Add a node_is_leader service to check for the leader states

It's possible to check for any kind of leader of specifically for a
standby leader.

CHANGELOG.md

@@ -8,6 +8,7 @@
 * Add a new service `cluster_has_scheduled_action` to warn of any scheduled switchover or restart.
 * Add options to `node_is_replica` to check specifically for a synchronous (`--is-sync`) or asynchronous node (`--is-async`).
 * Add `standby-leader` as a valid leader type for `cluster_has_leader`.
+* Add a new service `node_is_leader` to check if a node is a leader (which includes standby leader nodes)
 
 ### Fixed
 

README.md

@@ -42,6 +42,7 @@ Commands:
   cluster_is_in_maintenance     Check if the cluster is in maintenance...
   cluster_node_count            Count the number of nodes in the cluster.
   node_is_alive                 Check if the node is alive ie patroni is...
+  node_is_leader                Check if the node is a leader node.
   node_is_pending_restart       Check if the node is in pending restart...
   node_is_primary               Check if the node is the primary with the...
   node_is_replica               Check if the node is a running replica...
@@ -350,13 +351,37 @@ Options:
   --help  Show this message and exit.
 ```
 
+### node_is_leader
+
+```
+Usage: check_patroni node_is_leader [OPTIONS]
+
+  Check if the node is a leader node.
+
+  This check applies to any kind of leaders including standby leaders. To
+  check explicitly for a standby leader use the `--is-standby-leader` option.
+
+  Check:
+  * `OK`: if the node is a leader.
+  * `CRITICAL:` otherwise
+
+  Perfdata: `is_leader` is 1 if the node is a leader node, 0 otherwise.
+
+Options:
+  --is-standby-leader  Check for a standby leader
+  --help               Show this message and exit.
+```
+
 ### node_is_primary
 
 ```
 Usage: check_patroni node_is_primary [OPTIONS]
 
   Check if the node is the primary with the leader lock.
 
+  This service is not valid for a standby leader, because this kind of node is
+  not a primary.
+
   Check:
   * `OK`: if the node is a primary with the leader lock.
   * `CRITICAL:` otherwise

check_patroni/cli.py

@@ -21,6 +21,8 @@
 from .node import (
     NodeIsAlive,
     NodeIsAliveSummary,
+    NodeIsLeader,
+    NodeIsLeaderSummary,
     NodeIsPendingRestart,
     NodeIsPendingRestartSummary,
     NodeIsPrimary,
@@ -470,6 +472,8 @@ def cluster_has_scheduled_action(ctx: click.Context) -> None:
 def node_is_primary(ctx: click.Context) -> None:
     """Check if the node is the primary with the leader lock.
 
+    This service is not valid for a standby leader, because this kind of node is not a primary.
+
     \b
     Check:
     * `OK`: if the node is a primary with the leader lock.
@@ -486,6 +490,38 @@ def node_is_primary(ctx: click.Context) -> None:
     check.main(verbose=ctx.obj.verbose, timeout=ctx.obj.timeout)
 
 
+@main.command(name="node_is_leader")
+@click.option(
+    "--is-standby-leader",
+    "check_standby_leader",
+    is_flag=True,
+    default=False,
+    help="Check for a standby leader",
+)
+@click.pass_context
+@nagiosplugin.guarded
+def node_is_leader(ctx: click.Context, check_standby_leader: bool) -> None:
+    """Check if the node is a leader node.
+
+    This check applies to any kind of leaders including standby leaders.
+    To check explicitly for a standby leader use the `--is-standby-leader` option.
+
+    \b
+    Check:
+    * `OK`: if the node is a leader.
+    * `CRITICAL:` otherwise
+
+    Perfdata: `is_leader` is 1 if the node is a leader node, 0 otherwise.
+    """
+    check = nagiosplugin.Check()
+    check.add(
+        NodeIsLeader(ctx.obj.connection_info, check_standby_leader),
+        nagiosplugin.ScalarContext("is_leader", None, "@0:0"),
+        NodeIsLeaderSummary(check_standby_leader),
+    )
+    check.main(verbose=ctx.obj.verbose, timeout=ctx.obj.timeout)
+
+
 @main.command(name="node_is_replica")
 @click.option("--max-lag", "max_lag", type=str, help="maximum allowed lag")
 @click.option(

check_patroni/node.py

@@ -24,6 +24,45 @@ def problem(self: "NodeIsPrimarySummary", results: nagiosplugin.Result) -> str:
         return "This node is not the primary with the leader lock."
 
 
+class NodeIsLeader(PatroniResource):
+    def __init__(
+        self: "NodeIsLeader",
+        connection_info: ConnectionInfo,
+        check_is_standby_leader: bool,
+    ) -> None:
+        super().__init__(connection_info)
+        self.check_is_standby_leader = check_is_standby_leader
+
+    def probe(self: "NodeIsLeader") -> Iterable[nagiosplugin.Metric]:
+        apiname = "leader"
+        if self.check_is_standby_leader:
+            apiname = "standby-leader"
+
+        try:
+            self.rest_api(apiname)
+        except APIError:
+            return [nagiosplugin.Metric("is_leader", 0)]
+        return [nagiosplugin.Metric("is_leader", 1)]
+
+
+class NodeIsLeaderSummary(nagiosplugin.Summary):
+    def __init__(
+        self: "NodeIsLeaderSummary",
+        check_is_standby_leader: bool,
+    ) -> None:
+        if check_is_standby_leader:
+            self.leader_kind = "standby leader"
+        else:
+            self.leader_kind = "leader"
+
+    def ok(self: "NodeIsLeaderSummary", results: nagiosplugin.Result) -> str:
+        return f"This node is a {self.leader_kind} node."
+
+    @handle_unknown
+    def problem(self: "NodeIsLeaderSummary", results: nagiosplugin.Result) -> str:
+        return f"This node is not a {self.leader_kind} node."
+
+
 class NodeIsReplica(PatroniResource):
     def __init__(
         self: "NodeIsReplica",

