: Mix of valid delays and -1 ==="
+# ----------------------------------------------------------------------------------------
+cat > delay_cmd_mixed.sh << 'EOF'
+#!/bin/bash
+# One replica up (25ms), one down (-1)
+echo "25 -1"
+EOF
+chmod +x delay_cmd_mixed.sh
+
+sed -i.bak "s|delay_cmd_timeout.sh|delay_cmd_mixed.sh|" etc/pgpool.conf
+
+./startall
+wait_for_pgpool_startup
+
+# Wait for sr_check
+echo "Waiting for mixed delay test..."
+for i in {1..10}; do
+    if grep -q "node.*reported as down by external command" log/pgpool.log 2>/dev/null; then
+        echo "Mixed delay handling detected after ${i} seconds"
+        break
+    fi
+    sleep 1
+done
+
+# Should log one -1 and process one normal delay
+grep "node.*reported as down by external command.*delay -1" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo fail: -1 not logged
+    ./shutdownall
+    exit 1
+fi
+
+# Should also log the normal replica delay
+grep "Replication of node.*external command" log/pgpool.log >/dev/null 2>&1
+if [ $? != 0 ];then
+    echo "Note: Normal replica delay logging may not be visible with log_standby_delay settings"
+fi
+
+echo ok: mixed delay handling test succeeded
+./shutdownall
+
+echo "All validation tests passed!"
+exit 0
\ No newline at end of file
-- 
2.52.0