Document bug with sidecar usage of nop image #1464
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Sidecars are stopped by having their Image field swapped out to the `nop` image. When the nop image starts up in the sidecar container it is supposed to immediately exit because `nop` doesn't include the sidecar's command. However, when the `nop` image *does* contain the command that the sidecar is running, the sidecar container will actually never stop and the Task will eventually timeout. For most sidecars this issue will not manifest - the `nop` container that Tekton provides out of the box includes only a very limited set of commands. However, if a Tekton operator overrides the `nop` image when deploying the tekton controller (for example, because their organization requires images configured for Tekton to be built on their org's own base image) then there is a risk that `nop` will start offering more commands and therefore introduce a higher risk that a sidecar's command will be runnable by the `nop` image finally increasing the likelihood of Tasks with sidecars running until timeout. This issue is a known bug with the way sidecars operate at the moment and is being tracked in #1347 but should be documented clearly.
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Documenting this until we get a fix in place makes sense to me! /lgtm |
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Changes
Sidecars are stopped by having their Image field swapped out to the
nopimage. When the nop image starts up in the sidecar container it is supposed to immediately exit becausenopdoesn't include the sidecar's command. However, when thenopimage does contain the command that the sidecar is running, the sidecar container will actually never stop and the Task will eventually timeout.For most sidecars this issue will not manifest - the
nopcontainer that Tekton provides out of the box includes only a very limited set of commands. However, if a Tekton operator overrides thenopimage when deploying the tekton controller (for example, because their organization requires images configured for Tekton to be built on their org's own base image) then there is a risk thatnopwill start offering more commands and therefore introduce a higher risk that a sidecar's command will be runnable by thenopimage, finally increasing the likelihood of Tasks with sidecars running forever until timeout.This issue is a known bug with the way sidecars operate at the moment and is being tracked in #1347 but should be documented clearly.
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