Re: [libvirt] [PATCH v2 1/5] Add public API to register a callback to be invoked on connection close

26 Jul 2012

On Tue, Jul 24, 2012 at 14:17:01 +0100, Daniel P. Berrange wrote:
...
From: "Daniel P. Berrange" <berrange@redhat.com>
Define new virConnect{Register,Unregister}CloseCallback() public APIs
which allows registering/unregistering a callback to be invoked when
the connection to a hypervisor is closed. The callback is provided
with the reason for the close, which may be 'error', 'eof' or
'keepalive'.
The virConnectCloseReason enum also mentions 'client' reason.
...

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index fcef461..d9f0397 100644
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
...
@@ -1148,6 +1166,27 @@ int virConnectSetKeepAlive(virConnectPtr conn,
                            int interval,
                            unsigned int count);
+typedef enum {
+    VIR_CONNECT_CLOSE_REASON_ERROR     = 0, /* Misc I/O error */
+    VIR_CONNECT_CLOSE_REASON_EOF       = 1, /* End-of-file from server */
+    VIR_CONNECT_CLOSE_REASON_KEEPALIVE = 2, /* Keepalive timer triggered */
+    VIR_CONNECT_CLOSE_REASON_CLIENT    = 3, /* Client requested it */
+
+# ifdef VIR_ENUM_SENTINELS
+    VIR_CONNECT_CLOSE_REASON_LAST
+# endif
+} virConnectCloseReason;
...
diff --git a/src/libvirt.c b/src/libvirt.c
index 8315b4f..9cfabc5 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -18613,6 +18613,117 @@ error:
/**
+ * virConnectRegisterCloseCallback:
+ * @conn: pointer to connection object
+ * @cb: callback to invoke upon close
+ * @opaque: user data to pass to @cb
+ * @freecb: callback to free @opaque
+ *
+ * Registers a callback to be invoked when the connection
+ * is closed. This callback is invoked when there is any
+ * condition that causes the socket connection to the
+ * hypervisor to be closed.
+ *
+ * This function is only applicable to hypervisor drivers
+ * which maintain a persistent open connection. Drivers
+ * which open a new connection for every operation will
+ * not invoke this.
+ *
+ * The @freecb must not invoke any other libvirt public
+ * APIs, since it is not called from a re-entrant safe
+ * context.
+ *
+ * Returns 0 on success, -1 on error
+ */
+int virConnectRegisterCloseCallback(virConnectPtr conn,
+                                    virConnectCloseFunc cb,
+                                    void *opaque,
+                                    virFreeCallback freecb)
+{
+    VIR_DEBUG("conn=%p", conn);
+
+    virResetLastError();
+
+    if (!VIR_IS_CONNECT(conn)) {
+        virLibConnError(VIR_ERR_INVALID_CONN, __FUNCTION__);
+        virDispatchError(NULL);
+        return -1;
+    }
+
+    virMutexLock(&conn->lock);
+
+    virCheckNonNullArgGoto(cb, error);
+
+    if (conn->closeCallback) {
+        virLibConnError(VIR_ERR_OPERATION_INVALID, "%s",
+                        _("A close callback is already registered"));
+        goto error;
+    }
+
+    conn->closeCallback = cb;
+    conn->closeOpaque = opaque;
+    conn->closeFreeCallback = freecb;
+
+    virMutexUnlock(&conn->lock);
+
+    return 0;
+
+error:
+    virMutexUnlock(&conn->lock);
+    virDispatchError(NULL);
+    return -1;
+}
+
+/**
+ * virConnectUnregisterCloseCallback:
+ * @conn: pointer to connection object
+ * @cb: pointer to the current registered callback
+ *
+ * Unregisters the callback previously set with the
+ * virConnectRegisterCloseCallback method. The callback
+ * will no longer received notifications when the connection
s/received/receive/
...
+ * closes.
Is it worth noting that freecb() is called on opaque or is it obvious enough?
...
+ *
+ * Returns 0 on success, -1 on error
+ */
+int virConnectUnregisterCloseCallback(virConnectPtr conn,
+                                      virConnectCloseFunc cb)
+{
+    VIR_DEBUG("conn=%p", conn);
+
+    virResetLastError();
+
+    if (!VIR_IS_CONNECT(conn)) {
+        virLibConnError(VIR_ERR_INVALID_CONN, __FUNCTION__);
+        virDispatchError(NULL);
+        return -1;
+    }
+
+    virMutexLock(&conn->lock);
+
+    virCheckNonNullArgGoto(cb, error);
+
+    if (conn->closeCallback != cb) {
+        virLibConnError(VIR_ERR_OPERATION_INVALID, "%s",
+                        _("A different callback was requested"));
+        goto error;
+    }
+
+    conn->closeCallback = NULL;
+    if (conn->closeFreeCallback)
+        conn->closeFreeCallback(conn->closeOpaque);
I'd also reset closeFreeCallback and closeOpaque to NULL to avoid accessing
them by mistake in the future.
...
+
+    virMutexUnlock(&conn->lock);
+
+    return 0;
+
+error:
+    virMutexUnlock(&conn->lock);
+    virDispatchError(NULL);
+    return -1;
+}
+
+/**
  * virDomainSetBlockIoTune:
  * @dom: pointer to domain object
  * @disk: path to the block device, or device shorthand
...
ACK with nits fixed or ignored as not being worth it.

Jirka

    

Re: [libvirt] [PATCH v2 1/5] Add public API to register a callback to be invoked on connection close

Jiri Denemark