docs/make_readme.sh

@@ -172,6 +172,8 @@ readme "### node_is_alive"
 helpme node_is_alive
 readme "### node_is_pending_restart"
 helpme node_is_pending_restart
+readme "### node_is_leader"
+helpme node_is_leader
 readme "### node_is_primary"
 helpme node_is_primary
 readme "### node_is_replica"

tests/json/node_is_leader_ko.json

@@ -0,0 +1,26 @@
+{
+  "state": "running",
+  "postmaster_start_time": "2021-08-11 07:02:20.732 UTC",
+  "role": "master",
+  "server_version": 110012,
+  "cluster_unlocked": false,
+  "xlog": {
+    "location": 1174407088
+  },
+  "timeline": 58,
+  "replication": [
+    {
+      "usename": "replicator",
+      "application_name": "srv1",
+      "client_addr": "10.20.199.3",
+      "state": "streaming",
+      "sync_state": "async",
+      "sync_priority": 0
+    }
+  ],
+  "database_system_identifier": "6965971025273547206",
+  "patroni": {
+    "version": "2.0.2",
+    "scope": "patroni-demo"
+  }
+}

tests/json/node_is_leader_ko_standby_leader.json

@@ -0,0 +1,19 @@
+{
+  "state": "running",
+  "postmaster_start_time": "2023-08-23 14:30:50.201691+00:00",
+  "role": "standby_leader",
+  "server_version": 140009,
+  "xlog": {
+    "received_location": 889192448,
+    "replayed_location": 889192448,
+    "replayed_timestamp": null,
+    "paused": false
+  },
+  "timeline": 1,
+  "dcs_last_seen": 1692805971,
+  "database_system_identifier": "7270495803765492571",
+  "patroni": {
+    "version": "3.1.0",
+    "scope": "patroni-demo-sb"
+  }
+}

tests/json/node_is_leader_ok.json

@@ -0,0 +1,26 @@
+{
+  "state": "running",
+  "postmaster_start_time": "2021-08-11 07:02:20.732 UTC",
+  "role": "master",
+  "server_version": 110012,
+  "cluster_unlocked": false,
+  "xlog": {
+    "location": 1174407088
+  },
+  "timeline": 58,
+  "replication": [
+    {
+      "usename": "replicator",
+      "application_name": "srv1",
+      "client_addr": "10.20.199.3",
+      "state": "streaming",
+      "sync_state": "async",
+      "sync_priority": 0
+    }
+  ],
+  "database_system_identifier": "6965971025273547206",
+  "patroni": {
+    "version": "2.0.2",
+    "scope": "patroni-demo"
+  }
+}

tests/json/node_is_leader_ok_standby_leader.json

@@ -0,0 +1,19 @@
+{
+  "state": "running",
+  "postmaster_start_time": "2023-08-23 14:30:50.201691+00:00",
+  "role": "standby_leader",
+  "server_version": 140009,
+  "xlog": {
+    "received_location": 889192448,
+    "replayed_location": 889192448,
+    "replayed_timestamp": null,
+    "paused": false
+  },
+  "timeline": 1,
+  "dcs_last_seen": 1692805971,
+  "database_system_identifier": "7270495803765492571",
+  "patroni": {
+    "version": "3.1.0",
+    "scope": "patroni-demo-sb"
+  }
+}

tests/test_node_is_leader.py

@@ -0,0 +1,53 @@
+from click.testing import CliRunner
+from pytest_mock import MockerFixture
+
+from check_patroni.cli import main
+
+from .tools import my_mock
+
+
+def test_node_is_leader_ok(mocker: MockerFixture, use_old_replica_state: bool) -> None:
+    runner = CliRunner()
+
+    my_mock(mocker, "node_is_leader_ok", 200)
+    result = runner.invoke(main, ["-e", "https://10.20.199.3:8008", "node_is_leader"])
+    assert result.exit_code == 0
+    assert (
+        result.stdout
+        == "NODEISLEADER OK - This node is a leader node. | is_leader=1;;@0\n"
+    )
+
+    my_mock(mocker, "node_is_leader_ok_standby_leader", 200)
+    result = runner.invoke(
+        main,
+        ["-e", "https://10.20.199.3:8008", "node_is_leader", "--is-standby-leader"],
+    )
+    print(result.stdout)
+    assert result.exit_code == 0
+    assert (
+        result.stdout
+        == "NODEISLEADER OK - This node is a standby leader node. | is_leader=1;;@0\n"
+    )
+
+
+def test_node_is_leader_ko(mocker: MockerFixture, use_old_replica_state: bool) -> None:
+    runner = CliRunner()
+
+    my_mock(mocker, "node_is_leader_ko", 503)
+    result = runner.invoke(main, ["-e", "https://10.20.199.3:8008", "node_is_leader"])
+    assert result.exit_code == 2
+    assert (
+        result.stdout
+        == "NODEISLEADER CRITICAL - This node is not a leader node. | is_leader=0;;@0\n"
+    )
+
+    my_mock(mocker, "node_is_leader_ko_standby_leader", 503)
+    result = runner.invoke(
+        main,
+        ["-e", "https://10.20.199.3:8008", "node_is_leader", "--is-standby-leader"],
+    )
+    assert result.exit_code == 2
+    assert (
+        result.stdout
+        == "NODEISLEADER CRITICAL - This node is not a standby leader node. | is_leader=0;;@0\n"
+    )