Skip to main content
Version: 23.3.0

FAQ and troubleshooting


Maximum results returned

Use pagination to fetch the results in smaller chunks through multiple API calls with max and offset parameters. The error below indidcates that you have run into the maximum result limit:

{object} length parameter cannot be greater than 100 (current value={value_sent})

To remedy this, see the example requests below:

curl -X GET "https://$TOWER_SERVER_URL/workflow/$WORKFLOW_ID/tasks?workspaceId=$WORKSPACE_ID&max=100" \

-H "Accept: application/json" \

-H "Authorization: Bearer $TOWER_ACCESS_TOKEN"

curl -X GET "https://$TOWER_SERVER_URL/workflow/$WORKFLOW_ID/tasks?workspaceId=$WORKSPACE_ID&max=100&offset=100" \

-H "Accept: application/json" \

-H "Authorization: Bearer $TOWER_ACCESS_TOKEN"

Launch users: 403 HTTP response from requests to /workflow/launch

Launch users have more restricted workspace permissions than maintainers, admins, and owners. To launch pipelines via API calls, Launch users must specify additional values that are optional for other users.

Attempting to launch a pipeline without specifying a in the API payload is equivalent to using Start Quick Launch in a workspace (a feature not available to Launch users).

Launch users must add a to pipeline launch requests:

  1. Query the list of pipelines via the /pipelines endpoint. Find the pipelineId of the pipeline you intend to launch.

  2. Call the /pipelines/{pipelineId}/launch API to retrieve the pipeline's

  3. Include the in your request to the /workflow/launch API endpoint:

    "launch": {
    "id": "Q2kVavFZNVCBkC78foTvf",
    "computeEnvId": "4nqF77d6N1JoJrVrrgB8pH",
    "runName": "sample-run",
    "pipeline": "",
    "workDir": "s3://myBucketName",
    "revision": "main"

Alternatively, upgrade your user role to 'Maintain' or higher to be able to quick-launch pipelines.

Common Errors

Unknown pipeline repository or missing credentials error from public Github repositories

GitHub imposes rate limits on repository pulls (including public repositories), where unauthenticated requests are capped at 60 requests/hour and authenticated requests are capped at 5000/hour. Seqera Platform users tend to encounter this error due to the 60 request/hour cap.

Try the following:

  1. Ensure there's at least one GitHub credential in your workspace's Credentials tab.

  2. Ensure that the Access token field of all GitHub credential objects is populated with a Personal Access Token value and not a user password. GitHub PATs are typically longer than passwords and include a ghp_ prefix. For example:ghp*IqIMNOZH6zOwIEB4T9A2g4EHMy8Ji42q4HA

  3. Confirm that your PAT is providing the elevated threshold and transactions are being charged against it:

    curl -H "Authorization: token ghp_LONG_ALPHANUMERIC_PAT" -H "Accept: application/vnd.github.v3+json"

Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) error

This error can occur if incorrect configuration values are assigned to the backend and cron containers' MICRONAUT_ENVIRONMENTS environment variable. You may see other unexpected system behavior, like two exact copies of the same Nextflow job submitted to the executor for scheduling.

Please verify the following:

  1. The MICRONAUT_ENVIRONMENTS environment variable associated with the backend container:
    • Contains prod,redis,ha
    • Does not contain cron
  2. The MICRONAUT_ENVIRONMENTS environment variable associated with the cron container:
    • Contains prod,redis,cron
    • Does not contain ha
  3. You don't have another copy of the MICRONAUT_ENVIRONMENTS environment variable defined elsewhere in your application (such as a tower.env file or Kubernetes ConfigMap).
  4. If you're using a separate container/pod to execute, ensure there's no MICRONAUT_ENVIRONMENTS environment variable assigned to it.

No such variable error

This error can occur if you execute a DSL 1-based Nextflow workflow using Nextflow 22.03.0-edge or later.

Sleep commands in Nextflow workflows

The sleep commands in your Nextflow workflows may differ in behavior depending on where they are:

  • If used within an errorStrategy block, the Groovy sleep function will be used (which takes its value in milliseconds).
  • If used within a process script block, that language's sleep binary/method will be used. Example: this BASH script uses the BASH sleep binary, which takes its value in seconds.


