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https://github.com/ninesstack/sidecar-executor

Run Docker containers on Mesos with Sidecar service discovery!
https://github.com/ninesstack/sidecar-executor

docker docker-container golang mesos sidecar

Last synced: 7 months ago
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Run Docker containers on Mesos with Sidecar service discovery!

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README 

          
Sidecar Executor

===============



Run Docker containers on Mesos with

[Sidecar](https://github.com/newrelic/sidecar) service discovery! We're running

it with HubSpot's [Singularity](https://github.com/HubSpot/Singularity)

scheduler.



This is a Mesos executor that integrates with the service discovery platform

[Sidecar](https://github.com/newrelic/sidecar) to more tightly tie Sidecar into

the Mesos ecosystem. The main advantage is that the executor leverages the

service health checking that Sidecar already provides in order to fail Mesos

tasks quickly when they have gone off the rails.



With Sidecar and Sidecar Executor you get service health checking unified with

service Discovery, regardless of which Mesos scheduler you are running. The

system is completely scheduler agnostic to the extent possible.



Note that _unlike_ Sidecar, Sidecar Executor assumes that tasks are to be run

as Docker containers. You may of course still integrate non-Dockerized services

with Sidecar as normal.



Subset of Features

------------------



This executor does not attempt to support every single option that Docker can

support for running containers. It supports the core feature set that most

people actually use. If you are looking for something that it doesn't currently

provide, pull requests or feature requests are welcome.



### Currently supported:

 * Environment variables

 * Docker labels

 * Exposed port and port mappings

 * Volume binds from the host

 * Network mode setting

 * Capability Add

 * Capability Drop

 * Resolve environment variables stored in [Vault](https://www.vaultproject.io)

 * Enforce CPU and Memory limits via Docker cgroups



This set of features probably supports most of the production containers out

there.



Debugability

------------



This executor tries to expose as much information as possible to help with the

painful task of debugging a Mesos task failure. It logs each of the actions

that it takes and why. And, on startup it logs both the current environment

variables which the executor will run with, the settings for the executor, and

the Docker environment that will be supplied to the container. This can be

critical in understanding how a task failed.



When a task fails or is killed, the executor will fetch the last logs that were

sent to the container, and copy them to its own stdout and stderr. This means

that in most cases the Mesos logs will now contain the failure messages and

there is usually no need to dig further into logging frameworks to find out

what happened.



Additionally since each instance of the executor manages a single container,

the process name of the executor that shows up in `ps` output contains both

the ID of the Docker container and the Docker image name that was used to

start it.



Running the Executor

--------------------



A separate copy of the executor is started for each task. The binary is small

and only uses a few MB of memory so this is fairly cheap.



But, since the executor will always be running as long as your task, it will

have the file open and you won't be ablet to replace it (e.g. to upgrade) while

the task is running. It's thus recommended that you run the `executor.sh`

script as the actual executor defined in each of your tasks. That will in turn

copy the binary from a location of your choosing to the task's sandbox and then

execute it from there. This means that the copy of the executor used to start

the task will remain in the sandbox directory for the life of the task and

solves the problem nicely.



To upgrade the executor you can then simply replace the binary in the defined

location on your systems and any new tasks will start under the new copy while

older tasks remain running under their respective version. By default the

shell script assumes the path will be `/opt/mesos/sidecar-executor`.



Configuration

-------------



Each task can be run with its own executor configuration. This is helpful when

in situations such as needing to delay health checking for apps that are slow

to start, allowing for longer grace periods or a larger failure count before

shooting a container. You may configure the executor via environment variables

in the Mesos task. These will then be present for the executor at the time that

it runs. Note that these are separate from the environment variables used in

the Docker container. Currently the settings available are:



Setting                 | Default

------------------------|----------------------------

KillTaskTimeout         | 5 (seconds)

