Translate Memory Limit to Swap in API

in specgen, CLI path uses the given memory limit to define the swap value (if not already specified)
add a route to this piece of code from within the api handlers

resolves #13145

Signed-off-by: cdoern <cdoern@redhat.com>

pkg/api/handlers/libpod/containers_create.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"net/http"
+	"strconv"
 
 	"github.com/containers/podman/v4/libpod"
 	"github.com/containers/podman/v4/pkg/api/handlers/utils"
@@ -11,6 +12,7 @@ import (
 	"github.com/containers/podman/v4/pkg/domain/entities"
 	"github.com/containers/podman/v4/pkg/specgen"
 	"github.com/containers/podman/v4/pkg/specgen/generate"
+	"github.com/containers/podman/v4/pkg/specgenutil"
 	"github.com/pkg/errors"
 )
 
@@ -39,6 +41,20 @@ func CreateContainer(w http.ResponseWriter, r *http.Request) {
 		t := true
 		sg.Passwd = &t
 	}
+
+	// need to check for memory limit to adjust swap
+	if sg.ResourceLimits != nil && sg.ResourceLimits.Memory != nil {
+		s := ""
+		var l int64 = 0
+		if sg.ResourceLimits.Memory.Swap != nil {
+			s = strconv.Itoa(int(*sg.ResourceLimits.Memory.Swap))
+		}
+		if sg.ResourceLimits.Memory.Limit != nil {
+			l = *sg.ResourceLimits.Memory.Limit
+		}
+		specgenutil.LimitToSwap(sg.ResourceLimits.Memory, s, l)
+	}
+
 	warn, err := generate.CompleteSpec(r.Context(), runtime, &sg)
 	if err != nil {
 		utils.InternalServerError(w, err)
@@ -54,6 +70,7 @@ func CreateContainer(w http.ResponseWriter, r *http.Request) {
 		utils.InternalServerError(w, err)
 		return
 	}
+
 	response := entities.ContainerCreateResponse{ID: ctr.ID(), Warnings: warn}
 	utils.WriteJSON(w, http.StatusCreated, response)
 }

pkg/specgenutil/specgen.go

@@ -126,6 +126,16 @@ func getIOLimits(s *specgen.SpecGenerator, c *entities.ContainerCreateOptions) (
 	return io, nil
 }
 
+func LimitToSwap(memory *specs.LinuxMemory, swap string, ml int64) {
+	if ml > 0 {
+		memory.Limit = &ml
+		if swap == "" {
+			limit := 2 * ml
+			memory.Swap = &(limit)
+		}
+	}
+}
+
 func getMemoryLimits(s *specgen.SpecGenerator, c *entities.ContainerCreateOptions) (*specs.LinuxMemory, error) {
 	var err error
 	memory := &specs.LinuxMemory{}
@@ -135,14 +145,8 @@ func getMemoryLimits(s *specgen.SpecGenerator, c *entities.ContainerCreateOption
 		if err != nil {
 			return nil, errors.Wrapf(err, "invalid value for memory")
 		}
-		if ml > 0 {
-			memory.Limit = &ml
-			if c.MemorySwap == "" {
-				limit := 2 * ml
-				memory.Swap = &(limit)
-			}
-			hasLimits = true
-		}
+		LimitToSwap(memory, c.MemorySwap, ml)
+		hasLimits = true
 	}
 	if m := c.MemoryReservation; len(m) > 0 {
 		mr, err := units.RAMInBytes(m)

test/apiv2/python/rest_api/test_v2_0_0_container.py

@@ -328,6 +328,35 @@ class ContainerTestCase(APITestCase):
             self.fail("Server failed to respond in 10s")
         top.join()
 
+    def test_memory(self):
+        r = requests.post(
+            self.podman_url + "/v1.4.0/libpod/containers/create",
+            json={
+                "Name": "memory",
+                "Cmd": ["top"],
+                "Image": "alpine:latest",
+                "Resource_Limits": {
+                    "Memory":{
+                        "Limit": 1000,
+                    },
+                    "CPU":{
+                        "Shares": 200,
+                    },
+                },
+            },
+        )
+        self.assertEqual(r.status_code, 201, r.text)
+        payload = r.json()
+        container_id = payload["Id"]
+        self.assertIsNotNone(container_id)
+
+        r = requests.get(self.podman_url + f"/v1.40/containers/{container_id}/json")
+        self.assertEqual(r.status_code, 200, r.text)
+        self.assertId(r.content)
+        out = r.json()
+        self.assertEqual(2000, out["HostConfig"]["MemorySwap"])
+        self.assertEqual(1000, out["HostConfig"]["Memory"])
+
 
 if __name__ == "__main__":
     unittest.main()