Use rootless containers in Nextflow pipelines

Most containers use the root user by default. However, some users prefer to define a non-root user in the container to minimize the risk of privilege escalation. Because Nextflow and its tasks use a shared work directory to manage input and output data, using rootless containers can lead to file permissions errors in some environments:

touch: cannot touch '/fsx/work/ab/27d78d2b9b17ee895b88fcee794226/.command.begin': Permission denied

This should not occur when using AWS Batch from Seqera version 22.1.0. In other situations, you can avoid this issue by forcing all task containers to run as root. Add one of the following snippets to your Nextflow configuration:

// cloud executors
process.containerOptions = "--user 0:0"

// Kubernetes
k8s.securityContext = [
"runAsUser": 0,
"runAsGroup": 0


Seqera Enterprise 22.2.0: Database connection failure

Seqera Enterprise 22.2.0 introduced a breaking change whereby the TOWER_DB_DRIVER is now required to be org.mariadb.jdbc.Driver.

Clients who use Amazon Aurora as their database solution may encounter a java.sql.SQLNonTransientConnectionException: ... could not load system variables error, likely due to a known error tracked within the MariaDB project.

Please modify the Seqera Enterprise configuration as follows to try resolving the problem:

  1. Ensure your TOWER_DB_DRIVER uses the specified MariaDB URI.
  2. Modify your TOWER_DB_URL to: TOWER_DB_URL=jdbc:mysql://YOUR_DOMAIN:YOUR_PORT/YOUR_TOWER_DB?usePipelineAuth=false&useBatchMultiSend=false


API: Dataset upload failure

When uploading datasets via the Seqera UI or CLI, some steps are automatically done on your behalf. To upload datasets via the Seqera API, additional steps are required:

  1. Explicitly define the MIME type of the file being uploaded.
  2. Make two calls to the API:
    1. Create a dataset object.
    2. Upload the samplesheet to the dataset object.


# Step 1: Create the dataset object.
$ curl -X POST "$WORKSPACE_ID/datasets/" -H "Content-Type: application/json" -H "Authorization: Bearer $TOWER_ACCESS_TOKEN" --data '{"name":"placeholder", "description":"A placeholder for the data we will submit in the next call"}'

# Step 2: Upload the datasheet into the dataset object.
$ curl -X POST "$WORKSPACE_ID/datasets/$DATASET_ID/upload" -H "Accept: application/json" -H "Authorization: Bearer $TOWER_ACCESS_TOKEN" -H "Content-Type: multipart/form-data" -F "file=@samplesheet_full.csv; type=text/csv"

You can also use the tower-cli to upload the dataset to a particular workspace:

tw datasets add --name "cli_uploaded_samplesheet" ./samplesheet_full.csv

Datasets converted to 'application/' data type during upload using Firefox

This is a known issue when using Firefox browser with Seqera versions older than 22.2.0. You can either (a) upgrade to 22.2.0 or higher, or (b) use Chrome.

Seqera displays this error for this issue:

"Given file is not a dataset file. Detected media type: 'application/'. Allowed types: 'text/csv, text/tab-separated-values'"

v22.2: TSV-formatted datasets not shown in Tower launch screen input field drop-down menu

An issue was identified in Seqera version 22.2 which caused TSV datasets to be unavailable in the input data drop-down menu on the launch screen. This has been fixed in version 22.4.1.

Email and TLS

TLS errors

Nextflow and Seqera Platform both have the ability to interact with email providers on your behalf. These providers often require TLS connections, with many now requiring at least TLSv1.2.

TLS connection errors can occur due to variability in the default TLS version specified by your JDK distribution. If you encounter any of the following errors, there is likely a mismatch between your default TLS version and what is supported by the email provider:

  • Unexpected error sending mail ... TLS 1.0 and 1.1 are not supported. Please upgrade/update your client to support TLS 1.2
  • ERROR nextflow.script.WorkflowMetadata - Failed to invoke 'workflow.onComplete' event handler ... No appropriate protocol (protocol is disabled or cipher suites are inappropriate)

To fix the problem, try the following:

  1. Set a JDK environment variable to force Nextflow and Seqera containers to use TLSv1.2 by default:

    export JAVA_OPTIONS="-Dmail.smtp.ssl.protocols=TLSv1.2"
  2. Add this parameter to your nextflow.config file:

    mail {
    smtp.ssl.protocols = 'TLSv1.2'
  3. Ensure these values are also set for Nextflow and/or Seqera:

    • mail.smtp.starttls.enable=true
    • mail.smtp.starttls.required=true

Git integration

BitBucket authentication failure: Can't retrieve revisions for pipeline - - Cause: Get branches operation not supported by BitbucketServerRepositoryProvider provider

If you supplied the correct BitBucket credentials and URL details in your tower.yml and still experience this error, update your version to at least v22.3.0. This version addresses SCM provider authentication issues and is likely to resolve the retrieval failure described here.


Seqera Platform API healthcheck endpoint

To implement automated healthcheck functionality, use Seqera's service-info endpoint.