HttpTimeout             | 2s

SidecarRetryCount       | 5

SidecarRetryDelay       | 3s

SidecarUrl              | http://localhost:7777/state.json

SidecarBackoff          | 1m

SidecarPollInterval     | 30s

SidecarMaxFails         | 3

SidecarDrainingDuration | 10s

SeedSidecar             | false

DockerRepository        | https://index.docker.io/v1/

LogsSince               | 3m

ForceCpuLimit           | false

ForceMemoryLimit        | false

UseCpuShares            | false

Debug                   | false

MesosMasterPort         | 5050

RelaySyslog             | false

RelaySyslogStartupOnly  | false

RelaySyslogStartupTime  | 1m

SyslogAddr              | 127.0.0.1:514

ContainerLogsStdout     | false

SendDockerLabels        | []

LogHostname             | System Hostname



All of the environment variables are of the form `EXECUTOR_SIDECAR_RETRY_DELAY`

where all of the CamelCased words are split apart, and each setting is prefixed

with `EXECUTOR_`.



 * **KillTaskTimeout**: This is the amount of time to wait before we hard kill

   the container. Initially we send a SIGTERM and after this timeout we follow

   up with a SIGKILL. If your process has a clean shutdown procedure and takes

   awhile, you may want to back this off to let it complete shutdown before

   being hard killed by the kernel. **Note** that unlike the other settings,

   this, for internal library reasons, is an integer in seconds and not a Go

   time spec.



 * **HttpTimeout**: The timeout when talking to Sidecar. The default should be

   far longer than needed unless you really have something wrong.



 * **SidecarRetryCount**: This is the number of times we'll retry calling to

   Sidecar when health checking.



 * **SidecarRetryDelay**: The amount of time to wait between retries when

   contacting Sidecar.



 * **SidecarUrl**: The URL to use to contact Sidecar. The default will usually

   be the right setting.



 * **SidecarBackoff**: How long to wait before we start health checking to Sidecar.

   You want this value to be longer than the time it takes your process to start

   up and start responding as healthy on the health check endpoint.



 * **SidecarPollInterval**: The interval between asking Sidecar how healthy we

   are.



 * **SidecarMaxFails**: How many failed checks to Sidecar before we shut down

   the container? Note that this is not just _contacting_ Sidecar. This is how

   many _affirmed_ unhealthy checks we need to receive, each spaced apart by

   `SidecarPollInterval`.



 * **SidecarDrainingDuration**: How much time to wait before killing the container

   after instructing Sidecar to set the current service's status to `DRAINING`.

   Setting this to `0` will prevent the executor from telling Sidecar to trigger

   the `DRAINING` state and it will kill the container as soon as possible.



 * **SeedSidecar**: Should we query the Mesos master for the list of workers

   and then provide those in the `SIDECAR_SEEDS` environment variables?



 * **DockerRepository**: This is used to match the credentials that we'll store

   from the Docker config. This will follow the same matching order as

   [described here](https://godoc.org/github.com/fsouza/go-dockerclient#NewAuthConfigurationsFromDockerCfg).

   The executor expects to use only one set of credentials for each job.



 * **LogsSince**: When the container exits or is killed, the executor will copy

   logs from the Docker container output to its own stdout and stderr so that

   they show up in the Mesos logs. `LogsSince` is how far back in time we

   reach to get these logs.



 * **ForceCpuLimit**: Should we enforce the CPU limits in the request using

   cgroups (via Docker)?



 * **ForceMemoryLimit**: Should we enforce the memory limits in the request using

   cgroups (via Docker)?



 * **UseCpuShares**: By default we use the Linux Completely Fair Scheduler

   settings to control CPU limiting. This doesn't work well for certain

   workloads. Should we instead use the older CPU Shares relative workload

   limiting mechanism? Note that you should understand the difference before

   turning this on. 



 * **Debug**: Should we turn on debug logging (verbose!) for this executor?



 * **MesosMasterPort**: The port on which the Mesos Master node listens on.



 * **RelaySyslog**: Should we relay container logs to syslog? This is a bare UDP

   implementation suitable for loggers that don't care about syslog protocol.

