TikZ: edge should not interfere with other elements in the graph and label positioning

Question

I'm quite new to TikZ and I created the following graph:

\begin{tikzpicture}

\node[draw,circle] (n4) at (2, -3) {4};
\node[draw,circle] (n5) at (2, -4) {5};
\node[draw,circle] (n6) at (1, -5) {6};
\node[draw,circle] (n7) at (3, -5) {7};
\node[draw,circle] (n8) at (1, -6) {8};
\node[draw,circle] (n9) at (3, -6) {9};
\node[draw,circle] (n10) at (2, -7) {10};

\draw[->] (n4)--(n5) node[midway, right] {lengthy edge label 1};
\draw[->] (n5)--(n6) node[midway, left] {lengthy edge label 2};
\draw[->] (n5)--(n7) node[midway, right] {lengthy edge label 3};
\draw[->] (n6)--(n8) node[midway, left] {edge label 4};
\draw[->] (n7)--(n9) node[midway, right] {edge label 5};
\draw[->] (n9)--(n10) node[midway, right] {label 6};
\draw[->] (n8)--(n10) node[midway, left] {label 7};

\draw[->] (n10) -| +(4,0) -- +(4,0) node[midway, right]  {edge label 8} |- (n4);    

\end{tikzpicture}

An image of the output can be found here:

It took me quite a while for this graph to build. However, I couldn't come up with a solution for the following questions:

• Is it possible to set the path of the edge from node 10 to node 4 in such a way that it automatically bypasses the rightmost "inner" label? In the example above I have to adjust the value in \draw to something like +(5,0) so that it doesn't interfere with "lengthy edge label 3", but this seems quite cumbersome if the graph changes frequently
• How can I place "edge label 8" in the middle of the vertical path segment?
• Is it possible to increase the distances between the nodes without having to assign new coordinate points to each node?

Any hint is appreciated.

Answer 1

I used another node (c) and I added sme styles.

\documentclass[11pt]{scrartcl}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[y=1.5cm]

\begin{scope} [every node/.style={draw,circle}]
    \node (n4) at (2, -3) {4};
    \node (n5) at (2, -4) {5};
    \node (n6) at (1, -5) {6};
    \node (n7) at (3, -5) {7};
    \node (n8) at (1, -6) {8};
    \node (n9) at (3, -6) {9};
    \node (n10)at (2, -7) {10}; 
\end{scope}

\begin{scope}[->,every node/.style={ right}]
  \draw (n4)-- node{lengthy edge label 1} (n5);
  \draw (n5)-- node[left] {lengthy edge label 2}(n6)  ;
  \draw (n5)-- node (c) {lengthy edge label 3}(n7) ;
  \draw (n6)-- node[left] {edge label 4}(n8)  ;
  \draw (n7)-- node {edge label 5}(n9)  ;
  \draw (n9)-- node {label 6}(n10) ;
  \draw (n8)-- node[left] {label 7}(n10) ;
\end{scope}

\draw[->] (n10) -| (c.east) coordinate (d)  |-  (n4);
\node [right,anchor=west]  at (n7-|d) {edge label 8} ;   

\end{tikzpicture}
\end{document} 

update

The problem with positioning is to scale the picture. A possibility is to use

\begin{scope} [every node/.style={draw,circle}]
    \path
          ( 2 ,-3)  node  (n4)  {4}
      ++  ( 0 ,-1)  node  (n5)  {5}
      ++  (-1 ,-1)  node  (n6)  {6}
      ++  ( 0 ,-1)  node  (n8)  {8}
      ++  ( 1 ,-1)  node  (n10) {10}
      ++  ( 1 , 1)  node  (n9)  {9}
      ++  ( 0 , 1)  node  (n7)  {7}; 
\end{scope}

and if you don't like the coordinates

 \def\dn{++( 0 ,-1)}   \def\up{++( 0 ,1)}
 \def\rdn{++( 1 ,-1)}  \def\rup{++( 1 ,1)} 
 \def\ldn{++( -1 ,-1)} \def\lup{++( -1 ,1)}  
\begin{scope} [every node/.style={draw,circle}]
    \path
          ( 2 ,-3)  node  (n4)  {4}
              \dn   node  (n5)  {5}
              \ldn  node  (n6)  {6}
              \dn   node  (n8)  {8}
              \rdn  node  (n10) {10}
              \rup  node  (n9)  {9}
              \up   node  (n7)  {7}; 
\end{scope}

Answer 2

Also positioning library is suitable for such tasks...

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[node distance=6mm and 5mm,] %You can individually assign x and y distances

\node[draw,circle] at (2, -3)         (n4) {4};
\node[draw,circle,below= of n4]       (n5) {5};
\node[draw,circle,below left= of n5]  (n6) {6};
\node[draw,circle,below right= of n5] (n7) {7};
\node[draw,circle,below= of n6]       (n8) {8};
\node[draw,circle,below= of n7]       (n9) {9};
\node[draw,circle,below left= of n9]  (n10) {10};

\draw[->] (n4)--(n5) node[midway, right] {lengthy edge label 1};
\draw[->] (n5)--(n6) node[midway, left] {lengthy edge label 2};
\draw[->] (n5)--(n7) node[midway, right] (l1) {lengthy edge label 3};
\draw[->] (n6)--(n8) node[midway, left] {edge label 4};
\draw[->] (n7)--(n9) node[midway, right] {edge label 5};
\draw[->] (n9)--(n10) node[midway, right] {label 6};
\draw[->] (n8)--(n10) node[midway, left] {label 7};

\draw[->] (n10) -| (l1.east)  node[midway,right]  {edge label 8} |- (n4);
\end{tikzpicture}
\end{document}

Answer 3

Since the point How can I place "edge label 8" in the middle of the vertical path segment? wasn't fixed so far, my answer tries to address it.

Your initial midway in this case does not holds thus you can made use of the manual pos=.

For example:

% Basic code taken from percusse's answer
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[node distance=6mm and 5mm]

\node[draw,circle] at (2, -3)         (n4) {4};
\node[draw,circle,below= of n4]       (n5) {5};
\node[draw,circle,below left= of n5]  (n6) {6};
\node[draw,circle,below right= of n5] (n7) {7};
\node[draw,circle,below= of n6]       (n8) {8};
\node[draw,circle,below= of n7]       (n9) {9};
\node[draw,circle,below left= of n9]  (n10) {10};

\draw[->] (n4)--(n5) node[midway, right] {lengthy edge label 1};
\draw[->] (n5)--(n6) node[midway, left] {lengthy edge label 2};
\draw[->] (n5)--(n7) node[midway, right] (l1) {lengthy edge label 3};
\draw[->] (n6)--(n8) node[midway, left] {edge label 4};
\draw[->] (n7)--(n9) node[midway, right] {edge label 5};
\draw[->] (n9)--(n10) node[midway, right] {label 6};
\draw[->] (n8)--(n10) node[midway, left] {label 7};

\draw[->] (n10) -| (l1.east)  node[pos=0.9,right]  {edge label 8} |- (n4);
\end{tikzpicture}
\end{document}

will lead to:

Of course, the positioning thanks to pos=0.9 also applies to the method shown by Altermundus in his answer.