# Run a healthcheck and extract the HTTP response code:
$ curl -o /dev/null -s -w "%{http_code}\n" --connect-timeout 2 "" -H "Accept: application/json"


Login failures: screen frozen at /auth?success=true

From version 22.1, Seqera Enterprise implements stricter cookie security by default and will only send an auth cookie if the client is connected via HTTPS. Login attempts via HTTP fail by default.

Set the environment variable TOWER_ENABLE_UNSAFE_MODE=true to allow HTTP connectivity to Seqera (not recommended for production environments).

Restrict Seqera access to a set of email addresses, or none

Removing the email section from the login page is not currently supported. You can, however, restrict which email identities may log into your Seqera Enterprise instance using the trustedEmails configuration parameter in your tower.yml file:

# tower.yml
# Any email address pattern which matches will have automatic access.
- '*`
- ''

# Alternatively, specify a single entry to deny access to all other emails.
- ''

Users with email addresses other than the trustedEmails list will undergo an approval process on the Profile > Admin > Users page. This has been used effectively as a backup method when SSO becomes unavailable.

  1. You must rebuild your containers (docker compose down) to force Seqera to implement this change. Ensure your database is persistent before issuing the teardown command. See here for more information.
  2. All login attempts are visible to the root user at Profile > Admin panel > Users.
  3. Any user logged in prior to the restriction will not be subject to the new restriction. An admin of the organization should remove users that have previously logged in via (untrusted) email from the Admin panel users list. This will restart the approval process before they can log in via email.

Login failure: Admin approval is required when using Entra ID OIDC

The Entra ID app integrated with Seqera must have user consent settings configured to "Allow user consent for apps" to ensure that admin approval is not required for each application login. See User consent settings.

Google SMTP: Username and Password not accepted errors

Previously functioning Seqera Enterprise email integration with Google SMTP likely to encounter errors as of May 30, 2022 due to a security posture change implemented by Google.

To re-establish email connectivity, see these instructions to provision an app password. Update your TOWER_SMTP_PASSWORD environment variable with the app password, then restart the application.


v22.3.1: Broken Nextflow log file

A Seqera Launcher issue has been identified that affects the Nextflow log file download in version 22.3.1. A patch was released in version 22.3.2 that addresses this behavior. Update to version 22.3.2 or later.


Maximum parallel Seqera browser tabs

Due to a limitation of server-side event technology implementation in HTTP/1.1, up to five tabs can be open simultaneously (per browser product). Any more will remain stuck in a loading state.


Integration with 3rd-party Java-based Application Performance Monitoring (APM) solutions

Mount the APM solution's JAR file in Seqera's backend container and set the agent JVM option via the JAVA_OPTS env variable.

Retrieve the trace logs for a Seqera-based workflow run

Although it's not possible to directly download the trace logs via Seqera, you can configure your workflow to export the file to persistent storage:

  1. Set this block in your nextflow.config:

    trace {
    enabled = true
  2. Add a copy command to your pipeline's Advanced options > Post-run script field:

    # Example: Export the generated trace file to an S3 bucket
    # Ensure that your Nextflow head job has the necessary permissions to interact with the target storage medium
    aws s3 cp ./trace.txt s3://MY_BUCKET/trace/trace.txt

Runs monitoring: Seqera Platform intermittently reports Live events sync offline

Seqera Platform uses server-sent events to push real-time updates to your browser. The client must establish a connection to the server's /api/live endpoint to initiate the stream of data, and this connection can occasionally fail due to factors like network latency.

To resolve the issue, please try reloading the Seqera browser tab to reinitiate the client's connection to the server. If reloading fails to resolve the problem, please contact Seqera support for assistance with webserver timeout settings adjustments.

Nextflow configuration

Default Nextflow DSL version in Seqera

From Nextflow 22.03.0-edge, DSL2 is the default syntax.

To minimize disruption on existing pipelines, version 22.1.x and later are configured to default Nextflow head jobs to DSL 1 for a transition period (ending TBD).

You can force your Nextflow head job to use DSL2 syntax via any of the following techniques:

  • Add export NXF_DEFAULT_DSL=2 in the Advanced Features > Pre-run script field of Seqera Launch UI.

  • Specify nextflow.enable.dsl = 2 at the top of your Nextflow workflow file.

  • Provide the -dsl2 flag when invoking the Nextflow CLI (e.g., nextflow run ... -dsl2).

