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feat(agent/agentcontainers): implement sub agent injection#18245
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d49f84e to011a8aaCompare91ff08e to3960774Compare011a8aa to63f93bcCompare3960774 to1cf1905Compare63f93bc to0deaab8Compare1cf1905 tof190036Compare0deaab8 to8796ba3Comparedc146ab tod1447f3Compare8796ba3 toadbfd45Compared1447f3 to3547372CompareThis change adds support for sub agent creation and injection into devcontainers.Closescoder/internal#621
3547372 to7358ee0Comparea8e4495 toeb29bbaComparemafredri commentedJun 6, 2025
I'm still working on an integration test and the existing mocks are being a PITA (think those are about sorted now though). Promoting this to "ready for review" to get some feedback on the approach@DanielleMaywood@johnstcn. (Also going to break out the "follow-up PR" tasks into new issues before merging this.) |
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I still have to read some more but adding my comments so far.
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| err:=api.dccli.Exec(agentCtx,dc.WorkspaceFolder,dc.ConfigPath,agentPath, []string{"agent"}, | ||
| WithContainerID(container.ID), | ||
| WithRemoteEnv( | ||
| "CODER_AGENT_URL="+api.subAgentURL, | ||
| "CODER_AGENT_TOKEN="+agent.AuthToken.String(), | ||
| ), | ||
| ) |
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Would it make more sense to background this? If the parent agent ends up crashing and being restarted, we'll lose the sub-agents and have to re-inject them. We can keep track of the expected PID in e.g./.coder-agent/pid
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We could probably background it either on the host or inside the container, but not doing so has some nice properties:
- We immediately discover if a sub agent exits/crashes and we could restart immediately (we don't currently)
- Job control is simpler (simply cancel the context vs looking up processes and verifying against pid)
- With prebuilds, we can exit all sub-agents on claim and re-inject afterwards to ensure a clean slate
For the case where the parent agent crashes, keeping those sub-agents may be a bit hit-and-miss and those dev containers could be affected anyway on agent startup. I'm not aware of agents crashing though so this might not even be a concern we need to be mindful of now?
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Fair enough!
| if_,err:=api.ccli.ExecAs(ctx,container.ID,"root","setcap","cap_net_admin+ep",coderPathInsideContainer);err!=nil { | ||
| logger.Warn(ctx,"set CAP_NET_ADMIN on agent binary failed",slog.Error(err)) | ||
| } |
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This will probably fail unless the container is running as privileged or has the specific CAP_NET_ADMIN privilege set on the container?
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As per the comment, this is an optional networking boost. (See regular agent bootstrap script, I'll update the comment to reference it.) Did you have some action in mind?
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We could check for both of these things before trying? Not a blocker though.
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Sure, I don't think it's very high priority but let's create a ticket for future enhancement. 👍🏻
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| // Make sure the agent binary is executable so we can run it. | ||
| if_,err:=api.ccli.ExecAs(ctx,container.ID,"root","chmod","+x",coderPathInsideContainer);err!=nil { | ||
| returnxerrors.Errorf("set agent binary executable: %w",err) | ||
| } |
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Do we also need tochown the binary so that it's readable by the default container user?
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Good callout. I didn't consider this butdocker cp seems to follow the permissions of the file on disk. So unless wechown it could be nonsense within the container (non-existent user, etc).
It's unlikely that the permissions will be bad for the user (typically 0755), but we could improve it for sure. It might make sense to turn this into a script rather than N amount ofdocker execs.
| logger.Info(ctx,"starting subagent in dev container") | ||
| err:=api.dccli.Exec(agentCtx,dc.WorkspaceFolder,dc.ConfigPath,agentPath, []string{"agent"}, |
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Do we try to execute this as a non-root user?
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AFAIK this will get executed as the remote user configured bydevcontainer.json (or if unconfigured, container user), which seems like the correct behavior to me.
| injected:=make(map[uuid.UUID]bool,len(api.injectedSubAgentProcs)) | ||
| for_,proc:=rangeapi.injectedSubAgentProcs { | ||
| injected[proc.agent.ID]=true | ||
| } |
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This could probably be amap[uuid.UUID]struct{} instead, and then below on line 888 just check for_, found := injected[agent.ID]
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I don't foresee the memory savings being necessary here (will we have 1000s of sub agents?). The current form reads better and is simpler to use IMO (I always prefer this form for readability where applicable).
| for_,agent:=rangeagents { | ||
| ifinjected[agent.ID] { | ||
| continue | ||
| } | ||
| err:=api.subAgentClient.Delete(ctx,agent.ID) | ||
| iferr!=nil { | ||
| api.logger.Error(ctx,"failed to delete agent", | ||
| slog.Error(err), | ||
| slog.F("agent_id",agent.ID), | ||
| slog.F("agent_name",agent.Name), | ||
| ) | ||
| } | ||
| } |
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Should we set an upper bound on deletion attempts and raise if more than say 3 attempts fail?
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Are you suggesting silently ignoring failures unless >= 3 fail? Or perhaps adding retry logic?
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I'm mainly worried about spamming error logs into the void.
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These will be part of the parent agent log 🤔
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We can leave it as-is for now, but I think if this does start happening frequently (or all the time) it may be difficult to catch if it just goes into the parent agent log.
466bc6b to780483bCompareabe9116 tod5eb3fcComparemafredri commentedJun 9, 2025
@DanielleMaywood@johnstcn I've added I also added |
| token:=os.Getenv("CODER_AGENT_TOKEN") | ||
| ifurl==""||token=="" { | ||
| _,_=fmt.Fprintln(os.Stderr,"CODER_AGENT_URL and CODER_AGENT_TOKEN must be set") | ||
| return10 |
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Can we name these specific status codes as something more meaningful to human eyes?
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They don't really have a meaning, just something to differentiate the states and started at 10 since I got tired of bumping everything as I added more stuff 😅, the println should hopefully be helpful here.
| } | ||
| deferr.Body.Close() | ||
| t.Logf("Sub-agent request payload received: %+v",payload) |
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suggestion: do we perhaps want to allow the caller to run some function against the paylaod?
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We send it on the channel and do some verification already 👍🏻
| // The agent will copy "itself", but in the case of this test, the | ||
| // agent is actually this test binary. So we'll tell the test binary | ||
| // to execute the sub-agent main function via this env. | ||
| agentcontainers.WithSubAgentEnv("CODER_TEST_RUN_SUB_AGENT_MAIN=1"), |
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mafredri commentedJun 10, 2025
One last addendum, implemented a quick 'n dirty |
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This change adds support for sub agent creation and injection into dev
containers.
TODO:
requires on-diskimplemented viadevcontainer.jsonparsing,follow-up PRpwdcheck, we can improve this in the future via "materialized devcontainer.json" viadevcontainer read-configuration).customizations.coder.devcontainer.namefrom docker container label (materializeddevcontainer.jsonon creation,follow-up PR)Updatescoder/internal#621