(events): fails to attach more than one Lambda to EventBridge trigger

description of the bug: When adding multiple Lambda targets to EventBridge Rule, it only adds the trigger source to the first Lambda and it fails to properly add the trigger source to the other Lambdas. This behavior was first witnessed around 11/7-11/8/2020 and was working fine before then.

Reproduction Steps

import aws_cdk.aws_events as ev
import aws_cdk.aws_events_targets as evt
import aws_cdk.aws_lambda as lambda_
import aws_cdk.core as core


class TestStack(core.Stack):
    def __init__(self, scope: core.Construct, id: str, **kwargs) -> None:
        super().__init__(scope, id, **kwargs)

        # event bus
        event_bus = ev.EventBus(
            self,
            id="event_bus_id",
            event_bus_name="test_event_bus"
        )

        # event rule
        event_bus_rule = ev.Rule(
            self,
            id="event_bus_rule_id",
            event_bus=event_bus,
            rule_name="test_event_rule"
        )

        # lambda to trigger bus
        fn_0 = lambda_.Function(
            self,
            id="fn_0_id",
            code=lambda_.InlineCode("def lambda_handler(event, context): pass"),
            handler="index.lambda_handler",
            runtime=lambda_.Runtime.PYTHON_3_7,
            function_name="test_fn_0"
        )

        # event pattern for bus
        event_bus_rule.add_event_pattern(
            account=[self.account],
            resources=[fn_0.function_arn + ":$LATEST"]
        )

        # lambda 1 to be triggered
        fn_1 = lambda_.Function(
            self,
            id="fn_1_id",
            code=lambda_.InlineCode("def lambda_handler(event, context): pass"),
            handler="index.lambda_handler",
            runtime=lambda_.Runtime.PYTHON_3_7,
            function_name="test_fn_1"
        )

        # adding lambda 1 as target
        event_bus_rule.add_target(evt.LambdaFunction(fn_1))

        # lambda 2 to be triggered
        fn_2 = lambda_.Function(
            self,
            id="fn_2_id",
            code=lambda_.InlineCode("def lambda_handler(event, context): pass"),
            handler="index.lambda_handler",
            runtime=lambda_.Runtime.PYTHON_3_7,
            function_name="test_fn_2"
        )

        # adding lambda 2 as target
        event_bus_rule.add_target(evt.LambdaFunction(fn_2))

What did you expect to happen?

1. Create EventBridge and Rule with Event pattern
2. Lambda 0 to trigger rule with event pattern
3. EventBridge to create Targets for Lambdas 1 and 2
4. Attach trigger to Lambdas 1 and 2

What actually happened?

1. Created EventBridge and Rule with Event pattern
2. Lambda 0 to trigger rule with event pattern
3. EventBridge created Targets for Lambdas 1 and 2
4. EventBridge attached trigger to Lambda 1
5. EventBridge failed to attach trigger to Lambda 2

Environment

• CDK CLI Version : 1.77.0
• Framework Version: 1.77.0
• Node.js Version: 12.14.0
• OS: Mac 11.0.1 (Big Sur)
• Language (Version): Python (3.7.5)

Other

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This is 🐛 Bug Report

[juweeks]

Agreed #11217 with v1.72 looks like it. That release was around the same time when it got hit. Thanks for the prompt response @shivlaks !

[shivlaks]

was this behaviour observed with an upgrade to 1.77.0? - do you know the previous version where it was working? Since this might be a regression, classifying it as a p1 so we can prioritize getting a fix out.