Invoke Nextflow CLI run arguments during Seqera launch

From Nextflow v22.09.1-edge, you can specify Nextflow CLI run arguments when invoking a pipeline from Seqera. Set the NXF_CLI_OPTS environment variable via pre-run script:

# Example:
export NXF_CLI_OPTS='-dump-hashes'

Cloud compute environment execution: --outdir artefacts not available

Nextflow resolves relative paths against the current working directory. In a classic grid HPC, this normally corresponds to a subdirectory of the $HOME directory. In a cloud execution environment, however, the path will be resolved relative to the container file system, meaning files will be lost when the container is terminated. See here for more details.

Specify the absolute path to your persistent storage using the NXF_FILE_ROOT environment variable in your nextflow.config file. This resolves the relative paths defined in your Netflow script so that output files are written to your stateful storage, rather than ephemeral container storage.

Nextflow: Ignore Singularity cache

To ignore the Singularity cache, add this configuration item to your workflow: process.container = 'file:///some/singularity/image.sif'.

Nextflow error: WARN: Cannot read project manifest ... path=nextflow.config

This error can occur when executing a pipeline where the source Git repository's default branch is not populated with and nextflow.config files, regardless of whether the invoked pipeline is using a non-default revision/branch (e.g. dev).

Currently, you can resolve this by creating blank and nextflow.config files in the default branch. This will allow the pipeline to run, using the content of the and nextflow.config in your target revision.

Use multiple Nextflow configuration files for different environments

The main nextflow.config file will always be imported by default. Instead of managing multiple nextflow.config files (each customized for an environment), you can create unique environment config files and import them as config profiles in the main nextflow.config.


// nextflow.config


profiles {
test { includeConfig 'conf/test.config' }
prod { includeConfig 'conf/prod.config' }
uat { includeConfig 'conf/uat.config' }


AWS S3 upload file size limits

You may encounter WARN: Failed to publish file: s3://<bucket-name> log messages, often related to AWS S3 object size limitations when using the multipart upload feature.

See the AWS documentation for more information, particularly maximum number of parts per upload.

The following configuration is suggested to overcome AWS limitations:

  • Head Job CPUs: 16

  • Head Job Memory: 60000

  • Pre-run script: export NXF_OPTS="-Xms20G -Xmx40G"

  • Increase chunk size and slow down the number of transfers using nextflow.config:

    aws {
    batch {
    maxParallelTransfers = 5
    maxTransferAttempts = 3
    delayBetweenAttempts = 30
    client {
    uploadChunkSize = '200MB'
    maxConnections = 10
    maxErrorRetry = 10
    uploadMaxThreads = 10
    uploadMaxAttempts = 10
    uploadRetrySleep = '10 sec'

Nextflow unable to parse a params file from Seqera

Ephemeral endpoints can only be consumed once. Nextflow versions older than 22.04 may try to call the same endpoint more than once, resulting in an error:

Cannot parse params file: /ephemeral/example.json - Cause: Server returned HTTP response code: 403 for URL:

To resolve this problem, upgrade Nextflow to version 22.04.x or later.

Prevent Nextflow from uploading intermediate files from local scratch to AWS S3 work directory

Nextflow will only unstage files/folders that have been explicitly defined as process outputs. If your workflow has processes that generate folder-type outputs, ensure that the process also purges any intermediate files in those folders. Otherwise, the intermediate files are copied as part of the task unstaging process, resulting in additional storage costs and lengthened pipeline execution times.

Values specified in Git repository nextflow.config change during Seqera launch

Some values specified in your pipeline repository's nextflow.config may change when the pipeline is invoked via Seqera. This occurs because Seqera is configured with a set of default values that override the pipeline configuration.

Example: The following code block is specified in your nextflow.config:

aws {
region = 'us-east-1'
client {
uploadChunkSize = 209715200 // 200 MB

When the job instantiates on the AWS Batch compute environment, the uploadChunkSize is changed:

aws {
region = 'us-east-1'
client {
uploadChunkSize = 10485760 // 10 MB

This change occurs because Seqera superimposes its 10 MB default value rather than the value specified in your nextflow.config.

To force the Seqera-invoked job to use your nextflow.config value, add the configuration setting in the workspace Launch screen's Nextflow config file field. For our example above, you would add aws.client.uploadChunkSize = 209715200 // 200 MB.

Nextflow configuration values affected by this behaviour include:

  • aws.client.uploadChunkSize
  • aws.client.storageEncryption

Fusion v1 execution: Missing output file(s) [X] expected by process [Y] error

Fusion v1 has a limitation which causes tasks that run for less than 60 seconds to fail as the output file generated by the task is not yet detected by Nextflow. This is a limitation inherited from a Goofys driver used by the Fusion v1 implementation. Fusion v2 resolves this issue.

If you can't update to Fusion v2, this issue can be addressed by instructing Nextflow to wait for 60 seconds after the task completes.

