Metrics Confirmation CloudWatch metric NetworkIn stays below 80 % of the instance’s advertised bandwidth. Redshift STL_QUERY metric elapsed shows COPY duration < 20 minutes. Auto Scaling group health‑check failures drop to zero during the ingestion window. Post‑Deployment Smoke Test

aws cloudwatch get-metric-statistics \ --namespace AWS/EC2 \ --metric-name NetworkIn \ --dimensions Name=AutoScalingGroupName,Value=log‑ingest‑asg \ --statistics Average \ --period 300 \ --start-time $(date -u -d '-30 minutes' +%Y-%m-%dT%H:%M:%SZ) \ --end-time $(date -u +%Y-%m-%dT%H:%M:%SZ) Prevention – Operational Guardrails Capacity Planning: Use the EC2 Instance Types – Network Performance table to select instances whose baseline bandwidth exceeds the expected aggregate S3 read throughput. Health‑Check Grace Period: Set a minimum of 10 minutes for any job that may run longer than the default health‑check interval. Timeout Configuration: Always specify TIMEOUT in the COPY command for loads exceeding 5 minutes. IAM Role Consistency: Enforce instance profile attachment via launch template versioning; validate the role with a start‑up script. Monitoring & Alerts: Create CloudWatch alarms on: EC2 NetworkIn > 85 % of instance capacity. Redshift STL_LOAD_ERRORS count > 0. Auto Scaling InstanceReplace events during the ingestion window. FAQ – Common Follow‑Up Questions Why does the COPY command time out only during peak hours? Because the fleet’s aggregate network traffic exceeds the per‑instance ENA bandwidth ceiling, causing packet loss and TCP retransmissions that extend transfer time beyond the default 300 s timeout. Can I keep the default TIMEOUT and still avoid failures? Only if you guarantee that the combined S3 read throughput stays well below the instance’s network limit. In practice, setting an explicit longer TIMEOUT is safer. Do I need to modify Redshift’s WLM queues for these loads? Increasing the queue_timeout or moving COPY jobs to a dedicated queue can prevent query‑level aborts, but the primary issue is network throttling on the EC2 side. How can I verify that the IAM role is correctly attached after a scaling event? Add a start‑up health check script that calls the instance metadata endpoint and exits with a non‑zero code if the expected role name is missing; Auto Scaling will then replace the faulty instance. Is using S3 Transfer Acceleration a viable workaround? Transfer Acceleration can reduce latency for cross‑region transfers but does not increase the EC2 instance’s inbound bandwidth; it may help marginally but does not resolve the root cause of ENA bandwidth saturation. Related Topic Hub: Cloud Infrastructure Troubleshooting Hub

EC2 Batch Ingestion Timeouts During High Volume Redshift Loads

Q: Root Cause Analysis Network Bandwidth Saturation on ENA‑enabled Instances

According to the Amazon EC2 Instance Types – Network Performance and Bandwidth limits documentation, certain instance families provide “Up to 10 Gbps” of ENA bandwidth. When the Auto Scaling group scales up rapidly, the aggregate inbound S3 traffic can exceed the per‑instance network ceiling, causing packet loss, TCP retransmissions, and eventual timeout of the Redshift COPY operation (default 300 s as per the Redshift COPY command – Loading data from Amazon S3 and handling timeouts guide).

Q: Mis‑aligned COPY TIMEOUT Parameters

The default TIMEOUT parameter for COPY is 5 minutes. Large files (hundreds of gigabytes) or high concurrency can require more time, especially when network throttling is present. The lack of an explicit TIMEOUT clause causes the command to abort prematurely.

Q: Investigation and Debugging Steps 1. Capture Network Utilization

sudo yum install -y sysstat sar -n DEV 1 30 # monitor per‑interface bandwidth Expected output when the instance hits its limit:

Q: 2. Review Auto Scaling Activity History

aws autoscaling describe-scaling-activities \ --auto-scaling-group-name log‑ingest‑asg \ --max-items 20 Look for InstanceReplace events that overlap with COPY timestamps.

Q: 3. Inspect Redshift STL_LOAD_ERRORS

SELECT * FROM stl_load_errors WHERE starttime > dateadd(hour, -2, getdate()) ORDER BY starttime DESC; Sample rows:

Q: 4. Verify IAM Role Propagation

curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/ If the role name is missing or incorrect, the instance cannot read from S3.

Q: 5. Examine TCP Retransmission Counters

ss -i state established '( dport = :443 )' Look for retrans counts > 0, indicating packet loss.

