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https://github.com/containers/podman.git
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feat(exec): Add --no-session flag for improved performance
Fixes: #26588 For use cases like HPC, where `podman exec` is called in rapid succession, the standard exec process can become a bottleneck due to container locking and database I/O for session tracking. This commit introduces a new `--no-session` flag to `podman exec`. When used, this flag invokes a new, lightweight backend implementation that: - Skips container locking, reducing lock contention - Bypasses the creation, tracking, and removal of exec sessions in the database - Executes the command directly and retrieves the exit code without persisting session state - Maintains consistency with regular exec for container lookup, TTY handling, and environment setup - Shares implementation with health check execution to avoid code duplication The implementation addresses all performance bottlenecks while preserving compatibility with existing exec functionality including --latest flag support and proper exit code handling. Changes include: - Add --no-session flag to cmd/podman/containers/exec.go - Implement lightweight execution path in libpod/container_exec.go - Ensure consistent container validation and environment setup - Add comprehensive exit code testing including signal handling (exit 137) - Optimize configuration to skip unnecessary exit command setup Signed-off-by: Ryan McCann <ryan_mccann@student.uml.edu> Signed-off-by: ryanmccann1024 <ryan_mccann@student.uml.edu>
This commit is contained in:
ryanmccann1024
@@ -822,87 +822,7 @@ func (c *Container) ExecResize(sessionID string, newSize resize.TerminalSize) er
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}
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func (c *Container) healthCheckExec(config *ExecConfig, timeout time.Duration, streams *define.AttachStreams) (int, error) {
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unlock := true
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if !c.batched {
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c.lock.Lock()
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defer func() {
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if unlock {
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c.lock.Unlock()
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}
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}()
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if err := c.syncContainer(); err != nil {
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return -1, err
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}
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}
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if err := c.verifyExecConfig(config); err != nil {
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return -1, err
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}
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if !c.ensureState(define.ContainerStateRunning) {
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return -1, fmt.Errorf("can only create exec sessions on running containers: %w", define.ErrCtrStateInvalid)
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}
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session, err := c.createExecSession(config)
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if err != nil {
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return -1, err
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}
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if c.state.ExecSessions == nil {
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c.state.ExecSessions = make(map[string]*ExecSession)
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}
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c.state.ExecSessions[session.ID()] = session
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defer delete(c.state.ExecSessions, session.ID())
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opts, err := prepareForExec(c, session)
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if err != nil {
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return -1, err
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}
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defer func() {
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// cleanupExecBundle MUST be called with the parent container locked.
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if !unlock && !c.batched {
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c.lock.Lock()
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unlock = true
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if err := c.syncContainer(); err != nil {
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logrus.Errorf("Error syncing container %s state: %v", c.ID(), err)
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// Normally we'd want to continue here, get rid of the exec directory.
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// But the risk of proceeding into a function that can mutate state with a bad state is high.
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// Lesser of two evils is to bail and leak a directory.
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return
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}
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}
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if err := c.cleanupExecBundle(session.ID()); err != nil {
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logrus.Errorf("Container %s light exec session cleanup error: %v", c.ID(), err)
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}
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}()
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pid, attachErrChan, err := c.ociRuntime.ExecContainer(c, session.ID(), opts, streams, nil)
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if err != nil {
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return -1, err
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}
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session.PID = pid
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session.PIDData = getPidData(pid)
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if !c.batched {
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c.lock.Unlock()
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unlock = false
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}
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select {
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case err = <-attachErrChan:
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if err != nil {
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return -1, fmt.Errorf("container %s light exec session with pid: %d error: %v", c.ID(), pid, err)
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}
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case <-time.After(timeout):
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if err := c.ociRuntime.ExecStopContainer(c, session.ID(), 0); err != nil {
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return -1, err
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}
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return -1, fmt.Errorf("%v of %s", define.ErrHealthCheckTimeout, c.HealthCheckConfig().Timeout.String())
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}
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return c.readExecExitCode(session.ID())
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return c.execLightweight(config, streams, timeout)
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}
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func (c *Container) Exec(config *ExecConfig, streams *define.AttachStreams, resize <-chan resize.TerminalSize) (int, error) {
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@@ -1321,3 +1241,99 @@ func justWriteExecExitCode(c *Container, sessionID string, exitCode int, emitEve
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// Finally, save our changes.
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return c.save()
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}
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// execLightweight executes a command in a container without creating a persistent exec session.
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// It is used by both ExecNoSession and healthCheckExec to avoid code duplication.
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func (c *Container) execLightweight(config *ExecConfig, streams *define.AttachStreams, timeout time.Duration) (int, error) {
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if err := c.verifyExecConfig(config); err != nil {
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return -1, err
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}
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unlock := true
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if !c.batched {
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c.lock.Lock()
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defer func() {
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if unlock {
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c.lock.Unlock()
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}
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}()
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if err := c.syncContainer(); err != nil {
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return -1, err
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}
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}
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if !c.ensureState(define.ContainerStateRunning) {
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return -1, fmt.Errorf("can only create exec sessions on running containers: %w", define.ErrCtrStateInvalid)
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}
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session, err := c.createExecSession(config)
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if err != nil {
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return -1, err
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}
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if c.state.ExecSessions == nil {
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c.state.ExecSessions = make(map[string]*ExecSession)
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}
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c.state.ExecSessions[session.ID()] = session
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defer delete(c.state.ExecSessions, session.ID())
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opts, err := prepareForExec(c, session)
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if err != nil {
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return -1, err
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}
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defer func() {
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if err := c.cleanupExecBundle(session.ID()); err != nil {
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logrus.Errorf("Container %s light exec session cleanup error: %v", c.ID(), err)
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}
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}()
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pid, attachErrChan, err := c.ociRuntime.ExecContainer(c, session.ID(), opts, streams, nil)
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if err != nil {
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// Check if the error is command not found before returning
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if exitCode := define.ExitCode(err); exitCode == define.ExecErrorCodeNotFound {
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return exitCode, err
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}
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return define.ExecErrorCodeGeneric, err
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}
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session.PID = pid
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session.PIDData = getPidData(pid)
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if !c.batched {
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c.lock.Unlock()
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unlock = false
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}
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// Handle timeout for health checks
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if timeout > 0 {
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select {
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case err = <-attachErrChan:
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if err != nil {
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return -1, fmt.Errorf("container %s light exec session with pid: %d error: %v", c.ID(), pid, err)
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}
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case <-time.After(timeout):
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if err := c.ociRuntime.ExecStopContainer(c, session.ID(), 0); err != nil {
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return -1, err
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}
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return -1, fmt.Errorf("%v of %s", define.ErrHealthCheckTimeout, timeout.String())
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}
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} else {
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// For no-session exec, wait for completion without timeout
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err = <-attachErrChan
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if err != nil && !errors.Is(err, define.ErrDetach) {
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// Check if the error is command not found
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if exitCode := define.ExitCode(err); exitCode == define.ExecErrorCodeNotFound {
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return exitCode, err
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}
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return define.ExecErrorCodeGeneric, err
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}
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}
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return c.readExecExitCode(session.ID())
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}
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// ExecNoSession executes a command in a container without creating a persistent exec session.
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// It skips database operations and minimizes container locking for performance.
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func (c *Container) ExecNoSession(config *ExecConfig, streams *define.AttachStreams, _ <-chan resize.TerminalSize) (int, error) {
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return c.execLightweight(config, streams, 0)
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}
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