From Advanced options > Nextflow config file in Pipeline settings, add this line to your Nextflow configuration:

process.afterScript = 'sleep 60'

Jobs remain in RUNNING status when a pipeline run is canceled

Your instance's behavior when canceling a run depends on the Nextflow errorStrategy defined in your process script. If the process errorStrategy is set to finish, an orderly pipeline shutdown is initiated when you cancel (or otherwise interrupt) a run. This instructs Nextflow to wait for the completion of any submitted jobs. To ensure that all jobs are terminated when your run is canceled, set errorStrategy to terminate in your Nextflow config. For example:

process terminateError {
errorStrategy 'terminate'

<your command string here>

Cached tasks run from scratch during pipeline relaunch

When relaunching a pipeline, Seqera relies on Nextflow's resume functionality for the continuation of a workflow execution. This skips previously completed tasks and uses a cached result in downstream tasks, rather than running the completed tasks again. The unique ID (hash) of the task is calculated using a composition of the task's:

  • Input values
  • Input files
  • Command line string
  • Container ID
  • Conda environment
  • Environment modules
  • Any executed scripts in the bin directory

A change in any of these values results in a changed task hash. Changing the task hash value means that the task will be run again when the pipeline is relaunched. To aid debugging efforts when a relaunch behaves unexpectedly, run the pipeline twice with dumpHashes=true set in your Nextflow config file (from Advanced options > Nextflow config file in the Pipeline settings). This will instruct Nextflow to dump the task hashes for both executions in the nextflow.log file. Compare the log files to determine the point at which the hashes diverge in your pipeline when it is resumed.

See here for more information on the Nextflow resume mechanism.

Run failure: o.h.e.jdbc.spi.SqlExceptionHelper - Incorrect string value error

[scheduled-executor-thread-2] - WARN o.h.e.jdbc.spi.SqlExceptionHelper - SQL Error: 1366, SQLState: HY000
[scheduled-executor-thread-2] - ERROR o.h.e.jdbc.spi.SqlExceptionHelper - (conn=34) Incorrect string value: '\xF0\x9F\x94\x8D |...' for column 'error_report' at row 1
[scheduled-executor-thread-2] - ERROR i.s.t.service.job.JobSchedulerImpl - Unable to save status of job id=18165; name=nf-workflow-26uD5XXXXXXXX; opId=nf-workflow-26uD5XXXXXXXX; status=UNKNOWN

Runs will fail if your Nextflow script or Nextflow config contain illegal characters (such as emojis or other non-UTF8 characters). Validate your script and config files for any illegal characters before atttempting to run again.

Run failures: Nextflow script exceeds 64KiB

The Groovy shell used by Nextflow to execute your workflow has a hard limit on string size (64KiB). Check the size of your scripts with the ls -llh command. If the size is greater than 65,535 bytes, consider these mitigation techniques:

  1. Remove any unnecessary code or comments from the script.
  2. Move long script bodies into a separate script file in the pipeline /bin directory.
  3. Consider using DSL2 so you can move each function, process, and workflow definition into its own script and include these scripts as modules.

Nextflow Launcher

Seqera Platform / nf-launcher image compatibility

Your Seqera installation knows the nf-launcher image version it needs and will specify this value automatically when launching a pipeline.

If you're restricted from using public container registries, see Seqera Enterprise release instructions for the specific image to set as the default when invoking pipelines.

Specify Nextflow version

Each Seqera Platform release uses a specific nf-launcher image by default. This image is loaded with a specific Nextflow version that any workflow run in the container uses by default. Force your jobs to use a newer/older version of Nextflow with one of the following strategies:

  • Use a pre-run script to set the desired Nextflow version. For example: export NXF_VER=22.08.0-edge
  • For jobs executing in an AWS Batch compute environment, create a custom job definition which references a different nf-launcher image.


Optimized task failures: OutOfMemoryError: Container killed due to memory usage error

Improvements are being made to the way Nextflow calculates the optimal memory needed for containerized tasks, which will resolve issues with underestimating memory allocation in an upcoming release.

A temporary workaround for this issue is to implement a retry error strategy in the failing process that will increase the allocated memory each time the failed task is retried. Add the following errorStrategy block to the failing process:

process {
errorStrategy = 'retry'
maxRetries = ​3
memory = 1.GB * task.attempt


Use the Nextflow SQL DB plugin to query AWS Athena

From Nextflow 22.05.0-edge, your Nextflow pipelines can query data from AWS Athena. Add these configuration items to your nextflow.config (Note: the use of secrets is optional):

plugins {
id 'nf-sqldb@0.4.0'

sql {
db {
'athena' {
url = 'jdbc:awsathena://AwsRegion=YOUR_REGION;S3OutputLocation=s3://YOUR_S3_BUCKET'
user = secrets.ATHENA_USER
password = secrets.ATHENA_PASSWORD

Then, call the functionality in your workflow:

// Example
channel.sql.fromQuery("select * from test", db: "athena", emitColumns:true).view()

See here for more information.