   Logs will be sent in JSON format, using Logrus.



 * **RelaySyslogStartupOnly**: Should we relay container logs to syslog only

   for the startup duration? This is helpful for apps that do their own

   syslogging but are not able to log during their startup process. The length

   of time to relay logs is controlled by `RelaySyslogStartupTime`.



 * **RelaySyslogStartupTime**: By itself this configuration item does nothing.

   It controls the value for how long to log for when `RelaySyslogStartupOnly`

   is set.



 * **SyslogAddr**: If `RelaySyslog` is true, we'll use this as the remote address

   for syslog logging.



 * **ContainerLogsStdout**: Should we copy the container logs to stdout? The

   effect of doing this is that container logs (both stdout and stderr) will end

   up in the Mesos sandbox logs. Be careful here since the Mesos logs are *not*

   rotated by the Mesos worker. Requires that `RelaySyslog` be true. Note that

   if you don't want syslog but you do want this option, there is not *much* harm

   in turning on `RelaySyslog` since the UDP packets will just drop. **Note**:

   This only works with Docker log drivers `json-file` and `journald` because it

   uses the native Docker logging functionality to collect the logs.



 * **SendDockerLabels**: If `RelaySyslog` is true, should we augment JSON logs

   with some fields defined in Docker labels? This is a comma-separated list

   of labels. They will be sent with the field name being the Docker label name.



 * **LogHostname**: When relaying logs, we will add this as the `Hostname`

   field. Defaults to the OS hostname and can be overridden with `LOG_HOSTNAME`

   in the environment.



Special AWS Role Configuration

------------------------------



In addition to all the executor level settings above, you may also pass the

following env vars into the executor to enable the executor to maintain AWS

creds with a specific role via Vault:



 * `EXECUTOR_AWS_ROLE` - specifies the AWS role (pre-existing in IAM/Vault) to

   request. By itself this will give you the default TTL for the policy



 * `EXECUTOR_AWS_ROLE_TTL` - This will allow you extend the requested time, up to

   the max allowed by Vault for the policy. The value is a string, specified

   in [Go Duration format](https://golang.org/pkg/time/#ParseDuration). E.g.

   "1m40s" for 1 minute and 40 seconds.



Vault Configuration

-------------------



Because the executor uses the Vault library, it lets the Vault client configure

itself from its own environment settings. You can look these up in the Vault

[source](https://github.com/hashicorp/vault/blob/master/api/client.go#L28) if

you'd like to see them all. The executor adds a couple of others to better

control the Vault integration. You should specify at least the following:



 * `VAULT_ADDR` - URL of the Vault server.

 * `VAULT_MAX_RETRIES` - API retries before Vault fails.

 * `VAULT_TOKEN` - Optional if specified in a file or using userpass.

 * `VAULT_TOKEN_FILE` - Where to cache Vault tokens between calls to the

   executor on the same host.

 * `VAULT_TTL` - The TTL in seconds of the Vault Token we'll have issued note

   that the grace period is one hour so shorter than 1 hour is not possible.



**WARNING** If you are using Vault, you _really_ want to have the executor

cache tokens to a `VAULT_TOKEN_FILE`. If not you can build up quite a lot of

tokens in Vault, and that doesn't work well. Especially in a fast job failure

scenario where executors running on multiple machines might be generating

tokens constantly.



Configuring Docker Connectivity

-------------------------------



Sidecar Executor supports all the normal environment variables for configuring

your connection to the Docker daemon. It will look for `DOCKER_HOST`, etc in

the runtime environment and configure connectivity accordingly.



Contributing

------------



Contributions are more than welcome. Bug reports with specific reproduction

steps are great. If you have a code contribution you'd like to make, open a

pull request with suggested code.



Pull requests should:



 * Clearly state their intent in the title

 * Have a description that explains the need for the changes

 * Include tests!

 * Not break the public API



Ping us to let us know you're working on something interesting by opening a GitHub Issue on the project.