Q: Resolution – Making the Ingestion Pipeline Resilient 1. Upgrade to Network‑Optimized Instance Types

Switch from m5.large (up to 10 Gbps burst) to c5n.large (up to 25 Gbps) or r5n.2xlarge for higher sustained bandwidth.

In this article

Table of Contents

Problem – Intermittent EC2 Batch Ingestion Timeouts During High‑Volume Redshift Loads

A daily data pipeline runs on an Auto Scaling group of Amazon EC2 instances. Each instance reads structured log files from Amazon S3 and issues a COPY command to load the data into an Amazon Redshift cluster. During peak ingestion windows the following symptoms appear:

Copy jobs fail with timeout errors after roughly 5 minutes.
Partial data appears in Redshift; some rows are missing.
Log excerpts show TCP retransmissions and occasional ETIMEDOUT errors.
Scaling events trigger instance replacements that sometimes lack the required IAM role, leading to AccessDenied errors.

Typical error messages captured in the EC2 application logs:

ERROR: timed out after 300 seconds while reading from S3 – COPY command timeout

NetworkReadTimeoutError: Read timed out (ReadTimeoutError) while streaming data from S3 to Redshift

ETIMEDOUT: connect ETIMEDOUT 52.95.110.1:443 – EC2 unable to reach S3 endpoint during batch run

Root Cause Analysis

Network Bandwidth Saturation on ENA‑enabled Instances

According to the Amazon EC2 Instance Types – Network Performance and Bandwidth limits documentation, certain instance families provide “Up to 10 Gbps” of ENA bandwidth. When the Auto Scaling group scales up rapidly, the aggregate inbound S3 traffic can exceed the per‑instance network ceiling, causing packet loss, TCP retransmissions, and eventual timeout of the Redshift COPY operation (default 300 s as per the Redshift COPY command – Loading data from Amazon S3 and handling timeouts guide).

Auto Scaling Replacement Timing

The Auto Scaling policy uses a health‑check interval of 30 seconds. During a long‑running batch, an instance may be marked unhealthy and replaced before the COPY completes. The replacement instance is launched without the IAM role that grants s3:GetObject permissions, resulting in “AccessDenied” failures that abort the load.

Mis‑aligned COPY TIMEOUT Parameters

The default TIMEOUT parameter for COPY is 5 minutes. Large files (hundreds of gigabytes) or high concurrency can require more time, especially when network throttling is present. The lack of an explicit TIMEOUT clause causes the command to abort prematurely.

Investigation and Debugging Steps

1. Capture Network Utilization

sudo yum install -y sysstat
sar -n DEV 1 30   # monitor per‑interface bandwidth

Expected output when the instance hits its limit:

02:00:01 PM IFACE   rxpck/s   txpck/s   rxkB/s   txkB/s   rxcmp/s   txcmp/s   rxmcst/s
02:00:02 PM eth0      1250      1248    10240    10180       0        0        0
...

Values approaching the documented bandwidth ceiling (e.g., 10 Gbps ≈ 1.25 GB/s) indicate saturation.

2. Review Auto Scaling Activity History

aws autoscaling describe-scaling-activities \
    --auto-scaling-group-name log‑ingest‑asg \
    --max-items 20

Look for InstanceReplace events that overlap with COPY timestamps.

3. Inspect Redshift STL_LOAD_ERRORS

SELECT *
FROM stl_load_errors
WHERE starttime > dateadd(hour, -2, getdate())
ORDER BY starttime DESC;

Sample rows:

time                 filename               errcode  errreason
2024-06-28 03:12:45  s3://bucket/logs/2024-06-27.gz  5703  timed out after 300 seconds while reading from S3
2024-06-28 03:13:10  s3://bucket/logs/2024-06-27.gz  2900  AccessDenied: User: arn:aws:iam::123456789012:role/BatchIngestRole is not authorized to perform: s3:GetObject

4. Verify IAM Role Propagation

curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/

If the role name is missing or incorrect, the instance cannot read from S3.

5. Examine TCP Retransmission Counters

ss -i state established '( dport = :443 )'

Look for retrans counts > 0, indicating packet loss.

Resolution – Making the Ingestion Pipeline Resilient

1. Upgrade to Network‑Optimized Instance Types

Switch from m5.large (up to 10 Gbps burst) to c5n.large (up to 25 Gbps) or r5n.2xlarge for higher sustained bandwidth.