Private Docker registry integration

Seqera-invoked jobs can pull container images from private Docker registries, such as JFrog Artifactory. The method to enable this depends on your computing platform.

For AWS Batch, modify your EC2 Launch Template using these AWS instructions.

This solution requires Docker Engine 17.07 or greater, to use --password-stdin.

You may need to add additional commands to your Launch template, depending on your security posture:
cp /root/.docker/config.json /home/ec2-user/.docker/config.json && chmod 777 /home/ec2-user/.docker/config.json

For Azure Batch, create a Container registry-type credential in your Seqera workspace and associate it with the Azure Batch compute environment defined in the same workspace.

For Kubernetes, use an imagePullSecret, per #2827.

Nextflow error: Remote resource not found

This error can occur if the Nextflow head job fails to retrieve the necessary repository credentials from Seqera. If your Nextflow log contains an entry like DEBUG nextflow.scm.RepositoryProvider - Request [credentials -:-], check the protocol of your instance's TOWER_SERVER_URL configuration value. This must be set to https rather than http (unless you are using TOWER_ENABLE_UNSAFE_MODE to allow HTTP connections to Seqera in a test environment).


Missing AWS execution role arn error during Seqera launch

The ECS Agent must have access to retrieve secrets from the AWS Secrets Manager. Secrets-using pipelines launched from your instance in an AWS Batch compute environment will encounter this error if an IAM Execution Role is not provided. See Secrets for more information.

AWS Batch task failures with secrets

You may encounter errors when executing pipelines that use secrets via AWS Batch:

  • If you use nf-sqldb version 0.4.1 or earlier and have secrets in your nextflow.config, you may encounter nextflow.secret.MissingSecretException: Unknown config secret errors in your Nextflow log.
    Resolve this error by explicitly defining the xpack-amzn plugin in your configuration:

    plugins {
    id 'xpack-amzn'
    id 'nf-sqldb'
  • If you have two or more processes that use the same container image, but only a subset of these processes use secrets, your secret-using processes may fail during the initial run and then succeed when resumed. This is due to a bug in how Nextflow (22.07.1-edge and earlier) registers jobs with AWS Batch.

    To resolve the issue, upgrade your Nextflow to version 22.08.0-edge or later. If you cannot upgrade, use the following as workarounds:

    • Use a different container image for each process.
    • Define the same set of secrets in each process that uses the same container image.

Tower Agent

"Unexpected Exception in WebSocket [...]: Operation timed out Operation timed out" error

We have improved Tower Agent reconnection logic with the release of version 0.5.0. Update your Tower Agent version before relaunching your pipeline.

tw CLI

Connection errors when creating or viewing AWS Batch compute environments with tw compute-envs commands

tw CLI v0.8 and earlier does not support the SPOT_PRICE_CAPACITY_OPTIMIZED allocation strategy in AWS Batch. Creating or viewing AWS Batch compute environments with this allocation strategy will lead to errors. This issue will be addressed in CLI v0.9.

Segfault errors

Users of legacy tw CLI versions may experience segmentation faults in older operating systems.

To resolve segfault errors, first upgrade your tw CLI to the latest available version. If errors persist, use our alternative Java JAR-based solution.

Insecure HTTP errors

ERROR: You are trying to connect to an insecure server: http://hostname:port/api if you want to force the connection use '--insecure'. NOT RECOMMENDED!

This error indicates that your Seqera host accepts connections using insecure HTTP instead of HTTPS. If your host cannot be configured to accept HTTPS connections, add the --insecure flag before your CLI command:

$ tw --insecure info

HTTP must not be used in production environments.

Resume/relaunch runs with tw CLI

Runs can be relaunched with tw runs relaunch .

$ tw runs relaunch -i 3adMwRdD75ah6P -w 161372824019700

Workflow 5fUvqUMB89zr2W submitted at [org / private] workspace.

$ tw runs list -w 161372824019700

Pipeline runs at [org / private] workspace:

ID | Status | Project Name | Run Name | Username | Submit Date
5fUvqUMB89zr2W | SUBMITTED | nf/hello | magical_darwin | seqera-user | Tue, 10 Sep 2022 14:40:52 GMT
3adMwRdD75ah6P | SUCCEEDED | nf/hello | high_hodgkin | seqera-user | Tue, 10 Sep 2022 13:10:50 GMT


*Seqera-invoked pipeline contacting a workspace other than the launch workspace**

You may encounter this entry in your Nextflow log:

Unexpected response for request http://TOWER_SERVER_URL/api/trace/TRACE_ID/begin?workspaceId=WORKSPACE_ID

If the workspace ID in this message differs from your launch workspace, Seqera retrieved an incorrect Seqera access token from a Nextflow configuration file:

  • A Seqera access token may be hardcoded in the tower.accessToken block of your nextflow.config (either from the Git repository or an override value in the Seqera launch form).
  • In an HPC cluster compute environment, the credential user's home directory may contain a stateful nextflow.config with a hardcoded access token (e.g., ~/.nextflow/config).



EBS Autoscaling: EBS volumes remain active after job completion

The EBS autoscaling solution relies on an AWS-provided script which runs on each container host. This script performs AWS EC2 API requests to delete EBS volumes when the jobs using those volumes have been completed.

When running large Batch clusters (hundreds of compute nodes or more), EC2 API rate limits may cause the deletion of unattached EBS volumes to fail. Volumes that remain active after Nextflow jobs have been completed will incur additional costs and should therefore be manually deleted.

You can monitor your AWS account for any orphaned EBS volumes via the EC2 console or with a Lambda function. See here for more information.


ECS Agent Docker image pull frequency

As part of the AWS Batch creation process, Batch Forge will set ECS Agent parameters in the EC2 launch template that is created for your cluster's EC2 instances:

  • For clients using Seqera Enterprise v22.01 or later:
    • Any AWS Batch environment created by Batch Forge will set the ECS Agent's ECS_IMAGE_PULL_BEHAVIOUR to once.
  • For clients using Seqera Enterprise v21.12 or earlier:
    • Any AWS Batch environment created by Batch Forge will set the ECS Agent's ECS_IMAGE_PULL_BEHAVIOUR to default.

See the AWS ECS documentation for an in-depth explanation of this difference.

This behaviour can't be changed within Seqera Platform.

CannotPullContainerError: Error response from daemon: error parsing HTTP 429 response body: invalid character 'T' looking for beginning of value: "Too Many Requests (HAP429)"

Docker Hub imposes a rate limit of 100 anonymous pulls per 6 hours. Add the following to your launch template to avoid this issue:

echo ECS_IMAGE_PULL_BEHAVIOR=once >> /etc/ecs/ecs.config


If your run fails with an Essential container in task exited - CannotInspectContainerError: Could not transition to inspecting; timed out after waiting 30s error, try the following:

  1. Upgrade your ECS Agent to 1.54.1 or newer. See here for instructions to check your ECS Agent version.
  2. Provision more storage for your EC2 instance (preferably via EBS-autoscaling to ensure scalability).
  3. If the error is accompanied by command exit status: 123 and a permissions denied error tied to a system command, ensure that the ECS Agent binary is set to be executable (chmod u+x).


Multiple AWS Batch queues for a single job execution

Although you can only create/identify a single work queue during the definition of your AWS Batch compute environment in Seqera, you can spread tasks across multiple queues when your job is sent to Batch for execution via your pipeline configuration.

Add the following snippet to your nextflow.config, or the Advanced Features > Nextflow config file field of the Seqera Launch UI, for processes to be distributed across two AWS Batch queues, depending on the assigned name.

# nextflow.config

process {
withName: foo {
queue: `TowerForge-1jJRSZmHyrrCvCVEOhmL3c-work`

process {
withName: bar {
queue: `custom-second-queue`


Enable pipelines to write to S3 buckets that enforces AES256 server-side encryption

If you need to save files to an S3 bucket with a policy that enforces AES256 server-side encryption, the nf-launcher script which invokes the Nextflow head job requires additional configuration:

  1. Add the following configuration to the Advanced options > Nextflow config file textbox of the Launch Pipeline screen:

    aws {
    client {
    storageEncryption = 'AES256'
  2. Add the following configuration to the Advanced options > Pre-run script textbox of the Launch Pipeline screen:

    export TOWER_AWS_SSE=AES256

Note: This solution requires Seqera v21.10.4 and Nextflow 22.04.0 or later.


Batch compute environments

Use separate Batch pools for head and compute nodes

The default Azure Batch implementation in Seqera Platform uses a single pool for head and compute nodes. This means that all jobs spawn dedicated/on-demand VMs by default. To save cloud costs by using low priority VMs for compute jobs, specify separate pools for head and compute jobs:

  1. Create two Batch pools in Azure:
  2. Create a manual Azure Batch compute environment in Seqera Platform.
  3. In Compute pool name (step 10 in the guide linked above), specify your dedicated Batch pool.
  4. Specify the Low priority pool using the process.queue directive in your nextflow.config file (either via the launch form, or your pipeline repository's nextflow.config file).