Before	After
Instance type: `m5.large` Network: Up to 10 Gbps (burst)	Instance type: `c5n.large` Network: Up to 25 Gbps (baseline)

2. Adjust Auto Scaling Health‑Check Settings

aws autoscaling update-auto-scaling-group \
    --auto-scaling-group-name log‑ingest‑asg \
    --health-check-grace-period 900 \
    --health-check-type EC2

Extending the grace period to 15 minutes prevents premature termination during a 10‑minute load.

3. Explicitly Set a Longer COPY TIMEOUT

COPY schema.logs
FROM 's3://bucket/logs/'
IAM_ROLE 'arn:aws:iam::123456789012:role/RedshiftCopyRole'
TIMEFORMAT 'auto'
MAXERROR 0
TIMEOUT 1800;  -- 30 minutes

Increasing the timeout accommodates longer transfer times when network bandwidth is temporarily throttled.

4. Enable Redshift’s `MAX_CONCURRENCY_SCALING` (if applicable)

Allow Redshift to spin up temporary concurrency scaling clusters during peak loads, reducing the duration of each COPY and mitigating the chance of hitting the EC2 network ceiling.

5. Pin S3 Endpoint to the Same AZ

Configure the SDK to use the regional S3 endpoint that resolves to the same Availability Zone as the EC2 fleet, reducing latency and cross‑AZ traffic.

AmazonS3ClientBuilder.standard()
    .withRegion(Regions.US_EAST_1)
    .withEndpointConfiguration(
        new AwsClientBuilder.EndpointConfiguration(
            "s3.us-east-1.amazonaws.com", "us-east-1"))
    .build();

Validation – Confirming the Fix

Functional Verification

# Run a full‑scale batch manually
./run_batch.sh --date 2024-06-30

Expected log snippet:

COPY completed successfully in 12:34 minutes – 1,234,567 rows loaded.

Metrics Confirmation

CloudWatch metric NetworkIn stays below 80 % of the instance’s advertised bandwidth.
Redshift STL_QUERY metric elapsed shows COPY duration < 20 minutes.
Auto Scaling group health‑check failures drop to zero during the ingestion window.

Post‑Deployment Smoke Test

aws cloudwatch get-metric-statistics \
    --namespace AWS/EC2 \
    --metric-name NetworkIn \
    --dimensions Name=AutoScalingGroupName,Value=log‑ingest‑asg \
    --statistics Average \
    --period 300 \
    --start-time $(date -u -d '-30 minutes' +%Y-%m-%dT%H:%M:%SZ) \
    --end-time $(date -u +%Y-%m-%dT%H:%M:%SZ)

Prevention – Operational Guardrails

Capacity Planning: Use the EC2 Instance Types – Network Performance table to select instances whose baseline bandwidth exceeds the expected aggregate S3 read throughput.
Health‑Check Grace Period: Set a minimum of 10 minutes for any job that may run longer than the default health‑check interval.
Timeout Configuration: Always specify TIMEOUT in the COPY command for loads exceeding 5 minutes.
IAM Role Consistency: Enforce instance profile attachment via launch template versioning; validate the role with a start‑up script.
Monitoring & Alerts: Create CloudWatch alarms on:
- EC2 NetworkIn > 85 % of instance capacity.
- Redshift STL_LOAD_ERRORS count > 0.
- Auto Scaling InstanceReplace events during the ingestion window.

FAQ – Common Follow‑Up Questions

Why does the COPY command time out only during peak hours?
Because the fleet’s aggregate network traffic exceeds the per‑instance ENA bandwidth ceiling, causing packet loss and TCP retransmissions that extend transfer time beyond the default 300 s timeout.
Can I keep the default TIMEOUT and still avoid failures?
Only if you guarantee that the combined S3 read throughput stays well below the instance’s network limit. In practice, setting an explicit longer TIMEOUT is safer.
Do I need to modify Redshift’s WLM queues for these loads?
Increasing the queue_timeout or moving COPY jobs to a dedicated queue can prevent query‑level aborts, but the primary issue is network throttling on the EC2 side.
How can I verify that the IAM role is correctly attached after a scaling event?
Add a start‑up health check script that calls the instance metadata endpoint and exits with a non‑zero code if the expected role name is missing; Auto Scaling will then replace the faulty instance.
Is using S3 Transfer Acceleration a viable workaround?
Transfer Acceleration can reduce latency for cross‑region transfers but does not increase the EC2 instance’s inbound bandwidth; it may help marginally but does not resolve the root cause of ENA bandwidth saturation.

Related Topic Hub: Cloud Infrastructure Troubleshooting Hub