... /.git/HEAD.lock: Operation not supported error

This problem can occur if your Nextflow pod uses an Azure Files-type (SMB) Persistent Volume as its storage medium. By default, the jgit library used by Nextflow attempts a filesystem link operation which is not supported by Azure Files (SMB).

To avoid this problem, add the following code snippet in your pipeline's Pre-run script field:

cat <<EOT > ~/.gitconfig
supportsatomicfilecreation = true


Problem with the SSL CA cert (path? access rights?) error

This can occur if a tool/library in your task container requires SSL certificates to validate the identity of an external data source.

Mount SSL certificates into the container to resolve this issue. See SSL/TLS for more information.

Azure SQL database error: Connections using insecure transport are prohibited while --require_secure_transport=ON

This error is due to Azure's default MySQL behavior which enforces the SSL connections between your server and client application, as detailed here. To fix this, append useSSL=true&enabledSslProtocolSuites=TLSv1.2&trustServerCertificate=true to your TOWER_DB_URL connection string. For example:



VM preemption causes task interruptions

Running your pipelines on preemptible VMs provides significant cost savings, but increases the likelihood that a task will be interrupted before completion. It is a recommended best practice to implement a retry strategy when you encounter exit codes that are commonly related to preemption. For example:

process {
errorStrategy = { task.exitStatus in [8,10,14] ? 'retry' : 'finish' }
maxRetries = 3
maxErrors = '-1'

Seqera Service account permissions for GLS and GKE

The following roles must be granted to the nextflow-service-account:

  1. Cloud Life Sciences Workflows Runner
  2. Service Account User
  3. Service Usage Consumer
  4. Storage Object Admin

For detailed information, see this guide.


Invalid value: "xxx": must be less or equal to memory limit error

This error may be encountered when you specify a value in the Head Job memory field during the creation of a Kubernetes-type compute environment.

If you receive an error that includes field: spec.containers[x].resources.requests and message: Invalid value: "xxx": must be less than or equal to memory limit, your Kubernetes cluster may be configured with system resource limits which deny the Nextflow head job's resource request. To isolate the component causing the problem, try to launch a pod directly on your cluster via your Kubernetes administration solution. For example:

apiVersion: v1
kind: Pod
name: debug
app: debug
- name: debug
image: busybox
command: ["sh", "-c", "sleep 10"]
memory: "xxxMi" # or "xxxGi"
restartPolicy: Never

On-Prem HPC

java: command not found error

When submitting jobs to your on-prem HPC (using either SSH or Tower Agent authentication), the following error may appear in your Nextflow logs, even with Java on your $PATH environment variable:

java: command not found
Nextflow is trying to use the Java VM defined for the following environment variables:
JAVA_CMD: java

Possible reasons for this error:

  1. The queue where the Nextflow head job runs is in a different environment/node than your login node userspace.
  2. If your HPC cluster uses modules, the Java module may not be loaded by default.

To troubleshoot:

  1. Open an interactive session with the head job queue.
  2. Launch the Nextflow job from the interactive session.
  3. If your cluster uses modules:
    • Add module load <your_java_module> in the Advanced Features > Pre-run script field when creating your HPC compute environment in Seqera.
  4. If your cluster doesn't use modules:
    1. Source an environment with Java and Nextflow using the Advanced Features > Pre-run script field when creating your HPC compute environment in Seqera.

Pipeline submissions to HPC clusters fail for some users

Nextflow launcher scripts will fail if processed by a non-Bash shell (e.g., zsh, tcsh). This problem can be identified from certain error entries:

  1. Your .nextflow.log contains an error like Invalid workflow status - expected: SUBMITTED; current: FAILED.
  2. Your Seqera Error report tab contains an error like:
Slurm job submission failed
- command: mkdir -p /home//\<USERNAME\>//scratch; cd /home//\<USERNAME\>//scratch; echo <LONG_BASE64_STRING> | base64 -d > nf-<RUN-ID>; sbatch ./nf-<RUN-ID>
- exit : 1
- message: Submitted batch job <#>

Connect to the head node via SSH and run ps -p $$ to verify your default shell. If you see an entry other than Bash, fix as follows:

  1. Check which shells are available to you: cat /etc/shells
  2. Change your shell: chsh -s /usr/bin/bash (the path to the binary may differ, depending on your HPC configuration)
  3. If submissions continue to fail after this shell change, ask your Seqera Platform admin to restart the backend and cron containers, then submit again.